Analysis of thermal contact resistance between polymer and mold in injection molding

The objective of this work is to combine experimental and numerical approaches to evaluate the nature of thermal contact between polymer and mold through the different phases of a typical injection cycle. The key idea of this analysis is the simultaneous use for the first time of an infrared hollow waveguide pyrometer and a two-thermocouple probe specially devised for this study. The infrared waveguide pyrometer is used for the on-line monitoring of the temperature at the surface of the polymer within the cavity, while the two-thermocouple probe is used to determine via an inverse problem the local heat flux crossing the polymer–mold interface and the temperature at the cavity surface. Subsequently, a second inverse algorithm, which combines the latter estimated data and the temperature at the polymer surface measured with the infrared waveguide device, allows the determination of the thermal contact resistance. The results show that the thermal contact resistance between polymer and mold is not negligible, not constant with time, and strongly correlated with process conditions.