CHEMICAL-TRANSFORMATIONS RESULTING FROM PYROLYSIS AND CO2 ACTIVATION OF KEVLAR FLOCKS

The chemical and structural transformations which result from the pyro lisis of Kevlar (poly[p-phenyleneterephthalamide]) fibres in argon, an d from subsequent activations to differing levels of burn-off, under d iffering activation conditions in CO2, have been investigated using XP S, SEM and XRD. XPS indicates a marked decrease in surface oxygen afte r pyrolysis followed by the formation of oxygen functionalities at var ious levels depending upon the activation regime. Nitrogen levels appe ar relatively constant after pyrolysis indicating the condensation of stable aromatic nitrogen during pyrolysis. The corresponding oxygen an d nitrogen chemistry obtained from chemical shift data is also discuss ed. SEM indicates that the lamellar structure of polyaramid is preserv ed after carbonization and activation which is consistent with the obs ervations of other authors. XRD shows that the carbons produced are ge nerally more ordered than those resulting from coal, other organic pre cursors and some ex-PAN fibres. (C) 1997 Elsevier Science Ltd.