In-situ recycling of ghost gear and waste from seafood processing in the Madeleine Islands to produce functional materials

This study is part of a local valorization approach for plastic waste generated by the fishing industry, specifically polyamide 6 (PA6) fishing nets, polyolefin (PE/PP) ropes, and marine byproducts such as mollusk shells and wood from lobster traps. The overall objective is to develop 100% recycled, high-performance composite materials suitable for applications in the construction and automotive sectors, using simple, low-impact manufacturing processes that can be transferred to insular contexts. In a first phase, the discarded PE/PP ropes were characterized by Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and differential scanning calorimetry (DSC). The analyses revealed a blend of high-density polyethylene and polypropylene, with signs of surface oxidation and photodegradation. Cladding panels were manufactured via compression molding and tested for flexural performance (three-point bending) and Charpy impact resistance. While the recycled panels exhibited moderate mechanical performance compared to commercial counterparts, they demonstrated good thermal processability. In a second phase, several formulations were developed by incorporating either 30 wt% wood fibers, 30 wt% mollusk shell powder, or a balanced mixture of both reinforcements (15 wt% wood + 15 wt% shells) into the recycled rope matrix. Comparative analysis showed that the composite combining both fillers exhibited the most balanced performance, with over a 200% increase in flexural modulus, a 38% reduction in water absorption, and significantly slower flame propagation. Dynamic mechanical analysis (DMA) also showed an increase in storage modulus, indicating enhanced stiffness. Finally, in the third part of the study, composites intended for automotive applications were developed using recycled PA6 fishing nets reinforced with natural switchgrass (Panicum virgatum) fibers at contents ranging from 0 to 30 wt%. The samples were produced via extrusion followed by injection molding, and characterized through tensile testing, thermal analysis (DSC), DMA, melt flow rate (MFR), and scanning electron microscopy (SEM). At 30% fiber content, the composites exhibited a 23% improvement in tensile strength and a 126% increase in Young’s modulus, reaching 93% of the strength of virgin automotive-grade PA6. However, ductility decreased significantly and melt flow rate dropped from 19.35 to 8.63 g/10 min. SEM observations revealed uniform fiber dispersion up to 20%, followed by aggregation at 30%, which likely contributed to the observed performance limitations at high fiber loading. The results validate the technical and environmental feasibility of locally converting marine plastic waste into high-performance rigid composites, while accounting for processing constraints and formulation optimization. This work paves the way for the development of an insular recycling and eco-design sector based on abundant secondary resources, accessible processing technologies, and materials that meet the requirements of the construction and transport industries.