Effects of annealing on mechanical properties of injection mold polycarbonate parts

Residual stresses in transparent injection molded parts may have negative effects on optical and mechanical properties.Annealing is one of the important methods to eliminate or minimize the processing residual stresses.In this paper,the effects of annealing on residual stresses and mechanical properties were investigated and discussed by comparing the photoelastic birefringence results and the tensile properties of the injection molded PC parts before and after annealing treatment.After annealing,it was found that there was no obvious change in birefringence interference pattern while tensile strength and elongation were different at various processing parameters,including mold temperature,melt temperature,injection pressure,packing pressure,cooling time,packing time and injection time.According to the experimental results,after annealing the average tensile strength increased by 4.5% and the maximum value was 9%.And at the same time the average elongation decreased by 3% and maximum reduction reached 14%.