Assessment of injection moulded parts of PP/nanoclay produced with hybrid moulds

Abstract

The concept of hybrid mould combines the conventional techniques of mould manufacturing and Rapid Prototyping and Rapid Tooling, resorting to non-conventional materials for producing moulding blocks, e. g., epoxy resin composites. Composites based on an epoxy system with 15% volume fractions of short steel fibres (SSF) were considered adequate for improving the performance of moulding blocks. The epoxy composites moulding blocks were produced by vacuum casting in silicone moulds. Composites of polypropylene (PP) with a commercial PP masterbatch with 50% of nanoclay were injected in a mould hybrid under various processing conditions, resulting from a central composite design with 15 experiments. The moulding microstructure was assessed by Polarized Light Microscopy and Differential Scanning Calorimetry. The skin-layer morphology was observed and suggested that the low thermal conductivity of these epoxy composites produces a thinner skin when compared to steel. The nanoclay concentration was the variable with the most significant effect on skin thickness and crystallinity. The addition of 1 wt% nanoclay under certain processing conditions favours the formation of β-form spherulites and the increase of crystallinity.