Effects of cavity surface temperature on reinforced plastic part surface appearance in rapid heat cycle moulding

The influences of the cavity surface temperature just before filling on surface appearance and texture of the moulded reinforced plastic parts in rapid heat cycle moulding (RHCM) are investigated. Two typical reinforced plastics including ABS/PMMA/nano-CaCO3 and 20% fibre reinforced polypropylene (FRPP) are tested in experiments. The roughness, gloss and morphology of the part surface are characterized with white light interferometer, gloss meter, and optical microscope, respectively. It is observed that the cavity surface temperature just before filling has a significant influence on part surface appearance. With the increase of the cavity surface temperature just before filling, aesthetic quality of the moulded part can be greatly improved. There is a critical value of the cavity surface temperature just before filling for each plastic. As the cavity surface temperature reaches the critical value, part surface appearance will reach the optimal level with low roughness and high gloss. The weld mark for ABS/PMMA/nano-CaCO3 has a V-shaped structure while that for FRPP has a hump-shaped structure. With the increase of the cavity surface temperature just before filling, the width of the V-shaped weld mark reduces gradually until it disappears completely while the height of the hump-shaped weld mark decreases firstly and then increases. The mechanisms for the improvement of surface appearance by increasing cavity surface temperature just before filling and the generation of the V-shaped and hump-shaped weld mark are disclosed.