Toughening of polypropylene with styrene/ethylene- Butylene/Styrene tri-block copolymer: Effects of mixing condition and elastomer content

The effect of processing conditions and elastomer content on the toughening of Polypropylene (PP) by melt blending with styrene/ethylene-butylene/styr ene tri-block copolymer (SEBS) in a twin-screw extruder has been investigat ed. The parameters analyzed were: temperature profile, screw speed, and fee d rate of the blend components. Their effect was evaluated through the mech anical properties (tensile strength and Izod impact resistance at room temp erature) as well as the morphology of the dispersed phase by means of scann ing electron microscopy (SEM). The results showed that the impact resistanc e increases with increasing rotor speed and feed rate and decreases when th e temperature profile is increased. The parameter with the greatest effect on the mechanical properties was the variation in rotor speed. Despite the fact that impact resistance as high as 25 times that of neat PP has been ac hieved with blends containing 20 wt % SEBS, no significant modification in phase morphology has been observed. (C) 2001 John Wiley & Sons, Inc.