The Impact of Mechanical Recycling on Ligno-Cellulose Fibre Containing PLA Biocomposite

Biocomposites, made from biobased polymers with natural fibre reinforcement, offer a feasible path towards environment friendly and sustainable materials. However, biocomposites have struggled to attract ta market that is mostly dominated by conventional fossil-based polymers. To increase the cost efficiency and extend the lifespan of biocomposites, the effects of mechanical recycling on their properties should be thoroughly explored. While there has been some research on recycling natural fibre-reinforced biocomposites, limited attention has been paid to biocomposites reinforced with softwood fibre. This study investigates the impact of mechanical recycling on poly-lactic acid (PLA) biocomposites reinforced with bleached and unbleached softwood kraft pulp fibres at 15 wt% and 30 wt%. The results show that single-stage mechanical recycling improves Young’s modulus by 11–13% while maintaining impact strength. Tensile strength remains stable for biocomposites with 15 wt% fibre but decreases by 6–8% for with 30 wt% biocomposites. Recycling improves fibre dispersion by reducing agglomeration but leads to PLA degradation, which could potentially be mitigated by adding virgin polymer or chain extenders. These findings highlight the potential for reusing PLA-softwood fibre biocomposites while emphasizing the need for further research into multiple recycling cycles.