Supercritical carbon dioxide assisted impregnation and graft of polyamide acid into aramid fiber for formation of polar interface

Abstract

Contrapose the high inertness of para-aramid fiber (AF) with high strength modulus, surface modification in a green and effective way is one of the main challenges currently faced by fiber reinforced composites engineers. In this study, AF was treated by a two-step process combining hot air treatment (250 °C, 1 h) and graft reaction of polyamide acid (PAA) assisted with supercritical carbon dioxide (scCO2). The ester group displayed on the fiber surface suggested the successful graft reaction between AF and PAA. Additionally, the auxiliary effect of scCO2 increases the surface roughness, resulting in a more uniform grafted layer on the modified fiber surface. Specifically, in the process of graft modification of AF with 5% PAA assisted by scCO2, the thickness of the grafted layer was about 100 nm. Meanwhile, a 50.15% increment of the interfacial shear strength indicated an obvious enhancements of surface adhesion. This study provides a feasible method for interfacial modification of AF, and further widens the application of scCO2 as an auxiliary process in the surface modification of AF.

Keywords

• Aramid fiber
• Polyamide acid
• Graft reaction
• Supercritical carbon dioxide
• Interfacial adhesion