3D Printing of Natural Fibre Reinforced Recycled Polypropylene

The adverse effects that waste plastics are having on the environment is becoming increasingly apparent. However, the plastics recycling industry in New Zealand is entirely market driven, necessitating the development of new markets to account for increasing quantities of waste. Innovations in additive manufacturing (AM) have presented opportunities to recycle thermoplastics for use as AM feedstock material. Using waste thermoplastic materials to fabricate composites in this way, adds value to the polymer by enhancing mechanical and aesthetic properties. A range of composite filaments with differing fibre and gypsum weight contents were then produced using pre and post-consumer polypropylene (PP). The most successful filaments in terms of tensile properties consisted of 30 wt% harakeke in a post-consumer PP matrix which had a tensile strength and Young’s modulus of 41MPa and 3.8 GPa respectively. Comparing these results to those of plain PP filament, showed improvements in tensile strength and Young’s modulus of 77% and 275% respectively. Finally, a novel method of measuring shrinkage in 3d printed components was developed and used to compare relative shrinkage of different composites. The composite that showed the least shrinkage consisted of 30 wt% harakeke with a shrinkage value of 0.34% corresponding to a net reduction of 84% relative to plain PP