Effect of mold opening on microcellular polyether-ether-ketone fabricated by injection molding

Polyether-ether-ketone (PEEK) is an excellent engineering polymer with numerous advantages. Processing by microcellular injection molding (MIM) can reduce product weight and save energy consumption. However, conventional MIM is plagued with limited weight-reduction and poor surface quality, so there have been few reports on microcellular PEEK with high weight-reduction based on injection molding. In this study, microcellular PEEK with weight reduction of 49.6% was prepared by mold-opening microcellular injection molding (MOMIM). The effects of holding time, holding pressure and mold-opening distance on microcellular PEEK were studied. Results show that incremental holding time and holding pressure could increase PEEK's density, promote the formation of dense cells and improve mechanical properties. Meanwhile, larger mold-opening distance reduced product's density, raised cell size and cell density, and lowered tensile properties, while the flexural properties increased first and then decreased when the mold-opening distance became larger. In addition, the surface qualities of microcellular PEEK prepared by MIM and MOMIM were compared, and it was found that MOMIM could significantly improve the surface quality. These microcellular PEEK prepared by MOMIM with tunable properties can further promote the lightweight application of PEEK.