Etherification Modification Of Cellulose And Study On The Fiber Forming Behavior

With the increasing shortage of petroleum resources, cellulose as abundant renewable resources of nature is paid more attention in recent years, for its good biological compatibility and excellent degradation perfonnance. There are a large number of hydrogen bonds in the cellulose molecules, which makes it easy to form complex intermolecular and intramolecular hydrogen-bonding interactions. Therefore, cellulose possesses high crystal Unity, and is difficult to be dissolved in general solvent or used to manufacture cellulose fiber by melt-spinning.lt is significant and profound to explore new ways of using cellulose and its derivatives.Hydroxyethyl cellulose (HEC) is the etherification reaction product of cellulose between ethylene oxide (EO). Etherification can weaken intramolecular hydrogen-bonding interactions, which greatly enhance its dissolvability in alkali solvent. HEC with low molar substitution cannot dissolve in water, but is easily dissolved in dilute alkali solution, that is to say. it has a unique alkali-soluble ability. The alkali insoluble HEC has good film-forming, fiber-forming properties, which indicts its broad prospects of applications.Firstly, gas-solid reaction synthesis method was used to obtain unique alkali-soluble HEC based on previous studies. Key research was emphasized to investigate the effects of alkalinization time on structure and perfonnance of hydrated cellulose and HEC prepared. Infrared spectroscopy. X-ray diffraction analysis were adopted to characterize the structure of hydrated cellulose and HEC. and the solubility and viscosity of HEC solution prepared by complex alkaline solvent system were measured. It is revealed that with the increase of alkalization time, the crystallinity and solution viscosity of hydrated cellulose and HEC decreased, and the dissolubility of HEC enhanced. The HEC alkalized at lh havd good dissolubility, and was choosed in this thesis for shorter Alkalization time.Secondly, different coagulation bath conditions for the spinning solution were screened. Sulfuric acid, ammonium chloride, sodium hydroxide and ethanol were selected as coagulation bath under different coagulation temperature and coagulation time to manufacture HEC membranes. Proper coagulation bath was choosed considering mechanical behavior of HEC membranes prepared under different conditions. The results showed that HEC membranes prepared from the sulfuric acid solution had good mechanical properties and presented relatively dense structure. Furthermore, the sodium sulfate was added and orthogonal method based on the three components of coagulation bath introduced to obtain HEC membrane with high strength. It is observed that the coagulation temperature and sulfuric acid concentration were key factors which affected HEC membrane strength, next came the sodium concentration, the third one was coagulating time; the optimal conditions were12wt%sulfuric acid concentration.10%sodium sulfate. the coagulation bath temperature20℃.Finally, single factor experiments were employed to determine the best wet spinning process: the solution concentration of10wt%. spinneret extension ratio of1.27. water bath temperature was40°C and water bath drawing ratio was1.1. Dry breaking tenacity, wet breaking tenacity, dry breaking elongation and crystallinity degree of HEC fiber acquired under this condition were2.85cN/dtex.1.46cN’dtex.10.63%and37.8%. respectively. It is observed from scanning electron microscopy that HEC fiber had uniformly dense internal structure with approximately circular cross-section and grooves on surface. With the water bath draw ratio increasing, polarization birefringence of HEC fiber increased, indicating that the orientation degree of HEC increased. It is analyzed from X-ray diffraction spectrum that HEC fiber owned cellulose11crystalline structure and its crystallinity degree decreased compared with cellulose. Infrared and nuclear magnetic resonance spectrum analysis revealed that only physical changes occurred in HEC dissolving and spinning process. As can be seen from the thermogravimetric curve. HEC fiber and HEC raw materials possessed relatively higher moisture absorption ability and slightly lower thermal stability, compared with the cellulose.