Preparation of polypropylene/acrylonitrile-styrene copolymer alloys by one-step reactive blending

The compatibilization of polypropylene/acrylonitrile-styrene (PP/AS) blends through the addition of peroxide (DCP) was investigated in this study. The grafting reaction between PP and AS with the addition of peroxide occurred during the reactive-blending process. The in situ-formed grafting copolyme rs of PP-g-AS and AS-g-PP were then characterized by FTIR. The optimum conc entration of the initiator, DCP, was 0.2 wt %, and the reaction temperature should be above 195 degreesC. It was found that, when AS was the major com ponent of the blends, the grafting of AS onto PP was the main process; conv ersely, when PP was the major component, PP was grafted onto AS. These resu lts can be explained by the main-chain scission of PP during the reactive-b lending process. With increase of the AS component, the total degree of gra fting increased at first and then decreased after the composition of the bl ends reached 50/50. The maximum degree of grafting was found to be 6 wt % f or the 50/50 PP/AS/DCP blend. PP was more degradable than was AS in the pre sence of peroxide at high temperatures. The MFR values of the PP/AS/DCP ble nds were slightly greater than were those of the simple PP/AS blends, which means that blending is an effective way to protect PP from degradation. SE M micrographs of the cross section of PP/AS/ DCP showed a fine dispersion a nd a smaller domain size of the dispersed-phase particles, implying that th e in situ-formed grafting copolymers act as a compatibilizer to reduce the interfacial tension between the PP and AS phases. (C) 2001 John Wiley & Son s, Inc.