Morphology and nonisothermal crystallization behavior of PP/Novolac blends

The morphology and nonisothermal crystallization behavior of PP/Novolac blends were studied with scanning electron microscopy, differential scanning calorimeter, polarized optical microscopy (POM), and wide-angle X-ray diffraction (WAXD). The results showed that the crystallization of PP in PP/Novolac blends was strongly influenced by cooling rate, size of Novolac particles, crosslinking, and compatibilizer maleic anhydride-grafted PP (MPP). In dynamically cured PP/MPP/Novolac blends, the MPP grafted on the surface of cured Novolac particles and formed a chemical linkage through the reaction of anhydride groups with the hexamethylenetetramine. The graft copolymer not only improved interfacial compatibility but also acted as an effective heterogeneous nucleating agent, which accelerates the crystallization of PP. The combination of Avrami and Ozawa equations exhibited great advantages in treating the nonisothermal crystallization kinetics in dynamically cured PP/MPP/Novolac blends. The POM results showed that the spherulite morphology and the size of PP in PP/MPP/Novolac blends were greatly affected by Novolac. WAXD experiment demonstrates that the PP and dynamically cured PP/MPP/Novolac blends showed only the or. crystal form. At the same time, the addition of Novolac resin also affects the crystal size of PP. (c) 2007 Wiley Periodicals, Inc.