Demonstration of curing degree estimation approach of EVA foam during injection moulding by integrating thermal–physical characteristics and FEA simulation

Injection moulding is regarded as an effective solution for manufacturing EVA foam for sport footwear application. Characteristics of EVA foam are highly depended on the cross-linking chemical reaction and corresponding degree of curing of EVA foam during process. However, it is difficult to efficiently manage and observe the curing degree of EVA foam in accordance with the enclosed mould during injection moulding. For this reason, this study demonstrated a curing degree estimation approach for EVA foam, and the enthalpy and initial temperature for cross-linking are determined by DSC analysis, which are 13.245 J/g and 152.85 °C, respectively. Moreover, the temperature-dependent thermal–physical characteristics of EVA during foaming and cross-linking are subsequently extracted for exploring the thermal behaviour of concerned EVA foam. Aforementioned characteristics are further interpolating into FEA simulation to estimate the temperature and curing degree distribution of EVA foam during injection moulding process. The ideal and actual heat transfer conditions of mould are considered in simulation works, and it is found that the temperature profile and related degree of curing are significantly different for aforementioned conditions. In actual heat transfer condition of mould, fully cured region of EVA will significantly increase in accordance with the most of temperature in EVA foam across the initial temperature of 152.85 °C for cross-linking after the heating time at 170 °C over 450 s. Accordingly, the curing degree estimation approach is successfully demonstrated by the assistance of experiment and FEA simulation.