Modification of bismaleimide resin by poly(ethylene phthalate-co-ethylene terephthalate), poly(ethylene phthalate-co-ethylene 4,4 '-biphenyl dicarboxylate), and poly(ethylene phthalate-co-ethylene 2,6-naphthalene dicarboxylate)

Aromatic polyesters were prepared and used to improve the brittleness of bi smaleimide resin, composed of 4,4 ' -bismaleimidodiphenyl methane and o,o ' -diallyl bisphenol A (Matrimid 5292 A/B resin). The aromatic polyesters in cluded PEPT [poly(ethylene phthalate-co-ethylene terephthalate)], with 50 m ol % of terephthalate, PEPB [poly(ethylene phthalate-co-ethylene 4,4 ' -bip henyl dicarboxylate)], with 50 mol % of 4,4 ' -biphenyl dicarboxylate, and PEPN [poly(ethylene phthalate-co-ethylene 2,6-naphthalene dicarboxylate)], with 50 mol % 2,6-naphthalene dicarboxylate unit. The polyesters were effec tive modifiers for improving the brittleness of the bismaleimide resin. For example, inclusion of 15 wt % PEPT (MW = 9300) led to a 75% increase in fr acture toughness, with retention in flexural properties and a slight loss o f the glass-transition temperature, compared with the mechanical and therma l properties of the unmodified cured bismaleimide resin. Microstructures of the modified resins were examined by scanning electron microscopy and dyna mic viscoelastic analysis. The toughening mechanism was assessed as it rela ted to the morphological and dynamic viscoelastic behaviors of the modified bismaleimide resin system. (C) 2001 John Wiley & Sons, Inc. J Appl Polym S ci 81: 2352-2367, 2001.