Chemical Characterization of PAN based Carbon Fibers Produced by Microwave Assisted Plasma (MAP) Technology and effect of Plasma Treatment on Carbon Fiber Surface and Interphase with Polymer Matrix

The first objective of this research was to chemically characterize the surface of conventional carbon fiber and carbon fiber produced by microwave assisted plasma (MAP) manufacturing process. The chemical composition and functional groups on the surface of the fibers were determined by X-ray photoelectron spectroscopy (XPS). The untreated unsized MAP carbon fibers were compared to untreated unsized conventional carbon fibers and showed a significant amount of oxygen. Comparison between treated unsized MAP carbon fiber and treated unsized conventional carbon fiber reveal a 100% enhancement of oxygen elemental concentration.

Two plasma systems, remote applicator and atmospheric plasma were used to treat untreated unsized conventional carbon fiber. XPS results indicated that both systems have changed the chemical composition of carbon fiber surface. Oxygen-containing functional groups were found on carbon fiber surface after plasma treatment.

Auger electron spectroscopy combining with chemical deritivazation was used to investigate the effect of morphological structure of carbon fiber surface on the placement of carboxyl groups. It was found that carboxyl groups were located preferentially in the valleys. A model of surface morphological structure of carbon fibers treated with plasma was proposed.

Chemical bonding formed in the interphase between plasma treated carbon fiber and urethane was investigated using FTIR imaging. Directed evidence of formation of hydrogen bonding between carbon fiber and urethane was observed.