Evaluation of the crystallization kinetics and melting of polypropylene and metallocene-prepared polyethylene blends

The kinetics of the isothermal crystallization of a polypropylene (PP) random copolymer containing 5 mol % ethylene, a metallocene linear low-density polyethylene (m-LLDPE) with 3.3 mol % hexene-1 as a comonomer, and three blends were studied with differential scanning calorimetry at temperatures sufficiently high to prevent any crystallization of m-LLDPE. The analysis was carried out with the Avrami equation. The overall crystallization rate and the equilibrium melting temperature of the PP copolymer decreased with increasing amounts of m-LLDPE in the blends. The former was attributed to the effect of m-LLDPE in reducing the number of primary nuclei, and the latter was attributed to a lowering of the fold surface energy due to the limited partial miscibility of the blend components. (c) 2007 Wiley Periodicals, Inc.