RHEOLOGICAL PROPERTIES, CRYSTALLIZATION, AND MORPHOLOGY OF COMPATIBILIZED BLENDS OF ISOTACTIC POLYPROPYLENE AND POLYAMIDE

Blends of isotactic polypropylene (iPP) with the polyamide nylon-6 (N6 ), prepared by extrusion, were studied with a composition of up to 30% by weight polyamide. In the case of a 70/30 iPP/N6 blend, the influen ce of a compatibilizing agent based on polypropylene functionalized wi th maleic anhydride (PP-g-MA), with compositions of 1, 3, 5, and 10% b y weight in polypropylene, was followed. The influence of the concentr ation of N6 and the compatibilizing agent on the rheological and therm al properties, and the morphology of the blends, was analyzed by monit oring the melt viscosity at different shear rates, differential scanni ng calorimetry, and polarized light microscopy. Vibrational spectrosco py was used to characterize the blends and to study the effect of the compatibilizing agent. The viscosity-composition curves for the iPP/N6 blends, in the composition and shear rate ranges analyzed, show a neg ative deviation from the additive rule, while the opposite trend is ob served for the blends compatibilized with PP-g-MA. Important variation s in the spectroscopic behavior was observed between compatibilized an d noncompatibilized blends, which varied as a function of the compatib ilizing agent concentration. The crystallization rates of iPP in the i PP/N6 blends, under both dynamic and isothermal conditions, are much g reater than are those observed for pure iPP and are directly related t o the nucleating activity of the polyamide. This effect is much smalle r in the presence of the compatibilizing agent. The isothermal crystal lization of the polyamide N6 in compatibilized blends is affected by t he presence of iPP, reducing the crystallization rate due to the dilue nt effect of the polypropylene. (C) 1997 John Wiley & Sons, Inc.