Properties of epoxy resin cured by phenol novolac/4-hydroxyphenylmaleimide polymer blend hardeners

Phenol novolac/4-hydroxyphenylmaleimide (HPMI) homopolymer (PHPMI) blends or phenol novolac/HPMI-styrene copolymer (HPMI-St) blends were used as the hardener of epoxy resins. Curing behaviour of the above systems and thermal and mechanical properties of the cured epoxy resins were studied. It was not necessary to use a curing accelerator for this system because PHPMI or HPMI-St had an accelerating effect on the curing reaction. Curing behaviour was investigated by measurement of gelation time(JIS K 6910) and differential scanning calorimetry thermogram (JIS K 7122). Test pieces made from neat resins and from reinforced resins with glass fibre or fused silica were evaluated in terms of thermal and mechanical properties, respectively. It was found that the heat resistance and the mechanical properties improved with increase of PHPMI or HPMI-St content in the hardener.