Investigation on the Crystallization Process of Microcellular Injection Moulded Parts and the Influences of Parameters on the Crystallization by Simulation

Abstract Crystallization, as a physical transformation process, plays an important role on the final properties of a plastic part. Similar to other injection moulding processes, injection and cooling conditions in microcellular injection moulding (e.g. MuCell® process) determine the phase change transformation of the material (molten to solid) and consequently, nucleation, crystal growth and crystallinity. The crystallization process of microcellular injection moulded parts has been mainly investigated using laborious and time-consuming experimental characterization techniques, but no studies reported the use of numerical methods to estimate the crystallization process. This paper presents a mathematical model successfully used to simulate the crystallization process of microcellular injection moulded parts. Microcellular injection moulding was simulated using Moldex 3D, and the crystallization process was investigated using the Hoffman nucleation theory for the crystal nucleation rate, the Lauritzen-Hoffman growth theory for the crystal growth rate, and the Avrami model to calculate the relative crystallinity. Numerical simulations allowed to investigate the effect of key processing parameters (melt temperature, mould temperature, flow rate, gas dosage amount and shot volume) on the crystallization process. Moreover, the numerical model was validated considering published experimental data.