HEAT TRANSFER ASPECT TO UPGRADE THE QUALITY OF PLASTICS

The lecture delivers an innovative injection molding process whose concept was developed from the heat transfer point of view. The process is able to improve the optical quality and the transcribability of injection molded components by applying infrared radiation on the moving polymer melt injected in the mold cavity. The birefringence generated in the skin-layer of molded products can be reduced by radiative heating, and the feasibility of this technique was investigated experimentally using a CO laser beam as a radiation source. The numerical simulation clarified the effects of CO, laser radiation on the quality of molded polymer. The effects of radiative heating on the skin-layer of the molded polymer were observed using the mold with transparent windows, and the residual birefringence frozen in the molded specimen was measured. The results clearly snowed that the birefringence in the skin-layer of injection molded polymer strips was reduced by CO₂ laser heating. In addition, the transcribability from the surface nature of mold to the surface of polymer product by the proposed method was experimentally confirmed. It was noted to be upgraded so as to be applicable to products requiring a high quality. Another advantage is that the processing time is only slightly increased to process high quality components.