Investigation of the mechanism/effect of surface etching and post-process of Kevlar fiber by metal ions

The mechanism/effect of surface etching and post-process of Kevlar Fiber (KF) by metal ions were investigated in detail by etching Kevlar-29 fiber with different solutions. After the post-process of heat or solvent treatment, surface morphology changes of etched fibers were further discussed. Etching mechanisms have been demonstrated according to the results of Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, X-ray diffraction instrument, atomic force microscopy, and scanning electron microscopy. The results exhibited that the coarsening of KF surface was caused by stress cracking instead of chain degradation. Furthermore, the cracks produced by stress cracking will extend lengthwise along the fiber surface due to the breakdown of hydrogen bonds. In addition, it is shown that the stress concentration appears on the fiber surface. In all, the etching mechanism consists of two parts: stress cracking and crack propagation. The proposed etching mechanism is of great significance to further improve the fiber surface and enhance the bond with the resin.