Significant improvement of the low-temperature toughness of PVC/ASA/NBR ternary blends through the concept of mismatched thermal expansion coefficient

In this study, poly(vinyl chloride) (PVC)/acrylonitrile-styrene-acrylic terpolymer (ASA)/acrylonitrile-butadiene rubber (NBR) ternary blends were designed based on the concept of mismatched thermal expansion coefficient between different components, resulting in significant improvement of the low-temperature toughness. The large difference in thermal expansion coefficients strengthened the interfacial tensile force (i.e. negative pressure) on NBR phase and reduced its glass transition temperature (T_g) by nearly 20°C, which was attributed to the improvement in the free volume of NBR. As a result, the low-temperature toughness of PVC/ASA/NBR ternary blends improved significantly. With the incorporation of 12.5 phr NBR in the PVC/ASA (100/15, w/w) matrix, the blends could achieve the highest impact strength of 76.2 kJ/m² at 0°C and 10.7 kJ/m² at -30°C. Simultaneously, the brittle-ductile transition (BDT) of the toughness shifted to the high NBR content region with the decrease of temperature. However, the improvement in the toughness of PVC/ASA/NBR ternary blends was at the expense of a decrease in rigidity.