CROSS-LINKED POLYETHYLENE POLYPROPENE BLENDS .1. FORMATION OF INSOLUBLE PARTS, CRYSTALLIZATION AND MELTING

Crosslinked blends of low density Polyethylene/isotactic Polypropene (LDPE/iPP) were studied over the whole composition range. The degree of crosslinking was determined from the gel content and the degree of swelling. In the presence of a coagent an efficient crosslinking of polypropene can be observed in blends whereas in the absence of the coagent only the PE component is crosslinked. Thermal characterization of the blends by differential scanning calorimetry (DSC), i. e. heat of fusion, melting and crystallization temperatures suggest that the crosslinking results in the formation of a structure with molecules of both components being mutually connected. A two-phase structure is still maintained and crosslinked molecules of polypropene (PP) and polyethylene (PE) are found at the interface. The effect of crosslinking on the rate of crystallization is different for PE and PP. This phenomenon is explained by the superposition of the influence of crosslinking on the rate of crystal growth and nucleation.