Specialty Elastomer Modifiers with Isotactic Propylene Crystallinity for Polypropylene Modification

Abstract

Abstract Specialty elastomers possessing isotactic propylene crystallinity are a novel class of polyolefins made possible by advances in metallocene polymerization. These polymers contain a propylene rich component endowed with isotactic crystallinity, and the balance of the composition is ethylene with other alpha olefins. Typical molecular weight of these elastomers is greater than 100,000. These polymers, when used as modifiers for toughening polypropylene (PP) homopolymers demonstrate improved impact strength to stiffness balance, enhanced low temperature toughness and improved impact to flow balance over conventional ethylene alpha-olefin modifiers. Morphological features of the blends were determined using Transmission Electron Microscopy (TEM) and Atomic Force Microscopy (AFM). The detailed morphological characterization indicates that the isotactic propylene crystallinity species of the elastomers function by localizing themselves at the interface of the polypropylene matrix and the ethylene-alpha olefin component of the modifier. We believe that such a tailored localization is effective because of the simultaneous co-crystallization of the isotactic propylene crystallinity elastomers with the isotactic PP matrix, and the thermodynamic compatibility of the propylene crystallinity species with the other elastomeric components of the modifier.