Study On Streching Technology, Mechanism, Structure And Properties Of Pan Precursor

Carbon fiber (CF) has serials of excellent performance such as high strength, high modulus, anti-high temperature, anti-erosion and so on. So it had rapid development in recent decades. The high strength and high modulus performance of CF lies on the kind and quality of precursor, technology of pre-oxidation and carbonization and other factors. Precursor is one of the main factors that affect CF's performance. High quality polyacrylonitrile (PAN) precursor is perfect row material to produce high performance CF. But by now domestic organizations have not done enough work on high performance CF, especially on high performance PAN precursor. And the quality of PAN precursor has been the choke point to develop high performance CF in our country. The effect of spinning and stretching on fiber's structure and properties was studied in this thesis, using dimethylsulfoxide(DMSO) as solvent and by dry-jet wet-spinning technology. This is the foundation to produce high performance PAN precursor.In preface of this thesis, the development history and current status of CF, the quality parameters of high performance PAN precursor, the factors affecting spinning process and precursor's quality and the effects of the stretching technology on the properties of PAN precursor, etc. were expatiated, which are the theoretical foundation of experiment.The effects of the draw ratios of three-stage drawing including air drawing, boiling water drawing, dry-hot drawing and stream drawing on the properties of PAN fiber were studied in dry-jet wet spinning. The results showed that the increase of jet stretch ratio could greatly decrease the linear density of as-spun fiber and improve the strength; the increase of draw ratios in three-stage drawing process decrease the linear density of PAN fiber and obviously improve the strength, sonic orientation and crystal degree. The crystal structure is easy formed under the stream drawing conditions. The PAN fiber with strength higher than 7.0 cN/dtex could be produced by rationally adjusting the draw ratios of three-stage drawing process.Experiments were done on PAN fiber of wet spinning, and the effect of the drawing conditions on the maximum draw ratios and the properties of PAN fiber. The results showed that the concentration, the temperature and the time in plasticization could effect the maximum draw ratios and the properties of PAN fiber. The increase of the concentration, the temperature and the time in plasticization could increase the maximum draw ratios. But when the maximum draw ratios reached a certain number, continuous increase the concentration, the temperature and the time in plasticization, the maximum draw ratios no longer increase. Among the different drawing conditions tested, treated in 80% DMSO for 10s and 95 °C gave the higher precursor values of elastic modulus and tensile strength. But in drawing fiber tows, the properties of PAN fiber decrease when increase the concentration and the temperature of the plasticization.To investigates the difference between wet spinning and dry-jet wet spinning on the PAN precursor, oxide fiber and carbon fiber by normal analytical methods, X-ray and SEM. The results showed that the precursorand carbon fiber of dry-jet wet spinning is better than that of wet spinning on the structure and properties.