超细纤维素胶体和丙烯酰胺的接枝共聚

本文用纤维素材料经酸分解制备具有平衡聚合度（LODP）的微晶纤维素，再分散成超细纤维素胶体（准均相纤维素体系）。用扫描电镜（SEM）观察处理前后的纤维素颗粒尺寸，并比较它们和丙烯酰胺接枝共聚的反应速率、聚合转化率、接枝率、接技效率、聚丙烯酰胺支链的分子量及其分布的情况。     

Electrochemical insertion of sodium into hard carbons

The electrochemical insertion of sodium ions into different types of hard carbons was achieved in electrolytes composed of ethylene carbonate as the solvent and NaClO₄ as the salt. For all the materials studied the sodium uptake increases when the carbon highest heat treatment temperature (HTT) decreases. PAN-based carbon fibres appear to be suitable structures to allow significant sodium insertion. Thus, T650 ex-PAN fibres lead to a reversible capacity close to 209 mAh g⁻¹. In that case, sodium insertion occurs in two main ways: one is the adsorption on the single graphene layers and the other is the concomitant insertion into the porosity that occurs below 0.1 V versus Na⁺/Na. This second mechanism, which is indicated by a low-voltage plateau on the electrochemical curves, allows significant insertion. The compared electrochemical study of two saccharose-coke samples corresponding to different regions of Dahn's classification underlines the importance of the carbon precursor and of the manufacture process. The reversible capacity is equal to 184 mAh g⁻¹ for the sample heat treated at 800 °C which presents a high hydrogen content whereas it is close to 145 mAh g⁻¹ for the one characterized by a HTT of about 1500 °C and a low hydrogen content. The best electrochemical performances are obtained for pyrolyzed cellulose carbons. Indeed, the reversible capacity is about 279 mAh g⁻¹. Outgassing these carbons at 950 °C results in such a decrease of the reversible capacity down to 145 mAh g⁻¹. That can be related either to the thermal elimination of heteroelements or to modifications of the pore size distribution. Consequently, the most suitable hard carbon material for anodic applications in rechargeable sodium-ion batteries should both present a high residual hydrogen content and a significant microporosity.     

氧化纤维素的制备研究

介绍了氧化纤维素 (DAC)的制备过程 ,用正交法探讨了以NaIO4 作氧化纤维素时反应温度、溶液pH值、氧化剂浓度、反应时间以及交互作用对DAC醛基含量的影响 ,找到了影响醛基含量的主要因素为反应温度、反应温度与NaIO4 的交互作用、反应温度与溶液 pH值的交互作用。初步确定了制备氧化纤维素的反应工艺 ,使醛基含量较高时的最佳反应条件为 :反应温度 3 5℃ ,反应时间 3h ,NaIO4 质量分数 6.78% ,pH值为 2时 ,醛基含量达 68.2 0 %。     

纤维素衍生物液晶相转变和织态结构

本文综述了纤维素衍生物液晶态相转变和织态结构。描述了纤维素衍生物从各向同性态向液晶态的转变过程和液晶态的织构特征。讨论了溶液浓度和温度对液晶相织构的影响。探讨了各种因素,如溶剂、取代基含量、外加力场和外加磁场等对液晶相的形成及织态结构的影响。     

Infrared study of salt free and salt treated cellulose pyrolysis under nitrogen atmosphere

The pyrolysis under nitrogen of salt free and salt treated cellulose was studied by infrared spectroscopy. The results confirm the unzipping mechanism suggested by DTA and TGA studies, and show this mechanism to apply to the untreated and salt treated samples. The results also show the unzipping to stop at the stage of char formation. The onset of this stage was found to occur after the volatilization of only 45–50% of the initial sample of the borax treated cellulose, compared with 65–70% of the KCl treated cellulose and 80–85% of the untreated cellulose.     

纤维素醚的特点、制备及在工业中的应用

综述了纤维素醚的种类、制备方法、性能和特点,以及纤维素醚在石油、建筑、造纸、纺织、医药、食品、光电材料及日化工业中的应用,介绍了一些具有发展前景的纤维素醚类衍生物的新品种并展望其应用前景。     

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。     

Structure and properties of regenerated cellulose films coated with polyurethane–nitrolignin graft‐IPNs coating

A regenerated cellulose film (RC) was coated with a graft‐IPNs coating, which was composed of castor oil‐based polyurethane and 2.8 wt % nitrolignin (NL), to obtain water‐resistant films. The effects of NCO/OH molar ratio and different polyols, such as 1,4‐butanediol (BDO) and trimethanol propane (TMP), on the structure and properties of the coated RC films were investigated. With an increase of the NCO/OH molar ratio, the tensile strength of the coated films increased, but the water resistivity and size contraction hardly changed. The coated films with TMP exhibited the higher breaking elongation at 1.5 of the NCO/OH molar ratio, while those with BDO have more excellent tensile strength, water resistivity, and dimensional stability. The coated films with the graft‐IPNs coating exhibited superior water resistivity and dimensional stability. The light transmittance of the coated films was more excellent than that of the RC film. Moreover, the results from the IR and electron probe microanalysis (EPMA) showed that the chemical bonding occurred between cellulose and coating, and the introduction of NL plays an important role in the enhancement of the interface adhesion of the coated films. Atomic force microscopy (AFM) depicted the flat and dense surface of the coated films, which restricted the water vapor penetration and the size contraction, resulting in the enhancement of water resistivity. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 1799–1806, 2002     

羧甲基纤维素阳离子化衍生物的研究现状

羧甲基纤维素阳离子化改性是制备性能优良的天然两性高分子的重要方法之一。文章综述了迄今为止羧甲基纤维素阳离子化改性所用的阳离子单体的主要类型及其接枝的若干主要途径,其中包括自由基型接枝共聚、高分子侧基反应、聚合后功能化等三大类。     

亚砜基改性纤维素膜的SO2气体渗透性能研究

分别使用二甲基亚砜浸泡的物理方法及苯基乙烯基亚砜加成的化学方法对纤维素膜进行了改性,并对改性膜的性能进行了测试.结果表明改性后纤维素膜仍为致密结构,SO2的渗透性能及其对N2的分离性能明显提高,其中改性液中添加二甲基亚砜的均相化学加成反应所得的改性膜具有较好的SO2渗透稳定性.