Modeling of pvT behavior of semi-crystalline polymer based on the two-domain Tait equation of state for injection molding

Abstract

The absence of the influence of cooling rate in the pressure–specific volume–temperature (pvT) models makes them inadequate in the process simulation of injection molding. This work derived new equations of state (EoS) from the traditional two-domain Tait model that describes the pvT behavior of semi-crystalline polymers in both molten and solid state. Especially, the cooling rate was considered. The second aim of this work is to solve the discontinuity problem of the traditional two-domain Tait model. A continuous two-domain Tait EoS was developed. A good agreement between the calculations and experimental results was achieved. The new pvT models were successfully applied in the prediction of specific volume as a function of temperature, pressure and cooling rate during injection molding. A higher value of the specific volume was predicted when the cooling rate was considered. Combining the continuous two-domain Tait EoS, more accurate results can be obtained especially at the transition phase from melt to solid of the semi-crystalline polymer.