用于制备高强Lyocell纤维的纤维素混合浆粕的研究

研究了在高聚合度的纤维素浆粕中添加少量的中等聚合度浆粕,所形成的混合浆粕的纺丝情况及得到的Lyocell纤维的性能。在此基础上,利用凝胶渗透色谱法(GPC)测定了混合浆粕的相对分子质量及其分布,分析了混合浆粕的相对分子质量及其分布对可纺性及纤维性能的影响。结果表明:这种混合浆粕的相对分子质量分布明显变宽,其中高相对分子质量的峰几乎没有变化,但中低相对分子质量部分含量增多,出现了较小的中低相对分子质量峰。这些中低相对分子质量部分的纤维素起了增塑作用,使加工更容易,而高相对分子质量部分则赋予纤维良好的力学性能。     

聚丁二酸丁二醇酯/纤维素纳米晶复合纤维增强机制

采用熔融纺丝法制备了聚丁二酸丁二醇酯(PBS)/纤维素纳米晶(CNC)复合纤维,重点研究了CNC的分散性、PBS与CNC间氢键作用、PBS分子取向、CNC沿轴向排布以及PBS相结晶度对复合纤维强度的影响。通过光学显微镜和场发射扫描电镜观察发现:高牵伸倍率下的复合纤维较低牵伸倍率下的复合纤维侧面更加平整、光滑,且高牵伸倍率下CNC列。红外光谱图证实了PBS与CNC用力。此外,在提高牵伸倍率时,PBS复合纤维结晶度增大,并且其声速值也明显提高。多因素协同导致PBS/CNC(质量比99/1)复合纤维经4倍牵伸后断裂强度达3.59 cN/dtex,远高于相同处理条件下的纯PBS纤维。     

Viscoelastic properties of cellulose derivatives: 1. Cellulose acetate

The dynamic mechanical spectrum of cellulose acetate (CA) from −130°C to 240°C has been determined at different frequencies (from 0.1 to 30 Hz). Three relaxations, designated , β and γ in order of decreasing temperature, and one shoulder (β*) above room temperature were found. Comparison with calorimetric and thermogravimetric measurements yields the conclusion that the relaxation (197°C at 3 Hz) is related to the glass-to-rubber transition and the β* shoulder (50°C–100°C) is due to loss of moisture. The β relaxation (−38°C at 3 Hz, ΔH = 100 kJ mol⁻¹) is tentatively assigned to local motions of the main chain (glucopyranose rings). The low-temperature γ relaxation (−88°C at 3 Hz, ΔH = 46 kJ mol⁻¹), is humidity-dependent: its intensity decreases when the samples are dried to moisture contents lower than that obtained by normal room conditioning (about 3%). Higher water contents shift the relaxation to lower temperatures without increasing the intensity of the mechanical loss. It is suggested that water associated with the unesterified methylol groups of cellulose acetate is responsible of the dynamic mechanical γ dispersion.     

Methyl tert-butyl ether decomposition over heteropoly acid catalyst in a cellulose acetate membrane reactor

In this study the methyl tert-butyl ether (MTBE) decomposition over H₃PW₁₂O₄₀ was carried out in a cellulose acetate membrane reactor. The permeability of methanol through the cellulose acetate membrane was about 30 and 300 times higher than that of either isobutene or MTBE, respectively. The isobutene selectivity in the fixed bed reactor was only slightly higher than the methanol selectivity due to the side reaction. In the cellulose acetate membrane reactor, however, the isobutene selectivity in the rejected stream was 68% and the methanol selectivity in the permeated stream was up to 97%. The MTBE conversion in the membrane reactor was about 7% higher than that in the membrane-free fixed bed reactor under the same reaction conditions. The enhanced performance of the membrane reactor in this reversible reaction was mainly due to the selective permeation of methanol which resulted in a methanol-deficient condition suppressing MTBE synthesis reaction.     

纤维素酶的固体发酵

从来自国内外11株菌株的初步比较,筛选出酶活较高的康氏木霉N_2—78和瑞热埃木霉QM6a。对康氏木霉P_2和土曲霉3.3935所作的纤维素碳源试验中,发现木质纤维素较纯纤维素好,未经处理的木质纤维素比经处理的好。麸皮和稀土对康氏木霉P_2产酶作用影响较大,而对土曲霉3.3935则无明显的影响。     

聚砚基纤维素填充复合超滤膜材料的研究

以聚砜为原材料,通过向铸膜液中混入纤维素微纳晶体,采用浸没沉淀相转化工艺制备了纤维素填充聚砜基复合超滤膜材料。测定了超滤膜的水通量、截留率、平均孔径、孔隙率等性能,通过单因素影响试验分析了各个工艺因素对产品性能的影响;考察了膜的化学稳定性以及运行压力对性能的影响;通过扫描电镜观察了膜孔的结构;并通过浊点滴定实验得到膜液的三元相图,分析了纤维素的加入对成膜过程的影响。     

微晶纤维素的溶解及其阻燃性能

以氯代1-氨甲酰甲基-3-乙烯基咪唑离子液体([CmVIM]Cl)和四丁基氯化铵(TBAC)为溶剂,溶解微晶纤维素(MCC),加入不同阻燃剂三聚氰胺磷酸酯(MP)、聚磷酸铵(APP)、纳米二氧化硅(SiO2),制得了阻燃纤维素复合材料.通过偏光显微镜观察MCC的溶解过程,并利用FTIR、XRD、TGA和SEM对再生MCC的结构、结晶度、热稳定性和形貌变化进行了表征.通过垂直燃烧、极限氧指数(LOI)和热重分析对纤维素复合材料的阻燃性能进行了测试.结果表明,溶解温度为90℃,TBAC用量为[CmVIM]Cl质量的8％时,MCC的溶解率达6.3％,聚合度降至505;与原MCC相比,再生MCC结晶度指数由74.0％降至46.4％,初始热分解温度由310℃降至262℃,最大失重速率由2.6％/min降至1.4％/min.MCC表面由光滑平整的棒状结构转为凹凸不平的不规则结构.当MP、APP、SiO2质量分数分别为5％、10％和10％时,阻燃纤维素复合材料的极限氧指数提升至33.5％,垂直燃烧等级为Ⅴ-0.     

纤维素酶的应用研究进展

植物纤维原料是地球上极为丰富、廉价而又可再生的资源,它的利用一直是国内外的研究热点。纤维素酶是一种高活性生物催化剂,是一组能够降解纤维素生成葡萄糖的酶的总称,在食品、饲料、酿酒、纺织、中药提取和造纸等众多的工业领域有广泛的应用价值。     

黏胶纤维酶水解反应工艺研究

将黏胶纤维水解成糖类物质,是利用废弃黏胶纤维制备燃料乙醇的关键步骤.采用正交试验的方法,对纤维素酶催化黏胶纤维水解反应中的主要因素的影响进行了综合研究.结果表明,影响因素的显著性大小依次为:催化剂用量、固-液比、温度、pH值.对反应时间、温度、催化剂用量等影响因素进行的详细研究结果表明,酶的用量适当,反应温度选择在纤维素酶的适用温度上限,反应时间约为2 h是比较适宜的反应条件,黏胶纤维水解率约达87%.     

废棉布制备高粘度羧甲基纤维素

为纺织废料的再利用,本文以废棉布为原料制备高粘度羧甲基纤维,采用碱醚同釜法及正交实验,通过测试粘度得到最佳反应条件为:浴比为1∶3,氢氧化钠质量分数为30%,氯乙酸乙醇质量分数为30%,醚化时间为2 h,碱化时间为2 h,碱化温度为35~40℃,醚化初期温度为40~45℃,后期温度为70℃,羧甲基纤维素的的粘度值为932.6mPa.s。