Fiber reinforced rubber modified polypropylene

Abstract

Abstract Reinforcement can improve the modulus, heat distortion temperature and thermal expansion coefficient of rubber modified polypropylene. These improvements canbe obtained with a minimum sacrifice in resin ductility and impact toughness. Our studies have shown that reinforcement with small discontinuous fibers can provide a material with a good balance of stiffness and impact strength. The combination of small potassium titanate fiber reinforcement, polypropylene homopolymer and an impact modifier can produce a material with a tensile modulus of 470,000 psi, a notched Izod impact strength of 4.6 ft‐lb/in. and a Gardner imact strength of 320 in‐lb. Glass fiber reinforcement produces similar improvements in stiffness and retains Izod impact strength but drastically reduces Gardner impact strength. Polypropylene resin viscosity has a profound effect on composite impact strength. Transmission electron microscopy showed that a correlation exists between EPDM rubber particle size and impact strength: as rubber particle size is reduced, impact strength is increased. A 5 melt flow rate polypropylene was found to have the viscosity required to adequately shear and disperse the impact modifier. The paper describes an approach to broadening the utility of polypropylene homopolymers. The properties and flow of these materials compare very favorably with medium impact ABS.