Toughening effect of CPE on ASA/SAN binary blends at different temperatures

The effect of chlorinated polyethylene (CPE) on the impact toughness of acrylonitrile-styrene-acrylic (ASA) terpolymer/styrene-acrylonitrile copolymer (SAN) binary blends (25/75, w/w) was systematically investigated at three different temperatures (-30 °C, 0 °C, and 23 °C). With the addition of 60 phr CPE, the impact strength increased by 11 times at 23 °C and 10 times at 0 °C. However, the toughening effect was not obvious when the testing temperature was -30 °C. Since the glass-transition temperature (T_g) of CPE was about -18.3 °C as measured with dynamic mechanical analysis tests, the polymeric chains of CPE have been "frozen out" at -30 °C. As a result, CPE evidently cannot improve the toughness of the blend system. The morphology of impact-fractured surfaces observed by scanning electron microscopy also confirmed the effect of CPE on the impact toughness of ASA/SAN binary blends. The heat distortion temperature remained almost unchanged, indicating that the improvement in toughness did not sacrifice heat resistance. Furthermore, other mechanical properties were evaluated, and the possible interactions among components of the blends were also analyzed by Fourier transform infrared spectra.