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

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.