In situ NMR investigation into the thermal degradation and stabilisation of PAN

In situ broadline H-1 NMR has been used to assess the low temperature degra dation of polyacrylonitrile (PAN) under a variety of atmospheres and temper atures. In combination with conventional analytical techniques (solid state C-13 NMR and FTIR), the structural and conformational changes produced in the network have been correlated with its thermal behaviour. Degradation ha s also been shown to be both temperature and time dependent, irrespective o f reaction environment. Moreover, it has been demonstrated why air is the p referred medium for stabilisation in the production of fibre precursors. En hanced stability and resistance to char formation is observed in the air-mo dified polymer, which also becomes resistant to resoftening during low temp erature carbonisation. (C) 2001 Elsevier Science Ltd. All rights reserved.