【作者】 许海霞；

【导师】 胡盼盼；

【作者基本信息】 东华大学 ， 材料加工， 2006， 硕士

【摘要】 纤维素(C₆H₁₀O₅)_n是一种天然的可再生的高分子材料，生长和存在于大量的丰富的绿色植物中。纤维素材料本身无毒，可以粉状、片状、膜以及长短丝等不同形式出现，使得纤维素作为基质材料的潜在使用范围非常广泛。近年来，随着石油和煤炭储量的日益下降，以及各国对环境污染的日益关注和重视，利用可再生资源--纤维素正日益受到研究领域和产业界的关注。本论文以磷酸为溶剂制备纤维素的纺丝溶液，对溶解过程及溶解机理等做了大量的研究和探索工作，并对该溶剂体系中纤维素溶液的性能进行了研究。制备纤维素纺丝溶液的首要任务是制备无水的磷酸体系，因为磷酸中水的存在影响了磷酸的溶解能力。因此，通过混合多聚磷酸和磷酸，制得无水的混酸溶剂体系，得到的溶剂可以快速有效地溶解纤维素。本论文就混酸体系的P₂O₅含量、温度、搅拌强度对溶剂平衡时间（即溶剂体系达到无水的时间）的影响作了讨论。结果表明：溶剂中P₂O₅含量增大，平衡时间增长；温度升高，溶剂平衡时间缩短；剪切速率提高，溶剂的平衡时间也缩短。纤维素在磷酸中的溶解，是一个快速有效的过程。在较短的时间内，纤维素由最初的棒状纤维变化为凝胶粒子而后完全溶解，并出现液晶现象。其机理是磷酸与纤维素分子间形成氢键，生成中间产物而实现溶解。并且在此过程中产生了结晶变体，纤维素由原来的Ⅰ型变为纤维素Ⅱ型。磷酸对纤维素的溶解效果，本论文是通过溶剂中P₂O₅含量、纤维素含量及温度等影响因素来讨论的。本实验溶剂体系的P₂O₅含量选择在72％到76％之间。随着P₂O₅含量的增大，纤维素的溶解时间延长；固含量增大，纤维素的溶解时间缩短；溶解温度提高，纤维素的溶解时间缩短。从纺丝溶液的稳定性，均一性和可纺性方面综合考虑，最佳的溶解条件为：P₂O₅含量为74％，固含量为18％，溶解温度为0℃。本文通过自制的毛细管流变仪，对纺丝液的流变性能进行了测试，进而为纤维素的液晶纺丝成型提供实验依据。纤维素磷酸溶液在18％（wt）至20％（wt）的浓度范围内是切力变稀流体；溶液的粘流活化能ΔE_η随着溶液P₂O₅含量的增大而增大，随着溶液浓度的增大而增大，随着剪切力的增大而减小。为保证所制得的纤维素溶液的稳定性，必需在0℃以下低温密封保存，以避免纤维素降解，影响溶液粘度，进而影响纺丝工艺参数。本论文研究的主要创新点：1．采用了新的溶剂体系：磷酸／多聚磷酸的混合溶剂体系，能快速有效地制得纤维素溶液；2．相比于粘胶法制备纤维素溶液，该法缩短了溶解时间，操作简单，对环境污染小，而且溶剂来源广泛，价格低廉，无毒；3．制得了性能优良的纺丝溶液，且呈现明显的液晶现象。更多还原

【Abstract】 Cellulose is a kind of natural resources which can be found and regenerated from a wide range of green plants. It is an important innocuous macromolecule. It appears in many different kinds of shapes, such as powder, sheet, film, sleave and etc. Recently, the potential use of cellulose-based materials has been the subject of extensive investigations with the decline of oil and coal reserves. In this dissertation, phosphoric acid was chosen to be the solvent of cellulose, and the spinning solution was prepared. Also, the mechanism and process of dissolution were discussed.Because of weaker solubility with the increasing amount of water in the solvent, the preparation of anhydrous phosphoric acid was the chief task to obtain excellent cellulose spinning solution. It was found that an anhydrous solution was formed in a specific mixture of phosphoric acid and polyphosphoric acid. In order to obtain its new state of equilibrium, the influencing factors were studied. It had been shown that the equilibrium time prolonged with the increase of P₂O₅ concentration and it shortened with the increase of temperature and shear rate.Dissolution of cellulose in phosphoric acid was very fast and effective. Clavel cellulose first changed into gel particles and soon completely dissolved, after that anisotropic solutions were formed. Regenerated cellulose fibres which coagulated from ethanol had the different chemical composition as before, which formed a new mesophase in dissolution process. At the same time, the crystal structure was changed from celluloseⅠto celluloseⅡ.The influence of dissolution temperature, P₂O₅ concentration, cellulose concentration and the degrees of polymerization was examined. Phosphoric acid and polyphosphoric acid were mixed at different ratios so that the solvent had a P₂O₅ concentration between 74％and 76％. The result showed that dissolution time of cellulose prolonged with the increase of P₂O₅ concentration and it shortened with the increase of cellulose concentration and dissolution temperature. Considering the effects of dissolving temperature, solution concentration, equality and stability of solution on the dissolving process of cellulose, we could conclude the optimal conditions as follows: the P₂O₅ concentration was 74wt％, the dissolving temperature was around 0℃and the cellulose concentration was 18wt% or so.In this dissertation, rheological properties of the liquidcrystalline solutions of cellulose in phosphoric acid werediscussed by using homemade capillary rheometer. Also theinfluencing factors of cellulose concentration, temperature andshear rate were studied. These experimental results could providepowerful instructions for the spinning process of cellulose. Theresults indicated that: viscosity of solutions whose celluloseconcentration were from 18% to 20% were found to be dilutedwith the increase of shear rate. The viscous activation energy⊿E_ηof solutions increased with the increase of solution concentrationand P₂O₅ concentration. In the mean time, it decreased with theincrease of shear rate. The cellulose solution must be preserved inspecial temperature that was lower than 0℃and airproofed tomake sure that there was no degradation in the solution.The innovation points of this dissertation as follows:1. This dissertation selected the new solvent system that wasmixed with phosphoric acid and polyphosphoric acid, anddissolution of cellulose in this solvent was very fast and effective.2. Comparing with those of existing regenerated cellulosefibres, this preparation measures greatly reduced the dissolvingtime, simplified the operation and had no pollution to theenvironment. Also the solvent was innocuous, low-priced and convenient to obtain.3. This preparation measures could obtain excellent liquidcrystalline spinning solution and the cellulose fibers spinned hadexcellent properties.Xu Haixia （material Processing and Engineering）Supervised by Hu Panpan, Liu Zhaofeng更多还原