Polypropylene/talc/SEBS (SEBS-g-MA) composites. Part 2. Mechanical properties

Isotactic polypropylene/styrenic rubber block copolymer blends (iPP/SRBC) as well as the iPP/talc/SRBC composites with 12  vol.% of aminosilane surface treated talc were studied by the measurement of mechanical properties (tensile properties and notched impact strength). Mechanical properties and their relation with the structure of polypropylene blends and composites were investigated as a function of poly(styrene-b-ethylene-co-butylene-b-styrene) triblock copolymer (SEBS) and the SEBS grafted with maleic anhydride (SEBS-g-MA) content in the range from 0 to 20 vol.% as elastomeric components. Elongation at yield of the iPP/talc/SEBS-g-MA composites and impact strength of the iPP/talc/SEBS composites show synergistic effect at high elastomer content (20 vol.%). Higher molecular weight (and consequently higher viscosity, elasticity and impact strength) of thicker SEBS layers around highly oriented talc crystals and higher miscibility or interactivity of SEBS than SEBS-g-MA with iPP chains seem to contribute to enormous impact strength of the iPP/talc/SEBS composites. On the other side, a higher extent of encapsulation and disorientation of talc crystals by the SEBS-g-MA than by SEBS copolymer, and lower molecular weight of the SEBS-g-MA than SEBS copolymer may contribute to higher elongation at yield of the iPP/talc/SEBS-g-MA composite.