Decomposition behaviour of Kevlar 49 fibres: Part I. At T approximate to T-d

The structural changes which accompany decomposition of Kevlar 49 fibres at T= 500 degrees C and 550 degrees C, respectively, have been elucidated. At both these temperatures, cumulative thermal exposures of specific duration s, t(cum)(T), are required to result in decomposition. The conspicuous feat ures which characterize isothermal decomposition of the fibres are: (i) pro gressive reduction and an eventual total loss in fibre crystallinity, (ii) progressive loss in weight, (iii) introduction of surface damages, (iv) int roduction of hollowness, and (v) deterioration in tensile properties.