Effect of inhomogeneous mold cavity surface temperature rapid self-cooling on β phase contents and mechanical properties of injection-molded polypropylene

Abstract

A dynamic self-cooling inhomogeneous temperature gradient field was applied instead of steady-state temperature at the mold cavity surface to study the effect of different cooling rates on the crystallization progress after the melt flow. The results showed that both the crystallinity and the β phase content increased with the gradient of the inhomogeneous mold temperature. When the mold temperature gradient of the high-temperature and the low-temperature sides increased from 0 to 40 °C, the size of the shish-kebab in the shear layer and the amount of small β phase spherulites in the transition layer increased. During the melt flows, a cavity temperature gradient higher than 30 °C was required to increase the stability of β phase in the transition layer. The yield stress and the elongation at break increased with the temperature gradient, but decreased at the temperature gradient of 45 °C.