Fibre-on-fibre abrasion in oxidised polyacrylonitrile

This paper describes the analysis of a fibre-on-fibre abrasion test, in which two adjacent lengths of fibre contact one another in a twisted geometry. Consideration is given to the various factors contributing to the mechanical actions occurring during the test. Results are presented of a preliminary study, using this fibre-on-fibre abrasion technique, of the progressive changes accompanying the oxidative stabilisation of polyacrylonitrile (PAN) fibres in a set of partially-oxidised commercial samples. The effects of abrasion on the fibres are also examined using scanning electron microscopy (SEM). The analysis predicts that applied tension and level of twist should play major roles in determining the severity of the test, and this is borne out by experiment. Considering the influence of the oxidative treatment on PAN fibres, it is concluded that the abrasion life generally decreases as stabilisation proceeds. The SEM results indicate a transition from plastic to brittle behaviour, which can be accounted for in terms of simple structural models of PAN and oxdised PAN fibres.