EFFECT OF PROCESSING PARAMETERS ON FLOW HESITATION WITHGLASS-FILLED REINFORCED THERMOPLASTICS: EXPERIMENTAL INVESTIGATION WITH DIRECT VISUALIZATION

摘要

This study investigates the effect of processing parameters on flow hesitation with glass-filled reinforced (GFR) polymers. An inherently difficult to fill fishbone cavity geometry was utilized throughout the study where the side appendages along the main direction of flow are of varying cross-section. An L9 Taguchi method design of experiments (DOE) was performed for each material -PP, PBT and LCP. Parameters varied include mold temperature, melt temperature, injection rate, and packing pressure. To further investigate the flow hesitation dependency of the materials processed, direct visualization of the flow in real time was performed by incorporating a transparent window in the mold tool. Design limitations and constraints were thoroughly reviewed and are presented. Video imaging and acquisition of the molding process was conducted using a CCD (Charged-Coupled Device) camera. It was found that the flow hesitation is dependent of the material being processed, but is also heavily dependent on the melt temperature and packing pressure. Of the three materials processed, LCP exhibited superior flow properties, i.e. minimal flow hesitation, whereas PP and PBT were significantly affected by the processing conditions employed. LCP was the only polymer which yielded a completely filled part. In general, PP exhibited better flow properties than PBT.