Changes in physico-chemical and morphological properties of carbon fiber by surface treatment

Abstract

Surface treatment of high strength carbon fiber by air oxidation and heat treatment has been carried out and the changes in physico-chemical properties as well as the morphology have been investigated using weight loss measurement, the tensile test, SEM, AFM, ESCA, surface area and pore size distribution measurement, and the wettability test. The functional groups in the fiber surface were increased with the air oxidation and the surface area also increased substantially. The micropores were increased by air oxidation with the surface force improvement. However, the heat treatment of the carbon fiber resulted in a decrease in the functional groups and the micropores converted into the macropores and the surface area increased mildly with the increased surface force due to the enlargement of the surface area. Air oxidation followed by subsequent heat treatment did not change the pore size distribution and the surface morphology compared to that produced by air-oxidation alone. It has been demonstrated that the various prepolymer molecules hardly access the micropores of the air-oxidized fiber due to the steric hindrance effect although the fiber has an increased surface area and a large amount of functional groups.