Study on Impact Property and Fracture Morphology of Injection-molded Optical-grade Polycarbonate

The low-velocity, low-energy impact response of optical-grade polycarbonate (PC) was characterized by the Izod impact testing at ambient temperature. The following factors affecting impact response were investigated: mold temperatures (80, 90, 100, 110, and 120°C) and annealing treatment (120°C for 12 h). The results showed that the annealing treatment remarkably reduced the impact strength. The maximum impact strength was obtained when the mold temperature was 100°C for both unannealed samples and annealed ones. Moreover, the annealing treatment changed the failure mode of specimens from ductile failure to brittle failure, which was confirmed by fracture morphology analysis using scanning electron microscopy (SEM). The ductile failure was attributed to shearing behavior, and the fracture surfaces were rough and irregular with many river-shaped striations. The brittle fracture was caused by a craze failure mechanism. The brittle fracture sections could be divided into three regions: fracture origin, mist region, and end-wall banded region.