Mechanical Properties of Carbon Black-Filled Polypropylene/Polystyrene Blends Containing Styrene-Butadiene-Styrene Copolymer

Mechanical properties and morphology of carbon black (CB)-filled polypropylene/polystyrene (PP/PS) blends with and without styrene-butadiene-styrene (SBS) triblock copolymer were studied as a function of PP/PS volume ratio and CB content. Blends were prepared by melt mixing in a batch mixer followed by compression molding. Incompatibility of the PP/PS blends was found to negatively influence the blends' tensile properties. Addition of 5 vol% SBS to the CB-filled PP/PS blends was found to compatibilize the blends by reducing the interfacial tension and enhancing the interfacial adhesion. In general, SBS addition enhanced the yield stress of the co-continuous CB-filled PP/PS blends, reduced the Young's modulus and enhanced the elongation at yield for all blends studied. For the (70/30) PP/PS blends with and without SBS, yield stress of the blends filled with up to 3 vol% CB is close to that of the unfilled (70/30) PP/PS blends. Increasing CB loading to 5 vol% considerably increased the yield stress for the blends with and without SBS. A gradual increase in Young's modulus was reported with increasing CB content in the (70/30) PP/PS blends with and without SBS. Increasing CB loading up to 5 vol% did not influence the elongation at yield of the (70/30) PP/PS blend without SBS. POLYM. ENG. SCI., 49:693-702, 2009. (c) 2009 Society of Plastics Engineers