Degradation pathways and chemical stability of regenerated cellulose fiber-reinforced bio-polyamide 5.10 composites under acidic and alkaline conditions

Bio-based polyamides (PA) represent an emerging class of engineering biopolymers that combine high performance with renewable origins. In particular, PA5.10, derived from renewable monomers, offers an attractive alternative to petroleum-based matrices in sustainable composite applications. To advance the understanding of its environmental stability, this study explores the chemical resistance and degradation pathways of neat PA5.10 and regenerated cellulose fiber (RCF)-reinforced PA5.10 (20 wt%). Standardized specimens were prepared by twin-screw extrusion and injection molding and subsequently exposed to aqueous, acidic, alkaline, and organic environments for up to 168 h. Characterization included tensile testing, Fourier-transform infrared spectroscopy (FTIR), melt volume rate (MVR), moisture uptake, and scanning electron microscopy (SEM). Hydrolytic and chemical aging caused chain splitting processes, fiber swelling, and fiber-matrix debonding, as evidenced by viscosity reduction, altered FTIR spectra, and mechanical deterioration. The composites exhibited pronounced sensitivity in acidic and alkaline media, with moisture uptake further reducing tensile strength and modulus. These findings provide new insights into the chemical stability of bio-based polyamides and highlight key challenges for their long-term use in sustainable composite applications. Addressing these limitations through targeted material design will be essential to expand the application range of RCF-reinforced bio-based polyamides in automotive and engineering sectors.