ORGANOSILICIC CHEMISTRY

Author: MERCADO ROCA LUIS ADOLFO.
Year: 2005.
University: ROVIRA I VIRGILI.
Place of defense: FACULTAT DE QUIMICA.
Place of preparation: FACULTAT DE QUIMICA.

Summary: Epoxy resins are widely used in welding, coatings, adhesives and composite materials. In some applications require epoxy resins and versatile special functions, such as high commitment to the substrates, low shrinkage, under heat stress after curing, good toughness, low flammability, and good chemical resistance. The flammability of epoxy resins is one of the major drawbacks in its implementation because, as any organic polymer, are inherently fuels and in the presence of a heat source and oxygen are burned easily and quickly. Therefore, some flame retardant on the fire, such as brominated compounds, oxides of antimony compounds fósforo-halogenados, etc.. They are embedded in epoxy resins to reduce its flammability. These compounds are exceptionally effective but have the disadvantage that increase the quantities of smoke and decomposition products toxic and corrosive arising during combustion of the polymer. For this series of disadvantages at present has increased research into other heteroatoms such as the flame retardants to replace halogen. In recent years have described some approximations on epoxy resins together with silicon covalentemente the polymer matrix. They have been described modifications on commercial epoxy resins and copolimerizaciones of glycidyl monomers containing silicon with epoxy resins business, thereby improving the properties of the flame retardants without sacrificing mechanical properties of the cured resin. This work has arisen as a general objective the development of epoxy resins based on silicon with flame retardant properties to the flame. It has conducted the synthesis of silicon-containing monomers glycidyl in its structure. To establish a relationship between the presence and ratio of silicon and the physical properties of the resulting materials have been prepared from polymers thermostable mixtures of a glycidyl commercial monomers containing silicon and prepolymers obtained via reactions growth chain between DGEBA and silanodiol. There have also been synthesized monomers and curing agents that contain phosphorus in their structure and are prepared thermostable polymers containing both heteroatoms. To study the mechanism of reaction of monomers containing silicon with primary amines, has synthesized a monomer sililado monofuncional, fenilglicidiloxidimetilsilano (GDMPS), and has compared its reactivity against a primary amine, aniline, with a commercial glycidyl , fenilglicidiléter (GEA). The kinetic study was carried out by NIR and applied to the data obtained spectral analysis methods multivariate curve resolution (MCR-ALS). It has conducted the study kinetic curing a diglicidilo containing silicon, fenildiglicidiloximetilsilano (DGPMS), and mixtures thereof with DGEBA with a diamina primary, DBM, Insulated by DSC and dynamic. There have also been studied phenomena gelificacion and vitrification of these systems using DMTA mode shear and TMDSC. We have prepared thermostable polymers have been evaluated their properties termodinamomecánicas, thermal and retardancia the flame. The properties termodinamomecánicas have been estu 8 diadas m a5d ediante DMTA mode bending. The thermal stability of these compounds have been studied by thermogravimetric analysis atmosphere of nitrogen and air. The properties of retardancia the calls were evaluated by the test ASTM-D-2683 of limiting oxygen index (LOI). Finally, we have studied the thermal degradation of polymers obtained to establish the mode of operation of the silicon during degradation. To do so, the study of kinetic degradation from data obtained by TGA, studies of the initial stages of degradation through quimioluminiscencia (QL) and the characterization of the products formed by TGA-MS, GC-MS, ATR- FTIR and XRD. The results obtained have been able to establish the following findings: (1) It has been determined that the presence of silicon produce an increase in the reactivity of epoxide probably due to electronic effects. This increased reactivity also reduces the importance of the road autocatalítico in cured with primary amines. (2) The epoxy resins sililadas thermostable show a decrease in Tg and the density of intersecting with the increase in the percentage of silicon. This decline is related to an increase in volume due to the greater self-length links Si-O. (3) The thermostable polymers containing silicon show an increase of LOI from a silicon content of 3%. In polymers containing phosphorus and silicon, were found evidence of the existence of synergy between the two heteroatoms. (4) The degradation of polymers containing silicon, both in an inert atmosphere as an oxidant, involves the formation of cyclic oligomers of fenilmetilsiloxano, implying that part of the silicon abandons condensed phase. The residue contains silicon as SiO2, probably forming an insulating layer which acts as a barrier to heat and mass transfer thereby reducing the production of volatile.