FUNCTIONAL POLYPROPYLENE BLEND COMPATIBILIZERS

Solid phase dispersants, often referred to as blend compatibilizers, are the key components of high-value-in-use polypropylene blends with unusual property combinations. In multiphase polypropylene blends, functional blend compatibilizers enhance the dispersion of incompatible polymeric blend components, in particular of polar polymers, fibers of fillers, and improve the interfacial adhesion between polymer matrix and dispersed phases. Some of the major synthetic routes to functional polypropylene blend compatibilizers are discussed. A novel range of monofunctional polypropylenes containing a variety of functional endgroups, e.g., anhydrides, esters, amines, carboxylic acids, silanes, boranes, alcohols, and thiols, has been derived from mono-olefin-terminated polypropylenes. These olefinic polypropylene intermediates have been prepared with soluble metallocene catalysts which give excellent control of polypropylene molecular weight, molecular weight distribution, microstructure, and olefinic endgroups. Thiol-terminated isotactic polypropylenes have been used as polymeric chain transfer agents in styrene and styrene/acrylonitrile polymerization of form novel polypropylene-block-polystyrene and polypropylene-block-poly(styrene-co-acrylonitrile) block copolymers. In the case of poly(styrene-co-acrylonitrile) blends with polypropylene morphological studies demonstrate the efficiency of propylene block copolymer blend compatibilizers.