Surface structure of Kevlar® fiber studied by atomic force microscopy and inverse gas chromatography

Abstract

Kevlar® fiber surface structure was primarily and directly observed in the filament configuration by the tapping mode atomic force microscopy (AFM). The microfibrils feature was observed with an average width of 500nm, composed of various types of periodical units of an average size 50nm in a pleating appearance. At the less crystalline spot on the Kevlar® fiber surface, the periodical organizations exhibit the skin-core-like differentiation. In contrast, at the highly crystalline spot, the periodicity is more uniformly arranged by a rectangular network manner. Inverse gas chromatography (IGC) was used as a tool to investigate the surface structure heterogeneity by calculating the surface energy of different types of probes adsorbed on the Kevlar® fiber surface. The energy sites distribution plot of n-hexylamine adsorption at finite dilution exhibits a two-adsorbing-peaks curve. At the higher energy site, a possible hydrogen-bonding interaction was proposed between n-hexylamine and oxygen-containing groups formed at the less crystalline surface. According to the AFM and IGC results, a Kevlar® fiber surface organizations model at the nanometer scale was proposed.