Interfacial effects produced by crystallization of polypropylene with polypropylene‐ g ‐maleic anhydride compatibilitzers

Two anydride‐grafted isotactic polypropylene (PP) compatibilizers, HAC or high‐anydride compatibilizer (2.7 wt % grafted maleic anhydride) and LAC or low‐anydride compatibilizer (0.2 wt % anydride), were compared in PP‐rich blends with polyamide‐66 (25 wt %). A previous article demonstrated that LAC imparted a much higher fracture strain than did HAC at similar anydride concentrations. The present study shows that LAC is capable of cocrystallization with PP. HAC does not cocrystallize, but crystallizes as a second phase in binary PP/HAC blends studied by DSC and hot‐stage microscopy. A cocrystallization model is proposed to explain the higher fracture strain of PP/LAC/PA blends. A. separate phase crystallization model is proposed for PP/HAC/PA blends. The models are supported by peel tests, which demonstrate greater adhesion of PP with LAC than with HAC. © 1994 John Wiley & Sons, Inc.