FRACTURE TOUGHENING BEHAVIOR AND MECHANICAL-PROPERTIES OF POLYPHENYLENE OXIDE HIGH-IMPACT POLYSTYRENE BLENDS/

Blends of a poly(phenylene oxide) (PPO) with high-impact polystyrene ( HIPS) were injection molded. The static mechanical properties and frac ture toughness of the blends were determined by means of the uniaxial tension, Brinell hardness and three-point-bending measurements, From t he static mechanical test results, it was shown that the yield strengt h, Young's modulus and hardness values oi the PPO/ HIPS blends were co nsiderably higher than those of their PPO and HIPS component polymers, Dynamic mechanical measurements indicated that the PPO/HIPS blends ap pear to be miscible as shown by the existence of a single grass transi tion temperature. Furthermore, the J integral method based on ASTM E81 3-89 procedure was used to characterize the fracture toughness of PPO/ HIPS blends. The J integral analysis indicated that the PPO specimen e xhibited the lowest fracture toughness (J(c)), The PPO containing 50 w t% HIPS blend had the highest J(c). SEM observations revealed that the crack growth zone of the pure PFO is relatively smooth. However, cavi tation of the elastomeric particles and shear band formation were obse rved in the deformed zones ahead of the crack tip of the PPO with 50 w t% HIPS blend. The cavitation and shear band formation mould dissipate bulk strain energy and their formation was responsible for the highes t J,value observed in this blend.