Effect of multiple recycling on properties of poplar fiber reinforced high density polyethylene wood-plastic composites

Wood-plastic composites have developed rapidly in recent years and are used in various fields, so their recycling is crucial. This research aims to understand the recyclability of poplar fiber (PF) reinforced high density polyethylene (HDPE) wood-plastic composites. The PF/HDPE composites were prepared by melt blending and injection molding process, and were recycled six times. The composites were subjected to mechanical tests, thermogravimetric analysis, differential scanning calorimetry and water absorption tests. The surface and tensile fracture surface of the composites were also observed by scanning electron microscope. The results showed that after recycling, the mechanical properties of PF/HDPE composites decreased and the flexural modulus decreased the most. The thermal stability of the composite gradually increased with the increase of recycling times. Recycling also improved crystallinity and crystallization and melting rates, but there is no significant change in crystallization and melting temperature. The water absorption of the recycled composites was reduced, and the waterproof performance is improved. Scanning electron microscopy revealed that the surface and interface defects of the composites were reduced by recycling, and PF was better combined with HDPE. Experimental results show that the performance change of the recycled composites is within an acceptable range and have application value in some fields.