Effect of PC Percentages on Hardness and Notched Impact Strength of PBT/PC Blends

Abstract

Polybutylene terephthalate (PBT) has been proven to be a potential material for modern car bumpers. However, the potential of PBT is limited by its low notched impact strength. The main aim of this study is the improvement in the notched impact strength of PBT by blending with polycarbonate (PC). PBT/PC blend at different ratios (95/5, 90/10, 85/15, 80/20) is investigated in notched Izod impact strength (ASTM D256) and hardness (ASTM D2240). Results are compared to those of neat PBT. It was found that notched Izod impact strength decreased with increasing PC rate in the blend, overall, from 4.35 kJ/m2 of neat PBT to 3.37 kJ/m2 of 80/20 blend. The microstructure of testing samples was observed through FESEM images taken at fracture surfaces to determine the cause of the decrease. The low interfacial adhesion between PBT and PC phases is believed to be the main reason. However, an increase in notched impact strength was shown, from 4.18 kJ/m2 of 95/5 blend to 4,71 kJ/m2 of 90/10 blend. This result is presumed to be due to the compatibilizing effect of PBT-PC copolymers formed during the melt blending process. Hardness testing result demonstrates neither significant improvement nor deterioration. It concluded that it is possible to improve the notched impact strength of PBT by blending with PC. The PBT/10% PC blend is a suitable choice for car bumper material since its notch impact strength is higher than neat PBT.