A model for the filling stage of injection molding that includes wall solidification and crystallisation was used to investigate the interaction between solidification and pressure drop during the filling of a rectangular plate with high-density polyethylene. We find that wall solidification affects the pressure drop in a complex way, reflecting the interplay between reduction in the area available for flow and thermal insulation of the still-molten polymer. Development of crystallinity on the surface of the part is also modelled under conditions of uniform and spatially varying cooling. Results indicate that nonuniform cooling can results in complex crystallinity distributions which are determined by thermal history of solidified polymer, duration of filling stage and by exact dependence of crystallisation kinetics on temperature.
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