Study On The Preparation Of Ultra-high Molecular Weight Polyacrylonitrile By Aqueous Suspension Polymerization And The Properties Of Copolymers

Polyacrylonitrile (PAN) precursor is fundamental to making high-performance carbon fiber, so it is important to prepare precursor with high-qulity. The main contents of this thesis are as follows:1. The research of precursor and high-performace carbon fiber both in the international and the domestic academic circles were fully reviewed.2. The3-(Methoxycarbonylate)-2-methylenpropanamide (MMPA) containing both amino and ester group was synthesized and used as a comonomer to prepare Poly(acrylonitrile-co-3-methoxycarbonylate-2-methylenpropanamide) copolymers P(AN-co-MMPA) by aqueous suspension polymerization, and the molecular weight of obtained P(AN-co-MMPA) copolymers is up to9.6×105g/mol.3. The effect of polymerization time(4-24h), polymerization temperature (60-80℃), concentration of initiator (0.01-0.04wt%), concentration of total monomer (0.5-2.5wt%), concentration of dispersant (0.5-2.5wt%), and molar feed ratio of AN and MMPA on copolymerization were studied in detail. The results show that the polymerization conversion increases with the increase of polymerization time, polymerization temperature, concentration of initiator and concentration of monomer, but reduces with the increase of dispersant concentration and molar feed ratio of MMPA/AN. The viscosity average molecular weight of the P(AN-co-MMPA) copolymers decreases with the increase of initiator concentration, monomer concentration and molar feed ratio of MMPA/AN, however it firstly increases and then decreases after the rise reach a maximum value with the increase of polymerization temperature and dispersant content. It is also found that the viscosity average molecular weight of the P(AN-co-MMPA) copolymers remains almost unchanged after4hours’polymerization time.4. The structure and properties were investigated by differential scanning calorimeter (DSC), thermogravimetric analysis (TGA), element analysis (EA), and Fourier transform infrared spectroscopy (FTIR). The extent of stabilization of P(AN-co-MMPA) copolymers and PAN homopolymer stabilized at different conditions were calculated by Es based on the FTIR spectra. The EA、FTIR、Es results show that the oxygen (O) content in the P(AN-co-MMPA) copolymers increase with the increase of MMPA content in the feed, indicating the increase of MMPA content in the P(AN-co-MMPA) copolymers. From the results of DSC and TGA analysis, the stabilization of P(AN-co-MMPA) can be improved by the MMPA through ionic mechanism at lower stabilization temperature. It is also found that the P(AN-co-MMPA) copolymer is more stable than PAN homopolymer at high temperature.5. In order to investigate the spinnability of spinning dope, the rheological behavior of PAN/DMSO solutions was studied by rheological analysis. The results show the higher molecular weight of PAN is, the more sensitive the apparent viscosity is. Meanwhile, it is also found that the apparent viscosity decreases with the increase of spinning temperature.