GRAFT COPOLYMER COMPATIBILIZERS FOR BLENDS OF ISOTACTIC POLYPROPYLENEAND ETHENE PROPENE COPOLYMERS .2. FUNCTIONAL POLYMERS APPROACH

A graft polymer with isotactic polypropylene (iPP) arms pendant from a n ethene-propene (EP) copolymer backbone has been made and shown to ef fectively compatibilize EP/iPP blends. The synthesis of this molecule is by the reaction of mutually reactive functional polymeric component s: a succinic anhydride grafted polypropylene is reacted with an EP co ntaining primary amine groups, either in solution or in the melt state . This grafting has been demonstrated by infrared spectroscopy, solven t fractionation, and thermal analysis. The addition of less than 10% o f this graft polymer to an iPP/EP blend has a large effect on its morp hology and properties. Not only does the size of dispersed EP phase do mains shrink by a factor of 4 when the compatibilizer is added but als o the growth of the phase domains on thermal annealing in the melt is significantly reduced. The presence of the graft polymer in the interp hase of the blend is shown directly by electron microscopy. Improvemen ts in mechanical properties of iPP/EP blends containing compatibilizer s have been noted. The low-temperature impact strength is increased, a nd the temperature of the transition from ductile to brittle behavior is reduced by up to 20-degrees-C. Thus, such graft polymers work well as interfacial agents or compatibilizers to improve and stabilize blen d properties.