Publication: Termoestables híbridos organo-inorgánicos: síntesis, caracterización y propiedades
Loading...
Identifiers
Publication date
2003
Defense date
2003-11-17
Authors
Tutors
Journal Title
Journal ISSN
Volume Title
Publisher
Abstract
Se han preparado varios poliorganosiloxanos basados en el poli(3-aminopropilmetilsiloxano) (PAMS), mediante hidrólisis y condensación del monómero3-aminopropilmetildietoxisilano (APDES). La modificación de su funcionalidad se hallevado a cabo por reacción con pequeñas cantidades de fenilglicidil éter (PGE),formando aductos PAMS:PGE. Se ha analizado la miscibilidad de los polisiloxanossintetizados con una resma epoxídica base, el diglicidil éter del bisfenol-A (DGEBA).Las mezclas resultantes son inmiscibles inicialmente, aunque el avance de la reacciónepoxi/amina provoca su homogeneización parcial.Se ha estudiado el curado de los diferentes endurecedores poliaminosiloxánicos, PAMSy PAMS:PGE, con DGEBA. Se ha analizado el efecto que ejerce la presencia de gruposamina secundarios en la mezcla inicial, así como la influencia de la concentracióninicial de grupos hidroxilo, capaces de catalizar la reacción epoxi/amina. La reacción seajusta a un modelo autocatalítico, presentando una autoaceleración a relativas bajasconversiones. Al aumentar la proporción de aminas secundarias en la mezcla inicial, lareacción no-catalizada pierde importancia respecto a la autocatalizada. Por otra parte, elcalor de reacción y la energía de activación obtenidos son comparables a los reportadospara el curado de resinas epoxi con diaminas convencionales.Mediante diversas técnicas microscópicas, se ha analizado la morfología de los sistemascurados, observándose cierto grado de heterogeneidad composicional provocado por lainmiscibilidad inicial de los componentes. Se han encontrado “pseudodominios” ricosen silano distribuidos homogéneamente por la matriz epoxi. Dichos dominios estánconstituidos por gradientes de concentración en forma de capas concéntricas. Se hacomprobado que dicha heterogeneidad afecta a las propiedades mecánicas y quedisminuye a medida que aumenta el grado de entrecruzamiento.También se ha estudiado la capacidad de absorción de agua de la resmaDGEBA/PAMS. La máxima cantidad de agua absorbida es del 3% en peso. Se hapropuesto un nuevo procedimiento para el estudio del hinchamiento producido por laentrada de agua a través de n-FTIR. ------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Several polyorganosiloxanes were prepared. The synthesis of poly(3-aminopropylmethylsiloxane) (PAMS) was carried out by hydrolysis and condensation of 3-aminopropyl methyldiethoxysilane monomer (APDES). The ftinctionality modificationof PAMS was done by subsequent reaction with phenylglycidyl ether (PGE), formingPAMS:PGE adducts. The miscibility of the synthesised polysiloxanes with an epoxyresin, bisphenol A diglycidyl ether (DGEBA) was analysed. The initial mixtures areinmiscible, but the epoxy/amine reaction induces a partial compatibilisation.The curing reaction of DGEBA with the different polysiloxane hardeners, PAMS orPAMS:PGE, was studied. The influence of initial hydroxyl groups concentration, ableto catalyse the epoxy/amine reaction, and also, the presence of secondary amines in theinitial mixture, were analysed. Reaction foliows an autocatalytic model, showingautoacceleration at low conversion. When the secondary amine and hydroxyl groupsconcentrations are high in the initial mixture, the curing process occurs mainly by thecatalytic reaction. The non-catalytic path becomes almost negligible. The obtainedreaction heat and activation energy are similar to the reported for DGEBA curing withconventional diamines.The morphology of the cured products has been analysed by severa! microscopytechniques. A compositional heterogeneity was observed, caused by the initialinmiscibility of the components. The siloxane is concentrated in “pseudodomains”distributed homogeneous!y in the epoxy matrix. Concentric layers of gradientconcentration constitute these domains. This heterogeneity affects to the mechanicalproperties and decreases with crosslinking degree.Water absorption capacity of DGEBAIPAMS system has been also studied. Themaximum water absorption is 3% w/w. A novel procedure has been proposed forstudying the swelling phenomena by n-FTIR.
Several polyorganosiloxanes were prepared. The synthesis of poly(3-aminopropylmethylsiloxane) (PAMS) was carried out by hydrolysis and condensation of 3-aminopropyl methyldiethoxysilane monomer (APDES). The ftinctionality modificationof PAMS was done by subsequent reaction with phenylglycidyl ether (PGE), formingPAMS:PGE adducts. The miscibility of the synthesised polysiloxanes with an epoxyresin, bisphenol A diglycidyl ether (DGEBA) was analysed. The initial mixtures areinmiscible, but the epoxy/amine reaction induces a partial compatibilisation.The curing reaction of DGEBA with the different polysiloxane hardeners, PAMS orPAMS:PGE, was studied. The influence of initial hydroxyl groups concentration, ableto catalyse the epoxy/amine reaction, and also, the presence of secondary amines in theinitial mixture, were analysed. Reaction foliows an autocatalytic model, showingautoacceleration at low conversion. When the secondary amine and hydroxyl groupsconcentrations are high in the initial mixture, the curing process occurs mainly by thecatalytic reaction. The non-catalytic path becomes almost negligible. The obtainedreaction heat and activation energy are similar to the reported for DGEBA curing withconventional diamines.The morphology of the cured products has been analysed by severa! microscopytechniques. A compositional heterogeneity was observed, caused by the initialinmiscibility of the components. The siloxane is concentrated in “pseudodomains”distributed homogeneous!y in the epoxy matrix. Concentric layers of gradientconcentration constitute these domains. This heterogeneity affects to the mechanicalproperties and decreases with crosslinking degree.Water absorption capacity of DGEBAIPAMS system has been also studied. Themaximum water absorption is 3% w/w. A novel procedure has been proposed forstudying the swelling phenomena by n-FTIR.
Description
Keywords
Gomas y resinas, Polímeros