Curing and morphology of epoxy resin-silica hybrids

Abstract

Hybrids of epoxy resin and silica cured respectively with methyl nadic anhydride (MNA) and 4,4′-diaminodiphenyl sulfone (DDS) were prepared. Control of the morphology was achieved through functionalisation of a diglycidyl ether resin respectively with monofunctional and difunctional secondary amine trialkoxysilanes prior to being mixed with a solution of tetraethoxysilane (TEOS) and hardener. Scanning and transmission electron microscopy examinations (SEM and TEM) were carried out to study the morphology of the samples. The results have shown that the preparation conditions and nature of solvent play a vital role in the compatibilisation of the final hybrid. The addition of a hydrolysed TEOS solution into the epoxy resin to produce the corresponding hybrid was found to interfere with the cross-linking reactions with the hardener, inevitably resulting in a reduction in the T_g of the epoxy resin component. This was attributed to side reactions of MNA with the ethanol released from hydrolysis and condensation of the TEOS, producing monofunctional and difunctional esters which act as plasticisers and to decreased functionality of the epoxy resin from the reaction with the HCl used for the hydrolysis of TEOS.

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