Tailoring the Mechanical Properties of Isotactic Polypropylene by Blending Samples with Different Stereoregularity

Abstract

The structure and properties of some blends obtained by mixing two semicrystalline samples of isotactic polypropylene (iPP) characterized by different degree of stereoregularity have been analyzed in the whole range of composition. The two components are a highly isotactic and crystalline sample (iPP1) and a stereoirregular and less crystalline sample (iPP2), and have been synthesized using two different metallocene catalysts. The blends show separate and independent crystallization and melting of the two components, and crystallinity content decreasing almost linearly with increasing the concentration of the low stereoregular component. A continuous change of tensile properties with the composition occurs, with properties ranging from those of thermoplastic materials with high stiffness, typical of the neat iPP1, to those of high-strength elastomers, typical of neat iPP2. The mechanical properties of these blends reflect the complex lamellar morphology that develops upon crystallization, characterized by...