Non-isothermal crystallization and crystalline structure of PP/POE blends

Polypropylene (PP)/ethylene-octene copolymer (POE) blends with different content of POE were prepared by mixing chamber of a Haake torque rheometer. The crystallization behaviors and crystal structure of PP/POE blends were systematically investigated by differential scanning calorimetry (DSC), wide angle X-ray diffraction (WAXD) and polarized optical microscopy (POM). The results showed that PP spherulites became defective and the crystallization behavior was influenced intensely with the introduction of POE. At the low content of POE, the addition of POE decreases the apparent incubation period (Delta t(i)) and the apparent total crystallization period (Delta t(c)) of PP in blends due to the heterogeneous nucleation of POE, and small amount of beta-form PP crystals form because of the existence of POE. However, at high content of POE, the addition of POE decreases the mobility of PP segments due to their strong intermolecular interaction and chain entanglements, resulting in retarding the crystallization of PP, decreasing in the amount of beta-form PP crystals, and increasing in Delta t(i) and Delta t(c) of PP in blends.