Effect of comonomer composition on the properties of polyacrylonitrile precursor and resulting carbon fiber

Abstract Since the itaconic acid (IA) comonomer is the potential initiator of cyclization, therefore the introduction of IA comonomer into polyacrylonitrile (PAN) precursor can depress the onset of exotherm (or cyclized temperature) and peak temperature. However, the more the IA content, the lower the conversion of acrylonitrile (AN) in the polymerization reaction. Although 2‐ethylhexyl acrylate (2‐EHA) comonomer in PAN precursor may prevent the cyclization propagation of nitrile groups during oxidation, PAN precursor with a few percent of 2‐EHA comonomer has a more preferred orientation. As the content of 2‐EHA comonomer further increases, the orientation of the resulting carbon fiber decreases correspondingly. In this study, PAN precursor, with the composition of 98 mol % AN, 1.5 mol % 2‐EHA, and 0.5 mol % IA, and its resulting carbon fiber have the best mechanical properties. From the results, it is shown that there is a good relationship between the tenacity and modulus of PAN precursor and those of its resulting carbon fiber.