Fast cavity surface temperature evolution in injection molding: control of cooling stage and final morphology analysis

Fast mold surface temperature evolution in injection molding improves the surface finishing and replicability of the molded parts, and may significantly reduce frozen-in orientation. In this paper the effect of a fast control of cavity surface temperature evolution on the morphology and processing conditions of iPP molded parts has been characterized. Phenomena not previously encountered, such as a double pressure packing step when the cavity surface heating lasts longer than the packing step, have been pointed out. Significant effects on the samples frozen-in orientation have been observed by optical microscopy and confirmed by X-ray analysis. AFM analysis shows that it is possible to achieve isotropic morphology with cavity surface temperature kept constant at 150 degrees C for a long heating time and low holding pressure.