The Effect Of Non-Solvent Additive On The Properties Of PAN/DMSO Solution And The Performance Of PAN Precursor

Due to its a series of high performance, such as high strength, high modulus, heat-resistant, erosion-resistant etc. Carbon fiber(CF) is an advanced material used widely in all kinds of fields. However, there are large gaps in the properties and production of polyacrylonitrile(PAN) -based carbon fiber by domestic and foreign countries. PAN precursors have been the key factor for producing carbon fibers. In the membrane science, some additives such as mineral, organic small molecule and polymer are added to the membrane solution for modification because additive has an important effect on the formation mechanism of membrane by changing the phase separation time.In the dissertation, the effects of additive on the formation mechanism of PAN precursor were investigated. The effects of non-solvent additives on the PAN/DMSO solution, formation mechanismand fiber performance are discussed. H2O is chosen as the non-solvent additive(NSA) in the experiment using dry-jet wet-spinning technology. Their main results obtained are as follows:1. The research results showes that NSA has a remarkable effect on the properties of PAN/DMSO spinning solution, which can change the thermodynamics of PAN solution and the conformational array of PAN molecule. The characteristic viscosity of PAN in mixture solvent decrease with the increase of NSA, which can be proved by the above conclusion. Besides, the results of rheology showes that at lower shear velocity, with the increase of H2O contents in the mixed solvents the rheological curves go down first and then go up comparing with the system of PAN/DMSO. The viscosities of PAN/DMSO/H2O solution also decrease initially, and then increase with the increase of NSA concentration in the solution. In the curves, there is minimum viscosity that moved gradually along the direction of x axis with the increases of the temperature. Furthermore, the parameter of En increases with the increase of NSA concentration in the solution.2. Some useful results are got in the study on the spinnability: For the wet-spinning, the parameters of coagulation bath have an obvious effect on the spinnability. The higher concentration and lower temperature of coagulation bath have a negative effect on the spinnability. However, the parameters of coagulation bath have no obvious effect onthe spinnability for the dry-jet wet-spinning;NSA would decrease the spinnability of the dry-jet wet-spinning, and make the spinnability have an obvious sensitivity to the temperature;the spinnability would increase first and then decrease with the increases of spinning temperature. At last, it is concluded that for the dry-jet wet-spinning, the best spinning temperature is 70 °C, and the best air gap is 30 millimeter.3. In the last part of the thesis, the formation mechanism of PAN precursor and described the effect of NSA on the formation mechanism of PAN precursor are discussed. NSA would change the properties of PAN/DMSO spinning solution, and has an effect on the mass transfer dynamics of small molecule, phase separation and coagulation. The three dynamics behaviors related with the behavior of macromolecule would compete with each other. The last competition results would affect structure of the fiber.Tang Naijie (Material Science) Supervised by : Chen Huifang...