Post-Consumer Mechanical Recycling of Thermally Degraded Glass-Fiber Reinforced Polyamide 6,6 for Electrical Applications

Abstract

This study investigates post-consumer mechanical recycling of a glass-fiber reinforced polyamide 6,6 for electrical applications (PA66-GF25, brominated flame-retardant), using accelerated thermal ageing (180°C, 400 h) to simulate long-term thermo-oxidative degradation. Five material states are compared: virgin, aged, recycled-unaged (post-industrial analogue), recycled-aged (post-consumer analogue), and a 50 wt.% dilution of recycled-aged with virgin material. Mechanical characterization demonstrates that ageing primarily induces matrix embrittlement, reducing tensile strain at maximum stress from 4.19% to 2.50% while preserving tensile strength (81.5 to 82.7 MPa). Conversely, recycling predominantly compromises reinforcement efficiency through fiber attrition, with mean fiber length decreasing by 42%, resulting in a tensile strength reduction to 51.0 MPa for unaged recyclates. The post-consumer analogue exhibits cumulative degradation, yielding the lowest flexural strength (83.2 MPa compared to 112.4 MPa for virgin material). However, 50% dilution effectively restores flexural strength (112.1 MPa). Despite mechanical penalties, critical safety properties remain unaffected: all configurations maintain a GWFI of 960°C and a UL94 V-0 rating, while tracking resistance (CTI 400 V), lost during ageing, is fully recovered upon reprocessing. The results indicate that post-consumer recycling is feasible, with dilution as an effective route to restore performance while incorporating post-consumer content.