Improving the Mechanical and Surface Properties of Aramid Fiber by Grafting with 1,4-Dichlorobutane under Supercritical Carbon Dioxide

The mechanical and surface properties of aramid fiber were simultaneously improved by grafting with 1,4-dichlorobutane in supercritical carbon dioxide (scCO2). 1,4-dichlorobutane was penetrated and reacted with heterocyclic an aromatic polyamide backbone along with supercritical CO2 fluids. The surface roughness and surface energy of the modified aramid fiber—which were measured by scanning electron microscopy (SEM) and the dynamic contact angle (DCA) test, respectively—significantly increased. X-ray diffractometer (XRD) measurements indicated that the crystallinity of the aramid fiber obviously increased after treatment in scCO2 under stretching. A single fiber tensile test showed that the tensile strength of the aramid fiber greatly enhanced after the modification due to its improved crystallinity characteristics. Moreover, the monofilament pull-out tests indicated that the interfacial shear strength (IFSS) test of the aramid fiber/epoxy composite increased by 24.3% from 51.30 to 63.91 MPa after the modification. This research provides a novel method for the simultaneous surface modification and mechanical improvement of aramid fiber properties.