Pour voir les autres types de publications sur ce sujet consultez le lien suivant : Vulcanizatio.
Thèses sur le sujet « Vulcanizatio »
Créez une référence correcte selon les styles APA, MLA, Chicago, Harvard et plusieurs autres
Consultez les 50 meilleures thèses pour votre recherche sur le sujet « Vulcanizatio ».
À côté de chaque source dans la liste de références il y a un bouton « Ajouter à la bibliographie ». Cliquez sur ce bouton, et nous générerons automatiquement la référence bibliographique pour la source choisie selon votre style de citation préféré : APA, MLA, Harvard, Vancouver, Chicago, etc.
Vous pouvez aussi télécharger le texte intégral de la publication scolaire au format pdf et consulter son résumé en ligne lorsque ces informations sont inclues dans les métadonnées.
Parcourez les thèses sur diverses disciplines et organisez correctement votre bibliographie.
1
SUSANNA, ANTONIO. "Highly Efficient MeO Nanoparticles as Curing Activator for Rubber Composites." Doctoral thesis, Università degli Studi di Milano-Bicocca, 2016. http://hdl.handle.net/10281/129620.
Texte intégralRésumé :
The vulcanization of rubber by sulfur is a large-scale industrial process that improves the mechanical properties of unsaturated rubber by the cross-linking of polymer chains. Microcrystalline ZnO particles are currently used as activator to enhance the efficiency of the crosslinking. Due to their not easy dispersion in the rubber matrix and to the relatively small fraction of ZnO which actually reacts with the other curative compounds, a large amount of oxide is required for the process. This leads to a not homogeneous vulcanization with inefficient polymer network structure and a possible release of the metal in the environment with potentially negative effects. Thus, a possible improvement of ZnO efficiency as activator requires an enhancement of its availability, distribution and capability to release Zn2+ ions in the rubber matrix. Aim of this thesis, is the enhancement of the curing efficiency by employing ZnO nanoparticles (NPs) grown on silica filler particles. A simple low-temperature sol-gel procedure was exploited to grow amorphous spherical ZnO NPs directly on silica surface and linked by Si-O-Zn covalent bonds (ZnO/SiO2) which simultaneously behave as curing agent and reinforcing filler. The morphology and crystal structure of ZnO/SiO2 NPs were investigated by XRD and TEM. The nanometric size was assessed by UV reflectance measure, while the Si-O-Zn bond interaction was studied by NMR, ATR-FTIR and XPS and discussed in relation to the NPs dimensions. The ZnO/SiO2 NPs were used to prepare cured polyisoprene nanocomposites loaded with silica. Moreover, the curing efficiency and dynamic mechanical properties of vulcanized ZnO/SiO2 nanocomposites were compared to those obtained by using microcrystalline ZnO as activator in conventional curing processes. In the case of nanocomposite cured with ZnO/SiO2 NPs showed better curing efficiency, higher cross-linking density and improved mechanical properties than the same composites treated by conventional ZnO particles. In order to explain the better efficiency of ZnO/SiO2 NPs in the vulcanization, the pseudo activation energies of the different stages of the process were evaluated by performing DSC measurements on the nanocomposites. The presence of ZnO/SiO2 NPs induces lower activation energies and, therefore, faster kinetics compared to microcrystalline ZnO, particularly in the first steps of the reactions. This is in agreement with the highest ability of zinc in ZnO/SiO2 to react with curatives, thus improving the cross-linking density. The role of ZnO/SiO2 NPs in the crosslinking reaction was further studied by a model compound vulcanization (MCV) approach, using tetramethylethylene as model monomer and analyzing the cured products by LC-MS chromatography and 1H-NMR spectroscopy. The results evidence a higher crosslinking for ZnO/SiO2 due to the larger amount of more stable mono- and di-sulphide crosslinking chains than for conventional ZnO. The comparison between the two catalysts have been also discussed on the basis of FTIR investigation which evidence in ZnO/SiO2 the formation of highly reactive stearate bridged bidentate zinc complex as possible intermediate in accelerating the cross-linking reaction. These results suggest that the proposed material could be considered as promising system for curing industrial application with reduce zinc loading. Finally, similar activator/filler NPs loaded with CaO and MgO were also prepared and tested to replace the Zn in curing process. Nanosized dimension and high dispersion of the oxides improve the efficiency of this activators with respect to system with unsupported crystalline oxides even if their catalityc activity is confirmed to be much lower than ZnO.
2
Boonkerd, Kanoktip. "EFFECT OF EFFICIENCY OF SULFUR VULCANIZATION ON PROPERTIES OF GUM AND BLACK-FILLED NATURAL RUBBER VULCANIZATES." University of Akron / OhioLINK, 2006. http://rave.ohiolink.edu/etdc/view?acc_num=akron1144259529.
Texte intégral
3
Reis, Elton Aparecido Prado dos [UNESP]. "Preparação e caracterização de compósitos obtidos a partir de borracha natural com raspa de couro visando aplicações industriais." Universidade Estadual Paulista (UNESP), 2010. http://hdl.handle.net/11449/99697.
Texte intégralRésumé :
Made available in DSpace on 2014-06-11T19:30:19Z (GMT). No. of bitstreams: 0
Previous issue date: 2010-06-28Bitstream added on 2014-06-13T20:47:10Z : No. of bitstreams: 1
reis_eap_me_bauru.pdf: 5393371 bytes, checksum: 16962b43c55e24ca2edab26b06201e8e (MD5)<br>Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)<br>Neste trabalho é apresentado o método de preparação dos compósitos obtidos a partir da mistura de borracha natural (BN) com raspa de couro, gerada em uma das etapas do tratamento do couro nos cortumes. Os compósitos foram obtidos utilizando o método de prensagem e quente, em diferentes proporções em massa (m%). Também será apresentada a proporção calculada a partir da quantidade de BN utilizada (phr) e a técnica usada para a incorporação dos agentes de vulcanização, realizadas para vulcanizar a BN presente na mistura. Os compósitos, que no presente trabalho serão denominados BN/Couro, foram caracterizados utilizando as técnicas de análises de propriedades mecânicas, análises morfológicas, análises estruturais e análises térmicas. Os resultados obtidos foram comparados em função das propriedades físicas dos compósitos com as do couro utilizado comercialmente, com objetivo de se efetuar um direcionamento para uma possível aplicação industrial e comercial dos compósitos. De acordo com os resultados constatou-se que o material apresenta baixa capacidade de deformação, causada pela vulcanização realizada na BN e também pelas partículas de couro. Notou-se também que os compósitos apresentam bom grau de impermeabilidade e desgaste, quando comparado ao couro sola utilizado comercialmente, sendo averiguado que esta propriedades são relacionadas à proporção de BN presente na mistura, que por sua vez atua como agente encapsulador do couro, tornando-se predominante no material produzido. O que investigou o desenvolvimento deste trabalho foi a pretensão de obter um material de baixo custo, pois será produzido a partir de um resíduo gerado às toneladas<br>This work presents the method of preparation of composites from a mixture of natural rubber (NR) with leather waste, generated in one step in the treatment of leather in tanneries. The composites were obtained using the method of hot pressing, in different proportions by mass (wt%). Also presented the ratio calculated from the amount of NR used (phr) and the technique used for incorporation of curing agents, taken to vulcanize the NR in the mixture. The composites, which in this work will be called NR/Leather, were characterized using the techniques of analysis of mechanical properties, morphological analysis, structural analysis and thermal analysis. The results were compared on the basis of the physical properties of the composities with the leather used commercially, with the objective to make a direction for a possible industrial application and commercial composites. According to the results found that the material has a low capacity for deformation caused by vulcanization perfomed in NR and also by the particles of leather. It was also noted that the composites exihibit a good degree of impermeability and wear when compared to leather soles used commercially, and ascertained that these properties are related to the proportion of BN in the mixture, which in turn acts as an agent wrapper of leather making is predominant in the material produced. What prompted the development of this work was the intention of obtaining a low cost material, which be produced from a waste generated by the ton
4
Reis, Elton Aparecido Prado dos. "Preparação e caracterização de compósitos obtidos a partir de borracha natural com raspa de couro visando aplicações industriais /." Presidente Prudente, 2010. http://hdl.handle.net/11449/99697.
Texte intégralRésumé :
Orientador: Aldo Eloizo Job<br>Banca: Celia Regina Granhen Tavares<br>Banca: Silvio Rainho Teixeira<br>Resumo: Neste trabalho é apresentado o método de preparação dos compósitos obtidos a partir da mistura de borracha natural (BN) com raspa de couro, gerada em uma das etapas do tratamento do couro nos cortumes. Os compósitos foram obtidos utilizando o método de prensagem e quente, em diferentes proporções em massa (m%). Também será apresentada a proporção calculada a partir da quantidade de BN utilizada (phr) e a técnica usada para a incorporação dos agentes de vulcanização, realizadas para vulcanizar a BN presente na mistura. Os compósitos, que no presente trabalho serão denominados BN/Couro, foram caracterizados utilizando as técnicas de análises de propriedades mecânicas, análises morfológicas, análises estruturais e análises térmicas. Os resultados obtidos foram comparados em função das propriedades físicas dos compósitos com as do couro utilizado comercialmente, com objetivo de se efetuar um direcionamento para uma possível aplicação industrial e comercial dos compósitos. De acordo com os resultados constatou-se que o material apresenta baixa capacidade de deformação, causada pela vulcanização realizada na BN e também pelas partículas de couro. Notou-se também que os compósitos apresentam bom grau de impermeabilidade e desgaste, quando comparado ao couro sola utilizado comercialmente, sendo averiguado que esta propriedades são relacionadas à proporção de BN presente na mistura, que por sua vez atua como agente encapsulador do couro, tornando-se predominante no material produzido. O que investigou o desenvolvimento deste trabalho foi a pretensão de obter um material de baixo custo, pois será produzido a partir de um resíduo gerado às toneladas<br>Abstract: This work presents the method of preparation of composites from a mixture of natural rubber (NR) with leather waste, generated in one step in the treatment of leather in tanneries. The composites were obtained using the method of hot pressing, in different proportions by mass (wt%). Also presented the ratio calculated from the amount of NR used (phr) and the technique used for incorporation of curing agents, taken to vulcanize the NR in the mixture. The composites, which in this work will be called NR/Leather, were characterized using the techniques of analysis of mechanical properties, morphological analysis, structural analysis and thermal analysis. The results were compared on the basis of the physical properties of the composities with the leather used commercially, with the objective to make a direction for a possible industrial application and commercial composites. According to the results found that the material has a low capacity for deformation caused by vulcanization perfomed in NR and also by the particles of leather. It was also noted that the composites exihibit a good degree of impermeability and wear when compared to leather soles used commercially, and ascertained that these properties are related to the proportion of BN in the mixture, which in turn acts as an agent wrapper of leather making is predominant in the material produced. What prompted the development of this work was the intention of obtaining a low cost material, which be produced from a waste generated by the ton<br>Mestre
5
Pinheiro, Eduardo Gonçalves. "Modelos numéricos aplicados à vulcanização de pneus." Universidade de São Paulo, 2001. http://www.teses.usp.br/teses/disponiveis/3/3132/tde-25082003-090611/.
Texte intégralRésumé :
A vulcanização é um processo termo-químico aplicado aos polímeros elastoméricos, também chamados de borrachas. Devido à vulcanização, as borrachas adquirem propriedades físicas que as tornam adequadas a várias aplicações mecânicas, entre estas, se destaca aquela desempenhada pelo componente automotivo pneu. Durante a vulcanização as moléculas do elastômero são unidas em vários pontos através de ligações cruzadas. Isso ocorre através do aquecimento da borracha adicionada de enxofre. O correto dimensionamento do tempo que o calor deve ser transferido ao composto de borracha a ser vulcanizado é crucial para definir as características finais deste composto. Em condições extremas, se o tempo de exposição ao calor for insuficiente, o composto continuará com comportamento de baixa resistência às deformações. Por outro lado se o tempo de exposição ao calor for excessivo, além do desperdício energético e econômico, o composto de borracha entra numa fase de reversão, que significa diminuição das propriedades já alcançadas. O dimensionamento da vulcanização de um pneu necessita basicamente de dois suportes fundamentais de engenharia: a) um modelo numérico para a reação termo-química que leve em conta a cinética de cura de cada composto de borracha do pneu; b) um modelo numérico de transmissão de calor, capaz de calcular para qualquer ponto do pneu a sua evolução térmica durante a vulcanização. Esta dissertação apresenta uma revisão da literatura sobre vulcanização de pneus, os modelos utilizados, e um modelo proposto pelo autor. Nesse, questões como reologia da borracha em regime de temperatura variável e reversão do composto recebem um tratamento numérico específico. Através da validação experimental verifica-se que o modelo proposto é altamente eficaz para aplicações industriais.<br>Vulcanization is a thermochemical process applied to the elastomeric polymers also called rubbers. Due to the vulcanization, rubbers acquire physical properties that make them capable to support mechanical applications, such as pneumatic tire. During the vulcanization, the elastomer molecules are tied together in many points due to the crosslinking process. This process is made possible due to the heating of the mixing of rubber and sulfur. It is very important to define the right time under the heat a rubber requires to be vulcanized. This vulcanizing period will define the future rubber characteristics. If an insufficient curing time is used for vulcanization, the rubber compound will maintain the poor characteristics of a raw rubber. In the other extreme, if a very extensive cure time is used, besides the energetic and economic losses, it will provoke reversion on the rubber, that means the reduction of the desired cured rubber properties. In order to produce a precise dimensioning of the cure cycle two fundamental engineering supports are necessary: a) a numerical model for the thermochemical reaction, dealing with the curing kinetics of each rubber compound involved in a tire; b) a numerical model for the heat transfer process, capable to determine during the vulcanization period, the temperature evolution in any point of a single tire. This work presents a discussion of previous literature on the tire vulcanization area, their cure models, and a new model proposed by the author. This model treats questions like the rubber rheology in non isothermal condition, and the compound reversion, applying to them specific numerical treatments. The use of experimental validation showed the model to be very efficient for industrial applications.
6
Torani, Daiane. "Sistemas alternativos de ativadores de vulcanização em comparação ao sistema tradicionalmente utilizado em compostos elastoméricos de borracha natural." reponame:Repositório Institucional da UCS, 2017. https://repositorio.ucs.br/handle/11338/3381.
Texte intégralRésumé :
Submitted by Ana Guimarães Pereira (agpereir@ucs.br) on 2017-12-14T11:27:43Z
No. of bitstreams: 1
Dissertacao Daiane Torani.pdf: 659387 bytes, checksum: 1da8ec4adced63030a1d1600bee76d99 (MD5)<br>Made available in DSpace on 2017-12-14T11:27:43Z (GMT). No. of bitstreams: 1
Dissertacao Daiane Torani.pdf: 659387 bytes, checksum: 1da8ec4adced63030a1d1600bee76d99 (MD5)
Previous issue date: 2017-12-14<br>Coordenação de Aperfeiçoamento de Pessoal de Nível Superior, CAPES.
7
Bellander, Martin. "High pressure vulcanization : crosslinking of diene rubbers without vulcanization agents." Doctoral thesis, KTH, Polymer Technology, 1998. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-2713.
Texte intégralRésumé :
<p>High pressure vulcanization (HPV) is defined in this thesisas crosslinking of rubber materialsat elevated pressure andtemperature, without the use of any vulcanization agents. Thisis atotally new vulcanization technique, not used in theindustry today. The HPV technique,however, has an interestingpotential since no hazardous chemicals need to be handled,thematerial does not contain any additives. The phenomenon thatcertain rubber materials can be crosslinked in this way wasobserved already in the 1960s, but there has been a lack ofknowledge of the underlying reaction mechanisms, kinetics, theresulting network structure and also the correlation betweenthe molecular structure and the physical properties ofthesematerials. The purpose of this thesis is to increase theknowledge of high pressurevulcanization, with respect toreaction kinetics and mechanisms, network structure andphysical properties.</p><p>A low cis-polybutadiene was used as a model material forcrosslinking at high pressure (10-290 MPa) and temperature(240-250°C), and comparisons were made withperoxidevulcanizates. Both unfilled and carbon black filledsamples were studied. Nitrile- and styrene-butadienerubber werealso crosslinked successfully. Crosslink density is a centralconcept inthis thesis and was evaluated by swellingmeasurements. The microstructural changesoccurring duringvulcanization were studied by Fourier Transform InfraredSpectroscopy(FTIR) and 13 C solid state nuclear magneticresonance (NMR). The mechanical propertieswere investigated bydynamic mechanical thermal analysis (DMTA), tensile testing,and permanent set and stress relaxation measurements.Theprogress of the reaction proved to be well controlled by thetreatment time, temperature and pressure, resulting inmaterials with widely different properties within onesinglecompound due to the possibility of controlling thecrosslink density during the vulcanizationprocess. The reactionmechanism was shown to be of a radical type, and vinylunsaturations inthe polybutadiene are consumed concurrentlywith the crosslink formation. The effect ofpressure on thereaction is a decrease in molecular mobility, which results inhighercrosslinking reaction rate due to a decrease intermination reactions. When a carbon black filleris introduced,the number of polymer-filler interactions is increased due tothe ability of thepolymer to penetrate the carbon blackstructure under pressure. The mechanical properties areas goodas those of peroxide vulcanizates, and especially theresistance to deformation inservice-use at elevatedtemperatures suggests that the resulting material may be usedin gasketand seal applications. In spite of the difficulties ofmould sealing that arise at elevatedpressures, it was possibleto obtain vulcanized samples by common injection mouldingwithproperties comparable to those obtained by traditionalvulcanization.</p><p><b>Keywords:</b>High Pressure Vulcanization, Vulcanization,Crosslinking, Pressure, Elevated Temperature, Polybutadiene,Carbon Black, Rubber-Carbon Black Interactions, CrosslinkDensity, Peroxide Vulcanization, Injection Moulding,Nitrile-Butadiene Rubber.</p>
8
Weijh, André. "Metodologia para simulação de elastômeros considerando estratificação das propriedades de cura." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2018. http://hdl.handle.net/10183/178774.
Texte intégralRésumé :
Esse trabalho tem por objetivo desenvolver uma ferramenta para previsão das características da cura em borrachas, através da análise numérica de modelos fenomenológicos de vulcanização correlacionados às análises térmicas via método dos elemento finitos. A metodologia é baseada em simular o processo de vulcanização no molde, estimando-se a energia de ativação e simulando o histórico de temperaturas dentro do molde, estratificando o volume do componente por faixas de vulcanização. A partir da caracterização mecânica da borracha nos seus diversos estados de cura, as propriedades constitutivas são especificadas de forma segregada para cada diferente região do componente, que então é simulado em situação de operação. Desta forma, é possível analisar as consequências sobre o comportamento mecânico de componentes parcialmente curados ou melhorar o processo de moldagem a fim de minimizar as diferenças decorrentes do processo. Usam-se como objeto de estudo apoios elastoméricos de pontes não fretados, comparando alterações na resposta do componente perfeitamente curado com situações industriais onde isso não é possível. Como resultado, obtém-se uma estratificação de cura com erros de aproximadamente 2% para percentuais de cura superiores a 50% e diferenças consideráveis para o estado de tensões do modelo com cura homogênea e estratificada.<br>This work develops a tool to predict vulcanization properties in rubber, based on numerical analysis of phenomenological model correlated with the thermal history of rubber in mold vulcanization. This methodology simulates mold cure process by finite element method, estimating the activation energy and dividing the component into different cure regions. After the mechanical characterization of the rubber with different cure percentages, the constitutive properties are specified in a segregate form in each different cure region of the component, emulating the mechanical behavior of the component in operation. This way it is possible to analyze stresses and strains in components with 100% of cure and in components with incomplete cure. The methodology is applied to a thick rubber piece used to support the track in road bridges. As result, the mean error is about 2% for cure level above 50% and the stratified model present different state of stress in comparison with the homogeneous cure model.
9
Sun, Yu. "VULCANIZATION AND DEVULCANIZATION OF RUBBER." University of Akron / OhioLINK, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=akron1594830138675509.
Texte intégral
10
Van, Rooyen Jason Leigh. "A comparison of the vulcanisation of Polyisoprene by a range of Thiuram Diulfides." Thesis, Nelson Mandela Metropolitan University, 2007. http://hdl.handle.net/10948/733.
Texte intégralRésumé :
This study was initiated in an attempt to investigate dithiocarbamic acid accelerated sulfur vulcanisation. This was, however, found impossible due to the innate instability of dithiocarbamic acids. The focus of the study was then shifted toward thiuram disulfide accelerated sulfur vulcanisation, with emphasis being placed on a rate comparison. Three groups of accelerators were investigated, namely the aromatic, linear aliphatic and cyclic aliphatic thiuram disulfide adducts. The analysis methods that were employed were conventional rubber (cis-1,4-polyisoprene) techniques coupled to model (squalene) compound investigations. The data that was collected consisted of rheometrical torque vs. time data in the rubber system while the data obtained in the model compound study consisted of sulfur and accelerator concentration data as determined by means of high performance liquid chromatography (HPLC). The aromatic accelerators were synthesised in our labs by means of an addition reaction between the aromatic amine and CS2 in basic medium and subsequent oxidation with K3Fe(CN)6, all in a 1:1 molar ratio. The reaction yield was low due to the instability of the dithiocarbamate intermediates and a sluggish oxidation reaction. In the rate constant determination a first order mathematical approach was used for the rubber system as crosslinking is considered to roughly obey first order kinetics. The model compound data was also found to more accurately fit the first order rate law, with an initial slopes method also being applied to the system to determine secondary rate constants and relative rates for the system. The determination of vulcanisation rate constants in the cis-1,4-polyisoprene system was a success, while the rate data determined by means of the squalene model was more related to the rate of accelerator and sulfur consumption as opposed to the rate of crosslinking as is the case with the rubber rate data. The sulfur first order rate data mirrored the rate data derived from the rubber system more closely than the corresponding accelerator rate data, the relative rate data determined by means of initial slopes method, proved that the homolytic cleavage of thiuram disulfides and the subsequent formation of accelerator polysulfides were not limiting steps. This is seen in the similar relative rate data derived from both the raw sulfur and accelerator data in systems that exhibit vastly different vulcanisation rates. Squalene was deemed a suitable model for the cis-1,4-polyisoprene system, although one should consider the extent of charring and solution effects in the individual systems to account for possible incongruities that may be observed between the rubber and simulated system. The lack of agreement between the rubber and model compound rate constant data lies in the fact that the rate of crosslinking is not simplistically related to the rate at which accelerator and sulfur is consumed, this being especially true for the rate at which the accelerator is consumed. Thus the discussion over the acceleratory rates in the various accelerator systems was limited to observations made in the rubber system, with the model compound data was used exclusively to elucidate mechanistic processes. It was discovered that the groups of accelerators examined, namely linear, cyclic and aromatic thiuram disulfide adducts, produced vastly varied rate data. The aromatic thiuram disulfide adducts had only a slight acceleratory effect on the rate of vulcanisation as compared to the unaccelerated sulfur system. The morpholine adduct had a moderately larger rate of acceleration followed by tetramethyl and tetrethylthiuram disulfide, with N’N-dicyclopentamethylenethiuram disulfide having the fastest rate of acceleration.
11
Santos, Glaucia Cristina Mello. "Redução da biocarga e garantia de esterilidade em implantes mamários de silicone." Universidade de São Paulo, 2009. http://www.teses.usp.br/teses/disponiveis/9/9139/tde-01022010-161804/.
Texte intégralRésumé :
Os implantes mamários de silicone constituem-se em biomateriais os quais têm sido amplamente utilizados em cirurgias para reconstituição da mama após ocorrência de câncer, acidentes, correção do tamanho dos seios quando há uma diferença de volume entre eles, ou até mesmo, para o aumento do tamanho da mama por motivos estéticos. Com o intuito de conferir segurança em sua aplicação, intimamente ligada à saúde dos pacientes, grande atenção tem sido dada aos processos de esterilização aplicados a biomateriais. Ao avaliar o processo produtivo de implantes mamários de silicone, um dos processos de esterilização mais comumente empregados é o calor seco, que necessita de elevadas temperaturas por longo tempo para o sucesso da esterilização. A exposição do implante a tais condições potencialmente pode ocasionar alterações de suas características. De outro lado, uma etapa preliminar do processo produtivo do implante é a vulcanização, que consiste no aquecimento do implante a temperaturas da ordem de 165 ± 5°C por aproximadamente 9 horas. Considerando tempo e temperatura empregados nesta etapa, o objetivo deste estudo foi avaliar a carga microbiana dos implantes mamários de silicone antes do processo de vulcanização, assim como o decaimento da carga microbiana neste processo e também confirmar a esterilidade do gel contido internamente à membrana. Desta forma, foi possível observar que o nível de contaminação microbiana dos implantes gelatinosos é relativamente baixo e que a vulcanização foi um processo que possibilitou a inativação de até 108 esporos, a concentração de esporos mais alta utilizada no estudo. Os resultados mostraram que a vulcanização possibilitou não só a redução da carga microbiana, mas também consiste em mecanismo para garantir a esterilidade do gel interno ao produto. Desta forma, o processo esterilizante final teve como contribuição elevar o Nível de Garantia de Esterilidade (SAL ou Sterility Assurance Level), condição interessante ao se considerar a tendência de adoção da liberação paramétrica, assim como o conceito de validação combinado bioburden/indicador biológico em vez de sobre-morte. Avaliação complementar foi feita ao quantificar endotoxina nos implantes antes e após o processo de esterilização (calor seco e óxido de etileno), verificando-se que os processos considerados não alteram significativamente a quantidade de endotoxina. Ainda assim, em todas as situações foram obtidos níveis aceitáveis, conforme USP 31.<br>Silicone breast implants consist of biomaterials widely used in breast reconstitution surgeries after the occurrence of cancer, accidents, breast size correction (in case of different volume between both breasts)or in mammary augmentation for esthetic reasons. With a view to confer security in its application, directly related to patients health, great attention has been given to sterilization processes applied to biomaterials. Among these, dry heat is one of the most often employed. For a successful sterilization, it requires high temperatures for a long period, what may give rise to alteration of the implant characteristics. On the other hand, a preliminary stage of the implant production process is vulcanization, which consists of heating the implant to 165 ± 5°C for approximately 9 hours. Taking into account the time and temperature used in this stage, the aim of this work was to evaluate the bioburden of silicone breast implants prior to the vulcanization process and the decline in bioburden due to this process, and to confirm the sterility of the gel contained in the membrane. This study led us to the conclusion that the level of microbial contamination of gel implants is relatively low, and that vulcanization allowed for the inactivation of up to 100 million spores, the highest concentration of spores used in this study. The results obtained showed that vulcanization enabled not only the reduction of the microbial load, but also guaranteed the sterility of the gel inside the product. Thus, the final sterilizing process contributed to an increase in the Sterility Assurance Level, an interesting phenomenon if we consider the tendency toward adoption of parametric release and the concept of a combined validation bioburden/biological indicator rather than overkill. Complement evaluation was made measuring endotoxins in the implants before and after the sterilization process (dry heat and ethylene oxide), verifying that the considered processes do not modify the amount of endotoxin significantly, as expectation. Still thus, in all the situations had been gotten acceptable levels, as USP 31.
12
Braga, Fernanda Cristina Fernandes. "Obtenção de nanocompósitos a partir da co-coagulação da borracha nitrílica e hidrotalcita." Universidade do Estado do Rio de Janeiro, 2014. http://www.bdtd.uerj.br/tde_busca/arquivo.php?codArquivo=7610.
Texte intégralRésumé :
Coordenação de Aperfeiçoamento de Pessoal de Nível Superior<br>Partículas nanoestruturadas têm sido amplamente utilizadas como carga de reforço em matrizes elastoméricas, sendo substitutos eficazes das cargas convencionais, já consagradas, como o negro de fumo, mica, sílica. Em especial, as argilas têm mostrado grande potencial ao que se refere a melhor dispersão na matriz polimérica, em função de sua elevada razão de aspecto. Dentro do vasto universo de argilominerais, as argilas aniônicas, também conhecidas hidróxido duplo lamelar (HDL), apresentam como vantagem a possibilidade de ser projetada estruturalmente para as mais diversas finalidades, ao se modificar os ânions ou os cátions, ou até mesmo combiná-los na estrutura lamelar. E dentre os métodos existentes para se preparar compósitos a base de elastômero/argila, a co-coagulação do látex, é uma forma bastante eficaz e economicamente viável, uma vez que a borracha obtida após processo de coagulação já contém a carga incorporada. Este trabalho se dedicou a avaliar o processo de co-coagulação do látex de NBR e HDL, visando a obtenção de nanocompósitos. Para tanto HDL de composição Mg/Al-CO3 foi modificado com ânions DS, DBS e ST e foram preparadas suspensões aquosas, utilizando como ferramentas de dispersão ultraturrax e ultrassom de ponteira. As variáveis de processo avaliadas foram tipo e teor de HDL, tempo de mistura látex/suspensão aquosa de HDL, quantidade de coagulante e velocidade de agitação. Por fim, os coágulos obtidos foram formulados para avaliar a influência dos HDL na cinética de vulcanização e também para determinação das propriedades mecânicas convencionais. Os resultados obtidos comprovaram que a metodologia de dispersão de hidrotalcita ao látex nitrílico de modo prévio ao processo de coagulação é uma alternativa viável para a obtenção de nanocompósitos. O uso do ultrassom de ponteira como ferramenta na dispersão aquosa de HDL contribuiu para maior estabilidade da suspensão e o ajuste nos parâmetros do sistema de coagulação, levaram a obtenção de grumos uniformes do ponto de vista macroscópico e microscópico. As micrografias dos coágulos não vulcanizados obtidas por MEV-FEG confirmaram as informações apuradas a partir dos difratogramas de raios-X que apontou a formação de um sistema parcialmente esfoliado, em função da ausência dos picos característicos da hidrotalcita, além de indicarem a coexistência de partículas em dimensões micrométrica a nanométricas em uma mesma estrutura. A composição química do HDL, com a presença de átomos de magnésio e alumínio combinados com grupos hidroxila favoreceu a redução tanto o tempo de indução como de pré-cura. As propriedades mecânicas que se mostraram mais sensíveis ao grau de dispersão da carga foram a dureza, a deformação permanente à compressão (DPC) e o módulo de tração a 300% de deformação (E300), em especial para os compósitos contendo 10% m/m de HDL natural e modificado com estearato. A resistência à chama dos nanocompósitos de NBR-HDL vulcanizados apresentou um ligeiro aumento quando comparados à NBR pura, visto que esta é uma característica própria da hidrotalcita, decorrente da sua composição química<br>Nanostructured particles have been widely used as a reinforcing filler in rubber matrices and effective substitutes for, already established conventional fillers such as carbon black, mica and silica. In particular, clays have shown great potential when it comes better dispersed in the polymeric matrix due to its high aspect ratio. Within the vast universe of clay minerals, anionic clays, also known as layered double hydroxide (LDH), have the advantage of being able to be structurally designed for many different purposes, by modifying the anions or cations, or even combine them into lamellar structure. Among the existing methods to prepare elastomer-clay composites, the latex co-coagulation is an effective and economically viable, since method the rubber obtained after the coagulation process already contains the incorporated filler. This work was dedicated to evaluate the co-coagulation of NBR latex and LDH, aiming to obtain nanocomposites. This way, LDH with Mg/Al-CO3 composition was modified with anions dodecyl sulphate, dodecyl-benzene-sulphonate and stearate aqueous suspensions were prepared using ultraturrax as dispersion tools and the ultrasound probe. The process variables were evaluated in type and content of LDH, mixing time latex / aqueous suspension of LDH, quantity of coagulant and mixins speed. Finally, the clots obtained were formulated to verify the effect of LDH on the kinetics of vulcanization, and also for conventional determination of mechanical properties. The results obtained proved that the methodology of dispersion of the hydrotalcite in nitrile latex prior to the coagulation process is a viable alternative for obtaining nanocomposite. The use of ultrasound probe as a tool in the aqueous dispersion of LDH contributed to higher stability of the suspension and the adjusting the parameters of the coagulation system, led to obtainment of uniform clots of macroscopic and microscopic point of view. The micrographs of the clots obtained by SEM-FEG confirmed the information collected from the X-ray diffraction that showed the formation of a partially exfoliated system, due to the absence of the characteristic peaks of hydrotalcite, and indicated the coexistence of particles dimensions micrometric the nanometric within the same structure. The chemical composition of LDH in the presence of atoms of magnesium and aluminum combined with hydroxyl groups favored the reduction of both the induction time as pre-curing. The mechanical properties were more sensitive to the degree of dispersion of the charge were hardness, compression set, and tensile modulus at 300% strain (E300), particularly for composites containing 10% w/m for natural LDH and LDH modified with stearate. The flame resistance of nanocomposites NBR-LDH vulcanizates increased slightly compared to pure NBR, since this is a characteristic of hydrotalcite, due to its chemical composition
13
Vega, Sánchez Berta. "New insights in vulcanization chemistry using microwaves as heating source." Doctoral thesis, Universitat Ramon Llull, 2008. http://hdl.handle.net/10803/9292.
Texte intégralRésumé :
La vulcanització per microones és un procés madur i no hi ha dubte sobre la seva eficiència per produir articles de cautxú d'alta qualitat. Les microones són conegudes no només per la seva capacitat d'accelerar els processos i augmentar la eficiència de la transferència energètica, sinó que també són capaces en certs casos de canviar els camins de reacció. Hi ha evidències, basades en canvis en propietats físiques al comparar productes vulcanitzats amb el mètode convencional i amb microones, que indiquen que alguns canvis poden succeir al treballar amb diferents fonts d'escalfament. No obstant això, hi ha una falta d'informació sobre els efectes que les microones tenen en la química de la vulcanització. Per tant, el principal objectiu d'aquesta tesi es basa en estudiar la vulcanització assistida amb microones des d'una nova perspectiva, centrant-se en els efectes d'aquesta radiació en els ingredients principals de les formulacions de cautxú, en el mecanisme de vulcanització, en la reticulació de la xarxa polimèrica i també en el procés de devulcanització.<br/><br/>La primera part de la feina va consistir en desenvolupar i optimitzar tots els mètodes analítics necessàris per explorar totes les etapes del procés de vulcanització i identificar tots els intermedis formats. Estudis de Model Compound Vulcanization (MCV) utilitzant esqualè com a molècula model s'han realitzat per entendre millor la influència d'aquesta radiació en el mecanisme de la reacció, encara que alguns experiments també s'han realitzat amb mostres de cautxú natural. Tècniques com HPLC-MS, MALDI-TOF o GPC s'han utilitzat per caracteritzar les mostres de MCV, mentre que mesures d'inflament, de tensió-elongació, compressió i duresa s'han realitzat per caracteritzar les mostres de cautxú natural.<br/><br/>Dos dels sistemes de vulcanització més comuns han estat estudiats (sulfenamides i tiurams). A més, s'ha donat un especial èmfasi a l'estudi de la influència de les microones en el sistema activador, intentant reduir el contingut de ZnO i cercar, a través de diverses estratègies, substituts més amigables amb el medi ambient. Finalment, tot el coneixement adquirit en aquests estudis s'ha utilitzat per optimitzar el comportament devulcanitzant del disulfur de difenil (DPDS) amb l'ajut de les microones, demostrant que les microones poden ajudar a avançar en la recerca d'una solució al problema del reciclatge dels residus de cautxú.<br>La vulcanización por microondas es un proceso maduro y no cabe duda sobre su eficiencia para producir artículos de caucho de alta calidad. Las microondas son conocidas no sólo por su capacidad de acelerar los procesos y aumentar la eficiencia de la transferencia energética, sino que también son capaces en ciertos casos de cambiar los caminos de reacción. Hay evidencias, basadas en cambios en propiedades físicas al comparar productos vulcanizados con el método convencional y con microondas, que indican que algunos cambios pueden suceder al trabajar con diferentes fuentes de calentamiento. Sin embargo, hay una falta de información sobre los efectos que las microondas tienen en la química de la vulcanización. Por lo tanto, el principal objetivo de esta tesis se basa en estudiar la vulcanización asistida por microondas desde una nueva perspectiva, centrándose en los efectos de esta radiación en los ingredientes principales de las formulaciones de caucho, en el mecanismo de vulcanización, en la reticulación de la red polimérica y también en el proceso de devulcanización.<br/><br/>La primera parte del trabajo consistió en desarrollar y optimizar todos los métodos analíticos necesarios para explorar todas las etapas del proceso de vulcanización y identificar todos los intermedios formados. Estudios de Model Compound Vulcanization (MCV) utilizando escualeno como molécula modelo se han realizado para entender mejor la influencia de esta radiación en el mecanismo de la reacción, aunque algunos experimentos también se han realizado con muestras de caucho natural. Técnicas como HPLC-MS, MALDI-TOF o GPC se han utilizado para caracterizar las muestras de MCV, mientras que medidas de inflamiento, de tensión-elongación, compresión y dureza se han realizado para caracterizar las muestres de caucho natural.<br/><br/>Dos de los sistemas de vulcanización más comunes han sido estudiados (sulfenamidas y tiuramos). Además, se ha dado un especial énfasis al estudio de la influencia de las microondas en el sistema activador, intentando reducir el contenido en ZnO y buscar, a través de diversas estrategias, substitutos más amigables con el medio ambiente. Finalmente, todo el conocimiento adquirido en estos estudios se ha utilizado para optimizar el comportamiento devulcanitzante del disulfuro de difenilo (DPDS) con ayuda de las microondas, demostrando que las microondas pueden ayudar a avanzar en la búsqueda de una solución al problema del reciclaje de los residuos de caucho.<br>Microwaves vulcanization is a mature process and there is no doubt about its efficiency on producing high quality goods. Microwaves are found not only to speed up the processing and increase the energy transfer efficiency, but also to be in some cases able to change reaction pathways. There are some evidences, based on changes in physical properties when comparing conventional and microwaves vulcanization, that suggest that some changes occur when working with different heating sources. However, there is a lack of information of the effects of MW in vulcanization chemistry. Therefore, the principal aim of this thesis consists of studying microwave-assisted vulcanization from a new perspective, focusing on the effects of this radiation in the main ingredients of a rubber compound, in the vulcanization mechanism, in the final crosslinked network and also in the devulcanization process.<br/><br/>The first part of the work consisted in developing and optimizing all the analytical methods necessary to explore all the steps of vulcanization process and identifying all the intermediates formed. Model Compound Vulcanization (MCV) studies, using squalene as a model molecule, have been used to understand better the influence of this radiation in the reaction mechanism, even though some tests have been also performed in natural rubber samples. Techniques as HPLC-MS, MALDI-TOF or GPC have been used to characterize the MCV samples, whereas swelling measurements, stress-strain measurements, compression set or hardness have been used to characterized natural rubber samples. <br/><br/>Two of the most common vulcanizing systems have been studied (using sulfenamide and/or thiuram accelerator types). In addition, a special emphasis has been given to the study of the microwaves influence on the activator system, trying to reduce ZnO contents and finding more environmental friendly substitutes through different strategies. Finally, all the knowledge acquired in all these studies has been used to optimize the devulcanizing behavior of diphenyl disulfide (DPDS) with the help of microwaves, proving that microwaves can help to advance in the search of a solution to the problem of waste rubber recycling.
14
Jiang, Jiali. "Tearing of Black-Filled (N660) Natural Rubber Vulcanizates." University of Akron / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=akron1349395720.
Texte intégral
15
Li, Jiaxi. "Modified Soybean Oil-extended SBR Compounds and Vulcanizates." University of Akron / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=akron1398348924.
Texte intégral
16
Hong, Yang. "Tearing of Black-filled (N330) Natural Rubber Vulcanizates." University of Akron / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=akron1428194782.
Texte intégral
17
Saboya, Julio Cesar da Costa. "Efeito dos óleos vegetais de linhaça e de amendoim sobre a vulcanização da borracha natural (NR)." Universidade do Estado do Rio de Janeiro, 2014. http://www.bdtd.uerj.br/tde_busca/arquivo.php?codArquivo=7326.
Texte intégralRésumé :
O efeito de dois óleos vegetais, óleo de linhaça e óleo de amendoim, em composições
de borracha natural (NR) foi avaliado. Um sistema de vulcanização convencional foi
escolhido e, após a mistura, os parâmetros reométricos (Sℓ, Sh, ts1 e t90) foram analisados. A
cinética de vulcanização foi estudada através de dois modelos cinéticos um modelo
simplificado e o modelo proposto por Coran. Os resultados experimentais permitem concluir
que os óleos vegetais sozinhos ou combinados são capazes de atuar como ativadores e,
juntamente com os demais ingredientes da composição, de vulcanizar a borracha. No entanto,
uma densidade de ligações cruzadas satisfatória só é atingida quando o ácido esteárico está
presente. O modelo cinético de Coran permitiu também estudar os diferentes estágios da
vulcanização e verificar que a etapa crítica do processo é a formação do precursor de ligações
cruzadas (A → B). Provavelmente, a presença significativa de ácidos graxos insaturados na
composição dos óleos vegetais (principalmente, os ácidos oléico e linolênico) permita reações
laterais não esperadas, o que diminui o rendimento final em ligações cruzadas dos
vulcanizados.<br>The effect of two vegetable oils, linseed oil and peanut oil, in natural rubber (NR)
compositions was available. A conventional system was chosen and, after mixture, rheometer
parameters (Sℓ, Sh, ts1 e t90) were analyzed. Vulcanization kinetics was studied by two
kinetic models a simplified model and a model proposed by Coran. Experimental results
allow concluding that vegetable oils alone or combined are able to act as activators and,
together with others ingredients of composition, vulcanizing the rubber. However,
crosslinking density adequate is only reached when stearic acid is present. Kinetic model of
Coran also allowed to study the different steps of vulcanization and to identify that a critical
step is the formation of crosslink precursor (A → B). Probably, significant presence of
insaturated fatty acids in the chemical composition of the vegetables oils (mainly, oleic and
linolenic acids) allow side reactions unexpected, which decrease the final yield of crosslink in
the vulcanizates.
18
Jackson, Kevin David Oliphant. "Vibrational spectroscopy of elastomers." Thesis, University of Southampton, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.239467.
Texte intégral
19
Fagundes, Enio César Machado. "Elastômero termoplástico vulcanizado a base de PA/NBR." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2011. http://hdl.handle.net/10183/36117.
Texte intégralRésumé :
As propriedades mecânicas dos elastômeros termoplásticos vulcanizados, TPVs, dependem fortemente de sua morfologia, que por sua vez dependem dos polímeros primários, da composição, do sistema e processo de reticulação utilizados. A morfologia é definida durante a vulcanização dinâmica. Este trabalho estuda a influência do sistema de reticulação sobre as propriedades de TPVs a base de PA(6/66)/NBR (co-poliamida PA6/66 e borracha nitrílica) em diferentes composições (40/60, 35/65, 30/70 em massa). Peróxido de dicumila, bismaleimida, resina fenólica, um sistema acelerador/enxofre e peróxido de dicumila com dois coagentes (bismaleimida e enxofre) foram utilizados como agentes reticulantes. Os TPVs foram caracterizados quanto a sua resistência mecânica, resistência a solvente, deformação permanente à compressão, morfologia e propriedades térmicas. Todos os TPVs apresentaram propriedades superiores à blenda PA(6/66)/NBR correspondente. O sistema de cura constituído de peróxido de dicumila e bismaleimida/enxofre (DCP/BMI/enxofre) como coagentes resultou na morfologia melhor definida, e consequentemente, o TPV destacou-se por apresentar as melhores propriedades. A utilização de cargas inorgânicas, negro de fumo, N 330, ou argilas tipo montmorilonita, não trouxe benefícios aos TPVs baseados no sistema DCP/BMI/enxofre. Estes TPVs apresentaram, para as propriedades mecânicas, valores inferiores aos dos TPVs sem carga. A deformação permanente a compressão se manteve e a morfologia se apresentou cocontínua.<br>The mechanical properties of thermoplastic vulcanizates, TPVs, depend strongly on their morphologies, which themselves depend on the properties of the primary polymers, the composition of the TPV and the crosslink system and crosslink process. The morphology is defined during the dynamic vulcanization. This work deals with the study of the influence of crosslink systems on TPVs based on PA(6/66)/NBR (co-polyamide PA6/66 and nitrile rubber) in different compositions (40/60, 35/65, 30/70 in mass). Dicumyl peroxide, bismaleimide, phenolic resin, a sulfur-accelerated system and dicumyl peroxide with two co-agents were used as crosslinkers. TPVs were characterized by taking into account their mechanical strength, solvent resistance, compression set, morphology and thermal properties. All the TPVs exhibit better properties than the blend. The curing system constituted by dicumyl peroxide and bismaleimide/sulfur (DCP/BMI/sulfur) as co-agents resulted in a more defined morphology, and therefore the TPV exhibited the best properties. The addition of inorganic fillers as carbon black, N 330, or clay (montmorillonite), has not brought benefits to the system based on TPVs DCP/ BMI/ sulfur. The TPVs with fillers showed lower mechanical properties than the TPVs without fillers. The compression set was also the same, while a co-continous morphology could be observed in MEV analyses.
20
Sanchez, José Luiz Leite. "Avaliação das propriedades mecânicas e reológicas de composições de borracha nitrílica vulcanizadas com resina fenólica." Universidade do Estado do Rio de Janeiro, 2008. http://www.bdtd.uerj.br/tde_busca/arquivo.php?codArquivo=1848.
Texte intégralRésumé :
Neste trabalho de Dissertação de Tese, composições do copolímero de butadieno-acrilonitrila (NBR) foram vulcanizadas utilizando como agentes de vulcanização, a resina fenólica e o enxofre, com diferentes proporções de resina fenólica e uma única proporção de enxofre. O sistema ativador foi composto por policloropreno e óxido de zinco para as composições com resina fenólica, enquanto que por ácido esteárico e óxido de zinco para a composição com enxofre. Os materiais foram vulcanizados em uma temperatura de 190C. Foi avaliada a influência da variação dos componentes das composições sobre as propriedades reométricas, físico-mecânicas e reológicas dos materiais. Para auxiliar na interpretação dos resultados obtidos para as propriedades reométricas e físico-mecânicas, foi utilizado um planejamento estatístico de análise de variância para verificar a possibilidade da influência das variáveis e suas possíveis combinações nas propriedades avaliadas. Para as composições vulcanizadas com resina fenólica, os resultados mostraram que a composição de borracha nitrílica se tornou mais rígida com a presença da resina. Também foi observada a ocorrência de pós-cura nas composições vulcanizadas com resina fenólica. Os ensaios reológicos revelaram uma homogeneidade nas amostras submetidas aos testes de varredura de deformação, com desvio de linearidade a partir de 10% de deformação.<br>In this Thesis Dissertation, acrylonitrile-butadiene rubber (NBR) compositions were vulcanized using phenolic resin and sulfur as vulcanization agents with different proportions of phenolic resin and only one proportion of sulfur. The activator system was composed of polycloroprene and zinc oxide to phenolic resin compositions, while stearic acid and zinc oxide to sulfur composition. The materials were vulcanized in a temperature of 190C. The influence of the components content on rheometric, physico-mechanical and rheological properties of the materials was evaluated. In order to assist in the interpretation of the to physico-mechanical and rheometric properties results, a statistical planning of variant analysis was used to observe a possible influence of the variables and also their possible associations into the evaluated properties. The results showed that the nitrile rubber become more stiffness with the presence of phenolic resin. It was also observed the occurrence of post-vulcanization on the compositions vulcanized with phenolic resin. The rheological results showed homogeneity of the samples submitted to a strain sweep test, with a linear plateau until 10% of strain.
21
Taksapattanakul, Korn. "Thermoplastic Vulcanizates Based on Hydrogenated Natural Rubber/Polypropylene Blends." Thesis, Le Mans, 2016. http://www.theses.fr/2016LEMA1028/document.
Texte intégralRésumé :
La préparation du caoutchouc naturel hydrogéné (HNR) par réaction avec l'hydrazine et le peroxyde d'hydrogène et le latex de caoutchouc naturel a été intéressée. L’influence de conditions de réaction, types et volume de solvants, volume du réactionnel, la quantité d’hydrazine et de peroxyde d’hydrogène sur le degré d’hydrogénation du caoutchouc naturel a été étudiée. Le structure et détermination du degré d’hydrogénation des caoutchoucs naturel hydrogénés a été analysée par résonance magnétique nucléaire (RMN), transformée de fourier infrarouge (FTIR) et spectroscopie Raman. Un degré d'hydrogénation de 18 % a été obtenu à 1.0 - 2.0 du la molaire de d’hydrazine et de peroxyde d’hydrogène, température optimale de 50°C et le temps de réaction de 24h. Afin d'améliorer le degré d'hydrogénation, des solvants tels que le toluène et le hexane et l'effet de le volume du réactionnel ont été étudiée, ce qui a permis d'obtenir des degrés d’hydrogénation élevés (proches de 65% avec le toluène). D’autre part, des mesures de tailles de particules de latex ont montré que l’hydrogénation du caoutchouc naturel n’avait pas d’effet sur latex de caoutchouc naturel. Un résultat également intéressant concerne le détermination du taux de gel. Ce gel augmente avec le degré d’hydrogénation, prouvant que des réactions de réticulation ont eu lieu. Néanmoins aucun effet de degré d’hydrogénation sur le température de transition vitreuse n’est détecté. La dureté et viscosités Mooney augmentent, en lien avec l’augmentation du taux de gel. Par ailleurs, la résistance thermique du caoutchouc naturel hydrogéné est considérablement améliorée lorsque le degré d’hydrogénation augmente. Le partie suivante est consacrée à la vulcanisation du caoutchouc. Deux types de réticulation ont été utilisés : au soufre et au peroxyde. Les élastomères HNR réticulés montrent une meilleure résistance à l’ozone et l’UV que le NR réticulé. De plus, cette résistance à l’ozone et l’UV est plus élevée pour le réticulation au soufre, comparée à le réticulation au peroxyde. Une bonne corrélation entre les images de microscopie optique et les résultats des analyses Raman est obtenue. La préparation et l’étude de mélanges HNR/PP obtenus par vulcanisation dynamique en utilisant du peroxyde et du soufre comme agents de réticulation. Un degré d’hydrogénation de 65% a été choisi, et différentes ratio HNR/PP ont été étudiés, et comparés avec des mélanges NR/PP. La morphologie des mélanges a été caractérisée par spectroscopie Raman, ce qui a permis d’obtenir des images cartographie Raman indiquant de façon précise le localisation et la distribution des phases de caoutchouc et de PP. Une bonne corrélation entre le cartographie Raman et les images de microscopie électronique à balayage (SEM) est obtenue. Ainsi il apparaît que les particules de caoutchouc sont dispersées dans une phase continue de PP, ceci à la fois pour le HNR et le NR. L’étude des propriétés mécaniques a montré que celles-ci étaient gouvernées principalement par le phase continue de PP<br>The non-catalytic hydrogenation of natural rubber latex (NRL) was carried out by using diimide generated in situ from the reaction between hydrazine (N2H4) and hydrogen peroxide (H2O2). The effects of mole ratios of [C=C]:[N2H4]:[H2O2], reaction conditions, solvent types, solvent volumes and reaction scale-up on the hydrogenation levels were investigated. Nuclear magnetic resonance (NMR), Fourier transform infrared (FTIR), and Raman spectroscopic techniques were employed to investigate the chemical structure of the hydrogenated natural rubber (HNRs) and to quantify the hydrogenationlevels. It was found that variations in moles of N2H4 and H2O2 in the range of 1.0-2.0 moles resulted in degrees of hydrogenation in the range of 10-18%. Little improvement in hydrogenation levels of HNRs was obtained when NRL particles were swollen in solvents by which toluene yielded better results than hexane. The increase in toluenevolume resulted in the increase in hydrogenation levels up to 42 %. TEM micrographs revealed that swelling mainly occurred at the surface of NRL particles, implying that hydrogenation reaction confined largely at the surface of NRL particles. After removal of toluene, particle size and particle size distribution of partially hydrogenated NRL remained unchanged. To further improve degrees of hydrogenation, the reaction volume was extended and 65% hydrogenation levels were obtained. Therefore, 14%HNR, 33%HNR, and 65%HNR were successfully prepared under suitable reaction conditions. However, crosslinking and cis-trans isomerization were side-reactions occurring during hydrogenation. Gel and trans contents increased with increasing hydrogenation levels, leading to the increase in hardness of HNRs. Mooney viscosities of HNRs increased with increasing degrees of hydrogenation due to the increased gel contents. Mooney torquerelaxation of NR and HNRs were similar. Thermogravimetric analysis revealed that vi HNRs had greater thermal stability than NR and thermal stability increased with increasing degrees of hydrogenation. HNR vulcanizates were much better resistant to ozone and UV than cured NR. Sulfur-vulcanized rubbers had greater ozone resistance than peroxide-cure rubbers due to less amounts of carbon-carbon double bonds present in rubbers. In addition, modulus at low strain and tensile strength of sulfur-cured rubbers were higher than those of peroxide-cured rubbers, but lower elongation due to higher crosslink densities. Also, modulus at low strain and tensile strength increased with increasing hydrogenation levels of HNRs, in contrast to strain at break. Thermoplastic vulcanizates (TPVs) from blends of HNR and Polypropylene (PP) were prepared via dynamic vulcanization using peroxide and sulfur as curing agents. The effects of blend ratios on mechanical properties of TPVs were investigated. Tensile strength increased with increasing PP portions, but breaking strain decreased. Morphology of TPVs was characterized with Raman mapping and scanning electron microscope (SEM). The phase sizes of crosslinked rubber obtained from both techniques were correlated well
22
BRAZZO, PAOLO. "New strategies for the controlled release of vulcanization curatives in rubber blends." Doctoral thesis, Università degli Studi di Milano-Bicocca, 2018. http://hdl.handle.net/10281/199115.
Texte intégralRésumé :
La vulcanizzazione è un processo che trasforma la gomma (naturale o sintetica) in un prodotto durevole dotato di proprietà meccaniche superiori. L’agente vulcanizzante per eccellenza è lo zolfo; lo stato dell’arte del processo prevede l’utilizzo di acceleratori ed attivatori per massimizzare i risultati, la qualità del prodotto ed il tempo impiegato. Nell’industria degli pneumatici spesso si lavora con miscele polimeriche per poter conferire al materiale finale tutte le proprietà desiderate. Una delle principale conseguenze della presenza di miscele è la disomogenea ripartizione degli agenti vulcanizzanti in esse. Difatti, è stato mostrato come gli agenti vulcanizzanti si ripartiscano nelle diverse prima che la vulcanizzazione abbia luogo. Si osserva quindi un gap tra le proprietà meccaniche teoricamente raggiungibili e quelle reali del manufatto.
Il nostro progetto di ricerca mira a contenere la diffusione degli acceleranti primari di vulcanizzazione. La strategia seguita è ispirata al drug delivery: gli acceleranti vengono incapsulati in un materiale in grado di limitarne la diffusione fino al momento in cui la vulcanizzazione ha luogo. Il materiale scelto per l’incapsulamento è l’etilcellulosa, in quanto possiede delle temperature di rammollimento confrontabili con quelle del processo di vulcanizzazione. Inoltre è un materiale economico, diffuso e non tossico. Sono stati studiati, per confronto, anche altri materiali come il polimetilmetacrilato ed il policarbonato. L’accelerante incapsulato è il N-tert-butil-benzotiazol-2-sulfenamide (TBBS).
È stato ottimizzato un metodo in emulsione per la produzione delle capsule, ed è un metodo semplice, efficace, facilmente scalabile ed adattabile a diversi tipi di incapsulante e incapsulato. I test in fase di vulcanizzazione, tuttavia, evidenziano che la tenuta delle capsule non è adeguata. Non si osservano, infatti, delle differenze usando l’accelerante incapsulato o meno.
Siamo riusciti a ricondurre l’inefficacia delle capsule ad un fenomeno di collasso strutturale associato alla fusione dell’accelerante. Abbiamo quindi sviluppato un semplice metodo di reticolazione: l’etilcellulosa viene prefunzionalizzata con un epossido, e la reticolazione viene conclusa con un trattamento termico sulle capsule ottenute. In questo modo la stabilità termica delle capsule è preservata. Sorprendentemente, il materiale reticolato accelera notevolmente il processo di vulcanizzazione, anche a basse temperature. Questo è in disaccordo con quanto aspettato. Tuttavia, possiamo ipotizzare che la polarità dell’etilcellulosa faccia fungere l’etilcellulosa stessa da centro di aggregazione per il pacchetto vulcanizzante. Questo farebbe sì che attorno alle capsule si crei una sovrassaturazione di agenti vulcanizzanti, rendendo immediato il processo. Questo ultimo comportamento è ancora oggetto di studio.<br>Vulcanization is a process that converts rubber – natural or synthetic – into more durable objects with superior mechanical properties. Sulfur is the most used curing agent, but in the actual state-of-the-art processes new components – accelerators and activators – have been introduced to maximize the quality of the product and, meanwhile, decreasing the curing time. In tire industry is very common to work with polymer blends to achieve otherwise inaccessible properties. The main drawback is that the curatives can selectively diffuse into one phase, according to their partition coefficient. This result in a non-homogeneous vulcanization and in a gap between theoretical and real mechanical properties.
Our project face this issue using a drug-delivery-inspired process. The accelerator is enclosed in a capsule made of a material that hinders its diffusion at temperature lower than the vulcanization one. We chose ethylcellulose as encapsulating material, since its softening point is compatible with the vulcanization temperatures. We used N-tert-butyl-benzothiazole-2-sulfenamide (TBBS) as accelerator.
We optimized an emulsion process for the capsule production; in particular, this is a simple, easily scalable process, which can be extended to different core and encapsulating materials. However, the vulcanization test in rubber blends shows that the capsules are inefficient. In fact, there are no differences in terms of kinetics using the encapsulated accelerator or the pristine one.
We recognized that the capsules are intrinsically thermally instable; in fact, the vulcanization temperatures are higher than the melting point of the accelerator, and its melting causes the capsules collapse. To overcome this problem we developed an innovative crosslinking procedure. Ethylcellulose is prefunctionalized with an epoxy; the obtained capsules are crosslinked with a thermal treatment, which complete the reaction of the epoxy with ethylcellulose. The crosslinked capsules are now thermally stable, and no collapse is observed when the temperature is increased. However, the crosslinked capsules cause a dramatic acceleration of the vulcanization kinetics in the rubber blends, even at low temperatures. We hypothesize that, due to its polarity, ethylcellulose dredges all the polar components around the capsules, saturating the surrounding region with curatives. When TBBS leaks out of the capsule, it reacts immediately. Currently, this effect is still under observation.
23
MOSTONI, SILVIA. "From nanosized to single sites zinc-based activators for rubber vulcanization process." Doctoral thesis, Università degli Studi di Milano-Bicocca, 2019. http://hdl.handle.net/10281/241069.
Texte intégralRésumé :
I nanocompositi di gomma (NC) sono materiali comunemente usati nell’industria degli pneumatici. Le proprietà meccaniche dipendono sia dall’aggiunta delle nanoparticelle (NP) di filler rinforzanti e dal processo di vulcanizzazione. La reazione di vulcanizzazione a base zolfo si basa sulla formazione di un reticolo chimico tra le catene di polimero attraverso ponti mono-, bi- e poli-sulfurei. L’incremento della velocità di reazione e dell’efficienza di reticolazione è consentito da un complesso sistema catalitico, composto da acceleranti (ad esempio sulfenammidi), attivatori (ossidi metallici) e co-attivatori (acidi grassi). L’ossido di zinco (ZnO) è il principale attivatore usato industrialmente; un ruolo fondamentale è assegnato agli ioni zinco, in grado di influenzare aspetti cinetici e meccanicistici, come il processo di accorciamento dei ponti sulfurei nei prodotti di reticolazione (associato a maggiori densità di reticolo). Ciononostante, la bassa dispersione dell’ossido di zinco, dovuta ad una bassa affinità verso il polimero, porta ad un uso ingente di ZnO nelle gomme (3-5 parti per cento di gomma) e a problemi ambientali, connessi al rilascio dello zinco durante il ciclo di vita degli pneumatici.
In questo quadro, lo scopo del progetto di dottorato è stato lo sviluppo di attivatori innovativi a base zinco per il processo di vulcanizzazione, per ridurre il quantitativo di ZnO micro-cristallino nel processo industriale e diminuire il rilascio di zinco, mantenendo un’elevata efficienza del processo. A tal scopo, l’introduzione di siti reattivi di zinco è stata indagata. Partendo da NP di ZnO ancorate sulla superficie della silice (ZnO/SiO2), siti singoli di zinco (Zn/SiO2) dispersi su silice sono stati sintetizzati, sfruttando i vantaggi derivanti da una maggiore dispersione dello zinco nel composito e incrementando la reattività e disponibilità dell’attivatore nella reazione.
Inizialmente, la sintesi dei due materiali e le loro proprietà sono state studiate, tramite analisi strutturali, morfologiche e di superficie. NP di ZnO amorfe, con dimensioni e percentuali di carico su silice variabili, sono state sintetizzate utilizzando una procedura ottimizzata di tipo sol-gel, basata sul fenomeno di idrolisi e condensazione di un precursore di zinco in ambiente basico. Inoltre, centri isolati di zinco (II) sono stati preparati in una reazione a due fasi, in cui la silice è pre-funzionalizzata con un agente ancorante (3-amminopropil)trietossisilano, APTES) e in seguito fatta interagire con un precursore di zinco. La caratterizzazione sperimentale ha suggerito che ogni centro di zinco isolato fosse coordinato con due gruppi amminici e due gruppi labili (idrossidi o nitrati), che potessero promuovere una maggiore reattività.
I test in NC di gomma, comparati con NC preparati con ZnO micro-cristallino, hanno dimostrato maggiori efficienze di vulcanizzazione, migliorate proprietà meccaniche, elevate densità di reticolo e maggiore rinforzo in presenza dei due attivatori, usando metà del quantitativo tradizionale di ZnO. La cinetica di reazione è stata studiata tramite un approccio modello (Model Compound Vulcanization, MCV), evidenziando una migliore cinetica di processo e differenti meccanismi di reazione per ZnO/SiO2 e Zn/SiO2. Inoltre, i centri di zinco isolati hanno dimostrato di comportarsi da siti catalitici eterogenei, con una potenziale riduzione del rilascio di zinco e conseguenze dirette sulla distribuzione della reticolazione nel composito vulcanizzato, evidenziato tramite analisi avanzate di tipo morfologico e meccanico.
Infine, la modulazione dei parametri strutturali degli attivatori e il loro uso in sistemi non convenzionali, che includono compositi rinforzati da filler anisotropici e polimeri modificati organicamente, hanno dimostrato la possibile regolazione della reattività e l’alta versatilità dei due attivatori per applicazioni in diversi sistemi.<br>Rubber nanocomposites (NCs) are commonly used materials in tyres industries. Their mechanical properties are the combined result of the addition of reinforcing filler nanoparticles (NPs) and the vulcanization process. Sulphur vulcanization reaction is based on the formation of a chemical cross-link between polymer chains through mono-, bi- and poly-sulphide bridges. The enhancement of the vulcanization rate and cross-linking efficiency is achieved thanks to a complex catalytic system, composed of accelerators (as sulphenamides), activators (metal oxides) and co-activators (fatty acids). Zinc oxide (ZnO) is the primary industrial activator and a main role is recognized to zinc ions, able to influence both kinetic and mechanistic aspects of the reaction, through the shortening of sulphur bridges in the products (associated to higher cross-linking densities). Nevertheless, some drawbacks are connected to the low dispersion of ZnO, because of the low affinity with the rubber, such as the use of high ZnO amount in rubber (3-5 parts per hundred rubber) and environmental issues, due to zinc release during the lifecycle of tyres.
In this scenario, the aim of the PhD project is the development of innovative zinc-based activators for rubber vulcanization process, to reduce the amount of microcrystalline ZnO used in the industrial process and to decrease the zinc leaching during the preparation and use of the material, keeping a high vulcanization efficiency. Thus, the introduction of more active zinc species in the form of reactive sites has been proposed. Starting from nanosized ZnO particles anchored onto surface silica particles (ZnO/SiO2), single zinc sites (Zn/SiO2) dispersed on silica were synthesized, to exploit the advantages derived from the higher distribution, while increasing the availability and reactivity of the activator towards the other vulcanization reagents.
In the first part, the syntheses of the materials were studied and their properties deeply investigated, through structural, morphological and surface analyses. The formation of amorphous ZnO NPs with tunable zinc loading and size on silica was achieved exploiting an optimized sol-gel procedure, based on hydrolysis and condensation of a zinc precursor in a basic environment. Besides, isolated zinc(II) centres anchored to silica were synthesized in a two-step reaction, in which silica was pre-functionalized with a grafting agent ((3-aminopropyl)triethoxysilane, APTES) and then reacted with a zinc precursor. The experimental characterization suggested the coordination of each zinc isolated centres to two amine groups and two labile groups (hydroxide or nitrate), promoting a higher reactivity.
Both ZnO/SiO2 and Zn/SiO2 were tested as activators in rubber NCs and compared to microcrystalline ZnO; higher vulcanization efficiencies and improved mechanical properties were achieved, with increased cross-linking densities, using half of the conventional amount of ZnO. Lately, the kinetic of the vulcanization reaction was studied thanks to a model approach, called “Model Compound Vulcanization” (MCV). This study highlighted that the vulcanization process proceeded with an improved kinetic and following different reaction mechanisms. In particular, Zn centres were proved to behave as heterogeneous catalytic sites during the reaction, with a potential impact on the reduction of zinc leaching from rubber NCs and a direct consequence on the cross-linking distribution of the vulcanized rubber NCs, evidenced through advanced morphological and mechanical analyses.
Finally, the modulation of the structural parameters of the activators and the use into non-conventional systems, including anisotropic NPs reinforced NCs and organically modified polymers, demonstrated the possible modulation of their reactivity and the high versatility of the materials for applications into different systems.
24
Said, M. M. "Peroxide prevulcanization of natural rubber latex." Thesis, London Metropolitan University, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.233004.
Texte intégralRésumé :
The peroxide prevulcanization of NR latex using a range of commercially-available organic peroxides and an inorganic peroxide (potassium peroxydisulphate), in both activated and non-activated systems, has been investigated. A range of reducing agents and compounds that are known to promote peroxide-initiated emulsion polymerization and peroxide curing of po1yesters have been evaluated as promoters for the peroxide prevulcanization of NR latex. A few reactive peroxyesters have been found to be effective as prevulcanizing agents at temperatures in the range 80 °C-lOO °C. the effectiveness of the prevulcanization systems was characterized by the rate and efficiency of crosslinking achieved by these systems. Fructose-activated peroxyester and fructoseactivated hydroperoxide systems were found to effect prevulcanization at temperatures in the range 50 °C-80 °C. There is no clear correlation between the structure/reactivity of peroxyesters and the effectiveness of fructose-activated prevulcanization systems. The relative reactivity of the alkoxy radicals generated by the commercial hydro peroxides PQ~tly exp\a~~s the differences in the effectiveness of various fructose-activated hydroperoxide prevulcanization systems. The prevulcanization kinetics for the fructose-activated t-butyl peroxyisobutyrate (tBPIB) system have been investigated. The overal rate of tBPIB decomposition in NR latex, in both non-activated and fructose-activated systems was found to be first-order reaction with respect to tBPIB concentration. However, investigation of initial rate of tBPIB decomposition in NR latex indicates that the initial rate of tBPIB decomposition in NR latex is half order with respect to initial tBPIB concentration. This is probably a consequence of induced decomposition of tBPIB by certain non-rubber substances, and_termination by recombination of radicals derived from tBPIB. But, the reason for the difference in the reaction order with respect to tBPIB concentration, at the initial stage of the reaction and during the run is not clear. The prevulcanization kinetics also exhibit a number of other peculiar characteristics. Thus at temperatures greater than 70°C, and using a high fructose concentration, the rate coefficient for crosslink formation tends to be greater than that for peroxide decomposition. This is probably attributed to the differences in the temperature-coefficients of the various competing reactions during peroxide prevulcanization of NR latex. The instantaneous crosslinking efficiency was found to increase linearly with prevulcanization time. At temperatures greater than 70°C, the instantaneous crosslinking efficiency can attain values greater than 50%, indicating the involvement of alkyl radicals as well as the alkoxy radicals in the crosslinking reaction. The experimental activation energies for peroxide decomposition and crosslink formation were found to decrease to apparently constant values with increasing fructose/ peroxide concentration ratio. The rate of tBPIB decomposition was found to be significantly determined by activation free energy and not just activation energy for the decomposition. The factors which influence the physical properties of films from peroxide-prevulcanized NR latex have been investigated. The crosslink concentration was found to be the most important factor in determining the physical properties of films from peroxide-prevulcanized NR latex. Factors that account for the differences in the physical properties of films from peroxide- and sulphur-prevulcanized latices, and peroxide gum NR vulcanizates have been discussed. Attempts to improve the ageing properties of films from peroxideprevulcanized NR latex indicate that a preventive antioxidant is an essential component for an effective antioxidant system for these films.
25
Herrera, Julio César Alzate. "Desenvolvimento de borracha termoplástica por vulcanização dinâmica. TPV-(NBR+PP)." Universidade Federal de São Carlos, 2012. https://repositorio.ufscar.br/handle/ufscar/892.
Texte intégralRésumé :
Made available in DSpace on 2016-06-02T19:12:27Z (GMT). No. of bitstreams: 1
4913.pdf: 15206710 bytes, checksum: 2255e1ec15b6c862cd9ca4357c90af2b (MD5)
Previous issue date: 2012-09-14<br>Financiadora de Estudos e Projetos<br>The union of technology of thermoplastic and rubber has contributed to the development of thermoplastic elastomers (TPE), which was evidenced through the study of patents in TPE in the last 20 years, where Japan and the United States are the leaders. Trends in TPE are: modification to polymer structure in styrenic TPEs in order to employ the dynamic vulcanization, use of nanofibres and nanoclays, and resists oil TPEs using hydrogenated nitrile rubber to improve the properties of hot air and aging. The main variables in the development of TPE should take into account the surface energy the thermoplastic and elastomer, the elastomer entanglement, crystallinity of thermoplastic, proportions of the thermoplastic and compatibilizer. Typically the articles produced with nitrile, may be obtained using the technology or conventional rubbers (vulcanized), and not having possibility of recycling of defective products and materials vulcanizates. The purpose is to develop a thermoplastic nitrile rubber by dynamic vulcanization (TPV-(NBR + PP)) using conventional techniques for mixing between nitrile rubber and polypropylene. The development of nitrile rubber thermoplastic by dynamic vulcanization, TPV (NBR+PP) were studied with variation of vulcanization system, variation of proportion of NBR/PP and type of compatibilizer. The main results on development of TPV-(NBR+PP) were obtained with the use of system of vulcanization type phenolic resin, with compatibilizer Ph-PP and with 4,0phr of amine (6PPD). Developed a nitrile rubber thermoplastic by dynamic vulcanization (TPV-(NBR + PP)) with good performance in reprocessabilidade, using equipment and techniques conventional thermoplastic processing, which will help to satisfy the demands of industry.<br>A uniao da tecnologia de termoplastico e da borracha tem contribuido para o desenvolvimento de elastomeros termoplasticos (TPE), que foi evidenciada atraves do estudo de patentes em TPE nos ultimos 20 anos, onde o Japao e os Estados Unidos sao os lideres. As tendencias em TPE sao: modificacao da estrutura do polimero de estireno TPE para empregar a vulcanizacao dinamica, o uso de nanofibras e nanoargilas, e TPEs resistes ao oleo utilizando borracha nitrilica hidrogenada para melhorar as propriedades de ar quente e envelhecimento. As principais variaveis no desenvolvimento de TPE tem em conta a energia de superficie do elastomero e do termoplastico, o emaranhamento do elastomero, cristalinidade do termoplastico, as proporcoes do termoplastico e compatibilizante. Normalmente, os artigos produzidos com borracha nitrilica so podem ser obtidos utilizando-se a tecnologia ou tecnicas de processamento de borrachas convencionais (vulcanizados), apresentando a nao possibilidade de reciclagem de produtos defeituosos e materiais vulcanizados. O proposito e desenvolver uma borracha nitrilica termoplastica por vulcanizacao dinamica (TPV-(NBR+PP)), usando tecnicas convencionais para mistura entre borracha nitrilica e polipropileno. O desenvolvimento de borracha nitrilica termoplastica por vulcanizacao dinamica, TPV - (NBR + PP) foram enchido com variacao de sistema de vulcanizacao, a variacao da proporcao de NBR/PP e do tipo de compatibilizante. Os resultados principais sobre o desenvolvimento de TPV-(NBR + PP) foram obtidos com a utilizacao do sistema de vulcanizacao do tipo de resina fenolica, com compatibilizante Ph- PP e com 4,0 phr de amina (6PPD). Desenvolveu-se uma borracha nitrilica termoplastica por vulcanizacao dinamica (TPV-(NBR+PP)) com bom desempenho na reprocessabilidade, usando equipamentos e tecnicas convencionais de processamento de termoplasticos, que contribuira para satisfazer as exigencias da industria.
26
Laca, Alexander Arrillaga. "Modelling Vulcanization and Rheological Processes during Injection Moulding of Rubber Mixes using CAE." Thesis, London Metropolitan University, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.536732.
Texte intégral
27
Ohlemacher, Crittenden John. "Double Network Formation During Aging of a Natural Rubber Vulcanizate." University of Akron / OhioLINK, 2005. http://rave.ohiolink.edu/etdc/view?acc_num=akron1132327518.
Texte intégral
28
ARAUJO, SERGIO C. de. "Vulcanizacao do latex de borracha natural induzida com feixe de eletrons." reponame:Repositório Institucional do IPEN, 1993. http://repositorio.ipen.br:8080/xmlui/handle/123456789/10327.
Texte intégralRésumé :
Made available in DSpace on 2014-10-09T12:37:22Z (GMT). No. of bitstreams: 0<br>Made available in DSpace on 2014-10-09T14:09:16Z (GMT). No. of bitstreams: 1
02037.pdf: 3257325 bytes, checksum: 6f7184b35c6dddcd40410864962f58fe (MD5)<br>Dissertacao (Mestrado)<br>IPEN/D<br>Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP
29
Kiroski, Dusko. "The nature of the base polymer and the properties of N.B.R. gum vulcanizates." Thesis, University of Bath, 1995. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.295456.
Texte intégral
30
Rong, Guangzhuo. "Tearing of Black-filled (N115) Natural Rubber Vulcanizates at Various Temperatures." University of Akron / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=akron1308336251.
Texte intégral
31
MILANA, PAOLA. "Single-site metal activator for enhancing curing efficiency and substituting zinc in rubber vulcanization process." Doctoral thesis, Università degli Studi di Milano-Bicocca, 2022. http://hdl.handle.net/10281/381164.
Texte intégralRésumé :
I materiali elastomerici vengono utilizzati in molti ambiti, come ad esempio nella produzione di pneumatici. La loro performance dipende dal processo di vulcanizzazione e dall'impiego di filler di rinforzo, come le nanoparticelle di silice. Per aumentare la velocità del processo di vulcanizzazione, vengono utilizzati acceleranti e attivatori. L'attivatore maggiormente impiegato, in virtù delle sue caratteristiche, è l'ossido di zinco, che tuttavia presenta anche degli svantaggi, come ad esempio il fatto di essere tossico ed inquinante.
Lo scopo di questa tesi è sviluppare nuovi attivatori efficienti e più sicuri dell'ossido di zinco.
Sono stati sviluppati nuovi materiali basati sulla presenza di un centro metallico ( ioni Zn(II))ancorato sulla superficie della particella di silice, mediante la formazione di un complesso metallo-legante, L'efficienza catalitica di questo materiale dipende dalla natura chimica del complesso metallico, che può essere variata seguendo tre strategie:
1) variare il legante del complesso;
2) variare la localizzazione del centro catalitico;
3) cambiare centro metallico.
In questo studio sono stati testati vari leganti organici, aventi gruppi funzionali diversi che coordinano gli ioni Zn(II) ed è stato dimostrato che l'efficienza catalitica dell'attivatore dipende dalla stabilità del complesso che si forma. Complessi troppo stabili infatti, impediscono la partecipazione degli ioni Zn(II) alle reazioni di vulcanizzazione, mentre complessi stabili ma non troppo, aumentano l'efficienza di vulcanizzazione.
Una localizzazione diversa del centro catalitico può essere ottenuta mediante l'impiego di leganti aventi catena idrocarburica più lunga, così da influenzare la distribuzione dei crosslinks nella matrice polimerica e quindi le proprietà meccaniche del nanocomposito.
Infine, centri metallici di Fe(III) sono stati ancorati alla superficie della silice in sostituzione di ioni zinco, comportando la formazione di un attivatore di vulcanizzazione molto performante e più sicuro dell'ossido di zinco.<br>Rubber materials are nowadays used for many applications, ranging from shoes, adhesives, and gloves. Since most rubber is used to produce tires, both sulfur vulcanization and reinforcing fillers such as silica nanoparticles (SiO2 NPs) are used to obtain highly performant tires. To enhance the rate of the curing process, activators (ZnO), accelerators (sulfenamides) and co-activators (fatty acids) are usually used.
Zinc single site-based activator, previously developed and based on Zn (II) ions anchored on the SiO2 NPs through the formation of a metal complex, demonstrated to be more efficient than ZnO and to reduce the leaching phenomenon of Zn2+ ions, thus reducing the environmental impact. The aim of this research project was to achieve a complete knowledge of its catalytic activity, to tune and control the vulcanization efficiency and the mechanical behaviour of the final rubber nanocomposite (NC). To reach this objective the chemical nature of the zinc single site-based activator has been changed by following three strategies:
● change the ligand of the metal complex to study the activator’s vulcanization efficiency arising from the different coordination sphere of the metal centre;
● exploit a different localization of the metal centre on the filler surface or a different distribution of the activator in the polymer matrix to study the effect on the mechanical behaviour of the NC;
● change the metal of the complex, with the aim to reduce the zinc content in the rubber vulcanization process.
In the first part of the research, the catalytic activity of the zinc single site-based activator has been investigated by changing the coordination sphere of the metal using different organic ligands. Depending on the stability of the metal complex formed, a different vulcanization efficiency was observed: a too high stability of the complex, like the one observed using sulphur ligands, hinders the participation of Zn2+ ions to the curing reaction. Instead, stable bonds but reactive towards the curing reactions, such as in the case of amino and carboxyl ligands, promote higher catalytic activity of the activator.
Later on, the research focused on the study of the influence that the localization of the metal centre has on the mechanical behaviour of rubber NCs, underlying a strong relationship between the localization of Zn2+ ions and the density and distribution of crosslinks inside the polymer matrix. In order to study the influence on the NC mechanical behaviour, a different localization of the metal centre was achieved by using longer hydrocarbon chains-based ligands, and the different distribution of the activator in the polymer matrix was reached by assembling the activators NPs in supraparticles (SPs).
Finally, the approach of localizing the metal centre on the filler surface was used to develop a new activator based on Fe (III) ions anchored on SiO2 NPs. Its vulcanization efficiency was tested, and promising results were obtained, since higher efficiency than ZnO was observed, making the iron single site-based activator a possible substitute of ZnO in the rubber production.
32
Mondal, Manas. "Polypropylene and Natural Rubber based Thermoplastic Vulcanizates by Electron Induced Reactive Processing." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2013. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-125321.
Texte intégralRésumé :
Thermoplastic Vulcanizates (TPVs) are itself a commercially high valued group of polymer blend. They render technological properties of conventional vulcanized elastomers with the ease of thermoplastic melt (re)processability. With ever growing market, TPVs have got plenty of applications among various fields. Here, the technological properties of these TPVs were tailored according to the purpose by interplaying physical parameters of polymers and advanced high energy electron technology. Electron irradiation, though a well-known technique for cross-linking in polymer industry, is only restricted to final product treatment. We take it to the next level by coupling a conventional internal mixer and a high energy electron accelerator. Polypropylene (PP) and natural rubber (NR) based TPVs have been prepared using this new reactive processing technology, named Electron Induced Reactive Processing (EIReP). Various electron treatment parameters were explored to maximize technological properties of TPVs.
Effects of various polyfunctional monomers (PFM) were also studied. In an endeavor to develop a potential method for customization, deep insights of macroscopic and microscopic structure of these TPVs were presented with the help of various advanced scientific characterization techniques. Commonly faced difficulties like viscosity mismatch, cure rate mismatch, and incompatibility due to different molecular structures were furnished along with plausible solutions. Investigation of phase inversion from co-continuous matrix to thermoplastic matrix was dealt with special care as it helps to understand structure property correlation for all TPVs. To make the whole effort relevant, at the end of this thesis a summary of various technological properties has been given for the newly processed and commercially available TPVs.
33
Xue, Tianxiang. "Tearing of Black-Filled (N660) Synthetic Polyisoprene Rubber Vulcanizates at Various Temperatures." University of Akron / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=akron1366125713.
Texte intégral
34
Ribeiro, Gabriel Deltrejo. "Estudo do carbonato de cálcio tratado com agente de acoplamento Chartwell na substituição parcial de sílica em compósitos de borracha natural /." Bauru, 2020. http://hdl.handle.net/11449/192221.
Texte intégralRésumé :
Orientador: Renivaldo José dos Santos<br>Resumo: Durante o processo de fabricação dos artefatos de borracha natural (BN), é possível adicionar cargas, podendo ser combinadas em função das propriedades finais pretendidas. Nesse sentido o carbonato de cálcio vem sendo utilizado como carga de enchimento nas formulações com borracha natural, apenas para aumentar o volume da amostra para a mesma quantidade de borracha implementada, buscando apenas a redução do custo final. Devido a demanda industrial, surge a necessidade de investigar a possibilidade de fazer com que uma carga, ora antes utilizada como enchimento, passe a atuar como carga de reforço mecânico, ou seja, a realização de tratamentos superficiais se torna uma possibilidade viável, para que a carga consiga realizar ligações cruzadas entre as cadeias de carbono da BN. Dessa forma, foi proposto neste trabalho o estudo de compósitos de borracha natural tipo crepe claro com carbonato de cálcio ultrafino tratado com 2% do Chartwell C-515.71HR^® para substituição parcial da sílica comercial tratada com silano, buscando identificar a influência deste agente de acoplamento no processo de vulcanização, a fim de melhorar a interação entre a borracha natural e carbonato de cálcio ultrafino. O preparo ocorreu em um misturador aberto de cilindros com a variação de 10 em 10 phr para as cargas, nos híbridos, iniciou-se em 40/00 até 00/40 (sílica/carbonato de cálcio ultrafino), e foi produzida uma amostra controle, com a mesma formulação, porém sem carga, denominada goma pura. Foi po... (Resumo completo, clicar acesso eletrônico abaixo)<br>Abstract: During the manufacturing process of natural rubber (BN) artifacts, it is possible to add loads, which can be combined depending on the desired final properties. In this sense, calcium carbonate has been used as filler in formulations with natural rubber, just to increase the sample volume for the same amount of rubber implemented, seeking only to reduce the final cost. Due to industrial demand, there is a need to investigate the possibility of causing a load, previously used as a filler, to act as a mechanical reinforcement load, that is, the performance of surface treatments becomes a viable possibility, so that the cargo is able to cross-link the BN carbon chains. Thus, the main objective of this work is the study of natural rubber composites of light crepe type with ultrafine calcium carbonate treated with 2% of Chartwell C-515.71HR^® for partial replacement of commercial silica treated with silane, seeking to identify the influence of this coupling agent in the vulcanization process, in order to improve the interaction between natural rubber and ultrafine calcium carbonate. The preparation took place in an open cylinder mixer with a variation of 10 in 10 phr for the loads, in the hybrids, it started in 40/00 until 00/40 (silica / ultrafine calcium carbonate), and a control sample was produced , with the same formulation, but without load, called pure gum. It was possible to replace up to 75% of the silica with treated calcium carbonate, but the best response was to replac... (Complete abstract click electronic access below)<br>Mestre
35
CAMPOS, VANIA E. "Avaliacao toxicologica de filmes de borracha natural obtido do latex vulcanizado pelo processo convencional e pelo processo alternativo com radiacao ionizante." reponame:Repositório Institucional do IPEN, 1997. http://repositorio.ipen.br:8080/xmlui/handle/123456789/10654.
Texte intégralRésumé :
Made available in DSpace on 2014-10-09T12:42:46Z (GMT). No. of bitstreams: 0<br>Made available in DSpace on 2014-10-09T14:01:40Z (GMT). No. of bitstreams: 1
05348.pdf: 2001238 bytes, checksum: f83c139eda82acca7eed220227b57674 (MD5)<br>Dissertacao (Mestrado)<br>IPEN/D<br>Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP
36
Fagundes, Enio César Machado. "Estudo do sistema N-Ciclohexil-2-Benzotiazol-Sulfenamida(CBS)/enxofre na vulcanização da borracha natural." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 1999. http://hdl.handle.net/10183/159455.
Texte intégralRésumé :
O comportamento elástico dos reticulados de borracha natural, NR, obtidos a partir da reação com enxofre e acelerador, CBS foi examinado. Estudou-se a cinética de reação através das curvas reométricas para amostras com diferentes razões de concentração acelerador/enxofre. Observou-se que a reação de vulcanização é de primeira ordem, enquanto a energia de ativação cresce com a quantidade de enxofre e se mantém praticamente constante com a quantidade de acelerador. As amostras foram vulcanizadas sob calor e pressão e submetidas a medidas de tensãodeformação. Detemúnou-se a densidade de reticulação a partir do módulo de Young e pela teoria de Mooney-Rivlin. Paralelamente, a densidade de reticulação foi também obtida a partir de medidas de inchamento, aplicando-se a teoria de Flory - Rehnner. Este estudo indicou que a densidade de reticulação é proporcional a concentração de acelerador e também de enxofre. Nas amostras submetidas a análise mecânico-dinâmica, avaliou-se a tangente de delta, observando-se a mesma independente do grau de reticulação, na freqüência avaliada, enquanto a Tg aumenta com o grau de reticulação.<br>The elastic behavior of natural rubber networks, NR, obtained by reaction with sulfur and accelerator, CBS, was investigated. The kinetics of the reaction was studied through the rheometric curves for samples with different rations of accelerator/sulfur. It was observed that the vulcanisation showed first order kinectics, while the activation energy increase with the amount of sulfur and it stays constant with the increase of accelerator. The samples were vulcanisated under heat and pressure and submitted the stress-strain measurements. The crosslinking densities was determined by Y oung module and by Mooney - Rivlin theory. The crosslinking densities was also obtained from swell measurements, applying the Flory- Rehnner theory. This study indicated that the crosslinking densities is proportional the accelerator and sulfur concentration. Samples were submitted the dynamic mechanical analysis. The delta tangent was evaluated being observed that it independent of the crosslinking degree, in the appraised frequency, while Tg increases with the crosslinking degree.
37
Moreira, Maria Helena Polgati. "Elastômeros termoplásticos de EPDM/PP : uso do enxofre e caulim na vulcanização dinâmica." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2008. http://hdl.handle.net/10183/15732.
Texte intégralRésumé :
Neste trabalho foi avaliado o efeito da adição de carga mineral em composições de TPV obtidas a partir de misturas de polipropileno (PP) e elastômero EPDM vulcanizadas dinamicamente com sistema de reticulação a base de enxofre. Foram utilizados como cargas caulim não modificado e caulim modificado quimicamente com mercaptosilano. As misturas EPDM/PP foram preparadas com 2, 3 e 6 phr de carga, em câmara de mistura Haake acoplada a reômetro de torque. As composições foram caracterizadas quanto às suas propriedades físico-mecânicas, dinâmico-mecânicas e térmicas. A morfologia das composições foi analisada utilizando microscopia eletrônica de varredura. Verificou-se que o uso de caulim melhorou as propriedades de tensão/ deformação dos TPVs. O TPV que apresentou melhor resultado quanto à tensão de ruptura foi aquele com a composição contendo 2 phr de caulim modificado com mercaptosilano, cuja tensão máxima foi da ordem de 33,50 MPa. TPVs reticulados com enxofre foram comparados com amostra de composição igual de um produto comercial reticulado à base de resina fenólica. Os TPVs de EPDM/PP com caulim curados com enxofre apresentaram dureza semelhante e menor densidade que o TPV de referência.<br>In this work we studied the effect of the addition of mineral fillers to TPVs compositions based on polypropylene (PP) and one EPDM rubber. The TPVs were dynamically vulcanized with sulfur. Non-modified kaolin and mercaptosilane-modified kaolin were used as fillers. The systems EPDM/PP contained 2, 3 and 6 phr of filler and were prepared in a mixer Haake coupled with a torque rheometer. The compositions were characterized by means of its physico-mechanical, dynamic-mechanical and thermal properties. The morphology of the TPVs was studied through scanning electron microscopy. It was verified that the addition of kaolin particles improved the tensile properties of the TPVs. The best result was found for the composition containing 2 phr of mercaptosilane-modified kaolin that showed the value of 33,5MPa for the tensile strength. The properties of the TPVs were compared with a commercial product vulcanized with phenolic resin. The TPVs based on EPDM/PP with kaolin and vulcanized with sulfur showed similar values of hardness and the density was inferior compared with the TPV used as reference.
38
Ahmad, Aris Bin. "A study of the partition of plasticizer and filler for highly hysteretic rubber blends." Thesis, Open University, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.238370.
Texte intégral
39
SOUZA, AUREA de. "Comportamento do AnB/KOH/HPt-B na vulcanizacao do latex de borracha natural induzida com raios gama." reponame:Repositório Institucional do IPEN, 1994. http://repositorio.ipen.br:8080/xmlui/handle/123456789/10362.
Texte intégralRésumé :
Made available in DSpace on 2014-10-09T12:37:47Z (GMT). No. of bitstreams: 0<br>Made available in DSpace on 2014-10-09T13:56:13Z (GMT). No. of bitstreams: 1
05381.pdf: 5329504 bytes, checksum: c318444feb48e0e30c208b55d7e2217d (MD5)<br>Dissertacao (Mestrado)<br>IPEN/D<br>Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP
40
COLLANTES, HUGO D. C. "Fabricacao de luvas cirurgicas com latex de borracha natural vulcanizado com raios gama." reponame:Repositório Institucional do IPEN, 1995. http://repositorio.ipen.br:8080/xmlui/handle/123456789/9257.
Texte intégralRésumé :
Made available in DSpace on 2014-10-09T12:25:22Z (GMT). No. of bitstreams: 0<br>Made available in DSpace on 2014-10-09T14:02:20Z (GMT). No. of bitstreams: 1
05826.pdf: 6440180 bytes, checksum: 1c771858083be07c021d9ab59a4f8c36 (MD5)<br>Dissertacao (Mestrado)<br>IPEN/D<br>Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP
41
CANAVEL, VALDIR. "Efeito do antioxidante e do radiosensibilizador na estabilidade do latex de borracha natural vulcanizada com raios gama." reponame:Repositório Institucional do IPEN, 1993. http://repositorio.ipen.br:8080/xmlui/handle/123456789/10341.
Texte intégralRésumé :
Made available in DSpace on 2014-10-09T12:37:33Z (GMT). No. of bitstreams: 0<br>Made available in DSpace on 2014-10-09T14:03:17Z (GMT). No. of bitstreams: 1
05176.pdf: 1757273 bytes, checksum: c0ea92b1d81acc457b884deea188024c (MD5)<br>Dissertacao (Mestrado)<br>IPEN/D<br>Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP
42
Santos, Alex Calcagno de Sales. "Avaliação do efeito de resíduos galvânicos sobre a vulcanização e as propriedades da borracha natural (NR)." Universidade do Estado do Rio de Janeiro, 2009. http://www.bdtd.uerj.br/tde_busca/arquivo.php?codArquivo=1237.
Texte intégralRésumé :
Com a Revolução Industrial e a adoção do modelo econômico urbano e industrial, baseado no consumo, ocorreu o aumento da geração de resíduos, frutos das diferentes atividades humanas. A galvanoplastia é um processo que embeleza e protege mecanicamente peças metálicas e está presente nas indústrias do setor metal-mecânico de Nova Friburgo. Neste processo, dois resíduos importantes são gerados: um oriundo do pré-tratamento das peças metálicas e outro das estações de
tratamento de efluentes industriais. Neste trabalho, tais resíduos, denominados de (RGs), foram incorporados à borracha natural (NR) em substituição total ou parcial ao óxido de zinco (ZnO). O possível efeito ativador dos RGs sobre a vulcanização e as propriedades da borracha natural foi investigado. As misturas foram realizadas em um misturador de calandras, utilizando-se um sistema convencional (CV). A cinética de vulcanização foi estudada nas temperaturas de 150C, 160C e 170C, através de ensaios reométricos e a determinação de parâmetros tais como: tempo de pré-cura (ts1); tempo ótimo de vulcanização (t90); torques mínimo (Ml) e máximo (Mh); constantes de velocidade; e, energias de ativação. Com relação às propriedades mecânicas, a resistência à tração e a resistência ao rasgamento foram determinadas. As composições de NR contendo RGs apresentaram diminuição do tempo ts1, aumento das constantes de velocidade e diminuição das energias de ativação. No entanto, a resistência ao rasgamento foi mantida em um nível satisfatório apenas nas composições em que o ZnO foi substituído parcialmente em 25%.<br>With the Industrial Revolution and the adoption of urban and industrial economic model, based on consumption, there was an increased in the generation of wastes, as a result of different human activities. Electroplating is a process that embellishes
and mechanically protects metallic parts and it is present in the industries of metalmechanical segment of Nova Friburgo. In this process, two important wastes are generated: one from pre-treatment of metal parts, other from industrial sewage
station. In this investigation, these wastes, named RGs, were incorporated in the natural rubber (NR) in partial or total replacement to zinc oxide (ZnO). A possible activator effect of RGs upon vulcanization and properties of natural rubber was
investigated. Mixes are prepared in a two-roll mixer using a conventional system (CV). Vulcanization kinetics was studied at 150, 160 and 170C through of rheometric tests and the determination of parameters such as: scorch time (ts1);
optimum cure time (t90); minimum torque (Ml); maximum torque (Mh); constants rates (k); and, activation energies. In relation to mechanical properties, tensile and tear strength were determined. NR compositions with RGs presented a diminution in ts1 values, increase in the constants rates and diminution of activation energies. However, tear strength is maintained in a satisfactory level only in the compositions where ZnO was partially replaced in 25%.
43
Passador, Fabio Roberto. "Desenvolvimento de blendas poliméricas PVC/NBR através de processamento reativo e vulcanização dinâmica in situ." Universidade Federal de São Carlos, 2008. https://repositorio.ufscar.br/handle/ufscar/769.
Texte intégralRésumé :
Made available in DSpace on 2016-06-02T19:11:50Z (GMT). No. of bitstreams: 1
1971.pdf: 1916099 bytes, checksum: b1ac78cc29503b58427116dd446887d8 (MD5)
Previous issue date: 2008-02-28<br>Financiadora de Estudos e Projetos<br>Dynamic vulcanization is a process of vulcanization of an elastomer during melt mixing with a thermoplastic which results in a material with better chemical and mechanical properties at high temperature. The PVC/NBR blends were obtained by reactive processing and in situ dynamic curing. The crosslinking of PVC/NBR blends was accomplished using sulphur (S)/tetramethylthiuram disulphide (TMTD) and mercaptobenzothiazyl disulphide (MBTS) curative system during the reactive processing. The blends of PVC/NBR at the ratio of 90/10; 80/20 and 70/30 wt% were melt mixed using an internal mixer at 160°C and rotor speed of 60rpm. The degrees of crosslinking of the blends obtained by the reactive process were analyzed through Fourier Transform InfraRed (FT-IR), swelling and degree of cure. Higher crosslink densities were obtained the systems with higher amount of elastomer. The mechanical properties evaluated by tensile properties, tear strength, hardness and compression set showed that the dynamic vulcanized blends have a better performance compared to the similar conventional ones. It was observed an increase of 92% in the tensile stress to the dynamic vulcanized blend PVC/NBR (70/30) with partitioning agent of PVC and an increase of 205% in the Young´s modulus to the dynamic vulcanized blend PVC/NBR (90/10) with partitioning agent of CaCO3. The morphology of the blends examined by scanning electron microscopy evidenced the crosslinking formation only in the elastomeric phase. The vulcanized rubber particles are responsible by the increase of stiffness and consequently displayed better mechanical properties.<br>Vulcanização dinâmica é o processo de vulcanização de um elastômero durante a mistura no estado fundido com um termoplástico, que resulta em materiais com boa resistência química e mecânica em altas temperaturas. A obtenção de blendas PVC/NBR por processamento reativo e vulcanização dinâmica in situ foi realizada utilizando o sistema de cura a base de enxofre (S) e combinação dos aceleradores 2,2-ditiomercaptobenzotiazol (MBTS) e dissulfeto de tetrametiltiuram (TMTD), utilizando-se dois tipos de borracha nitrílica, com diferentes agentes de partição, que é utilizado para manter o elastômero particulado. As blendas PVC/NBR (90/10, 80/20 e 70/30 % em massa) foram processadas em um reômetro de torque Haake a 160°C, com rotação de 60rpm. Ensaios de FTIR, inchamento em solvente e determinação do grau de cura foram utilizados para quantificar a formação de ligações cruzadas nas blendas obtidas por processamento reativo, sendo obtida maior densidade de ligações cruzadas nos sistemas em que utilizaram maior quantidade de NBR. As propriedades mecânicas das blendas obtidas por processamento reativo foram avaliadas por ensaios de tração, rasgo, dureza e deformação permanente à compressão, sendo observado desempenho mecânico superior das blendas vulcanizadas comparadas às blendas convencionais, com aumento de 92% na tensão de ruptura para blenda vulcanizada com 30% em massa de NBR particulada com CaCO3, em relação à blenda convencional e aumento de 205% no módulo elástico de blendas vulcanizadas com 10% em massa de NBR particulada com PVC. A morfologia das blendas foi avaliada por microscopia eletrônica de varredura, que evidenciou a formação de ligações cruzadas apenas no interior da fase elastomérica, sendo responsável pelo aumento da rigidez e desempenho mecânico superior.
44
Sun, Ximei. "THE DEVULCANIZATION OF UNFILLED AND CARBON BLACK FILLED ISOPRENE RUBBER VULCANIZATES BY HIGH POWER ULTRASOUND." University of Akron / OhioLINK, 2007. http://rave.ohiolink.edu/etdc/view?acc_num=akron1176388229.
Texte intégral
45
Rao, Tingling. "Effect of Crosslink Density and N660 Carbon Black on Tearing Behaviors of Natural Rubber Vulcanizates." University of Akron / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=akron1347122467.
Texte intégral
46
Sun, Yu. "Tearing of Carbon Black-filled and Gum Natural Rubber Vulcanizates Cured with Dicumyl Peroxide (DCP)." University of Akron / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=akron1380201814.
Texte intégral
47
Li, Zhenpeng. "Effect of Carbon Black on the Tearing of Dicumyl Peroxide (DCP)-cured Natural Rubber Vulcanizates." University of Akron / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=akron1398358292.
Texte intégral
48
Takeshita, Elaine Vosniak. "Inchamento de borrachas vulcanizadas sob a ação de solventes orgânicos." reponame:Repositório Institucional da UFSC, 2012. http://repositorio.ufsc.br/xmlui/handle/123456789/93510.
Texte intégralRésumé :
Tese (doutorado) - Universidade Federal de Santa Catarina, Centro Tecnológico, Programa de Pós-Graduação em Engenharia Quimica, Florianópolis, 2010<br>Made available in DSpace on 2012-10-24T23:28:30Z (GMT). No. of bitstreams: 1
293902.pdf: 3016173 bytes, checksum: 8388be21f737fe927efe08c560a666ae (MD5)<br>Neste trabalho foram investigadas as propriedades de borrachas vulcanizadas sob a ação de solventes adulterantes de gasolina tipo C. Esta pesquisa visou obter dados experimentais e análise de modelos para o estudo do fenômeno de inchamento de borrachas vulcanizadas quando em contato com solventes. O objetivo é obter uma nova metodologia de análise da qualidade da gasolina utilizando borrachas como sensores. O inchamento das borrachas mostrou experimentalmente depender e ser uma função do tempo de exposição ao solvente e da composição do solvente, tanto em termos de quais tipos de compostos estão presentes quanto da concentração destes. A sensibilidade do método e a aplicabilidade do método em tempos curtos de análise foram testadas realizando-se um planejamento experimental de mistura. Os componentes do planejamento são a % v/v de gasolina C, heptano e tolueno e a borracha SBR, analisando-se o inchamento mássico e volumétrico para os tempos de 5 e 15 min. A análise da variância revelou que o método é eficiente e que existe uma alteração bastante significativa dos inchamentos em função do teor de tolueno na mistura. Foi verificado que a magnitude dos valores de inchamento é maior em termos volumétricos do que em mássicos. Também foi feito um estudo da influência do tipo de solvente sobre os perfis de inchamento das borrachas neoprene, nitrílica, natural, SBR, SBR alim. e silicone. Os resultados obtidos com silicone em relação ao inchamento com etanol mostraram-se extremos ao apresentado pelos solventes heptano, gasolina C e tolueno, o que demonstrou que esta borracha apresenta grande capacidade para o seu uso como um meio de detecção de excesso de etanol na gasolina. Foram obtidas equações polinomiais do inchamento do silicone e do SBR em função do teor de etanol anidro na mistura com gasolina A. Através dos altos coeficientes de correlação linear obtidos verificou-se uma boa capacidade de predição do teor de etanol anidro na gasolina através das medidas de inchamento, revelando também que a metodologia proposta apresenta sensibilidade suficiente para a verificação da adulteração da gasolina com excesso de etanol.<br>In this work, we investigated the properties of vulcanized rubber under the action of adulterant solvents of gasoline type C. This research aimed to obtain experimental data and analysis models to study the phenomenon of swelling of vulcanized rubbers in contact with solvents. The purpose of this work is to obtain a new methodology for assessing the quality of the gasoline using rubber as sensors. The swelling of the rubbers showed experimentally to depend and be a function of time of exposure to solvent and solvent composition, both in terms of that type of compounds are present as their concentration. The sensitivity and the applicability of the method for short times of analysis were tested by performing an experimental design of mixture. The components of planning are the % v / v gasoline type C, heptane and toluene and SBR rubber, analyzing the mass and volumetric swelling for up to 5 and 15 min. The analysis of variance, backed by high values of R2-adjusted (higher than 0.98 and 0.97 for mass and volume swells, respectively), showed that the method is efficient and that there is a very significant change in the swelling mass and volume due to changes in the content of toluene in the mixture. It was found that the magnitude of the swelling values are larger in terms of volume than mass, which indicates that the accuracy of the data obtained on the basis of volume measurement is more appropriate to study. It was also studied the influence of solvent on the profiles of swelling with rubber neoprene, nitrile, natural, SBR, SBR food grade and silicon. The results obtained with silicon in relation to swelling with ethanol proved to be the extremes presented by the solvent heptane, toluene and gasoline type C, demonstrating that this rubber has a great capacity for its use as a means of detecting excessive ethanol in gasoline. Polynomial equations were obtained from swelling of the silicone and SBR as a function of content in the mixture of anhydrous ethanol with gasoline, resulting in a coefficient R2 equal to 0.993. Through the high correlation coefficients obtained it was verified a good capability of predicting the content of anhydrous ethanol in gasoline by measuring the swelling, what also reveals that the proposed methodology was sufficiently sensitive to check the adulteration of gasoline with excessive ethanol.
49
MARTINS, CARLOS F. P. "Estudo da biodegradabilidade e envelhecimento de filmes de borracha obtidos por processos de vulcanização do látex por radiação induzida de fonte gama." reponame:Repositório Institucional do IPEN, 2005. http://repositorio.ipen.br:8080/xmlui/handle/123456789/11262.
Texte intégralRésumé :
Made available in DSpace on 2014-10-09T12:50:02Z (GMT). No. of bitstreams: 0<br>Made available in DSpace on 2014-10-09T13:58:47Z (GMT). No. of bitstreams: 1
10448.pdf: 3069198 bytes, checksum: 9d44970985c5146c199d7cc5f998e71e (MD5)<br>Dissertacao (Mestrado)<br>IPEN/D<br>Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP
50
Adepetun, Adeyemi Adedayo. "Effect of Carbon Black Loading and Temperature on Cut Growth in N990-Filled Natural Rubber Vulcanizates." University of Akron / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=akron1315575370.
Texte intégral