Synthesis, characterization, and thermomechanical properties of poly(acrylonitrile-co-2,3-dimethyl-1,3-butadiene-co-itaconic acid) as carbon fibre polymer precursors

Novel carbon fibre polymer precursor (CFP), viz., poly(acrylonitrile-co-2,3-dimethyl-1,3-butadiene-coitaconic acid) was synthesized using solution polymerization process. Structural identification, bonding network were established using infrared, and nuclear magnetic resonance spectroscopic techniques. Molecular characteristics, such as different kinds of average molecular weights were estimated applying solution viscometry and size exclusion chromatography. The char yield of the polymers were found to be 45% wt through thermal gravimetry. The thermomechanical behaviour of novel carbon fibre polymers were investigated employing several thermal techniques. Thermomechanical data confirm that newly synthesized copolymers exhibit higher coefficient of linear thermal expansion in the range 74-1716 degrees C-1, softening temperature at 51 degrees C in contrast to the conventionally used (37-810 degrees C-1). Differential scanning calorimetry results show a distinct bimodal curves with a wider thermal exotherm starting from 220 degrees C with two peaks at a temperature difference of 25 degrees C and an slower energy release rate 2.5-5.0 J g(-1) s(-1), thereby releasing the heat over a extended period of time than a sudden release of heat (14.75 J g(-1) s(-1)) as sharp peak as observed in the conventional precursors. The above facts indicate that new polymers can be used as polymer precursor for high tensile carbon fibres.