Effects of polystyrene-b-poly(ethylene/propylene)-b-polystyrene compatibilizer on the recycled polypropylene and recycled high-impact polystyrene blends

The recycled polypropylene/recycled high-impact polystyrene (R-PP/R-HIPS) blends were melt extruded by twin-screw extruder and produced by injection molding machine. The effects of polystyrene-b-poly(ethylene/propylene)-b-polystyrene copolymer (SEPS) used as compatibilizer on the mechanical properties, morphology, melt flow index, equilibrium torque, and glass transition temperature (T-g) of the blends were investigated. It was found that the notch impact strength and the elongation at break of the R-PP/R-HIPS blends with the addition of 10wt% SEPS were 6.46kJ/m(2) and 31.96%, which were significantly improved by 162.46% and 57.06%, respectively, than that of the uncompatibilized blends. Moreover, the addition of SEPS had a negligible effect on the tensile strength of the R-PP/R-HIPS blends. Additionally, the morphology of the blends demonstrated improved distribution and decreased size of the dispersed R-HIPS phase with increasing the SEPS content. The increase of the melt flow index and the equilibrium torque indicated that the viscosity of the blends increased when the SEPS was incorporated into the R-PP/R-HIPS blends. The dynamic mechanical properties test showed that when the content of SEPS was 10wt%, the difference of T-g decreased from 91.72 degrees C to 81.51 degrees C. The results obtained by differential scanning calorimetry were similar to those measured by dynamic mechanical properties, indicating an improved compatibility of the blends with the addition of SEPS.