Surface modification of poly(p-phenylene terephthalamide) fibers with HDI assisted by supercritical carbon dioxide

Abstract

A process of surface modification of poly(p-phenylene terephthalamide) fibers was reported to improve the adhesion to epoxy, in which the fibers were treated in supercritical carbon dioxide (ScCO₂) with hexamethylene diisocyanate (HDI). After the modification, the surface chemical composition of the fibers was identified using X-ray photoelectron spectroscopy (XPS), and the results showed Ph-NH₂ groups are formed on fibers after treatment in ScCO₂ with HDI. From the scanning electron microscope (SEM) and atomic force microscope (AFM) results, we can find the surface of fibers treated with HDI in ScCO₂ became much rougher. The interfacial properties of aramid/epoxy composites were investigated by microdebond test, the results showed that the interfacial shear strength (IFSS) was improved by 22%. It is beneficial for the application of the fiber material as reinforcement in an epoxy system that can improve the interfacial property of PPTA fibers with epoxy.