【作者】 郝艳萍；

【导师】 胡学超；

【作者基本信息】 东华大学 ， 材料物理与化学， 2005， 硕士

【摘要】 将纤维素溶于NMMO水溶液中生产的Lyocell纤维由于其生产工艺的无污染性、制备的lyocell纤维本身具有许多独特的优异性能和生物可降解性,获得了工业上的巨大成功。应用NMMO工艺制备的纤维素薄膜也有许多良好的性能和广泛的应用前景。本课题采用独特的挤出吹膜工艺来制备双轴拉伸管膜。这种双轴拉伸薄膜与单轴拉伸的平膜相比机械性能要更好。目前只有国外少数公司注重该薄膜的工业化生产开发,对该薄膜的理论研究则仅限少数学者,而国内对该领域的基础理论研究几乎还是空白。 本论文比较系统地研究了制膜过程中的牵引速度、吹胀比、凝固浴温度、空气隙长度等工艺条件对薄膜的机械性质(强伸度)、取向度和透水蒸气性的影响,并通过扫描电镜手段研究不同工艺参数下薄膜断面形态结构的变化,还首次就纤维素溶液吹膜过程中的拉伸流动行为进行了初探。研究表明: 不同的工艺条件对纤维素薄膜的结构和性能都有一定的影响。本论文研究了不同工艺条件对薄膜纵向拉伸强度、断裂伸长及模量的影响和取向度的变化。随着牵引速度、吹胀比和空气隙长度的增加,制得的薄膜总体取向度均变大。随着凝固浴温度的升高,薄膜的取向程度下降。薄膜的透水气性与纤维素更多还原

【Abstract】 The process using NMMO as the direct solvent of cellulose can be used to prepared Lyocell fibers. Lyocell fibers have excellent mechanical properties and biodegradable merit. Similarly, cellulose films prepared from NMMO process have also many good advantages and can be applied in many fields. In this paper, the cellulose tubal film is also prepared successfully by blown-extrusion technique. The biaxial elongational films from blown-extrusion technique have better properties than the uniaxial elongational flat films. At present, only several overseas companies are engaged in industrial study of this kind of films. Till now, few fundamental studies about this film have been done in the world.In this dissertation, the effects of process parameters on the mechanical properties, orientation and performance water vapor transmission of cellulose films are also studied. On the other hand, morphologies of film section have been studied through scan electronic microscopy (SEM). Elongational flow behavior ofcellulose solution in the blown-extrusion process is investigated for the first time. The main conclusions are as follows:In this paper, strength, modulus and elongation at break of the films in the longitudinal are discussed under the different process parameters. The chain orientations of cellulose increase with take up speed, blown-up ratio or air gap length, while decrease with the temperature of the coagulation bath. The performance of water vapor transmission has close relationship with the chain orientation of cellulose. It decreases with the length of air gap, take up speed and blown-up ratio, while increases with the temperature of the coagulation bath.At the same time, scan electronic microscopy (SEM) investigation has also done on the film section. An asymmetric structure can be obtained in the case of different inner and outer coagulation bath. Dry has also important effect on structure and morphologies of film section. The effects of different process parameters on film structure are also discussed.The rheology model of cellulose solution in the blowing process is deducted according to C.D.Han’s model. In this paper, elongational viscosities have been determined during the process of blown film. The results show that the elongational viscosity is affected by elongational rate, temperature and other processparameters. It shows that the elongational viscosities decrease first, then increase gradually along the extrusion direction. As the take up speed and the pressure difference inside and outside the tube increase, consequently the wall of the tube becomes thinner, elongation rate increases and the elongational viscosity deceases.更多还原