A process for improving the bonding properties of high modulus graphite fibers is provided that comprises treating the fibers with a solution of sodium iodate in aqueous dioxane; washing and drying the treated fibers; contacting the treated fibers with a solution of tin tetrachloride in 2-butanone; and heating the fibers to remove the 2-butanone. An epoxy resin composite having a greatly improved interlaminar shear strength is obtained when the treated graphite fibers are employed as a reinforcing material for epoxy resins.
An improved method of manufacturing articles containing carbon fibers when the fibers are temporarily plasticized to render them more flexible thereby permitting tortuous mechanical manipulation of the fibers to be carried out with little or no mechanical damage. The improvement comprises exposing the carbon fibers to agents capable of intercalating single crystals of graphite, such as bromine or iodine monochloride which have the effect of plasticizing the fibers by lowering their tensile modulus. While the fiber yarns are appreciably more flexible in the plasticized state, and have a higher elongation-at-break, on removal of the plasticizer they tend to return to their original state but retain a measurable degree of the shape imparted to them.
