The Study On Carbon Fiber Precursor Copolymerization System

Preparation of high performance carbon fiber demands precursor to be ultra-purified and to have homogeneous structure. However, comonomer and even the second comonomer have been added to the precursor to broaden exothermic peak and improve the spinnability at the beginning. So it has been a difficult point and hot point in the carbon fiber area to reaserch how to satisfy the exothermic and sppinnability requirement and just add one kind comonomer at the same time.Firstly, free radical copolymerization of AN with MA,IA initiated by AIBN were investigated in DMF, by adjusting the parameters of the experiment. Through the conversion of copolymerization, the molecular weight, DSC, FT-IR, and 1H-NMR analysis, we discussed the various experimental parameters on the conversion of copolymerization, the molecular weight and thermal properties of PAN. The results showed that: even the duration of the experiment maintained around 48 hour, despite changes of the experimental parameters, the conversion of copolymerization maintained at no more than 50 percent. The concentration of initiator and monomer were the main factors of molecular weight, by regulating the two parameters, we could significantly change the molecular weight. The content of comonomer could observably influence the thermal properties of PAN, particularly with the increase of the content of IA, the exothermic peak becomeed wider, and the value of the exothermic peak changed obviously.Then, with IA, methanol, ethanol, butanol, isopropanol, isobutanol and propanol as reactant, series ofβ-monoester itaconate were synthesized from selective esterification. The apparent reactivity ratio of AN/β-monoester itaconate copolymerization system were measured by Fineman-Ross method at 70℃using AIBN as initiator and DMF as solvent. It was found that the apparent reactivity ratio of AN/MIBI copolymerization system calculated by Fineman-Ross method was 0.523 for AN and 2.001 for MIBI, and rAN×rMIBI= 1.047≈1 indicated that the system approached general ideal copolymerization. The effect of MIBI's content, atmosphere, and temperature rise speed in the thermal stabilization process was studied by differential scanning calorimetry(DSC) and the results showed that MIBI could significantly lower copolymer's exothermic onset temperature, broaden exothermic peak and decrease heat release rate. It indicated that cyclization was caused by ion mechanism and then oxidation occured in thermal stabilization process. With the increase of temperature rise speed, exothermic onset temperature moved to high temperature region, heat release amount decreased, and peak shape changed gradually from double broadened peaks to one peak. With the increase of MIBI's content, contact angle between the copolymer and water increased from 62.5°to 80.5°, and this indicated that MIBI can't improve hydrophilicity. Crystallinity of copolymer was smaller than homo-polymer, and crystal size was much smaller. It indicated that MIBI may improve regularity of molecule chain, increase its flexibility and then improve the spinnability.