Material BehaviourPreliminary investigation on morphology in water-assisted injection molded polymer blends

Preliminary and pioneering investigation is reported on the phase morphology development of polymer blend in water-assisted injection molded (WAIM) parts. Experiments of WAIM curved ducts were carried out using polypropylene/polyamide 6 (PP/PA6) blend on equipment newly developed in our laboratory. The experimentally observed morphology was evaluated both qualitatively, in terms of spatial distribution of the dispersed phase, as well as quantitatively by analysis of the size of the dispersed phase. The phase morphology development was interpreted with the aid of stress and temperature fields within the mold cavity under melt filling and high-pressure water penetration during the WAIM process. The results showed that the phase morphology varies significantly across the residual wall of the WAIM curved ducts. Moreover, the morphology developed at the position near the water inlet is induced mainly by the melt filling, whereas that near the end of the water channel is mainly ascribed to the high-pressure water-assisted filling. Then, three processing parameters were investigated in terms of their effects on the morphology development of dispersed PA6 phase. It was demonstrated that higher water pressure, adequate melt temperature and higher injection speed results in a more obvious deformation of the dispersed PA6 phase.