| Cellulose products are commonly prepared through the well-known viscose process or the cuprammonium method. Both these two methods have serious environmental pollution. The green NMMO process using N-methyl-morpholine-N-oxide(NMMO) as the direct solvent of cellulose can be used to prepare the biodegradable cellulose membranes with improved mechanical properties and controllable pores. However, most of the research works of NMMO process are concerned on lyocell fiber, which also made by this process, instead of membrane or film.In this dissertation, the effects of process parameters on the performance and structure of cellulose membranes, studies on the mechanism of membrane formation and computer simulation were carried out. The cellulose tubular film with high strength was also prepared successfully by blown-extrusion technique. The main conclusions are read as follows:The process parameters of casting method were optimized. Not only the DP, but also the type and the original source of cellulose pulp, affect the permeation properties of the membranes but has almost no effect on the rejection of bovine serum albumin (BSA) solution. With a decreasing cellulose concentration of casting solution or an increasing temperature of coagulation bath, the mean pore ssze becomes larger, resulting in higher pure water flux and lower rejection of BSA. A finger-like pore structure of the membrane suppon layer is obtained in the case of high coagulation bath temperature. In the case ofhigh NMMO concentration of coagulation bath, the pure water flux is higher while the rejection can be kept at a relative high value. This is meaningful for ultrafiltration application A sponge-like pore structure of the membrane support layer is obtained when the coagulation bath is NMMO aqueous solution. The optimized process parameters are: the concentration of casting solution is higher than 9wt%, casting speed is 0 73m/min, temperature of wash bath is 45℃ and post-treatment is used.By using atomic force microscopy (AFM) investigation on the membrane surface, different separation properties can be explained very well according to the data of pore size. Increasing temperature or NMMO concentration of coagulation bath or decreasing concentration of casting solution leads to larger skin pore size, wider pore size distribution and higher values of the roughness parameters.Wide angle X-ray diffraction (WAXD) analysis shows that the crystalline modification of cellulose membrane made by NMMO process is cellulose II. With an increase of NMMO concentration of coagulation bath or concentration of casting solution, the crystallinity of membrane increases. However, an increase of temperature of coagulation bath is accompanied by a decrease of crystallinity of membrane. With increasing blow up ratio, both the axial orientation and the crystallinity of tubular films increase. With increasing draw down ratio, only the axial orientation increases while the crystallinity does not change significantly.The strength of flat film made by casting method is only 55MPa, while that of tubular film made by blown-extrusion method is high to 250MPa and is 2.5 times strength of cellophane. We believe the fine mechanical properties of tubular film are related to its fine chain orientation structure By using pole figure investigation and polarized Fourier transform infrared (FTIR) spectra analysis, the modes of orientation for flat and tubular films are obtained. It was found that the cellulose chains of the flat and tubular films have an uniplanar orientation mode with respect to the film surface. For flat films, the cellulose chains are almost unoriented within the plane parallel to the film surface. However, the cellulose chains of tubular films have obvious axial orientation with respect to the machine direction. Moreover, the casting speed, draw down ratio and blow up ratio also have significant influences on the film mechanical properties and supermolecular structure.The interaction parameter between NMMO and water was calculated through free...
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