Abstract
This study investigates virgin and recycled high-density polyethylene/multi-walled carbon nanotube (HDPE/MWCNT) composites using thermo-physical and mechanical characterization techniques to generate knowledge and understand recyclability of these composites. Firstly, virgin samples with 0.1–5 wt.% of MWCNTs were prepared by injection molding. Then, the HDPE/MWCNT composite waste was mechanically recycled and consecutively reprocessed by injection molding. The experimental results show that the degradation process of the end-user properties (mechanical and electrical properties) depends on the MWCNT wt.%. The higher the carbon nanotube loading, the higher the degradation of the end-user properties. The HDPE/MWCNT composites appear to be resistant to degradation at carbon nanotube loadings below the percolation threshold (which is located around 3 wt.%). In contrast, the recycled HDPE/MWCNT composites with 5 wt.% showed a reduction in viscosity, mechanical and electrical properties with recycling. After four reprocessing cycles, degradation in the Young modulus (−35%), tensile strength (−25%), elongation at break (−60%) and electrical conductivity (−2 orders of magnitude) of the HDPE/MWCNT composite with 5 wt.% was observed as compared with the virgin composite. From an industrial perspective, it is feasible to recycle HDPE/MWCNT composite waste by mechanical recycling and use it to manufacture products with favorable mechanical properties, covering insulating, antistatic and semiconducting ranges depending on the MWCNT loading, owing to the protective effect of carbon nanotubes against thermo-mechanical degradation.