Structural evolution of poly(acrylonitrile‐co‐dimethyl itaconate) copolymer during thermal oxidative stabilization

Abstract

The structural evolution of poly(acrylonitrile-co-dimethyl itaconate) [P(AN-DMI)] copolymer was investigated by Fourier transform infrared spectroscopy (FTIR) in detail and compared with the polyacrylonitrile (PAN) homopolymer. The extent of cyclization reactions was calculated from the FTIR data. It was found that DMI comonomer had the ability to promote the cyclization reactions significantly at the temperature of 240°C, compared to the PAN homopolymer. The results of quantitative FTIR analysis in the range of 1000-1800 cm À1 showed that the DMI comonomer not only promoted the cyclization reactions, but also facilitated the oxygen uptake reactions, especially the conjugated carbonyl group in an acridone ring in the ladder polymer chains, which proved that DMI comonomer had the potential ability to make successful thermal oxidative stabilization (TOS) process. The positive effects of DMI comonomer on TOS reactions and carbon yield were further confirmed by the dynamic thermogravimetry (TG) analysis.

The suitable itaconic acid content in polyacrylonitrile copolymers used for PAN‐based carbon fibers

“…As shown in Figure , there were two peaks of DSC curves to be observed obviously except that of PAI with 0.5 wt % IA, which indicated that too less IA content in PAI copolymer could not ease the concentration of heat releasing during the thermal treatment. But the DSC curve of PAI‐0.5 wt % is still broader than that of PAN homopolymer compared to our previous report . The DSC experiments of PAI copolymers were carried out under nitrogen condition without the presence of oxygen, so the DSC exotherms were attributed to the only cyclization reaction.…”

“…However, the overlapped peaks of 1800 − 1000 cm −1 make the quantitative analysis of TOS reactions very difficult and unreliable. Second derivative and curve‐fitting procedures have been applied to the structural evolution of PAN polymers to overcome those problems . The minima of the second‐derivative spectrum provided the numbers and positions of the overlapping peaks in the original spectrum.…”

Microwave pre‐oxidation for polyacrylonitrile precursor coated with nano‐carbon black

“…The band at 1728 cm −1 was attributed to the CO stretching vibration. The weak band at 1070 cm −1 may be attributed to the stretching vibration of CCN . The broad peak around 1600 cm −1 was assigned to conjugated CC , (CN) n structures , or to a combination of the two peaks .…”

“…The intensity of the out‐of‐plane bending of CH at 802 cm −1 slightly increased and shifted to 806 cm −1 . The carbonyl (CO) stretching band located at 1728 cm −1 was weakened and shifted to a lower wavenumber, and it was only observed as a shoulder on the main conjugation absorption with the increase of pre‐oxidation time, suggesting that the carbonyl group became a part of the conjugated structure . Moreover, the absorption near 1260 cm −1 for various COC stretches can be attributed to crosslinking bonds .…”