Redox copolymerization of acrylonitrile with fumaronitrile as a precursor for carbon fibre

Redox copolymerization of acrylonitrile (AN) with fumaronitrile (FN) was carried out in water at 40 °C using potassium persulphate (KPS) and sodium bisulfite (SBS) as initiators. Monomers feed used were 100:0, 97:3, 95:5, 90:10, 85:15 and 80:20 (AN:FN). Copolymers were characterized by Fourier transform infrared spectroscopy (FT-IR), Differential scanning calorimetry (DSC) and Thermogravimetric analysis. The effect of monomer composition on conversion and thermal properties of copolymer was studied. The DSC thermograms of copolymer samples are different from that of the homoPAN sample in the sense that the thermogram of the copolymer shows a doublet appearance and broad exothermic peak indicating that incorporation of fumaronitrile into copolymer system reduces the cyclization propagation rate with lower heat liberation (510 Jg⁻¹) as compared to that of homo(PAN) (758 Jg⁻¹). DSC thermograms also show that initial cyclization occurred at lower temperatures in copolymers as compared to homoPAN. The incorporation of 10% fumaronitrile into copolymer results the highest char yield (53%).