EFFECT OF THE MIXING PROCEDURE ON THE MORPHOLOGY AND PROPERTIES OF COMPATIBILIZED POLYPROPYLENE POLYAMIDE BLENDS/

Blends containing equal amounts of polypropylene (PP) and polycaprolac tam (PA6) were prepared by extrusion mixing, using 5% by weight of ck- poly(ethylene-stat-butylene)-block-polystyrene, modified by grafting w ith maleic anhydride (SEBS-MA), as the compatibilizer precursor. The b lends were obtained using three mixing procedures, representing differ ent ways of introducing the compatibilizer. The blends were prepared b y (A) one-step mixing of the three components, (B) mixing a preblend o f SEBS-MA and PP with PA6, and (C) mixing a preblend of SEBS-MA and ab out one-third of the total amount of PA6 with PP and the rest of the P A6. All of the blends contained dispersed PA6 domains, surrounded by a separate interphase of the self-assembling compatibilizing polymer. T he morphology of blends A and B were similar and markedly different fr om that of blend C, which contained dispersed phase domains of two cle arly distinguishable populations. Impact strength and elongation at br eak were lowest for C. The poor performance of blend C is due to the f act that a considerable fraction of the compatibilizer ended up in sma ll, well dispersed phase domains with a high weight ratio of compatibi lizer to PA6. (C) 1998 Elsevier Science Ltd. All rights reserved.