1
046
A. Ju et al.
reactions occured during this process. The E of cyclization
a
4. Gupta AK, Paliwal DK, Bajaj P. Acrylic precursors for carbon
fibers. J Appl Polym Sci. 1996;59:1819–26.
-1
reactions in PAN homopolymer is about 165 kJ mol ,
5
. Qin XH. Structure and property of electrospinning PAN nanofi-
bers by different preoxidation temperature. J Therm Anal Calo-
rim. 2010;99(2):571–5.
while in P(AN-co-MHI) the E has been splitted into two
a
parts. The first part assigned to the ionic cyclization reac-
tions is calculated from the first exothermic peak and the E
6. Burkanudeen A, Krishnan GS, Murali N. Thermal behavior of
carbon fiber precursor polymers with different stereoregularities.
J Therm Anal Calorim. 2013;112(3):1261–8.
a
-1
is about 88 kJ mol . The second part calculated from the
-1
second exothermic peak is about 151 kJ mol , which is
assigned to the radical cyclization reactions. Obviously, the
Ea of P(AN-co-MHI) has been reduced significantly com-
pared with PAN homopolymer, which is mainly attribute to
the change of cyclization mechanism caused by MHI [18].
7
. Bahrami SH, Bajaj P, Sen K. Effect of coagulation conditions on
properties of poly(acrylonitrile–carboxylic acid) fibers. J Appl
Polym Sci. 2003;89:1825–37.
8
. Liu JJ, Ge HY, Wang CG. Modification of polyacrylonitrile
precursors for carbon fiber via copolymerization of acryloni-
trile with ammonium itaconate. J Appl Polym Sci. 2006;102:
2175–9.
The decrease of E in P(AN-co-MHI) bipolymers further
a
confirms that the cyclization of nitrile groups has been
promoted by the bifunctional comonomer MHI, which is
beneficial to stabilization of PAN.
9. Devasia R, Reghunadhan Nair CP, Sadhana R, Babu NS, Ninan KN.
Fourier transform infrared and wide-angle X-ray diffraction studies
of the thermal cyclization reactions of high-molar-mass poly(acry-
lonitrile-co-itaconic acid). J Appl Polym Sci. 2006;100:3055–62.
0. Ouyang Q, Cheng L, Wang HJ, Li KX. DSC study of stabilization
reactions in poly(acrylo-nitrile-co-itaconic acid) with peak-
resolving method. J Therm Anal Calorim. 2008;94(1):85–8.
1
Conclusions
11. Devasia R, Reghunadhan Nair CP, Sivadasan P, Catherine BK,
Ninan KN. Cyclization reaction in poly(acrylonitrile/itaconic
acid) copolymer: an isothermal differential scanning calorimetry
kinetic study. J Appl Polym Sci. 2006;88:915–20.
The P(AN-co-MHI) bipolymers used as carbon fiber pre-
cursor were prepared successfully by solution polymeri-
zation. Both the conversion of polymerization and
molecular mass reduce with the increasing MHI amounts in
the feed due to the large molecular volume of MHI. The
reactivity ratios calculated by Fineman–Ross and Kelen–
T u¨ d o˜ s methods show good agreement and the bifunctional
comonomer MHI possesses higher reactivity than AN,
which can be further confirmed by the elemental analysis.
From the FTIR, DSC, and XRD results, it can be found that
the stabilization of P(AN-co-MHI) bipolymers has been
significantly improved by MHI with lower initiation tem-
perature, broadened exothermic peak, and larger extent of
stabilization, which is mainly attributed to the ionic
cyclization reactions initiated by MHI; it is further con-
1
2. Tsai JS, Lin CH. Polyacrylonitrile precursors by copolymer and
additive with itaconic acid. J Mater Sci Lett. 1990;9:869–71.
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boxylic acid and amide structures. Eur Polym J. 1972;8:257–69.
4. Coleman MM, Sivy GT. Fourier transform ir studies of the
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comparative rates of the degradation of three copolymers below
1
1
1
2
00 C and under reduced pressure. Carbon. 1981;19:133–5.
5. Catta P, Sakata S, Garcia G, Zimmermann JP, Galembeck F,
Galembeck F, Giovedi G. Thermal behavior of polyacrylonitrile
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acrylic fibers. J Polym Sci Part B. 2003;41:2949–58.
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properties of copolymers of acrylonitrile and monomethyl itac-
onate for carbon fiber. Polym Mater Sci Eng. 2010;26:146–8.
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ization reactions of poly(acrylonitrile-co-b-methylhydrogen it-
aconate). J Mater Res. 2012;27(20):2668–76.
1
1
firmed by the calculation of E based on Kissinger method
a
1
1
2
2
and Ozawa method.
Acknowledgements Financial support of this work from National
Science Foundation of China (No 20974018) and Important National
Research Program ‘‘863’’ (No 2012AA030313-1) was gratefully
acknowledged.
9. Devasia R, Reghunadhan Nair CP, Ninan KN. High char-yielding
poly[acrylonitrile-co-(itaconic acid)-co-(methyl acrylate)]: syn-
thesis and properties. Polym Int. 2005;54:1110–8.
0. Chen H, Liang Y, Wang CQ. Kinetics of copolymerization of
2
acrylonitrile with ammonium itaconate in a H O/dimethyl
formamide mixture. J Appl Polym Sci. 2004;94:1151–5.
1. Gupta VB, Kumar S. The effect of heat setting on the structure
and mechanical properties of poly(ethylene terephthalate) fiber.
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