GLASS-TRANSITION BEHAVIOR OF POLYPROPYLENE POLYSTYRENE/STYRENE-ETHYLENE-PROPYLENE BLOCK-COPOLYMER BLENDS/

The glass transition behavior of ternary blends of polypropylene (PP), polystyrene (PS) and styrene-ethylene-propyl ene-styrene block copoly mer (S EP S) was investigated. The blends were prepared by an internal mixer, and their dynamic mechanical properties and morphology were me asured. The blends showed phase inversion at around 75wt% PS compositi on. The glass transition temperature (Tg) of the PP phase shifted to l ower temperature as the PS contents were increased in PP/PS binary ble nds, probably due to the mismatch of thermal expansion coefficients be tween two components. As the SEPS copolymer contents were increased, t he Tg's of the PP phase in the blends increased. In particular, the la rge increase in Tg of the PP phase was observed in the PP/PS (25/75) b lends where the phase inversion takes place.