Evaluation of injection‐molding simulation tools to model the cure kinetics of rubbers

Abstract

Rubber injection molding is a process whereby a rubber mix is injected into a closed mold where the material is shaped to the desired geometry. Having completely filled the cavity rubber mix is vulcanized. Vulcanization is the process whereby a viscous and tacky uncured rubber is converted into an elastic material through the incorporation of chemical crosslinks between the polymer chains. The degree of cure achieved depends on the formulation recipe and the time–temperature history endured by the material during the curing process while in the mold. The aim of this study was to check the capability of commercial injection‐molding simulation tools, such as Moldflow and Cadmould, to predict the degree of cure achieved in spiral‐shaped parts when subjected to various cure cycles. To use the simulation tools, it was necessary to characterize the material in terms of their thermal properties and kinetic behavior during curing. The degrees of cure were determined with swelling techniques and by the measurement of the residual cure exotherms with differential scanning calorimetry. On comparing the experimental values of the degree of cure with those predicted by the simulation tools, we found that the initial simulations underestimated the degrees of cure. Consequently, the criteria used to calculate the cure model parameters were modified to invoke faster cures. In so doing, good agreement was achieved between the degrees of cure predicted by the simulations and those obtained experimentally.© 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

Analysis of Reactive Injection Compression Molding by Numerical Simulations and Experiments

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