Room temperature and low temperature toughness improvement in PBA-g-SAN/α-MSAN by melt blending with TPU

Abstract

Poly(butyl-acrylate)-g-poly(styrene-co-acrylonitrile)/α-methyl-styrene-acrylonitrile/thermoplastic polyurethane elastomer (PBA-g-SAN/α-MSAN/TPU) ternary blends were prepared with different composition ratios via melt blending. This work is mainly focused on improving the toughness of PBA-g-SAN/α-MSAN blends at room temperature (25 °C) and low temperature (0 °C and −30 °C). The results of notched Izod impact strength tests revealed that TPU had good toughening efficiency at 25 °C and 0 °C. With addition of 30 phr TPU, the impact strength of the blends increased from 5.3 kJ m⁻² to 26.5 kJ m⁻² at 25 °C, and increased from 2.9 kJ m⁻² to 18.7 kJ m⁻² at 0 °C. Obvious brittle-tough transition of the ternary blends was observed with increasing TPU content at 25 °C and 0 °C. The toughening efficiency of TPU was not notable when the impact temperature dropped to −30 °C, but the impact strength of the blends still increased with increasing TPU content. The glass transition temperature (T_g) of the blends was mainly responsible for the temperature dependence of toughening efficiency, which was proved by dynamic mechanical thermal analysis. It was also found the addition of TPU could lead to the slightly decreased T_g of the blends in the low temperature region. The probable reason for this is the unique structure formed in ternary blends, which was proved by attenuated total reflection infrared analysis and contact angle tests. The impact-fracture surfaces of blends were observed by scanning electron microscopy. The introduction of TPU brought with it a slight decrease of tensile strength, but the elongation at break of the blends increased greatly. Flexural strength, flexural modulus and heat resistance showed a decreasing tendency with increasing TPU content.