Investigation of vacuum annealing effects on physical–mechanical properties of thermoplastic parts

Impact and tensile strength of polystyrene and nylon 6 samples, which have been produced by injection molding before and after annealing in different conditions are obtained. Polystyrene samples that are heated on vacuum conditions can deform highly even in temperatures much less than polystyrene glass temperature. This phenomenon is reduced significantly by heating samples to annealing temperature in atmospheric pressure and then removing air from sample environment in constant temperature. Deformation problems for nylon were not so important but due to high temperature implied for annealing of nylon parts, some color change due to oxidative degradation are observed. So for nylon parts a complete vacuum was need to eliminate such oxidative degradation. Analysis of obtained results shows some reduction in impact and strength of annealed samples that can be due to elimination of longitudinal orientation observed normally in injection-molded parts.