Sustainable eco-composites obtained from agricultural and urban waste plastic blends and residual cellulose fibers

The use of blends of recycled agricultural plastic and post-consumer high-density polyethylene from municipal solid wastes, as matrices for sustainable eco-composites, was investigated with the aim of boosting the use of recycled materials and reducing the waste plastic environmental impact. It was proposed that proper selection of blends of different waste plastics will allow the production of composites with optimized properties. The two plastics and their blends were characterized by using different spectroscopic techniques and thermal analysis, and measuring the flow curves. The eco-composites were obtained by compounding a selected blend of recycled agricultural plastic and post-consumer polyethylene with different proportions of coupling agent and waste cellulose fibers in a pilot-plant twin-screw extruder. The structure of the final materials and the role of the coupling agent were analyzed by using scanning electron microscopy. Finally, the novel eco-composites were compared to their counterparts without post-consumer polyethylene, revealing that the incorporation of polyethylene increases the strength and stiffness of the eco-composites, without compromising the impact strength. The incorporation of 40 wt% of polyethylene caused increases in moduli as high as 175% for the polymer and 47% for composites with 30% of fibers. The tensile strength increased up to 21% for the same composites. The decreases in processability caused by the incorporation of polyethylene can be corrected by increasing the coupling agent content. The improved balance between stiffness, strength and toughness without compromising processability can increase the recyclability of the polymer and cellulose wastes used in this work.