Effect of cyclization degree of nitrogen thermal pretreatment on radial structure of PAN stabilized fibers.

The effect of cyclization degree of nitrogen thermal pretreatment on the radial structure difference of polyacrylonitrile(PAN) oxide fibers is explored. In this paper, PAN fibers were isothermally heated in nitrogen at 170°C, 190°C and 210°C for 0, 10, 20, 30, 40, and 50 min, respectively, so as to obtain pre‐treated fibers with cyclization degrees of 0%, 19.96%, 35.18%, 38.92%, 42.80%, and 53.12%, respectively. The pre‐treated fibers were further stabilized in an oxygen atmosphere. The scanning results show that the radial structure difference of oxide fibers first decreases and then increases with cyclization degree increasing. Through FTIR, SEM and Raman characterization, it is found that this phenomenon is mainly related to the influence of nitrogen thermal pretreatment on oxygen diffusion. Therefore, to improve the thermal stability efficiency of PAN fibers by means of nitrogen thermal pre‐treatment, it is necessary to control the degree of cyclisation, and the appropriate degree of cyclisation in the present work is about 35%. [ABSTRACT FROM AUTHOR]