Film insert injection molding (FIM) is an increasingly popular technique to impart decoration onto moldings. In this study, FIMs were produced by using amorphous and crystalline polymers that were evaluated based on their film-substrate interfacial adhesion strength. Interfacial bonding between amorphous polymers could be achieved at any temperature above the glass transition, though higher temperatures are favorable to enhance diffusion rates. As for crystalline polymers, melting of the crystalline phase in the film was needed to create mobile molecular chains before any significant bonding could take place. Hence, the resin temperature should be sufficient to induce melting of the film surface. Regardless of materials characteristics, certain criteria have to be met to ensure good interfacial bonding. Good film-substrate intimacy should be attained to provide a wider contact area for interfacial diffusion. Resins with low Mw and linear chain structures could easily diffuse across the interface and form molecular entanglements with sufficient cooling. Hence, barrel and mold temperatures were the most important parameters that governed the interfacial strength during molding.

This study mainly investigates the effect of talc and calcium carbonate (CaCO3) as monotonic and hybrid fillers on the thermal, mechanical and morphological properties of polypropylene (PP). The hybrid composites, through the synergistic coalescence of positive characteristics from both fillers, have exhibited exceptionally good strength and toughness as compared to the monotonic composites. The nucleating ability and high aspect ratio of talc contributed towards the increment in strength while the isotropic nature of CaCO3 enhanced the toughness of the hybrid composites. Titanate surface treatments on talc and CaCO3 dramatically enhanced the ductility of both monotonic and hybrid composites. The composites were also subjected to natural weathering in Penang, Malaysia for 6 months. After exposure, the mechanical properties of monotonic composites deteriorated due to severe physical and chemical degradation. However, the hybrid composites exhibited better retention in mechanical properties albeit having undergone some degree of surface-degradation. Filler surface treatments were also effective in preventing further deterioration in composite performance during natural weathering.