Polysulfone and poly(phenylene sulfide) blends. III: Rubber toughening

Melt-blended polysulfone (PSF) and poly(phenylene sulfide) (PPS) are notch sensitive. A significant improvement in the notched Izod impact toughness occurs when at least 10 wt.% of a shell-core rubber modifier (Paraloid EXL 3607 MBS, Stereon 840A butadiene--styrene multi-block copolymer, Kraton D1101 styrene--butadiene--styrene bloc copolymer) is incorporated into the blend. At rubber modifier levels > 15 wt.%, the notched Izod impact strength was essentially retained upon annealing at 160 deg C for 2 h, while < 15 wt.% of rubber modifier, the notched Izod impact strength decreases after annealing under the same conditions. Izod impact fracture surface morphology was studied using scanning electron microscopy (SEM). Fracture surfaces without a rubber modifier exhibit cavitation around the dispersed phase, i.e. PPS. On the other hand, fracture surface morphology of the rubber toughened blends with the same PSF/PPS composition show no cavitation surrounding the dispersed phase. Blend morphology was also studied using transmission electron microscopy (TEM).