Molecular and thermal studies of carbon fiber precursor polymers with low thermal-oxidative stabilization characteristics

In this investigation, terpolymers, copolymers, and homopolymer of acrylonitrile with dimethylaminopropyl acrylamide (DMAPA), itaconic acid (IA) viz., poly(acrylonitrile-ran-3-dimethylaminopropyl acrylamide-ran-itaconic acid) [P(AN-DMAPP-IA)], poly(acrylonitrile-co-3, dimethylaminopropyl acrylamide) [P(AN-DMAPP)] were synthesized with varying amounts of comonomers using solution polymerization process. The chemical structure, composition, bonding network were determined employing infrared, 1H and, 13-carbon nuclear magnetic resonance spectroscopic techniques. Molecular characteristics of as-synthesized polymers such as different kinds of average molecular weights, molecular weight distribution were estimated applying solution viscometry and size exclusion chromatography. The influence of comonomers (DMPAA, IA) on the thermal stabilization characteristics of acrylonitrile terpolymers in comparison with copolymers and homopolymers of acrylonitrile were studied using differential scanning calorimetry (DSC), hyphenated thermal techniques (thermal gravimetry coupled with differential thermal analyzer).The DSC curves of P(AN-DMAPP-IA) exhibit a distinct broader bimodal peaks with thermal exotherm initiating at as low as 165 degrees C, and followed by two peaks with temperature difference of 42 degrees C, releasing the evolved heat at a release rate of 0.7-0.11Jg(-1)s(-1)over 10 min as compared to 1.2, 7.5Jg(-1)s(-1) in 4.5, 2 min as observed in P(AN-DMAPP), polyacrylonitrile, respectively. The thermal stability of P(AN-DMAPP-IA) and P(AN-DMAPP), as evidenced by TGA-DTA was found to be higher than PAN homopolymers. Specific heat capacity measurements confirmed the DSC results. Bulk densities of P(AN-DMAPP-IA) were in the range 0.31-0.35 g/cc. These results confirm the low-temperature stabilization characteristics and suitability of P(AN-DMAPP-IA) as low cost carbon fiber precursor polymers. (c) 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 46381.