Mechanical recycling of biobased polyethylene-agave fiber composites

Abstract

Biobased polymers have emerged as a promising alternative to petroleum-based polymers in terms of lower environmental impact. However, to improve their carbon footprint, it is important to study strategies, such as recycling, extending the useful life of these biopolymers, and mitigate their higher costs compared to petroleum-based polymers. Adding agro-industrial wastes as fillers or reinforcements is another option to reduce the cost and increase the biobased content to produce composites. This study aimed to evaluate the addition of agave fibers to biobased linear low-density polyethylene (bio-LLDPE) and their effect on its reprocessing by extrusion, i.e., close-loop mechanical recycling. The results revealed that it was possible to reprocess the bio-LLDPE alone as limited changes in their physical properties were observed up to 34 cycles. However, for the composites, the viscosity changed in the first eight cycles mainly due to fiber break-up (lower aspect ratio). The dimensions of the agave fibers are modified by reprocessing. In the initial 8 cycles, there is a notable decrease in fiber dimensions, affecting the tensile, flexural, and impact properties of the composites. The water uptake was found to decrease with each cycle due to better fiber dispersion and the reduction of interfacial voids/defects. Nevertheless, the color of the bio-LLDPE and its composites showed significant changes by reprocessing, which is associated with thermal and oxidation degradation. Despite minor property losses, the study reveals that bio-LLDPE/agave fiber composites exhibit a commendable level of sustainability. This characteristic enables their extended reuse and reprocessing over a prolonged duration.