Promotion of crystallization of polyamide 6 at an interphase and a mechanical interlocking effect at an interface due to surface irregularities of carbon fibers

Abstract

The effect of surface irregularities in the carbon fiber (CF) axial direction on the interfacial properties of polyamide 6 (PA6) was investigated using CFs with different amounts of oxygen functional groups on the surface, that is, chemical reactivity. The interfacial shear strength between PA6 and CF was measured using the microdroplet method. The crystal structure of PA6 at the interphase was characterized using unpolarized and polarized micro-Raman spectroscopy and polarized light microscopy. Not only the chemical interactions at the interface but also the surface irregularities of the CF were found to contribute to the formation of oriented crystals of PA6 in the CF axial direction at the interphase, and these oriented crystals of PA6 at the interphase enhanced the interfacial shear strength. The surface irregularities of the CF were found to cause mechanical interlocking effects. This study demonstrates the importance of CF surface irregularities in controlling interfacial properties.