Literatura académica sobre el tema "Blocked isocyanates"
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Artículos de revistas sobre el tema "Blocked isocyanates"
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Mohammed, Issam A. y Govindarajan Sankar. "Synthesis, deblocking and cure reaction studies of secondary alcohol-blocked isocyanates". High Performance Polymers 23, n.º 7 (noviembre de 2011): 535–41. http://dx.doi.org/10.1177/0954008311421833.
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A series of 1,3-dichloro-2-propanol-blocked diisocyanates, based on diisocyanates including 4,4′-methylene di(phenyl isocyanate), toluene-2,4-diisocyanate, isophorone diisocyanate and 1,6-diisocyanatohexane, were prepared and characterized thoroughly by Fourier transform infrared, 1 H-NMR, 13 C-NMR spectroscopic methods and elemental analysis (CHN). The blocking reaction of 1,3-dichloro 2-propanol with aromatic diisocyanates occurs faster than with the aliphatic isocyanates. The deblocking temperature of blocked isocyanates was determined by thermogravimetric analysis, differential scanning calorimetry and the CO2 evaluation method. Cure reactions of blocked isocyanates with hydroxyl-terminated polybutadiene were also followed to establish the structure–property relationship of the 1,3-dichloro-2-propanol-blocked isocyanates. The deblocking studies reveal that the aromatic isocyanates undergo deblocking more easily than aliphatic isocyanates. The dissolution behavior of 1,3-dichloro-2-propanol-blocked isocyanates in Terathane-2000, polypropylene glycol-2000, polycaprolactone diol-2000 and hydroxyl-terminated polybutadiene-2500 was also studied, and it was found that all adducts are soluble in these polyols.
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Wicks, Douglas A. y Zeno W. Wicks. "Blocked isocyanates III". Progress in Organic Coatings 41, n.º 1-3 (marzo de 2001): 1–83. http://dx.doi.org/10.1016/s0300-9440(00)00164-8.
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Choi, Moonhyun, Maeng Gi Kim, Kevin Injoe Jung, Tae Hee Lee, Miran Ha, Woochan Hyung, Hyun Wook Jung y Seung Man Noh. "Reactivity and Curing Efficiency of Isocyanate Cross-Linkers with Imidazole-Based Blocking Agents for Low-Temperature Curing of Automotive Clearcoats". Coatings 10, n.º 10 (13 de octubre de 2020): 974. http://dx.doi.org/10.3390/coatings10100974.
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For the application of low-temperature curing on automotive clearcoats, isocyanate cross-linkers blocked with imidazole derivatives were newly synthesized. The effect of the alkyl groups in the imidazole derivatives on the deblocking behavior and curing kinetics was investigated. The free isocyanate groups exposed by the deblocking of imidazole-based blocking agents were monitored by real-time Fourier-transform infrared spectroscopy. The bond dissociation energy, activation energy of deblocking, and H–N distance were interpreted through density functional theory simulation of various imidazole-based blocked isocyanates. To evaluate their applicability to automotive clearcoats, the synthesized imidazole-based blocked isocyanates were mixed with a polyol binder containing hydroxyl groups, and the clearcoat samples were cured at relatively low curing temperatures (100, 110, and 120 °C). The real-time storage modulus was measured using a rotational rheometer to elucidate the thermal curing dynamics by the blocking agents. In addition, the surface hardness of the cured clearcoat layers, which is affected by the chemical structure of the imidazole derivatives, was evaluated by nanoindentation test. In-depth analyses of the deblocking behaviors and thermal curing properties of clearcoats using imidazole-based blocked isocyanates demonstrated that the newly developed coating system could be suitably applied for the development of low-temperature curing technology.
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Mirčeva, A., M. Janežič, M. Žigon y T. Malavašič. "Characterization of blocked isocyanates". Journal of Molecular Structure 267 (marzo de 1992): 129–34. http://dx.doi.org/10.1016/0022-2860(92)87021-m.
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Lattimer, M. B., C. D. Weber y Z. R. Hardt. "An Improved Adhesive System for Textile-Reinforced Rubber Products". Rubber Chemistry and Technology 58, n.º 2 (1 de mayo de 1985): 383–91. http://dx.doi.org/10.5254/1.3536072.
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Abstract Resorcinol Formaldehyde Latex (RFL) adhesive systems have been used for over forty years to bond synthetic fibers to rubber compounds. The original RFL formulation was developed by Charch and Maney. The adhesive was applied primarily to rayon fibers and later extended to nylon and glass fibers. At the same time, the formulation evolved with the introduction of synthetic latexes and preformed resorcinol formaldehyde resin solutions. The RFL treated fibers are used to reinforce rubber products (e.g., tires, conveyor belts, hoses, V-belts). With the commercialization of polyester fibers, it was found that the RFL system did not satisfactorily adhere polyester to rubber compounds. The difficulty in bonding to polyester fibers has been attributed to the lack of reactive sites in the polymer structure, as well as its hydrophobic nature. New adhesive systems were developed which consisted of free isocyanates in solvent solutions. These systems were undesirable due to the associated health and fire risks. As a result, the use of aqueous dispersions of blocked isocyanates was investigated. Blocked isocyanates consist of isocyanate molecules which are chemically reacted with a blocking agent to prevent reactions with other materials at room temperature conditions. At higher temperatures, the blocking materials dissociate to free the reactive isocyanate groups. The blocked isocyanates are generally available in solid form and are chemically stable in water. Common blocking materials include phenols, oximes, and lactams. Shoaf developed a two-step, water based, adhesive system that effectively bonded polyester to rubber. This system consists of a first-step dip application which contains a polyepoxide and blocked aromatic polyisocyanate. In the second step, the treated fiber is overcoated with an RFL mixture. The reaction product of the polyepoxide and polyisocyanate has been identified as a polyurethane structure which physically adheres to polyester. Iyengar attributed this physical interaction to the similarity between the cohesive energy density values for the polyester and polyurethane structures.
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Ivanovich, Ryan A., Dilan E. Polat y André M. Beauchemin. "Oxygen-Substituted Isocyanates: Blocked (Masked) Isocyanates Enable Controlled Reactivity". Advanced Synthesis & Catalysis 359, n.º 24 (18 de octubre de 2017): 4289–93. http://dx.doi.org/10.1002/adsc.201701046.
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Parker, Dane K., Howard A. Colvin, Arthur H. Weinstein y Sun-Lin Chen. "Reactively Curable Rubbers—I: Diene Elastomers with Pendant Isocyanate and/or Hydroxyl Functionality". Rubber Chemistry and Technology 63, n.º 4 (1 de septiembre de 1990): 582–98. http://dx.doi.org/10.5254/1.3538275.
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Abstract In conclusion, we have demonstrated that modified diene elastomers containing active hydrogens and/or blocked-isocyanate derivatives can be crosslinked (cured) by three distinct methods. These methods include: 1. reaction of polymer-bound active hydrogens with monomeric polyisocyanates (Type I), 2. reaction of polymer-bound isocyanates with compounds containing two or more active hydrogens (Type II), and 3. reaction between polymer segments that contain both polymer-bound isocyanates and active hydrogens (Type III). Additionally, we have shown that the new polymerizable blocked-isocyanate derivatives (Type II and III systems) can be readily incorporated into SBR and NBR elastomers by standard emulsion-polymerization techniques. The degree and distribution of these monomers within the elastomer matrix were shown to be controlled by knowledge of their reactivity ratios. Furthermore, we have shown that the processing and properties of these systems can be readily controlled by the proper combination of isocyanate blocking group, active-hydrogen component, and catalyst. In many cases, these modified elastomers can be coagulated, dried, compounded, and cured using methods common to the rubber industry. Although not optimized, we have also shown that useful vulcanizates can be produced from extremely simple recipes. Conventional acceleration systems e.g., sulfur, accelerator, zinc oxide, are eliminated. The resulting urethane or urea crosslinks are remarkably durable under both thermal and hydrolytic conditions. Obviously, the possibilities for these uniquely reactive elastomers have not been exhausted. Many other intriguing applications of this technology are currently being explored. These applications will be the subject of future publications.
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Jones, R. "Cross-linking organic coatings with blocked isocyanates". Transactions of the IMF 86, n.º 2 (marzo de 2008): 75–79. http://dx.doi.org/10.1179/174591908x264464.
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Taylan, E. y S. H. Küsefoğlu. "Blocked isocyanates and isocyanated soybean oil as new chain extenders for unsaturated polyesters". Journal of Applied Polymer Science 119, n.º 2 (30 de julio de 2010): 1102–10. http://dx.doi.org/10.1002/app.32660.
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Yang, H., S. K. Mendon y J. W. Rawlins. "Nanoencapsulation of blocked isocyanates through aqueous emulsion polymerization". Express Polymer Letters 2, n.º 5 (2008): 349–56. http://dx.doi.org/10.3144/expresspolymlett.2008.41.
Texto completoTesis sobre el tema "Blocked isocyanates"
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Derasp, Joshua. "Development of Cascade Reactions and Strategies for Carbon Centred Nucleophilic Additions to Blocked Isocyanates". Thesis, Université d'Ottawa / University of Ottawa, 2019. http://hdl.handle.net/10393/39326.
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Isocyanates are invaluable bulk chemicals that play a central role in the synthesis of various polymers and provide a key platform for the synthesis of nitrogen-containing molecules such as carbamates and ureas. Unfortunately, isocyanates suffer from high toxicity, low functional group tolerance, and a propensity to undergo deleterious side-reactions. Consequently, blocked (masked) isocyanate derivatives have been the subject of increased interest resulting from their reduced toxicity and exceptional control over isocyanate reactivity. This strategy has largely been relegated to the polymerization literature, although its use in the synthesis of complex urea and carbamate derivatives is well established in synthetic organic chemistry.
However, prominent gaps in the blocked isocyanate literature were clear at the outset of this research project. First and foremost, the development of heteroatom-substituted isocyanates, such as N- and O-substituted derivatives, remained relatively scarce despite their potential for the synthesis of important nitrogen-containing derivatives. Furthermore, the additions of carbon-centred nucleophiles on blocked N-, O-, and even C-substituted blocked isocyanates were exceedingly rare. Finally, the use of a blocking group strategy in catalytic transformations of isocyanates remained largely absent from the literature. This was particularly striking given the widespread development of catalytic transformations of isocyanates.
As such research efforts began focusing on furthering the development of blocked N-isocyanates as a vital platform for heterocyclic synthesis (chapter 2). Initially, the cascade reactivity of blocked N-iso(thio)cyanates was expanded to incorporate electrophiles such as alkynes (section 2.2). This readily provided access to imidazolone and thiazolidine products. Subsequently, the development of a cascade reaction providing access to 1,2,4-triazin-3(2H)-ones was explored (section 2.3). This provided the first examples of an N-isocyanate cascade which hinged on the use of acid catalysis. Moreover, insight into hydrazone isomerization was gained. Finally, these efforts culminated in the development of cascade reactions providing access to a rare class of 1,2,4-triazinones as well as 5-aminopyridazinones (section 2.4). This provided the first example of a cascade reaction involving a C-C bond formation onto a blocked N-isocyanate derivatives. Furthermore, this development was pivotal in re-focusing attention on the development of general strategies to achieve addition of carbon nucleophiles onto blocked isocyanate derivatives.
Towards this end, the development of two strategies to achieve carbon-centred nucleophilic additions on both blocked N- And O-isocyanates were developed (chapter 3). Inspiration from the isocyanate literature led to the development of carboxylic acids as formal carbon nucleophiles (section 3.2). This strategy was found to be quite general for the synthesis of hydroxamates from blocked O-isocyanates. Furthermore, encouraging results were generated on the ability of Grignard reagents to form similar products (section 3.3). Particularly important is the paradigm shift this allows from C-N bond formation to C-C bond formation for the synthesis of hydroxamate derivatives. Furthermore, lead results suggest the potential of this reactivity to translate to blocked N-substituted derivatives, a transformation which had failed with carboxylic acids.
Finally, the development of a catalytic amide synthesis from blocked isocyanate precursors was targeted (chapter 4). The use of a blocking group strategy was able to address the current major limitation of isocyanates as amide precursors, that is functional group tolerance (section 4.2). Indeed, a commercially available rhodium catalyst was found to allow efficient amidation of various ambiphilic blocked isocyanate derivatives using arylboroxines as nucleophiles. Mechanistic studies including the use of variable time normalization analysis supported the presence of two alternative kinetic regimes contingent on the reaction conditions employed. Furthermore, these data suggested the success of this transformation, in the case of ambiphilic derivatives, hinged on a rate determining isocyanate release (chapter 4). Finally, initial results strongly support the potential for Boc-carbamates to provide a general platform for amidation in the presence of strong nucleophiles such as primary amines.
The potential of a blocking group strategy in catalytic reaction development was further displayed with the development of a palladium catalyzed amidation of blocked derivatives with arylboroxine nucleophiles (section 4.3). Indeed, the use of blocked isocyanates was found to be absolutely key in achieving efficient reactivity with the palladium catalyst. This result, coupled with the sparse reports on blocked isocyanates in catalysis, strongly suggest that the use of such a strategy could allow the development of reactivity otherwise unattainable when using free isocyanates.
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Clavette, Christian. "Synthesis of Beta-Aminocarbonyl Compounds and Hydrazine Derivatives Using Amino- and Imino-Isocyanates". Thesis, Université d'Ottawa / University of Ottawa, 2015. http://hdl.handle.net/10393/32004.
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Over the past recent years, β-aminocarbonyls have been of great interest to medicinal chemists. As a practical method to obtain these moieties, alkene aminocarbonylation, accounting for the formation of a C-N and a C-C bond, has been the subject of limited research efforts (very specific intramolecular metal-catalyzed variants have been reported). Direct aminocarbonylation of alkenes constitutes a challenging and an important potential innovation in the synthesis of β-aminocarbonyls such as β-amino acids. The research efforts described in the present thesis have been primarily directed towards the development of concerted pathways for the amination of alkenes using hydrazine derivatives as bifunctional reagents. Building on our previous report on the reactivity of hydrazides, progress on the aminocarbonylation of alkenes along with the synthetic scope of this reactivity are herein provided. Therefore, the first part of the present thesis (Chapter 2) focuses primarily on the development of thermolytic conditions for the intramolecular aminocarbonylation of alkenes using amino-isocyanates. Alongside, development of imino-isocyanates have provided complementary synthetic tools for aminocarbonylation. The second part (Chapter 3) describes the work accomplished towards intermolecular aminocarbonylation of alkenes and the synthesis of complex azomethine imine products (Chapter 3). Finally, the last part of the discussion (Chapter 4) will be on the development of new hydrazide reagents for the intramolecular Cope-type hydroamination of alkenes. In doing so, description of the synthetic utility of amino-isocyanates as amphoteric reagents for cascade reactions and heterocyclic synthesis will be provided.
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Delebecq, Etienne. "Compréhension et améliorations d'élastomères silicone de type Liquid Silicone Rubber". Thesis, Montpellier, Ecole nationale supérieure de chimie, 2011. http://www.theses.fr/2011ENCM0014/document.
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L'objectif de ces travaux de thèse était d'améliorer les performances d'étanchéité de connecteurs automobiles fabriqués en silicone. La première approche visait à comprendre les relations entre les structures chimiques présentes dans les formulations LSR et les propriétés mécaniques afin de proposer des additifs favorisant la résistance à la déchirure. Lors d'une étude préalable, nous avons étudié l'effet synergétique du platine et de la silice sur la dégradation thermique de formulations silicone. Ce travail a permis de décrire le mécanisme et de proposer de nouvelles formulations plus performantes en terme de taux de résidu après pyrolyse. Cette première étude alliée à d'autres techniques a permis d'analyser les structures chimiques présentes dans huit formulations commerciales. Nous avons également caractérisé la réactivité ainsi que la structure du réseau polymère obtenu après réticulation. Les relations liant les structures chimiques à la structure des réseaux ont été établies. Enfin, les propriétés mécaniques telles que la déformation rémanente à la compression, les propriétés ultimes (force et élongation à la rupture) et la résistance à la déchirure des matériaux ont été corrélées avec les différentes structures des réseaux.La seconde partie était dédiée à la synthèse d'un additif fonctionnel thermiquement activable permettant de réparer a posteriori une déchirure. Afin de sélectionner le meilleur système correspondant au cahier des charges, une revue complète de la bibliographie a été réalisée sur la réversibilité des fonctions urées et uréthanes, en portant une attention particulière sur la chimie des isocyanate bloqués. Deux molécules bloquantes ont été sélectionnées après étude de la réactivation thermique de la fonction isocyanate. Un monomère portant cette fonction isocyanate bloqué a été engagé dans une réaction de copolymérisation afin d'obtenir plusieurs générations d'additifs testés selon les normes appliquées aux connecteursThis PhD work aimed at improving the water and air-proofing properties of automotive connectors made of silicones. The first approach consisted of understanding the relationships between the chemical structures added in the LSR formulations and their ultimate mechanical performances so as to propose additives which would improve tear resistance of the materials. In a preliminary study, we investigated the synergistic role of platinum catalyst and silica on the thermal degradation of silicone formulations. These investigations allowed us to describe the degradation mechanism and to suggest new formulations in order to improve the residue content at high temperature. This first study, combined with other techniques, allowed us to analyze the chemical structures present in eight commercial formulations. We also characterized the reactivities as well as the network topologies obtained after curing the formulations. Correlations between the chemical structures and the network topology were then established. Finally, some mechanical properties, i.e. the compression set, the ultimate properties (tensile strength and elongation at break) and the tear resistance of final materials were matched with network topologies. The second part was dedicated to the synthesis of a functional additive which could be thermally reactivated to heal a tear. In order to select the best system according to the strict specifications of this work, a complete literature review on the reversibility of urea and urethane bonds was done, with special emphasis on blocked isocyanate chemistry. After a study on the isocyanate group thermal reactivation, two blocking molecules were chosen. A monomer bearing this blocked isocyanate function was then copolymerized to obtain different generations of additives which were finally tested according to standard norms applied to connectors
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Lo, Valvo Lorenzo. "Isocyanate-free Polyurethane: from synthesis to applications". Master's thesis, Alma Mater Studiorum - Università di Bologna, 2021.
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Polyurethanes (PUs) are currently one of the polymers most used in worldwide for many applications such as rigid and flexible foams, coatings, elastomers, adhesives and sealants. However, the synthesis of conventional polyurethanes relies on isocyanate reactants as crucial starting materials. Toxicity, water-sensitivity and phosgene-based synthesis of isocyanates have required to focused research on more sustainable processes that use ecofriendly and non-hazardous materials. After a first part dedicated to conventional PU technology, this thesis provides an overview of current isocyanate-free pathways for PU synthesis and application, with focus on comparison of conventional PU characteristics with isocyanate-free PU. The first alternative consists in the use of blocked isocyanate which exploits the reversibility of isocyanate bonds through thermal dissociation and regeneration of isocyanate function. The second includes alternative chemistry, focusing on the formation of Non-Isocyanate Polyurethanes (NIPU) via transurethanization and aminolysis of polycyclic carbonates. Their advantages and limitations are outlined and finally the use of non-isocyanate polyurethane to recover applications of classic polyurethane in industry is examined. Blocked isocyanate technology shows different advantages in comparison with conventional polyurethane and has a great potential for further investigation due to the variety of possibilities in isocyanate chemistry. Despite some limitations in terms of kinetics, conversion and molar masses, the reaction of cyclic carbonates and amines appeared as the most promising substitute for the synthesis of non-isocyanate polyurethanes thanks to the possibility of producing hybrid NIPU with other polymers such as polyepoxide, polyacrylates and polysiloxanes which overcome these problems.
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Polenz, Ingmar, Andreas Laue, Tamas Uhrin, Tobias Rueffer, Heinrich Lang, Friedrich Schmidt y Stefan Spange. "Thermally cleavable Imine Base / Isocyanate Adducts and Oligomers suitable as Initiators for Radical Homo- and Copolymerization". Universitätsbibliothek Chemnitz, 2014. http://nbn-resolving.de/urn:nbn:de:bsz:ch1-qucosa-152196.
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The addition of isocyanates to C=N double bonds of imines gives triazindione heterocycle structures; their thermal properties are reported. Mono-isocyanates were used to form 2:1 adducts with the imine bases 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU), 1,5-diazabicyclo[4.3.0]non-5-ene (DBN) and 2-tert-butyl-1,1,3,3-tetramethylguanidine (tBuTMG). A 2:1 stoichiometry of the adducts was proven by NMR and IR spectroscopy, and single crystal X-Ray diffraction; certain cleavage temperatures (70 and 160 °C) were measured. Thermal analysis (TG-MS) of adducts indicates the release of free isocyanate during adduct cleavage. Furthermore, a new class of step-growth oligomers (MN = 750–7,000 g∙mol–1) composed of multi-functional isocyanates and these imine bases was introduced. Their systematic spectroscopic and thermal analysis is shown revealing the similarity in their chemical properties to the 2:1 adducts. Radical homo- and copolymerization of acrylates is initiated by the meta-stable adducts and oligomers of this work; the generation of novel telomeric block-copolymer architectures composed of polyacrylate and oligourea building blocks is demonstratedDieser Beitrag ist aufgrund einer (DFG-geförderten) Allianz- bzw. Nationallizenz frei zugänglich
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Guillem, Parra Maite. "Desarrollo de nuevos agentes bloqueantes derivados de fuentes renovables para poliuretanos de aplicación en piel sintética y textil". Doctoral thesis, Universitat Rovira i Virgili, 2020. http://hdl.handle.net/10803/670933.
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La síntesi de poliuretans (PUs), basada en la reacció d'un isocianat i un alcohol o poliol, ofereix un ampli ventall de possibilitats que dona lloc a un gran nombre de materials amb diferents propietats. No obstant, el major inconvenient d'aquesta síntesi és l'elevada toxicitat dels isocianats, així com la seva reactivitat i sensibilitat a la humitat. Per solucionar-ho, aquesta tesi es centra en l'estudi de PUs amb grups isocianat bloquejats, de manera que l'agent bloquejant s'allibera a l'augmentar la temperatura i / o en presència de grups nucleòfils, deixant lliure el grup isocianat i possibilitant la posterior reacció amb aquests nucleòfils.
En aquest treball, s'ha estudiat l’ús d'agents bloquejants d'isocianats convencionals, com ara metil etil cetoxima (MEKO), 3,5-dimetilpirazol (3,5-DMP), diisopropilamina (DIPA), imidazol i ε-caprolactama. S'han sintetitzat PUs amb grups isocianat bloquejats amb els agents bloquejants nomenats per a dues aplicacions: "high solids" per pell sintètica i dispersions aquoses com a fixadors del color en tèxtil.
Un dels grans reptes de la societat actual és el desenvolupament sostenible, d'altra banda a nivell industrial tant la reducció de la contaminació com de la toxicitat dels materials emprats són de gran interès. La majoria dels agents bloquejants esmentats són tòxics, motiu pel qual en aquesta tesi s'ha estudiat la síntesi i la utilització de nous agents bloquejants: formiat de butil i les oximes de l'acetoacetat de metil, metil vinil cetona, derivats de l'àcid levulínic i de el piruvat de metil.
L'oxima de levulinato de metil és la que millors prestacions ha donat, per aquest motiu s'ha utilitzat per a la síntesi i aplicació dels PUs en les aplicacions esmentades. A causa dels bons resultats s'ha fet un estudi de toxicitat, s'ha optimitzat la seva síntesi per a l'escalat a planta pilot i s'ha patentat el seu ús.La síntesis de poliuretanos (PUs), basada en la reacción de un isocianato y un alcohol o poliol, ofrece un amplio abanico de posibilidades que da lugar a un gran número de materiales con diferentes propiedades. Sin embargo, el mayor inconveniente de esta síntesis es la elevada toxicidad de los isocianatos, así como su reactividad y sensibilidad a la humedad. Para solucionarlo, esta tesis se centra en el estudio de PUs con grupos isocianato bloqueados, de modo que el agente bloqueante se libera al aumentar la temperatura y/o en presencia de grupos nucleófilos, dejando libre el grupo isocianato y posibilitando su posterior reacción con dichos nucleófilos. En este trabajo, se ha estudiado el empleo de agentes bloqueantes de isocianatos convencionales, tales como metil etil cetoxima (MEKO), 3,5-dimetilpirazol (3,5-DMP), diisopropilamina (DIPA), imidazol y ε-caprolactama. Se han sintetizado PUs con grupos isocianato bloqueados con dichos agentes bloqueantes para dos aplicaciones: “high solids” para piel sintética y dispersiones acuosas como fijadores del color en textil. Uno de los grandes retos de la sociedad actual es el desarrollo sostenible y a nivel industrial tanto la reducción de la contaminación como de la toxicidad de los materiales empleados son de gran interés. La mayoría de los agentes bloqueantes mencionados son tóxicos, motivo por el cual en esta tesis se ha estudiado la síntesis y el empleo de nuevos agentes bloqueantes: formiato de butilo y las oximas del acetoacetato de metilo, metil vinil cetona, derivados del ácido levulínico y del piruvato de metilo. La oxima del levulinato de metilo es la que mejores prestaciones ha dado, por lo que se ha empleado para la síntesis y aplicación de los PUs en las aplicaciones mencionadas. Debido a los buenos resultados se ha hecho un estudio de toxicidad, se ha optimizado su síntesis para el escalado a planta piloto y se ha patentado su empleo.
The synthesis of polyurethanes (PUs), based on the reaction of an isocyanate and an alcohol or polyol, offers a wide range of possibilities that leads to a large number of materials with different properties. However, the main drawback of this synthesis is the high toxicity of the isocyanates, as well as their reactivity and sensitivity to humidity. To solve this, this thesis focuses on the study of PUs with blocked isocyanate groups, so that the blocking agent is released with increasing temperature and / or in the presence of nucleophilic groups, leaving the isocyanate group free and enabling its subsequent reaction with said nucleophiles. In this work, the use of conventional isocyanate blocking agents, such as methyl ethyl ketoxime (MEKO), 3,5-dimethylpyrazole (3,5-DMP), diisopropylamine (DIPA), imidazole and ε-caprolactam, has been studied. PUs with isocyanate groups blocked with said blocking agents have been synthesized for two applications: "high solids" for synthetic leather and aqueous dispersions as color fixatives in textiles. One of the great challenges of today's society is sustainability and at an industrial level, both the reduction of pollution and the toxicity of the materials used are of great interest. Most of the aforementioned blocking agents are toxic, which is the reason of studying the synthesis and use of new blocking agents: butyl formate and the oximes of methyl acetoacetate, methyl vinyl ketone, derivatives of levulinic acid and of methyl pyruvate. The oxime of methyl levulinate is the one that has given the best performance, so it has been used for the synthesis and application of PUs in the mentioned applications. Due to the good results, a toxicity study has been carried out, its synthesis has been optimized for scaling up to a pilot plant and its use has been patented.
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Polenz, Ingmar. "Neuartige Radikalische Polymerisation von Vinylmonomeren über eine Iminbase / Isocyanat-vermittelte Initiierung". Doctoral thesis, Universitätsbibliothek Chemnitz, 2012. http://nbn-resolving.de/urn:nbn:de:bsz:ch1-qucosa-84166.
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Gegenstand dieser Arbeit ist die Entwicklung einer neuartigen Initiierungsmethode zur Polymerisation von Vinylmonomeren über die Kombination von gewöhnlichen organischen Isocyanaten und Iminbasen. Der radikalische Charakter dieses Polymerisationstyps wurde durch Copolymerisationsexperimente verifiziert. Mit verschiedenen Iminbase / Isocyanat-Kombinationen als Initiatoren wurde die Homopolymerisation von diversen (Meth)-Acrylaten, Styrol, Acrylnitril und Methacrylnitril untersucht. Parameter, wie die Brutto-Polymerisationsgeschwindigkeitskonstante und die Aktivierungsenergie wurden ermittelt und Aussagen zur Polymerisation getroffen. Über die Auswertung von Massenspektren niedermolekularer Polymer-Proben wurden Vermutungen zum ablaufenden Initiierungsmechanismus abgeleitet. Das Anwendungspotential dieser Methode wurde in Hinblick auf die Synthese diverser Polymerarchitekturen untersucht. Neben der Oberflächenpolymerisation an funktionalisierten Kieselgel-Partikeln mittels „grafting-from“ wurden neuartige Block- und Kammpolymer-Strukturen hergestellt und analysiert. Zudem wurde die durch reine Iminbasen vermittelte Polymerisation von (Meth-)Acrylaten untersucht. Ferner wird der positive Einfluss der Zugabe katalytischer Mengen Ionischer Flüssigkeiten auf beide Systeme gezeigt und diskutiert.
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Hsieh, Ang-Zheng y 謝昂政. "Studies on Thermal Decomposition Reaction Kinetics of Blocked Isocyanate and Polyurethane Prepolymer". Thesis, 2017. http://ndltd.ncl.edu.tw/handle/28627674901586859725.
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碩士國立高雄應用科技大學
化學工程與材料工程系博碩士班
105
A series of blocked isocyanate and polyurethane prepolymers, based on 3,5-dimethylpyrazole and using Sodium Bisulfite as blocked agent were prepared, Blocked-isophorone diisocyanate and polyurethane prepolymer including polyethylene glycol were synthesized and characterized by Fourier transform infrared spectroscopy , respectively. The deblocked temperature of the blocked isocyanate and prepolymer was investigated using thermo-gravimetric analysis. Using differential scanning calorimetry analysis and Kissinger Equation and Crane Equation , the thermal decomposition reaction kinetics were studied. Blocked-polyurethane prepolymer at different molecular weight polyethylene glycol were synthesized. It was found that the deblocked temperature were at 86.5℃ and 82.7℃, respectively. The calculated activation energy were 944.5 and 1830.7 kJ/mol, respectively. The reaction order were 0.83 and 0.88, respectively. With the increasing molecular weight of polyethylene glycol, deblocked temperature, activation energy and reaction order decreased. All of the blocked polyurethane prepolymer decomposing order was not an exact integer because of the presence of side reactions of isocyanate. The water soluble blocked polyurethane prepolymer present in the polymerization of polyaniline was used as the curing agent of epoxy resin.
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Wu, Yio Don y 吳友棟. "Study on blocked isocyanate modified epoxy cured with amine and the toughness of the modified system with polyol". Thesis, 1995. http://ndltd.ncl.edu.tw/handle/32884590878132101814.
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Polenz, Ingmar. "Neuartige Radikalische Polymerisation von Vinylmonomeren über eine Iminbase / Isocyanat-vermittelte Initiierung". Doctoral thesis, 2011. https://monarch.qucosa.de/id/qucosa%3A19676.
Texto completoResumen
Gegenstand dieser Arbeit ist die Entwicklung einer neuartigen Initiierungsmethode zur Polymerisation von Vinylmonomeren über die Kombination von gewöhnlichen organischen Isocyanaten und Iminbasen. Der radikalische Charakter dieses Polymerisationstyps wurde durch Copolymerisationsexperimente verifiziert. Mit verschiedenen Iminbase / Isocyanat-Kombinationen als Initiatoren wurde die Homopolymerisation von diversen (Meth)-Acrylaten, Styrol, Acrylnitril und Methacrylnitril untersucht. Parameter, wie die Brutto-Polymerisationsgeschwindigkeitskonstante und die Aktivierungsenergie wurden ermittelt und Aussagen zur Polymerisation getroffen. Über die Auswertung von Massenspektren niedermolekularer Polymer-Proben wurden Vermutungen zum ablaufenden Initiierungsmechanismus abgeleitet. Das Anwendungspotential dieser Methode wurde in Hinblick auf die Synthese diverser Polymerarchitekturen untersucht. Neben der Oberflächenpolymerisation an funktionalisierten Kieselgel-Partikeln mittels „grafting-from“ wurden neuartige Block- und Kammpolymer-Strukturen hergestellt und analysiert. Zudem wurde die durch reine Iminbasen vermittelte Polymerisation von (Meth-)Acrylaten untersucht. Ferner wird der positive Einfluss der Zugabe katalytischer Mengen Ionischer Flüssigkeiten auf beide Systeme gezeigt und diskutiert.:ABKÜRZUNGSVERZEICHNIS 6
1 EINLEITUNG UND AUFGABENSTELLUNG 10
1.1 Einleitung 10
1.2 Motivation und Zielsetzung 13
2 ALLGEMEINER TEIL UND THEORETISCHE GRUNDLAGEN 15
2.1 Grundlagen der freien radikalischen Polymerisation 15
2.2 Atom Transfer Radical Polymerization (ATRP), Reversible Addition-Fragmentation Chain Transfer Polymerization (RAFT) und Nitroxide Mediated Radical Polymerization (NMP) als Beispiele für kontrollierte radikalische Polymerisationen 25
2.3 Theorie zur Copolymerisation von Vinylmonomeren 34
2.4 Applikation von Ionischen Flüssigkeiten bei der radikalischen Polymerisation 43
3 ERGEBNISSE UND DISKUSSION 49
3.1 Iminbase/Isocyanat-vermittelte (IBI) Polymerisation von Vinylmonomeren 49
3.1.1 Empirische Befunde und Klassifizierung der IBI-Systeme 50
3.1.2 Ergebnisse zu den IBI-Polymerisationen mit unmittelbarem Verbrauch der Initiator- Komponenten (Typ A) 58
3.1.3 Verwendung der Iminbase–Isocyanat-Addukte zur Polymerisation von MMA 70
3.1.4 Ergebnisse der Polymerisationen mit Typ B IBI-Kombinationen 78
3.1.5 Bestimmung und Auswertung kinetischer Parameter der IBI-Polymerisation 85
3.1.6 Studien zum Initiierungsmechanismus durch die Iminbase/Isocyanat-Kombination 102
3.2 Iminbasen-(Meth-)Acrylat-induzierte (IBA) Polymerisation 124
3.2.1 Phänomenologische Untersuchungen zur IBA-Polymerisation 124
3.2.2 Kinetik der IBA-Polymerisation und mechanistische Studien 129
3.3 Beschleunigung beider Polymerisationstypen über die Zugabe katalytischer Mengen Ionischer Flüssigkeit 143
3.3.1 Untersuchungen zur Wechselwirkung von Ionischen Flüssigkeit mit den Reaktanden mit Hilfe der ATR-FT-MIR-Spektroskopie 144
3.3.2 Ergebnisse zu den IL-katalysierten IBI-Polymerisationen 151
3.3.3 Ergebnisse zu den IL-katalysierten IBA-Polymerisationen 162
3.4 Applikation der neuartigen Polymerisationssysteme zur Blockcopolymerisation 171
3.4.1 Oberflächenpolymerisation an Siliziumdioxid-Partikeln 172
3.4.2 Blockcopolymer-Synthese mit Typ A IBI-Oligomeren 186
3.4.3 Kammpolymer-Synthese über die Anwendung der IBI- bzw. IBA-Methode 192
4 ZUSAMMENFASSUNG UND AUSBLICK 200
5 EXPERIMENTELLER TEIL 208
5.1 Verwendete Geräte 208
5.2 Verwendete Chemikalien 210
5.3 Details zur Berechnung der Copolymerisationsparameter, Beladungen und Pfropfgrade 210
5.4 Synthesen und Polymerisationen 213
5.4.1 Allgemeine Vorgehensweise und Ergebnisse bei den Homo- und Copolymerisationen 213
5.4.2 Synthese der Iminbase–Isocyanat Addukte 222
5.4.3 Synthese der funktionalisierten Siliziumdioxid-Partikel und deren
Oberflächenpolymerisation 236
5.4.4 Abspaltung von kovalent gebundenem PMMA mittels Dimethylsulfat / NaOCH3 242
5.4.5 Vorgehensweise bei der Verwendung der Spritzenpumpen-Apparatur 246
5.4.6 Synthese und Charakterisierung der organischen Blockcopolymere 247
6 LITERATURVERZEICHNIS 253
7 ANHANG 264
7.1 Kristallographische Daten zu den ermittelten Strukturen 264
7.2 Weiterführende Details zu den durchgeführten Konzentrations-Zeit-Beziehungen 278
7.2.1 Iminbase / Isocyanat-vermittelte (IBI) Polymerisation 278
7.2.2 Iminbase-(Meth-)Acrylat-vermittelte (IBA) Polymerisation 302
7.3 Fineman und Ross Beziehungen und Copolymerisationsdiagramme 314
7.4 Nachtrag zu den konzentrationsbezogenen IR-Messungen 322
DANKSAGUNG 324
SELBSTÄNDIGKEITSERKLÄRUNG 327
LEBENSLAUF 328
LISTE AN VERÖFFENTLICHUNGEN 329
Capítulos de libros sobre el tema "Blocked isocyanates"
1
Carlson, G. M., C. M. Neag, C. Kuo y T. Provder. "FT-IR and Thermal-Mechanical Cure Characterization of Blocked Isocyanate Containing Coatings". En Fourier Transform Infrared Characterization of Polymers, 197–212. Boston, MA: Springer US, 1987. http://dx.doi.org/10.1007/978-1-4684-7776-4_9.
Texto completoActas de conferencias sobre el tema "Blocked isocyanates"
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Briggs, Rodney L. "The Use of Blocked Isocyanates in Automotive OEM Clearcoats". En International Congress & Exposition. 400 Commonwealth Drive, Warrendale, PA, United States: SAE International, 1995. http://dx.doi.org/10.4271/950800.
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Mohd Shafian, Siti Rohaida, Abd Azim Bin Hassan, Suzylawati Ismail, Ling Kong Teng y Sonny Irawan. "Blocked Isocyanate Fluid System for Water Shut Off Application". En IADC/SPE Asia Pacific Drilling Technology Conference and Exhibition. Society of Petroleum Engineers, 2010. http://dx.doi.org/10.2118/132813-ms.
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Holzworth, Kristin, Gregory Williams, Bedri Arman, Zhibin Guan, Gaurav Arya y Sia Nemat-Nasser. "Polyurea With Hybrid Polymer Grafted Nanoparticles: A Parametric Study". En ASME 2012 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/imece2012-88395.
Texto completoResumen
The basis of this research is to mitigate shock through material design. In this work, we seek to develop an understanding of parametric variations in polyurea-based nano-composite materials through experimental characterization and computational modeling. Blast-mitigating applications often utilize polyurea due to its excellent thermo-mechanical properties. Polyurea is a microphase-separated segmented block copolymer formed by the rapid reaction of an isocyanate component and an amine component. Block copolymers exhibit unique properties as a result of their phase-separated morphology, which restricts dissimilar block components to microscopic length scales. The soft segments form a continuous matrix reinforced by the hard segments that are randomly dispersed as microdomains. The physical properties of the separate phases influence the overall properties of the polyurea. While polyurea offers a useful starting point, control over crystallite size and morphology is limited. For compositing, the blending approach allows superb control of particle size, shape, and density; however, the hard/soft interface is typically weak for simple blends. Here, we overcome this issue by developing hybrid polymer grafted nanoparticles, which have adjustable exposed functionality to control both their spatial distribution and interface. These nano-particles have tethered polymer chains that can interact with their surrounding environment and provide a method to control well defined and enhanced nano-composites. This approach allows us to adjust a number of variables related to the hybrid polymer grafted nanoparticles including: core size and shape, core material, polymer chain length, polymer chain density, and monomer type. In this work, we embark on a parametric study focusing on the effect of silica nanoparticle size, polymer chain length, and polymer chain density. Preliminary results from experimental characterization and computational modeling indicate that the dynamic mechanical properties of the material can be significantly altered through such parametric modifications. These efforts are part of an ongoing initiative to develop elastomeric composites with optimally designed compositions and characteristics to manage blast-induced stress-wave energy.