Fracture mechanisms in preformed polyphenylene oxide particle-modified bismaleimide resins

Fracture toughness and failure mechanisms in preformed poly(2,6-dimethyl-1, 4-phenylene oxide) (PPO) particle-modified bismaleimide (BMI) systems are i nvestigated. The fracture toughness of BMI can be significantly improved by incorporating preformed PPO particles without causing significant deterior ation in other mechanical and thermal properties. The fracture mechanisms i n BMI/PPO appear to be dominated by craze-like damage. Further investigatio n of the craze-like damage zone using transmission electron microscopy reve als that crazes are formed inside the PPO particle phase and dilatation ban ds, which appear to be triggered by the crazes inside the PPO particle, are formed in the BMI matrix. Particle bridging is also found to contribute to the toughening of BMI/PPO. The benefits of using preformed PPO particles t o toughen BMI and other brittle thermosets for composite and adhesive appli cations are discussed. (C) 1999 John Wiley & Sons, Inc.