MECHANICAL-PROPERTIES AND THERMAL AGING OF A PERFLUOROETHER-MODIFIED EPOXY-RESIN IN CASTINGS AND GLASS-FIBER COMPOSITES

Castings from a bisphenol epoxy resin cured with methyl nadic anhydrid e, and containing varying amounts of a miscibilized carboxy-terminated perfluoroether oligomer (CTMF), were produced in such a manner as to display two different morphologies: one consisting of fine heterophase interpenetrating networks (IPNs) and the other comprising precipitate d dispersed particles. High-temperature accelerated ageing showed that compositions containing 15% CTMF exhibit higher flexural strength and ductility than unmodified resins, irrespective of the type of morphol ogy. Castings of CTMF-modified resin with an IPN morphology, however, displayed superior property retention characteristics with respect to thermal ageing and consequently were chosen as the matrix for the prod uction of unidirectional fibre composites. The composites, on the othe r hand, were found not to exhibit the same improvements in heat ageing resistance as the castings. The cause has not been established but th e increase in peak tan delta temperature over that exhibited by the ca stings suggests that the matrix is more highly crosslinked.