Pressure influence on crystallization kinetics during injection molding

This work presents the measurement of the temperature at the center of the cavity during the molding of PP material using an embedded thermocouple probe. The measured temperature curves show a plateau shape related to the crystallization phenomenon. Measurements, done at various pressures show an increase in the crystallization plateau temperature depending on the cavity pressure. The change in the measured crystallization temperature allows the identification of the pressure dependence on the Hoffman-Lauritzen crystallization kinetics parameters: T-m and T-g. The T-m pressure dependence leads to a good agreement with the data of reported studies that used other experimental devices. The obtained results also show a decrease in cavity pressure duration related to the increase in the gate freezing speed as a result of the pressure increase. The identified pressure dependence laws for T-m and T-g introduced in the crystallization kinetics and the thermal model, allow to describe a temperature change in good agreement with the temperature measured down to the crystallization plateau. (C) 2011 Elsevier B.V. All rights reserved.