Material BehaviourProperties of polypropylene and metallocene-prepared polyethylene blends: Crystallization behavior and interaction parameter

Blends of metallocene linear low-density polyethylene (m-LLDPE) and polypropylene random copolymer (PP) with three different weight ratios of 10/90, 30/70 and 50/50 m-LLDPE/PP were prepared using a twin screw extruder. The crystallization kinetics and spherulite growth rate of the parent polymers and their blends were then studied by using a differential scanning calorimeter (DSC) and a polarized optical microscope, respectively. The temperatures were high enough to allow only PP to crystallize. The equilibrium melting point and fold surface free energy of PP lamella decreased with increasing the m-LLDPE content in the blend, suggesting that there was a limited miscibility between the components. The negative value determined for interaction parameter was also in agreement with this finding.