Characterization of oxidised pan fibres

A comprehensive study of mechanical properties of PAN fibres, oxidised for various times, is made. The decrease in strength and secondary modulus of oxidised fibres with oxidation time shows that the oxidation reaction is intramolecular and not intermolecular. The increase in formation of ladder polymer with oxidation time is confirmed by X-ray studies. The variation of strength of carbon fibres (H.T.T. 1000°C) with change in preoxidation time is reported and it is shown that the strength of carbon fibres starts decreasing after a certain optimum pre-oxidation time. Carbon fibres with slow heating rate during preoxidation stage are found to be stronger than those with quick heating during preoxidation. The implications are discussed.