Predicting the Long‐Term Mechanical Performance of Polycarbonate from Thermal History during Injection Molding

Abstract

The influence of the thermal history experienced during injection molding on the mechanical properties of polycarbonate is investigated. Distributions of the yield stress as they result from inhomogeneous cooling during processing, predicted by a previously developed modeling approach, are validated and are in good agreement with experiment. Predictions of the mechanical performance for different mold temperatures during processing are also validated over a range of applied strain and deformation rates and applied stresses and forces, for simple tensile bars and an actual product. Good agreement is found. It is shown that mold temperature has a tremendous influence on the life time of polymer products, which can differ by more than two orders of magnitude.magnified image

Predicting the low-velocity impact behavior of polycarbonate: Influence of thermal history during injection molding

“…In this study, the prediction of yield stress of PC from processing thermal history is based on a phenomenological approach developed by Govaert et al [19][20][21]. They assumed the physical processes of the evolution of yield stress during processing are identical to those governing the evolution of yield stress during annealing.…”

“…R is the universal gas constant, T is the annealing temperature and T ref is the reference temperature. Govaert et al [19][20][21] proposed a logarithmic evolution equation of the yield stress during annealing process by using the master curve: …”

“…In this process, the melted polymer is injected into a mold cavity with a desired shape and then cooled down under a high packing pressure. It has been known that the mechanical properties of an injection molded polymer are influenced by its thermal history during the processing stage [19][20][21][22]. In the work of Govaert et al [19,20], it was proved that the thermal history experienced upon solidification from the melt has an influence on the yield stress of molded PC products.…”

“…The evaluation of the yield stress from thermal history during injection molding is based on the method developed by Govaert et al [19][20][21]. The notched Izod impact tests are carried out to analyze the impact behaviors of PC specimens with different thermal histories.…”

The Influence of Molecular Orientation on the Yield and Post‐Yield Response of Injection‐Molded Polycarbonate

“…[5] Computed yield stresses of injection-molded plates proved in excellent agreement with the experimental values, including their dependence on mold temperature and plate thickness. [2,3] Moreover, it was demonstrated that the method can be extended to quantitatively predict both short-and long-term failure of polymer products, [6] thus making it a powerful tool for true product optimization. A point of possible concern regarding this approach is that it completely neglects the influence of molecular orientation.…”