Synthesis and properties of novel styrene acrylonitrile/polypropylene blends with enhanced toughness

BACKGROUND: Although polypropylene (PP) has been widely used, its brittleness restricts even further applications. METHODS: In this study, we have used a melt blending process to synthesize styrene acrylonitrile (SAN)/PP blends containing 0, 5, 10, 15 and 20 wt% SAN. The effects of adding various amount of SAN on the blends characteristics, mechanical properties, thermal behavior and morphology were investigated. RESULTS: The results demonstrated that SAN had no obviously effect on crystal form but reduced the crystallinity of PP and increased the viscosity. The heat deflection temperature and Vicat softening temperature were enhanced for all SAN/PP blends, in particular for blends with low SAN content (5 and 10 wt%). The morphology of SAN/PP blends with 10 wt% SAN revealed the presence of nanoparticles dispersed on the surface, while SAN/PP blends with 20 wt% SAN exhibited the presence of spherical droplets and dark holes. All SAN/PP blends showed higher impact strength compared to pure PP, especially for SAN/PP blend containing 10 wt% SAN for which the impact strength was 2.3 times higher than that of pure PP. CONCLUSIONS: The reason for significant increase in impact properties seemed to have a strong correlation with nanoparticles morphology and the decrease of PP crystallinity.