Unveiling the microstructural evolution of carbon fibers derived from polyamide-6

Polyacrylonitrile-based carbon fibers have dominated the industry for decades, but the high cost of polyacrylonitrile has prevented the widespread adoption of carbon fiber in high-volume structural applications. As such, a significant amount of research has been dedicated to finding an alternative, low-cost carbon fiber precursor. In this work, carbon fibers were produced from polyamide-6 using metal salt impregnation and a thermo-oxidative stabilization step. To gain further insight into the carbonization process and microstructural transformation, the morphologies, crystallinities, elemental compositions, and thermal stabilities of the fibers were characterized at various stages of processing. The stabilization step resulted in a significant increase in carbon yield, indicating a dramatic increase in thermal stability. This is due to the crosslinking of polyamide-6 chains, which was confirmed by functional group analysis. The crystallinity of the fibers was also significantly altered during processing, as the produced carbon fibers consisted of pseudo-amorphous carbon with two distinct regions of metal salt impregnation. The findings and microstructural evolution mechanisms provide guidelines for further research into carbon fiber produced from polyamide-6.