Investigation of mechanical properties of polypropylene-based hybrid nanocomposites using experimental design

Polypropylene has a poor toughness and impact strength. So, it needs to modification for some applications. Addition of elastomers to PP to enhance the toughness is a traditional way, but it causes to decrease of the modulus and tensile strength of products. In this research a hybrid composite system including PP, thermoplastic elastomer, nanoparticle and compatibilizer was prepared by melt mixing method. The interaction effect of nanoparticle, thermoplastic elastomer, and compatibilizer on the tensile and impact properties of composites were studied using the experimental design technique; response surface methodology. The results of microscopy analysis showed that the blends were two-phase, where thermoplastic elastomer was dispersed phase. The elastomeric particle size was in the range of 100-400 nm and by increasing the rubber content, rubber particle size increased. Nanosilica dispersed in the presence of compatibilizer had a particle size between 40-90 nm, while the lack of compatibilizer created some agglomerations of nanoparticles. As elastomer content increased, the strain of failure and impact strength of nanocomposites increased, while the Young modulus and tensile strength were decreased. Addition of nanosilica to the PP in the absence of compatibilizer lowered the tensile and impact strengths. While, addition of nanosilica along with compatibilizer improved the tensile modulus of blends. According to the experimental design results, some mathematical relations were presented to predict the mechanical properties. The optimal hybrid nanocomposite had significantly higher impact strength than pure PP while their moduli were in the same order.