Curing of epoxy/novolac system modified with reactive liquid rubber and carbon filler

Abstract

The curing behaviour of epoxy resins modified with reactive liquid rubber, using a novolac resin as a hardner was studied by means of differential scanning calorimetry in isothermal (100, 130 and 150 °C) and non-isothermal conditions (2, 5, 10 and 15 °C min-1). The influence of carboxyl- (CTBN) and epoxy- (ETBN) terminated butadiene-acrylonitrile copolymers on the kinetic parameters and glass transition temperature (Tg) of cured epoxy systems was determined. The effect of grinded bituminous coal as an organic filler into epoxy network was also investigated. The carboxyl-end groups strongly enhanced the curing rate, in contrast to the epoxy-terminated rubber (ETBN) that had only a minor effect on the curing reactions. The presence of coal accelerated curing in its early stage. The Tg of completely cured epoxy was practically unaffected by the presence of carbon filler and reactive rubbers and was equal about 132 °C. The apparent curing activation energies were determined. A smaller activation energy was observed only for CTBN/epoxy/novolac system. The effect of reactive rubber and coal on the Charpy impact resistance of cured epoxy systems was also discussed.