Recycling polyamide 6 fishing nets and carbon fibers for the development of novel sustainable composites: Properties and LCA process analysis

Fishing nets and related gear account for approximately 20% of the total plastic waste in the ocean, amounting to around 640,000 tons per year. Efforts are underway to develop circular economy strategies for the reuse and recycling of marine plastics. In this context, the present study introduces an innovative approach for developing advanced composite materials, employing recycled polyamide 6 (rPA6) derived from fishing nets and reinforced with recycled carbon fibers (rCF) recovered from epoxy resins through a novel thermo-oxidative process. The process involves pyrolysis at 510 °C in nitrogen to degrade the epoxy matrix, followed by gasification in air to produce clean rCF with enhanced adhesion to rPA6, eliminating the need for new sizing. This treatment increases the presence of polar groups on the surface of rCF compared to virgin carbon fibers (vCF), improving the O/C ratio (from 0.021 to 0.054 wt%) while maintaining their dimensions (7–8 μm) and surface smoothness, resulting in similar mechanical properties (293 ± 20 versus 282 ± 35 GPa). The improved compatibility of rCF with rPA6, compared to vCF, is demonstrated by the enhanced tensile modulus (11.1 and 13.1 GPa) and impact toughness (25.9 and 28.4 kJ/m 2 ) observed in vCF/rPA6 and rCF/rPA6 composites, respectively, at the highest fiber loading of 15 wt%, in contrast to pure rPA6 (3.2 GPa and 11.8 kJ/m 2 ). A Life Cycle Assessment (LCA) was conducted to evaluate the environmental sustainability of the CF-polyamide 6 composites. Three production scenarios were compared: Scenario 0 (virgin PA6 and vCF), Scenario 1 (rPA6 and vCF), and Scenario 2 (rPA6 and rCF). Scenario 2 showed the highest reduction in emissions, saving 5.74E+03 kg of CO 2 equivalents. While off-site wastewater treatment increased some emissions, the use of recycled materials consistently reduced the overall environmental impact, highlighting the benefits of sustainable waste recovery. • Polyamide fishing nets significantly contributes to ocean plastic pollution. • Recycled polyamide 6 reinforced with reclaimed carbon fibers were developed. • The designed composites outperform conventional ones made from virgin resources. • LCA analysis shows a lower environmental impact than traditional composites.