Visualization of the morphology at the interphase of glass fibre reinforced epoxy-thermoplastic polymer composites

This work deals with the effect that the use of glass fibres has on the morphology developed by a thermoplastic polymer modified epoxy. In particular, three surface modifications of the glass fibres were studied: calcinations desizing, activation with hydrochloric acid and coating with 3-aminopropyltriethoxy silane. As the epoxy polymer, a model system based on the full reaction of DGEBA and 2-methyl-1,5-diaminopentane was used. As the modifiers of the epoxy thermoset, two thermoplastic polymers were used: poly(methylmethacrylate) and polystyrene. The morphologies were examined either in the polymer bulk or at the interfaces by means of scanning electron microscopy and atomic force microscopy. After a thoroughly examination of the samples it was found that the thermoplastic polymers preferentially accumulate at the interfaces of these materials when activated and silanized glass fibres are used. These results might be attributed to a gradual phase separation process due to stoichiometric gradients which, on the other hand, seems to be conditioned by the nature of glass fibres surface.