Structure-property correlation of an impact- modified random polypropylene copolymer

Abstract

The combination of rheological and interfacial properties is utilized in this work to explain the thermal and mechanical properties of a random polypropylene copolymer (RPP) toughened with an ethylene-propylene copolymer (EPR). RPP/EPR blends are directly prepared by injection molding. The EPR exhibits higher viscosity in comparison with the RPP over the evaluated shear rate, while the RPP/EPR blends show similar viscosities at high shear rates. The interfacial properties indicate a strong interaction between the RPP and EPR domains. Differential scanning calorimetry analyses indicate that the EPR does not act as a nucleating agent for the RPP, with the RPP crystallinity only decreasing at high EPR contents, suggesting that the EPR can modify the RPP crystallite size. Scanning electron micrographs of the blends demonstrate a ductile fracture surface, indicating that EPR can increase the RPP tenacity. The RPP impact strength is improved by up to 102% in the RPP/EPR 90/10 wt.% blend, while the RPP deformation at break is increased from 183% to 246% after the incorporation of 10% EPR. The tensile strengths of the RPP and RPP/EPR blends are very similar, indicating that the RPP achieves a good balance between stiffness and toughness after being blended with the EPR.