It was widely established that many end-use properties of the final parts are considerably affected by the macromolecular hierarchical structures formed during the cooling stage of injection molding, especially for crystalline polymers which undergo both solidification and crystallization processes simultaneously. Enthalpy transformation method (ETM) has been demonstrated to give the reasonable descriptions of the temperature profiles for real processing operations (e.g., injection molding, gas-assisted injection molding, and compression molding, etc.) in our previous work. However, to observe the phase-change plateau, where rapid cooling rate is imposed, is not easy in traditional treatments using the enthalpy approach. In this work, “modified cooling curves” (i.e., temperature versus time, plotted in logarithmic scale) at various locations in the mold cavity were found to show similar trend with an obvious turning point indicating the occurrence of phase transition. Mold temperature is more effective in controlling the cooling rate than melt temperature. Turing point of the cooling curves in the plot of ln θ vs. ln t can be used to estimate the minimum cooling time of the injection molding of crystalline polymers. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013
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