Mechanical recycling and composition effects on the properties and structure of hardwood cellulose-reinforced high density polyethylene eco-composites

Knowledge of recycling capability of cellulose-reinforced eco-composites is of great interest due to sustainability and market reasons. Reprocessing by injection molding of hardwood cellulose-reinforced HDPE composites with a wide fiber content range (10–48wt%) and two coupling agents with different molecular weights and maleic anhydride (MA) contents was studied. Recycling and composition effects on composite structure and properties were analyzed by ATR–FTIR, SEM, AFM, flow and tensile testing. Increases in fiber content resulted in lower tensile strength (σt) increases for reprocessed composites. σt was revealed as the property with the highest sensitivity to the fiber breakage found upon recycling. The greater M‾w and MA content coupling agent was revealed as the less sensitive to reprocessing and experienced a lower degradation upon recycling, still benefiting the recycled composites σt. Statistically-contrasted models for quantitative prediction of composite flow and tensile properties upon recycling were developed. Composites withstood five severe reprocessing cycles without unacceptable property detriments.