纤维素/NMMO·H_2O溶液体系流变性能的研究

利用 Brookfield DV-Ⅱ型粘度计对纤维素/NMMO·H2O 溶液体系的流变性能进行了研究,讨论了温度、纤维素浓度、浆粕聚合度及添加剂等对溶液粘度的影响。结果表明,纤维素/NMMO·H2O 溶液的流动活化能较低,因此其表观粘度随温度的变化不大;纤维素浓度和浆粕聚合度的增加都可使溶液粘度增大,但纤维素浓度对溶液粘度的影响更显著;抗氧化剂没食子酸丙酯(GPE)的加入减缓了加热时溶液粘度的下降,降低了纤维素的氧化降解;二甲亚砜(DMSO)的加入可有效地控制溶液粘度,改善溶液的加工性能。     

NMMO工艺纤维素膜成膜性能的研究

主要研究了NMMO工艺纤维素膜的成膜特性及不同因素对该工艺纤维素膜的物理和机械性能的影响。结果表明,纤维素浓度为4%～8%(W/W)时易于成膜,且随着浆粕聚合度的增大、纤维素浓度的增加、凝固浴温度的降低,制成的膜的力学性能较好。     

NMMO法制备的球形纤维素珠体的性能研究

对N-甲基吗啉-N-氧化物(NMMO)制备的球形纤维素的物化性能进行研究,检测了球形纤维素珠体的含水率、粒径分布、耐酸碱能力,结晶结构,比表面积。结果表明,该法制备的球形纤维素珠体的含水率为74.0%,粒径主要分布在0.20～0.45mm,球形度好、比表面积大(190.5m2/g),耐酸碱度高。此外,利用NMMO法制备的球形纤维素珠体主要为纤维素(Ⅱ)结晶变体。     

NMMO工艺纤维素膜结晶度与强度性能初探

以纤维素为原料,N-甲基吗啉-N-氧化物(NMMO)为溶剂,采用相转化法制备非对称纤维素膜。利用X-射线衍射仪对NMMO工艺纤维素膜的结晶状况进行检测,并利用拉力机检测出薄膜的拉伸强度。结果表明:随着铸膜液中纤维素含量的增加,薄膜结晶度与拉伸强度均提高;随着溶解纤维素的温度提高,薄膜结晶度与拉伸强度降低;随着刮膜剪切力增大,薄膜结晶度和拉伸强度提高;并且薄膜结晶度的增加有利于薄膜拉伸强度的提高。     

再生细菌纤维素薄膜的制备工艺

详细介绍了利用N-甲基吗啉-N-氧化物(NMMO)为溶剂溶解细菌纤维素以及制备再生细菌纤维素薄膜的工艺流程,并对NMMO溶解细菌纤维素机理进行了简要的分析。     

木浆纤维素/NMMO·H_2O溶液的流变性能研究

以含水率13.7%的N-甲基吗啉-N-氧化物(NMMO)为溶剂溶解木浆纤维素形成溶液,采用红外光谱分析仪对木浆纤维素的溶解过程进行表征,并采用黏度计研究了木浆纤维素/NMMO·H2O溶液的流变性能。结果表明:木浆纤维素在NMMO中先溶胀后溶解,且可完全溶解;木浆纤维素/NMMO·H2O溶液的流动呈现切力变稀的假塑性流体特征;木浆纤维素质量分数为6%时,溶液的非牛顿流动特征明显,溶液的表观黏度(ηa)随木浆纤维素浓度的增加明显增加,随剪切速率(γ)及温度的上升而下降,当γ高于一定值即logγ大于1.3时,溶液的ηa不受温度的影响,只随γ的上升而下降,且剪切应力不随γ变化而变化,为恒定值。     

NMMO法球形纤维素珠体的制备及粒径分布的研究

以N-甲基吗啉-N-氧化物(NMMO)和马尾松漂白硫酸盐浆为原料,制备出纤维素/NMMO/H2O溶液,并以纤维素/NMMO/H2O溶液为原料,采用程序降温反相悬浮技术制备球形纤维素珠体,通过单因素实验和正交实验确定成球优化条件为:纤维素/NMMO/H2O溶液的纤维素质量分数为8.0%,含水率为15.8%,以变压器油为分散相,油∶溶液(V/V)=4∶1,Span80作为分散剂,用量为纤维素/NMMO/H2O溶液的1.5%,搅拌速度为300 r/min。在上述条件下可制得粒径分布在0.45～0.20 mm占70.0%以上的球形纤维素珠体。     

竹纤维素/NMMO·H_2O溶液流变性能的研究

采用HAAKE RS150L型旋转流变仪对竹纤维素/NMMO.H2O溶液的流变性能进行了研究。结果表明,竹纤维素/NMMO.H2O溶液为切力变稀流体;随着竹浆粕平均聚合度的增大,溶液的非牛顿指数n减小,而溶液表观黏度η、稠度系数K、黏流活化能Eη和结构黏度指数Δη增加;随着温度的升高,溶液的表观黏度下降,非牛顿指数增大;碱处理竹纤维素/NMMO.H2O溶液的流变性能受竹纤维素原料的聚合度、α-纤维素含量(或半纤维素含量)及杂质含量等因素的综合影响。     

超声波处理后纤维素结构的变化及在NMMO中的溶解性能

用超声波预处理纤维素,并利用电子显微镜、X射线衍射和红外光谱对纤维素预处理前后的结构变化进行表征。结果表明,用超声波处理后,纤维素的结晶结构发生了很大的变化。用N-甲基吗啉-N-氧化物水溶液(NMMO·H2O)溶解预处理前后的纤维素,溶解过程及结果说明,超声波预处理可以加快纤维素的溶解速度,降低纤维素的分解。     

纤维素在NMMO水溶液中的溶胀行为研究

通过离心分离法表征纤维素在N-甲基吗啉-N-氧化物水溶液中的溶胀行为,研究了NMMO浓度、温度对纤维素浆粕溶胀的影响;用显微镜追踪拍摄纤维素的溶胀过程,测定纤维的溶胀率,验证了离心分离法的可行性。结果表明:随着NMMO浓度、溶胀温度的升高,纤维素溶胀率增大,溶胀效果变好;纤维素在NMMO水溶液中的最佳溶胀条件为NMMO质量分数78%、温度75℃,溶胀时间40 min。     

纤维素-丝素复合膜的制备与表征

通过NaOH/尿素/硫脲/水新型溶剂溶解原生木浆纤维素得到纤维素溶液,并与丝素溶液混合制备纤维素-丝素复合膜.利用扫描电镜、红外光谱、X-射线衍射对复合材料的结构进行表征.SEM结果表明复合材料表面粗糙,比表面积较大,可以作为潜在的生物医用材料.IR和X-衍射结果表明再生纤维素与丝素分子之间存在着强烈的氢键作用,且二者相容性较好.     

纤维素/海藻酸钠共混膜的制备及力学性能

将纤维素和海藻酸钠分别溶于氢氧化钠/尿素/硫脲体系,制得纤维素膜和纤维素/海藻酸钠共混膜,通过正交实验和单因素实验法分析,确定制备纤维素膜的最佳工艺条件,在此基础上研究了纤维素/海藻酸钠共混膜的制备工艺。结果表明:质量分数为4.5%的纤维素溶液所制得的膜在25℃的5%的硫酸溶液中凝固15 min,20%的甘油溶液中塑化30 min,其膜的拉伸强度较佳为5.2 MPa;纤维素/海藻酸钠共混膜的较佳工艺:质量分数分别为4.5%的纤维素溶液和3%的海藻酸钠溶液按质量比100/5共混后先浸入5%硫酸溶液中反应15 min,再放入10%氯化钙溶液中凝固10 min,用15%甘油溶液塑化15 min后,共混膜的拉伸强度达到3.50 MPa。     

单壁碳纳米管/再生纤维素复合纤维的制备及性能

将经过酸化处理和十二烷基苯磺酸钠处理后的单壁碳纳米管(SWNTs)与离子液体和再生纤维素共混制得纺丝溶液,通过干湿法纺丝制得SWNTs/再生纤维素复合纤维.考察了SWNTs处理前后的结构及在离子液体中的分散性;研究了复合纤维的力学性能和热性能.结果表明:经酸化和功能化处理后的SWNTs的直径有所减小,SWNTs在离子液...     

高吸水醋酸纤维素胶囊膜的制备

把醋酸纤维素制成胶囊膜，并将高吸水树脂封入胶囊中，制成高吸水醋酸纤维素胶囊膜，此膜可以用来浓缩水中的脲酶或悬浮微粒。     

Properties of cellulose/PAN blend membrane

The water flux of a cellulose/PAN blend membrane increased with the PAN content, while retention to glucosan T40 decreased. The water flux decreased and the retention increased with the whole solid content. The membrane obtained had a high ability to remove creatinine and urea. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 3105–3111, 2002; DOI 10.1002/app.10021     

Morphology and properties of cellulose/chitin blends membranes from NaOH/thiourea aqueous solution

Blend membranes of chitin/cellulose from 12 : 50 to 12 : 250 were successfully prepared from cotton linters in 1.5M NaOH/0.65M thirourea solution system. Two coagulation systems were used to compare with each other, one coagulating by 5 wt % H₂SO₄ (system H), and the other by 5 wt % CaCl₂ and then 5 wt % H₂SO₄ (system C). The morphology, crystallinity, thermal stabilities, and mechanical properties of the blend membranes were investigated by electron scanning microscopy, atomic absorption spectrophotometer, infrared spectroscope, elemental analysis, X‐ray diffraction, different scanning calorimeter, and tensile tests. The cellulose/chitin blends exhibited a certain level of miscibility in the weight ratios tested. There were great differences between the two blends H coagulated with H₂SO₄ and C coagulated with CaCl₂ and H₂SO₄, respectively. The membranes H have a denser structure, higher thermal stability, tensile strength (σ_b), and crystallinity (χ_c), and values of σ_b (90 MPa for chitin/cellulose 12 : 150) were significantly superior to that of both chitin and regenerated cellulose membrane. However, the blend membranes C have much better breaking elongations (?) than that of membranes H, and relatively large pore size (2r_e = 210 μm), owing to the removal of a water‐soluble calcium complex of chitin as pore former from the membranes C. When the percentage content of chitin in the blends was from 5 to 7.5%, the values of breaking elongation for the blend membranes H and C all were higher than that of unblend membranes, respectively. The blends provide a promising way for application of chitin as a functional film or fiber in wet and dry states without derivates. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 2025–2032, 2002     

Preparation and characterization of cellulose carbamate membrane with high strength and transparency

In this study, cellulose carbamate was synthesized from alkali cellulose and urea by a low-cost solid–liquid phase method. Cellulose carbamate was dissolved in cuprammonium solution to form a regenerated cellulose membrane with high strength and high transparency. The mass fraction of cellulose dissolved was greatly increased (up to 17%), and the thermal stability of cellulose was retained. The surface of the membrane is compact and there are regular microchannels in it. The factors influencing the transparency and mechanical properties of regenerated cellulose membrane were discussed by the range analysis of orthogonal experiment. The light transmittance is 95.50%, the breaking strength is 98.35 MPa, the elongation at break is 21.74%. The ability of heat preservation and moisture preservation of regenerated cellulose membrane was tested, and the effect was close to that of conventional polyethylene membrane. The membrane material has broad application prospects in packaging, food preservation, agriculture, and other fields.     

Preparation and characterization of dense cellulose film for membrane application

Regenerated cellulose films were prepared with environmentally friendly process by utilized N‐methylmorpholine‐N‐oxide (NMMO)‐Cellulose system. To prepare a dense cellulose film for membrane application, some parameter process which influence porous forming such as cellulose DP, cellulose concentration, addition NMMO in coagulation bath, coagulation bath temperature, and drying condition were investigated. We resumed that the porosity and pore size of cellulose membrane decrease with lower cellulose DP, higher cellulose concentration, addition of NMMO in coagulation bath, applying room temperature in coagulation bath and drying, and applying vacuum on drying process resulted in membranes with porosity in range of 24–41% and pore size 13.4–20.2 nm. The main factor for controlling porosity and pore size of dense cellulose membrane was coagulation process condition especially addition of NMMO into coagulation bath. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012