Crystallization and Melting of Components in Blends of Polyethylene and Polypropylene

Abstract

Blends of polymers are, in most cases, heterogeneous systems in which components partially preserve their individual properties because of the incompatibility of polymers. In blends of semicrystalline polymers, the properties of components are strongly dependent on crystallinity and crystalline morphology. If the crystallizing polymer is dispersed in the blend, its properties are usually different from those in bulk. First of all this can be observed for polymers which crystallize forming supermolecular structures like the spherulites in which crystallization kinetics and resultant morphology are related to temperature dependent nucleation and growth rates of spherulites. In such polymers in the bulk when the nucleation rate is not very high, one nucleus can involve the crystallization in a relatively large volume, i.e. the volume of the final spherulite. In the blend in which the polymer is dispersed into small particles, the range of the influence of an individual nucleus is limited to the size of particles.