Study On The Efficiency Of Dimethyl Itaconate In Improving The Thermal Oxidative Stabilization Reactions Of Polyacrylonitrile

The defect structure of carbon fiber is the most important factor affecting the performance of carbon fiber.The unevenness of the carbon fiber radial structure,that is,the sheath-core structure is one of the main structural defects of the finished fiber.In order to eliminate the skin-core structure,the polymer structure can be optimized from the molecular design,and a PAN can be modified by using a monomer that can promote oxygen diffusion without adversely affecting the cyclization reaction.In our previous investigation,it was found that dimethyl itaconate(DMI)has the abovementioned functions.In this paper,DMI was used to modify PAN,and the mechanism of DMI to improve the thermal and oxygen stabilization was further studied.At the same time,the effect of DMI content on the oxidation reaction was discussed.(1)Poly(acrylonitrile/dimethyl itaconate)(P(AN/DMI))copolymer was prepared by solution polymerization,by differential thermal scanning calorimetry(DSC),thermal weight loss(TG),Fourier Leaf infrared spectroscopy(FTIR)and other testing methods were used to analyze the structural changes and thermal behavior of the copolymer during the heat treatment process,and the role of DMI in the heat treatment process of P(AN/DMI)was studied in detail.The results show that due to the side group effect,the two ester groups of DMI provide a channel for oxygen to diffuse into the structure,reducing the resistance of oxygen molecules to movement,which can effectively promote the oxidation reaction and cyclization reaction,and with the content of DMI The increase of the cyclization reaction and the concentration of oxygencontaining groups increase accordingly.(2)Poly(acrylonitrile/itaconic acid/dimethyl itaconate)(P(AN/IA/DMI))copolymer was prepared by aqueous phase precipitation polymerization.The physical and chemical structure evolution during the heat treatment of the copolymer was analyzed by scanning electron microscope(SEM),FTIR and other testing methods.The research results show that the addition of DMI can promote the oxygen uptake reaction and the formation of a longer ring structure,thereby effectively improving the crosssectional homogeneity of the PAN copolymer film and slowing the skin-core structure phenomenon.