Bonding epoxide functions to nitric acid-oxidized carbon fibers using epichlorohydrin; A reliable analytical determination of epoxide functions on fiber surfaces Original Research Article

Epoxide functions were successfully bonded onto the surfaces of nitric acid-oxidized PAN-based high-strength carbon fibers by reacting surface acidic functions with epichlorohydrin. A two-stage process that included ring opening and ring closure under anhydrous conditions was employed to avoid polymer formation on the surface. Typically, more than 30 μeq of epoxy groups were bound to one gram of fibers (7-micron diameters), which initially had 60 μeq of acidic groups. The first reliable method was also developed to quantitatively analyze epoxy groups on fiber surfaces using HBr and a bromide-selective electrode. The measured epoxide concentrations on fiber surfaces ranged from a few μeq/g to 40 μeq/g.