Assessment of Injection Moulded Parts of PP/Nanoclay Produced with Hybrid Moulds

摘要

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% weight fraction of short steel fibres (SSF) were considered adequate for improving the performance of moulding blocks.The epoxy/short steel fibre composite moulding blocks were produced by vacuum casting in silicone moulds.Polypropylene (PP) was mixed with a commercial PP masterbatch with 50% of nanoclay and injected in a hybrid mould under various processing conditions.These were chosen from a central composite design with 15 experiments.The moulding microstructure was assessed by polarized light microscopy and differential scanning calorimetry.The skin-core morphology was observed and suggested that the low thermal conductivity of the epoxy composite produces a thinner skin when compared to all-steel moulds.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 p-form spherulites and the increase of crystallinity.