Morphology, crystallization, and thermal behavior of isotactic polypropylene/polymethylmethacrylate blends: Effects of the addition of a graft copolymer of propylene with methylmethacrylate

Optical microscopy, differential scanning calorimetry, and small angle Xray scattering techniques were used to study the influence of crystallization conditions on the morphology and thermal behavior of samples of ternary ble nds constituted of isotactic polypropylene (iPP), atactic polymethylmethacr ylate (aPMMA), and a novel graft copolymer of unsaturated propylene with me thylmethacrylate (uPP-g-PMMA). The purpose was to assess the uPP-g-PMMA cap ability to act as compatibilizer for iPP/aPMMA materials. It was shown that the presence of uPP-g-PMMA copolymer affects the interfacial tension betwe en the iPP and aPMMA phase in the melt state, the aPMMA particle size, and particle-size distribution is modified. After complete crystallization of t he iPP phase at relatively low undercooling, in a range of crystallization temperatures, the presence of the uPP-g-PMMA phase was found to modify both mode and state of dispersion of minor component and spherulitic texture an d inner structure of spherulites fibrillae. The extent of the induced modif ications was dependent on a combination of composition and undercooling. Al so, relevant thermodynamic parameters of the iPP phase, such as the equilib rium melting temperature and the surface free energy of folding, were stron gly affected by the presence of the uPP-g-PMMA phase, opposite effects bein g observed depending on the uPP-g-PMMA content. The observed melting temper ature and surface free energy of folding values were accounted for by the g rowth of iPP lamellar crystals with different perfection, thickness, and su rface disorder. (C) 2000 John Wiley & Sons, Inc.