An Experimental Study of Skin Layer in Rapid Heat Cycle Molding

The skin layer formation is directly related to the surface quality of the plastic produced. However, in Rapid Heat Cycle Molding (RHCM), the formation and movement mechanism of the skin layer is different from that of traditional molding. Therefore, the study on skin layer is of great significance for enriching RHCM theory and obtaining high surface quality products. This article reports results of experiments conducted on RHCM, utilizes multipoints sampling in the simulation and experimental results, and comparatively studies the skin layer structure of a single point as well as the thickness and orientation of multipoints with their variations by SEM and XRD method. Experimental results show that the product skin layer has asymmetric structure on two sides. The thickness of both the upper and lower skin layer decreases when its distance from the filling gate increases. Furthermore, it has been observed that the skin layer is mainly formed by alpha- and beta-crystal type, in which the percentage of the beta crystal and skin layer orientation are affected by the mold temperature and distance from the pouring gate.