The effect of injection molding process parameters on mechanical and fracture behavior of polycarbonate polymer

In this work, the mechanical and failure behavior of injection molded aviation standard optical grade polycarbonate (PC) was investigated through uniaxial tensile testing. The effect of different injection molding process parameters including injection velocity, packing pressure, cooling time, mold temperature, and melt temperature were determined to observe their effect on yield and postyield behavior of PC. Out of these examined parameters, the mold and melt temperature show significant effect on mechanical behavior of studied polymer. The yield and flow stresses in polymer increase with the increase in mold and melt temperature during injection molding. However, other process parameters i.e., packing pressure, injection velocity, and cooling time showed little effect on mechanical performance of the polymer. The molded specimens were annealed at different temperatures and residence time to evaluate its effect on mechanical behavior and fracture morphology. The yield stress increases gradually with the increase in annealing temperature and time. The annealing treatment also changed the failure mode of PC specimens from ductile to brittle. In addition to process parameters, the effect of increased loading rate was also undertaken which shows substantial effect on mechanical and failure behavior of PC.