Yh. Bang et al., EFFECT OF METHYL ACRYLATE COMPOSITION ON THE MICROSTRUCTURE CHANGES OF HIGH-MOLECULAR-WEIGHT POLYACRYLONITRILE FOR HEAT-TREATMENT, Journal of applied polymer science, 68(13), 1998, pp. 2205-2213
The acrylate comonomer in polyacrylonitrile (PAN) precursor markedly i
nfluences the microstructure of PAN fiber and its resulting carbon fib
er. In this study, the change occurring during the heat treatment of P
AN copolymers (acrylonitrile-co-methyl acrylate) in the presence of ai
r up to 260 degrees C has been examined using both physical and chemic
al techniques. Considering the effect of the methyl acrylate content o
f PAN copolymers on the cyclization mechanism and fine structural chan
ges in polymer chains under various heat treatment conditions, the com
position of acrylonitrile and methyl acrylate = 98 : 2 to 97 : 3 mol %
was suitable for the precursor preparation because the cyclization me
chanism and fine structural changes in the boundary of this compositio
n of copolymers were significantly different. With increasing MA conte
nt, the exothermic onset and peak in the thermogram was found to shift
, toward higher temperatures, and the aromaticity index decreased. Thi
s evidence indicates that MA was believed not to activate at all but t
o interfere with the cyclization. Additionally, by means of C-13 nucle
ar magnetic resonance (C-13-NMR) analysis, the tacticities of copolyme
rs were nearly same, regardless of the copolymer composition, and the
cyclization occurred nonstereospecifically during the initial heat tre
atment at 240 degrees C for 1 h. (C) 1998 John Wiley & Sons, Inc.