酸化炭素繊維の表面における酸無水物型官能基の存在とその反応性

抄録

The nature of functional groups on the surface of oxidized carbon fiber was investigated through the chemical reactions, particularly with focussing on the weaker acidic groups than carbonic acid.
A pitch-based carbon fiber, prepared by 1000°C heat treatment, was oxidized with 60% nitric acid under various conditions and the cation exchange capacities of the oxidized fibers for NaOH and Na₂ CO₃ (Ct-NaOH and Ct-Na₂ CO₃, respectively) were determined. The proportion of the less acidic groups (Ct-NaOH-Ct-Na₂CO₃) to the total acidic groups (Ct-NaOH) was found to increase with the increasing Ct-NaOH value. One of the oxidized fibers, whose Ct-NaOH and -Na₂CO₃ were 2.84 meq/g and 1.98 meq/g, was treated with hexamethylenediamine resulting in a weight increase of about 5%, a nitrogenintake of 1.28 matom/g, and a Ct-NaOH decrease of 2.42 meq/g. On the basis of stoichiometry from these results it was concluded that the surface of the oxidized carbon fiber in question must be tightly covered mainly with quinone-type carbonyl groups and carboxyl groups, some of the carboxyl groups exist in the form of intramolecular acid anhydride, and, as a result, the fiber can combine directly with an amine reagent forming the imide group.