Dissertations / Theses: 'Polyolefins'

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Назаренко, В. В. "Polyolefins in Packing." Thesis, Київський національний університет технологій та дизайну, 2017. https://er.knutd.edu.ua/handle/123456789/7345.

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2

Ofoma, Ifedinma. "Catalytic Pyrolysis of Polyolefins." Thesis, Georgia Institute of Technology, 2006. http://hdl.handle.net/1853/10439.

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Due to the migration of scientists towards green chemistry, landfilling and incineration will no longer be acceptable options for plastics waste disposal in the future. Consequently new methods for recycling plastics and plastic products such as carpets are being researched. This study serves as a preliminary effort to study the catalytic feedstock recycling of polyolefins, specifically PP and PE, as source for gasoline range fuels, as well as an alternative for plastic waste disposal. Several studies have been conducted on the pyrolysis of waste polyolefins using commercial cracking catalysts (FCC), however, the effect of catalyst size and mode of catalyst dispersion have been studied sparsely. This thesis proposes to study these effects in the catalytic pyrolysis of polypropylene (PP), a component of carpets, using both fresh and used FCC catalysts. The same study will be applied to polyethylene (PE), which accounts for an enormous amount of municipal solid waste in the US today. Furthermore, the catalytic impact of calcium carbonate, a filler component of tufted carpet, will be investigated. Using thermogravimetric analysis, the global kinetics of the PP pyrolysis using various FCC catalysts will be derived and applied in the modeling of the pyrolysis reaction in a twin screw extruder. Furthermore, an economic analysis on the catalytic pyrolysis of PP is presented.

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Hall, Denise K. "Factors affecting adhesion to polyolefins." Thesis, Loughborough University, 1994. https://dspace.lboro.ac.uk/2134/31958.

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Factors affecting the adhesion of paint to polyolefins have been studied. These include solvent pre-treatment, types of primer and their method of interaction, flame treatment and the addition of a surface migratory additive to the polyolefin. Surface analysis techniques X-ray photoelectron spectroscopy (XPS), attenuated total reflection infra-red spectroscopy (FTIR-ATR) and contact angle measurements were used along with electron microscopy, diffusion measurements and a lap shear test. Sol vent treatments were found to affect the topography of surface, as determined by atomic force microscopy, this causes a reduction in the receding contact angle of water indicating a reduced tendency for the coating to de-wet. This gives a greater joint strength. In the case of chlorinated polyolefin primers it has been shown that chain entanglement at the polymer/primer interface is an important factor determining the joint strength and can account for up to 50% of the strength in the systems studied. Chemical interaction between the polyolefin and the paint produced after flame treatment of the polyolefin improves adhesion. Factors determining migration of additives to the polymer surface have been studied. Surface migratory material has been identified but formation of weak boundary layers can lead to little or no improvement in adhesion properties. Further work is needed in this area.

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Smith, P. W. R. "NMR investigations of solid polyolefins." Thesis, University of East Anglia, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.373108.

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France, C. N. "Some morphological aspects of polyolefins." Thesis, University of Southampton, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.381233.

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Lungu, Cristian 1968. "Crystallization behavior and kinetics of polyolefins." Thesis, McGill University, 2000. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=31061.

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In order to understand crystallization behavior and to predict polymer resin properties, crystallization kinetics and morphology studies are performed. Thermal analysis of sixteen polyethylene and polypropylene resins was carried out, using Differential Scanning Calorimetry (DSC) to study the crystallization kinetics and mechanism of crystallization. Attention is given to different polyethylene grades, particularly linear low-density polyethylenes (LLDPE) manufactured with Ziegler-Natta and metallocene catalysts. The polymers are obtained with different monomers (1-butene, 1-hexene or 1-octene). Some polymers are based on gas phase polymerization, while others are based on solution polymerization. The isothermal crystallization data were treated to account for transients and to compensate for instrument errors. The data were fitted to the Avrami and Tobin equations, and the corresponding kinetic parameters are reported. The non-isothermal data were fitted to the Ziabicki equation, in order to determine the relevant parameters. Subsequently, the non-isothermal data were compared to the predictions of the Nakamura equation, with good agreement. An effort was made to compare the isothermal and non-isothermal crystallization behavior of the various resins to evaluate the effect of co-monomer and catalyst type. The results indicate significant differences among the resins, and reveal the utility of the DSC as a tool for distinguishing the characteristics of the various resins.

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Kefaleas, Christos. "Physical properties of molecules in polyolefins." Thesis, University of Sussex, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.391878.

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8

Harding, Gareth. "The structure-property relationships of polyolefins." Thesis, Stellenbosch : University of Stellenbosch, 2009. http://hdl.handle.net/10019.1/1386.

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Thesis (PhD (Chemistry and Polymer Science))--University of Stellenbosch, 2009
Polypropylene is an extremely versatile material and has a broad spectrum of applications due to the variations in properties which are possible with this material. The variations in the properties of the material are governed by the microstructure of the chains constituting the polymer. The microstructure varies according to the production methods, i.e. the polymerisation conditions. Varying the manner in which the polymer is produced therefore changes the properties of the material allowing the polymers’ use for different applications. The most important factor affecting the way in which the polymers are produced is the nature of the active sites on the catalyst. Changing the chemical environment of the active sites changes the way in which the polymerisation is controlled and greatly affects the types of chains produced and thus polymer properties. The study examines the structure-property relationships of polyolefins with specific focus on the polypropylene homopolymer. The temperature rising elution fractionation (TREF) technique is used extensively in order to isolate specific fractions of the polymer. The importance of specific TREF fractions is investigated via a two pronged investigative methodology. On the one hand specific TREF fractions are removed from a sample, allowing the analysis of the properties of the material without that specific fraction, thereby revealing the influence which the fraction in question has on the properties. The other branch of the study investigates the chemical modification of the active sites of a Ziegler-Natta catalyst so as to be able to modify the properties of the polymer in the reactor, in a similar manner to physically removing fractions. The techniques are related and it was discovered that the amount of the fractions of the polymer, found to be important using the one technique, also turned out to be important using the other method. Initial method development work utilised a polypropylene-1-pentene copolymer since the molecular heterogeneity of this material is such that large differences are observed upon removal of fractions. The technique was then applied to a Ziegler-Natta catalysed polypropylene homopolymer. Each TREF fraction is successively removed and the residual material analysed. Specific TREF fractions were found to play a significant role in determining the polymer properties since there was a drastic reduction in properties upon removal of these fractions. The polymerisation of propylene was also performed at a variety of conditions in order to investigate different ways in which the catalyst system could be modified. Specific reaction conditions were chosen for in-depth analysis and structure-property correlation. The chemical modification of the active sites was accomplished via the introduction of an external Lewis base (electron donor) to the polymerisation system, and also by varying the external donor/catalyst ratio used. Two different external donors were used during the study namely Diphenyl-dimethoxysilane (DPDMS) and methyl-phenyl-dimethoxysilane (MPDMS). It is observed that there are definite links between the amounts of specific fractions present in the polymer and the polymer properties, as observed via both the physical removal of fractions and the chemical modification of active sites.

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CARMELI, ENRICO. "Crystallization behaviour of recycled polyolefins blends." Doctoral thesis, Università degli studi di Genova, 2022. http://hdl.handle.net/11567/1071022.

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A novel tailor-made thermal fractionation protocol, based on the Successive Self-nucleation and Annealing (SSA) method, was developed to investigate the complex chemical composition of PE/PP blends derived from recycling. The temperature regions where co-crystallization among the blend components do not occur were assessed, enabling the development of the quantitative method. Furthermore, a set-up for achieving Continuous Cooling Curve diagrams was designed, and allowed to study the crystallization kinetics at processing-relevant cooling conditions of the phases in the blends. An “inversion point” in the crystallization order of the two polymers arises from the difference in crystallization rates between PP and PE with increasing cooling rate. Mutual nucleating effects, found at the interface between the phases, correlate with the inversion point. Moreover, the order of crystallization of the two polymers at low cooling rates, i.e., before the inversion point, can be tuned by employing neat or nucleated PP. This demonstrates the importance of knowing and controlling the type of components in recycled blends. Finally, the nature of such nucleating effects was revealed by a novel approach for studying surface-induced crystallization in the blends. The method consists of detecting variations in the crystallization kinetics of the dispersed phase (PE) with changing the crystalline state of the matrix (PP) through self-nucleation. The enhancement of crystallization kinetics of PE that was achieved when increasing the lamellar thickness of PP, together with the very low value found for the interfacial free energy difference, are evidence that such nucleating effects occur through epitaxial growth.

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Luruli, Nyambeni. "New synthetic and characterization strategies for polyolefins." Thesis, Stellenbosch : Stellenbosch University, 2007. http://hdl.handle.net/10019.1/21672.

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Thesis (PhD)--University of Stellenbosch, 2006.
ENGLISH ABSTRACT: Metalloxycarbene complexes [(CO)5M1=O(R)M2(Cl)L2] (M1 = Cr , W; M2 = Zr, Hf; L = Cp, Cp*) were synthesized from the reaction between anionic Fischer-type carbene complex salts [(CO)5M1=C(O)R][NEt4] and metallocene chlorides. The molecular and crystal structures of [(CO)5W=C(Me)OZr(Cp)2Cl], [(CO)5Cr=C(Me)OZr(Cp)2Cl] and [(CO)5W=C(Ph)OHf(Cl)Cp2] determined by X-ray methods, show a short Ccarbene-O and relatively long O-Zr and O-Hf separations. Metalloxycarbene complexes in the presence of MAO are active catalysts for homo- and copolymerization of -olefins and produce polymers with heterogeneous properties. 1-Pentene oligomers, homopolymers of ethylene and ethylene/1-pentene copolymers were successfully synthesized using metalloxycarbenes/MAO and the results obtained were critically compared with those synthesized with metallocene/MAO catalysts. The GC and GPC show that 1-pentene oligomers produced with both metalloxycarbenes and metallocenes catalysts range from simple dimers to more complicated high molecular weight (2 600 g/mol) products. The properties of polyethylene and ethylene/1-pentene copolymers were evaluated by, among others, GPC, SEC-FTIR, preparative molecular weight fractionation and HPer DSC. Generally the polymers obtained using metalloxycarbene/MAO catalysts have broad and bimodal molecular weight distributions. The copolymers have higher concentration of 1- pentene in the lower molecular weight fraction than those produced with metallocene/MAO as shown by SEC-FTIR. Consequently, HPer DSC shows a decrease of melting and crystallization temperature towards the low molecular weight fractions.
AFRIKAANSE OPSOMMING: Metaaloksikarbeenkomplekse [(CO)5M1=C(R)OM2(Cl)L2] (M1 = Cr , W; M2 = Zr, Hf; L = Cp, Cp*] is gesintetiseer in die reaksie tussen anioniese Fischer-tipe karbeenkomplekssoute, [(CO)5M1=C(O)R][NEt4], en metalloseen dichloriedes. Die molekulêre- en kristalstrukture van [(CO)5W=C(Me)OZr(Cp)2Cl], [(CO)5Cr=C(Me)OZr(Cp)2Cl] en [(CO)5W=C(Ph)OHf(Cl)Cp2] bepaal deur X-straalkristallografiese metodes, toon die aanwesigheid van kort Ckarbeen-O- en relatief lang O-Zr- en O-Hf-bindings. Metaaloksikarbeenkomplekse, in die aanwesigheid van MAO, is aktiewe katalisatore vir die homo- en ko-polimerisering van α-olefiene en is verantwoordelik vir die vorming van polimere met heterogene eienskappe. 1-Penteen oligomere, homopolimere van etileen en etileen/1-penteen ko-polimere is suksesvol gesintetiseer met metaaloksikarbeenkomplekse/MAO en die resultate sodoende verkry, is krities vergelyk met produkte gesintetiseer vanuit metalloseen/MAO prekatalisatore. Die GC en GPC resultate toon dat die 1-penteen oligomere, geproduseer met beide metaaloksikarbeenkomplekse en metallosene, kan wissel van eenvoudige dimere tot meer komplekse, hoë molekulêre massa (2 600g/mol) produkte. Die polietileen en etileen/1- penteen ko-polimere is gekarakteriseer deur onder andere gevorderde, GPC, SEC-FTIR, preparatiewe molekulêre massa fraksionering en HPer DSC. In die algemeen het die polimere verkry met metaaloksikarbeen/MAO katalisatore, breë en bimodale molekulêre massaverspreidings. Die ko-polimere bevat hoër konsentrasies van 1-penteen in die lae molekulêre massa fraksie in vergelyking met dié gevorm vanuit metalloseen/MAO–gekataliseerde mengsels, soos aangedui deur SEC-FTIR-analise. HperDSC wys 'n verlaging in smelt- en kristallisasietemperature in die laer molekulêre massa fraksies.

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11

Dias, Peter Simon. "Structure-Property Relationships in Some Novel Polyolefins." Case Western Reserve University School of Graduate Studies / OhioLINK, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=case1213046882.

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12

Suharty, N. S. "Reactive processing of polyolefins using antioxidant systems." Thesis, Aston University, 1993. http://publications.aston.ac.uk/9769/.

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Various monoacrylic compounds containing a hindered phenol function (e.g.3,5-di-tert.-butyl-4-hydroxy benzyl alcohol, DBBA and vinyl-3-[3',5'-di-tert.-butyl-4-hydroxy phenyl] propionate, CDBP), and a benzophenone function (2-hydroxy-4-[beta hydroxy ethoxy] benzophenone, HAEB) were synthesised and used as reactive antioxidants (AO's) for polypropylene (PP). These compounds were reacted with PP melt in the presence of low concentration of a free radical generator such a peroxide (reactive processing) to produce bound-antioxidant concentrates. The binding reaction of these AO's onto PP was found to be low and this was shown to be mainly due to competing reactions such as homopolymerisation of the antioxidant. At high concentrations of peroxide, higher binding efficiency resulted, but, this was accompanied by melt degradation of the polymer. In a special reactive processing procedure, a di- or a trifunctional reactant (referred to as coagent), e.g.tri-methylol propane tri-acrylate, Tris, and Divinyl benzene, DVB, were used with the antioxidant and this has led to an enhanced efficiency of the grating reaction of antioxidants on the polymer in the melt. The evidence suggests that this is due to copolymerisation of the antioxidants with the coagent as well as grafting of the copolymers onto the polymer backbone. Although the 'bound' AO's containing a UV stabilising function showed lower overall stabilisation effect than the unbound analogues before extraction, they were still much more effective when subjected to exhaustive solvent extraction. Furthermore, a very effective synergistic stabilising activity when two reactive AO's containing thermal and UV stabilising functions e.g. DBBA and HAEB, were reactively processed with PP in the presence of a coagent. (DX185,650)

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Larrazabal, Hector J. Hrymak A. N. "Effects of the die wall conditions on the extrusion of linear polyolefins /." *McMaster only, 2004.

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Sriniwas, Ganti Ravi. "Estimation and control of a polyolefin reactor." Thesis, Georgia Institute of Technology, 1992. http://hdl.handle.net/1853/10266.

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15

Parrondo, Aitor. "Optimisation and mode of action of antioxidant stabilisation in film grade high-density polyethylene." Thesis, Manchester Metropolitan University, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.366053.

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Enriquez, Sevilla Luis Javier. "Activity of phosphite antioxidants in synergistic blends in the thermal and photooxidation of high-density polyethylene (HDPE)." Thesis, Manchester Metropolitan University, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.364483.

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Murray, Michael Conrad. "Preparation of polyolefins using titanium and chromium initiators." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape3/PQDD_0008/NQ52841.pdf.

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18

Vandervorst, Philippe. "Diffusion and Solubility of Additive Mixtures in Polyolefins." Thesis, University of Sussex, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.506964.

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Okopi, I. A. "Solubility and migration of stabilizing additives in polyolefins." Thesis, University of Sussex, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.382571.

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This thesis describes a series of studies of the physical behaviour of commercially important stabilizing additives in polyolefins. A series of nickelthiocarbamates have been synthesised and their solubilities measured as a function of temperature in linear hydrocarbon solvents, low density polyethylene and isotactic polypropylene. The results are compared with predictions from a regular solution model. The loss of three benzophenone UV-stabilizers from supersaturated solution has been investigated with the aim of determining whether the loss is a diffusion controlled blooming or involves phase separation. Our data shows this phenomenon is a diffusion controlled blooming process. The volatilities of these same UV-stabilizers have been measured as a function of temperature. The solubility of a typical hindered amine (Tinuvin 770) has been investigated in hydrocarbon solvents and in polypropylene by infrared methods. Low solubility values were obtained in all cases. The diffusion of Tinuvin 770 in polypropylene has been monitored by an infrared method developed for the purpose and the diffusion coefficient estimated over a range of temperatures. Litp.rature data on solubility of additives together with our own data are critically reviewed and the effect of structure on solubility is analysed. Data on the benzophenone additives allows prediction of loss times and mechanisms to be made for the first time.

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Yeung, R. R. "Nuclear spin relaxation and morphology of solid polyolefins." Thesis, University of East Anglia, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.356619.

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21

Coker, Magnus R. S. "Effect of processing on sulphur antioxidants in polyolefins." Thesis, Aston University, 1986. http://publications.aston.ac.uk/14517/.

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The effect of processing on the antioxidant activity of sulphur-containing compounds, with particular reference to nickel dialkyldithiophosphates and their corresponding di sulphides, were studied in polyolefins under melt, thermal and photo-oxidative conditions. These compounds were evaluated both at low (normal) and high (concentrates) concentrations. In general, the dithiophosphates were found to be very efficient melt stabilisers at normal concentrtion levels, and compare quite favourably with the best commercially available systems. The nickel dithiophosphates were also found to be very efficient thermal stabilisers for polyolefins, but their activity is highly dependent on the alkyl substituent in the molecule. The corresponding disulphides on the other hand showed very little activity under thermal oxidative conditions, and this was attributed to their inefficiency in scavenging alkyl peroxyl radicals since both compounds possess similar peroxidolytic activity. Furthermore, the nickel dithiophosphates were found to be excellent photo stabilisers for mildly-processed polyolefins while the corresponding disulphides only offer slight protection to the polymer. Oxidative processing of the disulphide, however, results in a dramatic improvement in their photo antioxidant activity. Thionophospho-ric acid, a major oxidation product of dithiophosphates, was also shown to have photo antioxidant activity similar to that of the disulphides. A combination of a U.V. absorber with the nickel complex and/or the disulphide resulted in a synergistic stabiliser system which was further augmented by oxidative processing. Moreover, the dilute analogues of such multicomponent stabiliser concentrates also showed excellent melt, thermal and photo-stabilising activity. The mechanistic studies carried out on the nickel complex and the corresponding disulphide clearly identified the thionophosphoric acid a a major transformation product although various triesters were formed as reaction intermediates. The mechanisms of the antioxidant action of the dithiophosphates, which is believed to involve a cyclical process similar to that shown for simple alkyl sulphides and nitroxyls, are discussed.

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Sharma, Parmode. "A study of phosphorus-containing antioxidants in polyolefins." Thesis, Aston University, 1988. http://publications.aston.ac.uk/10243/.

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Issenhuth, Sylvie. "The antioxidant role of vitamin E in polyolefins." Thesis, Aston University, 1996. http://publications.aston.ac.uk/9588/.

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Polymers are subject to oxidation throughout their lifecycle. Antioxidants are generally incorporated in polymers to inhibit or minimise oxidative degradation. Hindered phenolic antioxidants are important stabilisers for polyolefins. However, hindered phenols undergo chemical transformations while performing their antioxidant function during processing and fabrication. In addition, antioxidants are subject to loss from polymers during processing, or subsequently in-service. Migration of antioxidants is a major concern in applications involving polymers in direct contact with food and human environment. This concern is compounded by the realisation that very little is known about the nature and the migration behaviour of antioxidant transformation products. In this work, the antioxidant role of the biological antioxidant -tocopherol (Vitamin E) , which is structurally similar to many synthetic hindered phenols, is investigated in low density polyethylene (LDPE) and polypropylene (PP). The melt stabilising effectiveness of -tocopherol (Toc) was found to be very high, higher than that of commercial hindered phenol antioxidants, such as Irganox 1076 (Irg 1076) and Irganox 1010 (Irg 1010), after multiple extrusions, especially at very low concentrations. The high antioxidant activity of Toc was shown to be due, at least in part, to the formation of transformation products during processing. The main products formed are stereoisomers of dimers and trimers, as well as aldehydes and a quinone - the relative concentration of each was shown to depend on the processing severity, the initial antioxidant concentration and oxygen availability. These transformation products are shown to impart better, similar or lower melt stability to the polymer than the parent antioxidant. The nature of the products formed from Toc during processing was compared with those formed during processing of Irg 1076 and Irg 1010 with LDPE and a mechanism for the melt stabilisation of Toc was proposed and compared with the stabilisation mechanisms of the synthetic antioxidants Irg 1076 and Irg 1010.

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Mani, M. R. "Development of nanoparticle based nucleating agents for polyolefins." Thesis(Ph.D.), CSIR-National Chemical Laboratory, Pune, 2016. http://dspace.ncl.res.in:8080/xmlui/handle/20.500.12252/5887.

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Githuku, David N. "Melt strength of polyolefins and its role in plastics processing." Thesis, McGill University, 1986. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=65328.

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Rao, Baihua. "Size exclusion chromatography of polyolefins and evaluating local polydispersity." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp01/MQ33961.pdf.

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Conceicao, Luis M. "Flow behaviour and foaming of recycled polyolefins and nanocomposites." Thesis, Loughborough University, 2007. https://dspace.lboro.ac.uk/2134/14026.

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The flow behaviour of post-consumer recycled polyolefins, their blends and layered-silicate nanocomposites was studied by capillary rheometry and freesurface melt state elongational measurements to assess suitability for foaming applications. A novel, extrusion foaming technique and a flow simulation model were developed to attempt to correlate flow and foaming behaviour. The recycled polyolefins were high-density polyethylene (HOPE), low-density polyethylene (LOPE) and polypropylene (PP) of high-molecular weight, suitable for extrusion; that also contained also paper and inorganic fillers. LOPE-PP and HOPE-PP blends were prepared in a batch mixer with and without compatibilising agents, ethylene-propylene rubber (EPR) and ethylene-propylene (EP) copolymer. Several mixing conditions (temperature, time, rotor speed) were used to modify the morphology and the flow behaviour of the blend systems. In shear flow diverse pseudoplastic index, zero shear rate viscosity and the extensional viscosities, whilst, in uniaxial extensional flow the effects of process conditions on strain energy density, elongation at break and melt modulus were detected. The melt strength of uncompatibilised LOPE-rich systems is generally higher. The use of small quantities of EPR, 2.5 and 5.0% (w/w) can further improve the rheological properties in uniaxial extension, but shear flow behaviour is virtually unchanged by the compatibilisers. EP didn't improve the extensional flow behaviour of HOPE-PP blends. The influence of processing conditions and composition on the preparation of melt intercalated HOPE and HOPE-PP layered-silicate nanocomposites was conducted as a way of enhancing foaming behaviour; montmorillonite particles were dispersed with the aid of a compatibilising agent. Ideal mixing conditions (temperature, rotor speed and time) were determined for these nanocomposites based on rheological measurements. In HOPE nanocomposites, the melt elongation at break is reduced and the tensile modulus increased. The clay content has a significant influence on the melt tensile modulus. Wall slip behaviour appeared enhanced comparatively to unmodified HOPE. In HOPE-PP nanocomposite blends it is possible to modify the melt tensile modulus and elongation by changing blend composition and clay dispersion morphologies. A finite element model of capillary die flow was developed using commercial simulation software to assist the interpretation of an extrusion foaming technique. Experiments were carried out using azodicarbonamide as a blowing agent and a capillary rheometer and extruding the materials through a capillary die. Extruding at a shear rate of 300s-1 and at a temperature close to the melting point yielded the lowest foam densities; LOPE, the material with the highest melt strength and extensibility, achieved a density of 430 kg m-3. Blends of HOPE-PP, LOPE-PP and HOPE-PP nanocomposites didn't show an improved foaming behaviour with densities always above 600 kg m- 3 Oensities of 360kg m-3 and 500 kg m-3 were obtained with HOPE nanocomposites and unmodified HOPE, respectively.

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Trabajo, Pedro Garcia. "The chemistry and physics of stabiliser additives in polyolefins." Thesis, University of Sussex, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.318606.

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29

Parkinson, A. "Photostabilising action of a p-hydroxybenzoate compound in polyolefins." Thesis, Manchester Metropolitan University, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.378038.

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30

Coben, Collin. "Use of Pyrolyzed Soybean Hulls as Fillers in Polyolefins." University of Akron / OhioLINK, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=akron1590601881643166.

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31

Surry, I. R. "The mechanochemical modification of polyolefins using reactive modifier systems." Thesis, Aston University, 1990. http://publications.aston.ac.uk/9737/.

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The principal objective of this work was to improve the mechanical properties of glass fibre reinforced polypropylene (PP) composites by the mechanochemical modification of the PP. The modification of the PP was carried out by reactive processing of the PP with a modifier in a Buss Ko-Kneader. Two main types of modifier were evaluated one type based on N-substituted maleimides the others based on 2-allylamino-4,6-dichloro-1,3,5-triazine (ACCT). The modification of the PP was carried out in two stages. Firstly the PP was reactively processed with the modifier and a free radical initiator. The objective of this stage was to bind the modifier to the PP. In the second stage the modified PP was reactively processed with the glass fibre. The objective in this stage was to form a chemical bond between the bound modifier and the silane coupling agent on the surface of the glass. Two silane coupling agents were evaluated these had a aliphatic chloro group and an aliphatic amino group respectively available for reaction with the modifier. The modifiers synthesised for this work had two main functional groups. The first was a double bond for free radical addition to the PP. The second was an organic group chosen for its potential reactivity to the silane coupling agent. A preliminary investigation was carried out using maleic anhydride (MA) as the modifier, this is reactive to the amino silane coupled glass. Studies of a commercially available system were also carried out for comparison purposes. During the work it was found that the amino silane coupled glass fibres produced, without any modification being made to the PP, mechanical properties comparable to the commercial system. Further any modification added to the amino silane system failed to improve the mechanical performance and in some cases acted in the opposite fashion. This failure was evident even when a chemical bond between glass fibre and PP could be shown. In the case of the chloro silane coupled glass fibres the mechanical properties of the composite without modification were poorer than those of the commercial system. It was found that the mechanical properties of these systems could be enhanced by the modifiers, however, no system tested significantly out performed the commercial system. Of the two modifier systems tested those based on the n-substituted maleimides were more successful at enhancing mechanical properties than those based on ACCT. This was attributed to the Poor chemical binding of the ACCT based modifiers to the PP. During the work it was found that several of the modifiers improved the properties of the PP when no glass fibres were present, particularly the % elongation and impact strength. It is possible that these modifiers could be used to improve the impact performance of PP, this may be of particular interest in recycling. These modifiers have only been tested for improving the properties of glass fibre composites. The N-substituted maleimide based modifiers could be used as compatibleisers for alloys of PP and other polymers. These could function by the formation of the bond with PP via the double bond whilst the group attached to the nitrogen atom could react with the alloying polymer.

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32

Kamdar, Akshay R. "Miscibility and Structure-Property Relationships in Some Novel Polyolefins." Cleveland, Ohio : Case Western Reserve University, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=case1234451598.

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Thesis (Ph.D.)--Case Western Reserve University, 2009
Abstract Department of Macromolecular Science and Engineering Title from PDF (viewed on 16 April 2009) Available online via the OhioLINK ETD Center

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33

Balamurugan, S. "Surface modification of polyolefins by chemical & plasma methods." Thesis(Ph.D.), CSIR-National Chemical Laboratory, Pune, 1998. http://dspace.ncl.res.in:8080/xmlui/handle/20.500.12252/3390.

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34

Megkoulas, Nikolaos. "Physical properties of single additives and additive mixtures in polyolefins." Thesis, University of Sussex, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.410363.

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35

Lator, B. G. "Structural consequences arising from the application of stress to polyolefins." Thesis, University of Southampton, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.381128.

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36

Whiteman, David James. "The physical chemistry of stabilising additives in rubber toughened polyolefins." Thesis, University of Sussex, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.285136.

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37

Suh, Jaein. "COMPARATIVE STRUCTURE DEVELOPMENT OF VARIOUS POLYOLEFINS IN INJECTION MOLDING PROCESS." University of Akron / OhioLINK, 2007. http://rave.ohiolink.edu/etdc/view?acc_num=akron1185501428.

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38

Lin, Yijian. "Structure-Property Relationship of Polyolefins Used as Packages and Adhesives." Case Western Reserve University School of Graduate Studies / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=case1290044976.

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39

Islam, Shahida. "Time controlled photo-oxidation of polyolefins by polymer bound additives." Thesis, Aston University, 1992. http://publications.aston.ac.uk/9770/.

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A variety of iron compounds containing vinyl or thiol functional groups (used as photoactivators) have been synthesised and some of these were successfully bound to both polyethylene and polypropylene backbones during processing in the presence of peroxide and interlinking agent. Concentrates (masterbatches) of the photoactivators in PP and PE were prepared and the pro-oxidant effect of the diluted masterbatches in absence and presence of an antioxidant was evaluated. An antioxidant photoactivator (FeDNC ) was found to sensitise the photoactivity of pro-oxidants (Metone A / Metone M) whereas an antioxidant (ZnDNC) was found to stabilise the polymer (PP and PE) containing both of these combinations. It was observed that the lower concentration of FeDNC sensitises the stability of the polymer containing very small concentration of NiDNC whereas higher concentration of FeDNC stabilises the polymer (LDPE) containing same amount of NiDNC compared to FeDNC alone. The photostability of unstabilised PP containing FeAc could be varied by varying the concentration of ZnDEC. Both the induction period and the UV - life time of the polymer increased by increasing concentration of ZnDEC. It is suggested that ligand exchange reaction may take place between FeAc and ZnDNC. A polymer bound UV stabiliser (HAEB) and a thermal stabiliser (DBBA) were used with a non extractable photoactivator (FeAc) in PP. Small concentrations of the stabilisers (HAEB and DBBA) in combination with the photoactivator (FeAc) sensitise the polymer. The antioxidant present in commercial polymer (LDPE and PP) was found to be of a hindered phenol type, which was found to antagonise with ZnDNC when used in combination with the photoactivators.

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40

Mani, R. "Study of thermal and photo-degradation and stabilization of polyolefins." Thesis(Ph.D.), CSIR-National Chemical Laboratory, Pune, 1994. http://dspace.ncl.res.in:8080/xmlui/handle/20.500.12252/2824.

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41

Arnold, Billy Dean. "Application of Kalman filtering to a polyolefin polymerizer." Thesis, Georgia Institute of Technology, 1991. http://hdl.handle.net/1853/11291.

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42

Brand, M. "Investigation of molecular weight effects during the solution crystallisation of polyolefins." Thesis, Link to the online version, 2008. http://hdl.handle.net/10019/815.

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43

Peng, Xi. "Oxidation and stabilisation chemistry of mteallocene-based polyolefins during melt processing." Thesis, University of Southampton, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.403838.

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44

Popat, Rohit P. "Functionalisation of polyolefins and its effects on surface chemistry and energetics." Thesis, Loughborough University, 1995. https://dspace.lboro.ac.uk/2134/22023.

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The surface functionalisation of polyethylene and polypropylene by industrial and laboratory scale corona treatments and by laboratory flame treatment was studied. The surface sensitive techniques of X-ray photoelectron spectroscopy (XPS), attenuated total reflection infra-red spectroscopy (FTIR-ATR), contact angle measurement and electron microscopy (SEM and TEM) were employed. Corona and flame treatments resulted in incorporation of oxygen only into the surfaces of both polyethylene and polypropylene, resulting in improved surface wettabilities. A variety of oxygen functional groups were introduced by the two treatments. The industrial and laboratory scale treatments of both polymers were found to be similar in terms of the oxygen concentrations incorporated and surface wettabilities achieved. The presence of significant amounts of chain scission products were indicated on corona treated surfaces, while only minimal quantities were indicted on flame treated surfaces. This was attributed to their volatilisation during flame treatment. Introduction of sulfur dioxide into the flame and corona regions during treatment resulted in significant improvements in surface wettability. Incorporation of sulfur and nitrogen resulted from the presence of sulfur dioxide. A possible mechanism involving the formation of sulfonic acid groups and ammonium sulfonate groups was suggested. An oxidation depth model developed for use with variable take-off angle XPS showed that significantly deeper oxidation occurred in the presence of sulfur dioxide. Corona treatment was more effective in improving surface wettabilities than flame treatment, this being attributed to heat induced functional group reorientation during flame . treatment for polyethylene and to differences in surface chemistry resulting from the two treatments in the case of polypropylene. The surface wettability of poly ethylene was more readily improved than the surface wettability of polypropylene after all the treatments investigated. A method for estimating functional group concentrations using chemical derivatisation and contact angle measurement was developed. Functional group estimates for flame treated polyethylene were found to be in good agreement with chemical derivatisation used in conjunction with XPS measurements.

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45

Wirjosentono, Basuki. "The role of stable nitroxyl radical precursors as antioxidants in polyolefins." Thesis, Aston University, 1991. http://publications.aston.ac.uk/9749/.

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Various 2,2,6,6-tetramethyl piperidines and their N-alkyl derivatives of stable nitroxyl radical precursors containing acrylic(s) and methacrylic(s) groups were reactively processed in the presence of a peroxide as bound-antioxidant masterbatches for polyolefin stabilisation. It was found that grafting of the antioxidant monomers onto the polymer backbone was inevitably in competition with homopolymerisation of the monomers as well as melt degradation of the polymer and other side reactions. As previously reported, binding efficiency of bisacrylic nitroxyl precursor was maximum due to formation of unextractable homopolymer of the antioxidant. On the other hand, the binding efficiency of monoacrylic derivatives was low and the homopolymers were found extractable, which suggests that the bound monoacrylic derivatives are entirely grafted onto the polyolefin backbone. Application of bis and tri-functional coagents gave improved binding efficiency of the monoacrylic monomers. This may be due to copolymerisation of the antioxidants with the coagents and grafting of the copolymers onto the polymer backbone. Comparison of photostabilising activity of the fully extracted bound antioxidants to those of the corresponding unbound analogous showed lower results for the former. However, thermal stabilising activity of the bound antioxidants was higher than that of the unbound analogous due to better substantivity. Analysis using physical techniques and GPC for molecular weight distribution of masterbatches containing the bound monoacrylic antioxidants showed formation of high molecular weight products. Model reaction of a secondary amine derivative in liquid hydrocarbon and analysis of the product using FTIR and NMR spectroscopy indicated a possibility of side reaction, i.e. involvement of the amine active group (>N-H) of the antioxidant in the binding process to form the high molecular weight product.

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46

Peng, Xi. "Oxidation and stabilisation chemistry of metallocene-based polyolefins during melt processing." Thesis, Aston University, 2004. http://publications.aston.ac.uk/9657/.

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Metallocene catalyzed linear low density polyethylene (m-LLDPE) is a new generation of olefin copolymer. Based on the more recently developed metallocene-type catalysts, m-LLDPE can be synthesized with exactly controlled short chain branches and stereo-regular microstructure. The unique properties of these polymers have led to their applications in many areas. As a result, it is important to have a good understanding of the oxidation mechanism of m-LLDPE during melt processing in order to develop more effective stabilisation systems and continue to increase the performance of the material. The primary objectives of this work were, firstly, to investigate the oxidative degradation mechanisms of m-LLDPE polymers having different comonomer (I-octene) content during melt processing. Secondly, to examine the effectiveness of some commercial antioxidants on the stabilisation of m-LLDPE melt. A Ziegler-polymerized LLDPE (z-LLDPE) based on the same comonomer was chosen and processed under the same conditions for comparison with the metallocene polymers. The LLDPE polymers were processed using an internal mixer (torque rheometer, TR) and a co-rotating twin-screw extruder (TSE). The effects of processing variables (time, temperature) on the rheological (MI, MWD, rheometry) and molecular (unsaturation type and content, carbonyl compounds, chain branching) characteristics of the processed polymers were examined. It was found that the catalyst type (metallocene or Ziegler) and comonomer content of the polymers have great impact on their oxidative degradation behavior (crosslinking or chain scission) during melt processing. The metallocene polymers mainly underwent chain scission at lower temperature (< 220°C) but crosslinking became predominant at higher temperature for both TR and TSE processed polymers. Generally, the more comonomers the m-LLDPE contains, a larger extent of chain scission can be expected. In contrast, crosslinking reactions were shown to be always dominant in the case of the Ziegler LLDPE. Furthermore, it is clear that the molecular weight distribution (MWD) of all LLDPE became broader after processing and tended generally to be broader at elevated temperatures and more extrusion passes. So, it can be concluded that crosslinking and chain scission are temperature dependent and occur simultaneously as competing reactions during melt processing. Vinyl is considered to be the most important unsaturated group leading to polymer crosslinking as its concentration in all the LLDPE decreased after processing. Carbonyl compounds were produced during LLDPE melt processing and ketones were shown to be the most imp0l1ant carbonyl-containing products in all processed polymers. The carbonyl concentration generally increased with temperature and extrusion passes, and the higher carbonyl content fonned in processed z-LLDPE and m-LLDPE polymers having higher comonomer content indicates their higher susceptibility of oxidative degradation. Hindered phenol and lactone antioxidants were shown to be effective in the stabilization of m-LLDPE melt when they were singly used in TSE extrusion. The combination of hindered phenol and phosphite has synergistic effect on m-LLDPE stabilization and the phenol-phosphite-Iactone mixture imparted the polymers with good stability during extrusion, especially for m-LLDPE with higher comonomer content.

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47

Gozzi, Matteo. "Characterization of secondary polyolefins from household waste and automotive shredder residues." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2012. http://amslaurea.unibo.it/3393/.

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48

Lapenta, Rosita. "New metal catalysts for the synthesis of polyolefins and bioderived polymers." Doctoral thesis, Universita degli studi di Salerno, 2018. http://hdl.handle.net/10556/2980.

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2016 - 2017
The aim of PhD project is the synthesis of new metal catalysts active in the polymerization of polar monomer and α-olefins. In the last decade, transition metal complexes bearing tetradentate bis(phenolato) ligands are widely studied for their high polymerization control and activity.1 The bis(phenolato) ligand is composed of two phenoxide groups linked by a bridge comprising two donor heteroatoms; when the donors are two sulfur atoms, the ligand is called of OSSO-type... [edited by Author]
XXX ciclo

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49

Klash, Abdalah. "Imaging and quantifying the different crystalline structures of polypropylene with the atomic force microscope." Thesis, Link to the online version, 2006. http://hdl.handle.net/10019/1070.

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50

Salmazo, Leandra Oliveira [UNESP]. "Cinéticas de espumación y control de la estructura celular en materiales basados en caucho natural y poliolefinas." Universidade Estadual Paulista (UNESP), 2015. http://hdl.handle.net/11449/132730.

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Made available in DSpace on 2016-01-13T13:27:47Z (GMT). No. of bitstreams: 0 Previous issue date: 2015-05-12. Added 1 bitstream(s) on 2016-01-13T13:33:15Z : No. of bitstreams: 1 000856214.pdf: 9579626 bytes, checksum: c9ab90acbda3c48ccb29d6ed3f016074 (MD5)
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Dissertations / Theses on the topic 'Polyolefins'

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