响应面法优化废旧毛涤粘面料溶解工艺

采用磷酸/多聚磷酸混酸溶剂体系对废旧毛涤粘混纺面料中的粘胶进行溶解,混酸溶剂体系溶解粘胶的最佳工艺为P_2O_5质量分数74%,固含质量分数14%,温度25℃。采用由尿素、亚硫酸氢钠和十二烷基硫酸钠(SDS)组成的还原C体系对混纺面料中的羊毛纤维进行溶解,通过响应面法探讨了尿素浓度、亚硫酸氢钠浓度、SDS浓度、时间等参数对羊毛溶解率和角蛋白提取率的影响,优化羊毛溶解工艺条件为:尿素400 g/L,亚硫酸氢钠40 g/L,SDS 20 g/L,时间6 h,浴比1∶20,p H为11;最优溶解方案下的羊毛溶解率和角蛋白的提取率分别是89.53%和49.32%。     

纤维素/磷酸纺丝溶液的制备

相对于粘胶法溶解纤维素,以磷酸为溶剂溶解纤维素具有操作简单、价格低廉、溶解温度较低、溶解速度较快,而且对环境污染较小等优势。通过混合多聚磷酸和磷酸制备了无水的混合磷酸溶剂体系,分析了P2O5含量、温度和搅拌速率对溶剂平衡时间的影响,并对纤维素在该溶剂体系中的溶解性能进行了研究,探讨了P2O5含量、固含量和温度对纤维素溶解性能的影响。从纺丝溶液的稳定性、均一性和可纺性方面考虑,最佳的溶解条件为:混合磷酸溶剂体系中的P2O5含量为74%,纤维素固含量为18%,溶解温度为0℃。     

NaOH-硫脲-H2O溶剂体系对木质纤维素的溶解及组分分离

实验研究了NaOH硫脲H2O组成的碱溶剂体系对木屑的溶解规律,并结合酸沉方法分离木质纤维素的3种主要成分.结果表明,碱溶剂处理后剩余的固体物质为木质素,滤液经酸沉后沉淀的主要成分是纤维素,半纤维素全部水解.单因素实验确定最佳溶解条件为:液固比30mL/g、溶解温度70℃、溶解时间2.0h,在此条件下,木屑的溶解率达60.3%,酸沉后纤维素收率为39.2%.对溶解及酸沉后剩余固体物质进行了结构分析,证明分离方法的可行性.     

甲酸―盐酸体系下木质纤维素的组分分离

研究了常压下甲酸―盐酸体系中木屑的溶解规律,结合酸回收和碱沉方法实现了木屑的组分分离。经酸体系处理后的剩余物主要成分为纤维素,滤液经酸回收和碱沉后得到的沉淀是木质素,半纤维素全部水解。实验确定了最佳分离条件:在甲酸―盐酸(体积比3∶1)体系中,溶解温度为60℃,溶解时间为180min,液固比为10∶1,在此条件下,木屑的溶解率可达48.8%,木质素收率为23.2%。通过FTIR、XRD及NMR等方法对溶解后及甲酸回收后剩余物质的结构进行了分析确证。     

细菌纤维素在LiCl/DMAc溶剂体系中的溶解性能研究

纤维素经过活化后可以溶解在LiCl/DMAc溶剂体系中,研究了乙二胺活化对细菌纤维素溶解性能的影响,得到最佳活化条件;研究了LiCl的浓度、溶解温度和搅拌时间对溶解性能的影响,得到最佳溶解条件;研究了细菌纤维素在LiCl/DMAc极性溶剂体系中的溶解机理。     

微晶纤维素在EMIM-DEP中的溶解与再生

通过微波法合成1-乙基-3-甲基咪唑磷酸二乙酯离子液体(EMIM-DEP)并用其溶解微晶纤维素。用偏光显微镜观察微晶纤维素在离子液体中的溶解。随温度的升高纤维素的溶解度增加,超声辅助可以很好地提高微晶纤维素在离子液体中的溶解度。溶解之后再生的纤维素通过红外光谱(FT-IR)、X-射线衍射(XRD)、扫描电镜(SEM)和热重分析(TGA)表征,结果显示微晶纤维素在EMIM-DEP中是直接溶解没有发生衍生反应;再生的纤维素晶型由纤维素Ⅰ型转化为纤维素Ⅱ型;回收后的离子液体结构没发生变化,重复利用仍保持较好的溶解微晶纤维素的能力。     

细菌纤维素在LiCI/DMAc溶剂体系中的溶解性能研究

纤维素经过活化后可以溶解在Lic1/DMAc溶剂体系中,研究了乙二胺活化对细菌纤维素溶解性能的影响,得到最佳活化条件;研究了LICl的浓度、溶解温度和搅拌时间对溶解性能的影响,得到最佳溶解条件;研究了细菌纤维素在LiCl/DMAc极性溶剂体系中的溶解机理。     

超声波处理纤维素的结构变化及其在多聚磷酸中的溶解

研究了超声波预处理方法对纤维素在磷酸体系中溶解的影响。利用偏光显微镜跟踪观测纤维素的过程;通过X射线衍射,红外光谱分析,电子显微镜研究预处理前后纤维素的结构变化。实验证明,用超声波处理后,纤维素晶体类型无变化,仍为纤维素I晶体,但纤维素表面积增加,可及度增加。通过对原纤维素和超声波处理条件下的纤维素用磷酸进行溶解,溶解过程和溶解结果说明用超声波对纤维素进行预处理,可以加快纤维素的溶解速度。     

纤维素氧化体系的研究进展

概述了纤维素的选择性氧化及其氧化体系的研究进展,主要介绍了2,2,6,6-四甲基哌啶-1-氧自由基(TEMPO)类复合氧化体系氧化纤维素的降解机理,针对该降解机理提出抑制降解的基本方法。与其他氧化体系相比,过碘酸和过碘酸盐对纤维素C2、C3位仲羟基的选择性氧化能力极强,TEMPO系列氮氧基类氧化体系对纤维素C6位伯羟基的选择性氧化能力极强,但纤维素在各个氧化体系中的降解非常剧烈,纤维素在各个氧化体系中的降解机理有所不同。     

纤维素在磷酸-磷酸化合物中的溶解性能

使用超声波、18%NaOH溶液及饱和CaCl_2水溶液对纤维素进行预处理,预处理前后纤维素的结构利用偏光显微镜、扫描电子显微镜、红外光谱及X-射线衍射进行表征。将不同条件预处理后的纤维素溶解在磷酸与磷酸脲的复合溶剂中,可以发现,超声波对加快纤维素溶解的效果最为明显。又分别将预处理后的纤维素溶于磷酸(H_3PO_4)-磷酸脲(H_3O_4P·CH_4N_2O)、磷酸-六偏磷酸钠(Na_6P_6O_(18))、磷酸-磷酸二氢钾(KH_2PO_4)、磷酸-磷酸氢二钾(K_2HPO_4)中,通过对比发现,纤维素在35℃下磷酸-磷酸脲中的溶解效果最好,并且聚合度降解最小。     

纤维素热解机理研究进展：以中间态纤维素为核心的纤维素演变

纤维素热解的机理研究对于生物质能的热利用至关重要,能够有效指导工业实际应用。基于著名的Broido-Shafizadeh模型,纤维素热解被分为两步,首先转变为活性的熔融态中间体（中间态纤维素）,然后通过解聚和开环生成左旋葡聚糖、5-羟甲基糠醛、羟基乙醛等重要的化工原料。在这两步转变中,主要涉及低温段氢键网络的断裂、中间态纤维素的生成,以及高温段的解聚和吡喃环开环反应。本文从这3个部分对前人的研究进行了综述,着重介绍了中间态纤维素的生成和表征,综述了纤维素热解几个研究方向：结晶度和结晶形态对热解的影响、纤维素解聚反应方式、吡喃环开环方式等,详细阐述了二次反应对纤维素热解的影响,并提出了部分解决方案。关于纤维素热解依然存在诸多未知和争论,需要进一步的实验研究和理论计算对其进行揭示。     

Thermal degradation of cellulose and cellulose esters

Cellulose, cellulose diacetate (CDA), cellulose triacetate (CTA), cellulose nitrate (CN), and cellulose phosphate (CP) were subjected to dynamic thermogravimetry in nitrogen and air. The thermostability of the cellulose and its esters was estimated, taking into account the values of initial thermal degradation temperature T_d, the temperature at the maximum degradation rate T_dm, and char yield at 400°C. The results show that these polymers may be arranged in the following order of increasing thermostability: CN < CP < regenerated cellulose < filter cotton < CDA < CTA. The activation energy (E), order (n), and frequency factor (Z) of their degradation reactions were obtained following the Friedman, Chang, Coats–Redfern, Freeman–Carroll, and Kissinger methods. The dependence of T_d, T_dm, E, n, Ln Z, and char yield at 400°C on molecular weight and test atmosphere is also discussed. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 68:293–304, 1998     

纤维素氨基甲酸酯法制备纤维素海绵

海绵因具有蓬松度好、质地柔软、吸水性好等优点而得以广泛应用。但目前市面上的聚氨酯海绵,不仅原料紧缺,制备过程有污染物产生,而且废弃后难降解,会产生二次污染。为开发可自然降解的纤维素海绵无污染制备工艺,研究了采用纤维素氨基甲酸酯法制备纤维素海绵的工艺。结果表明：由纤维素氨基甲酸酯的氢氧化钠溶液捏合而成的海绵混合体经蒸煮,纤维素再生,成孔剂溶于水中而留下空隙,所得纤维素海绵孔径均一,表面光滑平整,具有较好的柔韧性和黏弹性,完全具有普通聚氨酯海绵的基本特征。     

Chain conformations in cellulose I and cellulose II

There is strong evidence in the literature that cellulose chains have different conformations, as well as forming different crystalline lattices, in cellulose I and cellulose II. New data on the birefringence of amine-treated fibers (cellulose III) support this view.     

Trimethylsilyl cellulose as precursor to regenerated cellulose fiber

Trimethylsilyl cellulose (TMSC) has been found to melt at 320–340°C in the absence of oxygen. When TMSC is prepared from chemical cellulose, using hexamethyldisilazane and a catalytic amount of chlorotrimethylsilane/pyridine in dimethylformamide, a thermoplastic material is obtained which may be melt spun into a fiber. This fiber, when treated with mild aqueous acid, yields regenerated cellulose plus hexamethyldisiloxane. The hexamethyldisiloxane can be converted back to hexamethyldisilazane by known chemistry. The fiber properties of the regenerated cellulose were found to be comparable to commercially available rayons. X-Ray diffraction analyses of the cellulose suggest formation of an unusual polymorphic form.     

Carbon membranes from cellulose and metal loaded cellulose

The focus of this work was to find a low-cost precursor for carbon molecular sieve (CMS) membranes, and a simple way of producing them. In addition, several ways of modifying a carbon material are described. The modification method used in this study was metal doping of carbon. CMS membranes were formed by vacuum carbonization of cellulose and metal loaded cellulose. Metal additives include oxides of Ca, Mg, Fe(III) and Si, and nitrates of Ag, Cu and Fe(III).The carbon membrane containing Fe-nitrate has promising separation performance for the gas pairs O₂/N₂ and CO₂/CH₄. Carbon containing nitrates of Cu or Ag show high selectivity, but reduced O₂ and CO₂ permeability compared to carbon with Fe-nitrate. Element analysis indicates that Cu migrates to the carbon surface, creating an extra layer resistance to gas transport. A silver mirror is also seen on the surface of Ag-nitrate-containing carbon. However, the Ag- and Cu-containing membranes show a high H₂ permeability. Adding metal oxides makes the carbon membranes retard the transport of easily condensable gases (e.g. CO₂). This can be exploited for enhanced H₂/CO₂ separation efficiency.     

Thermal degradation studies of cellulose phosphates and cellulose thiophosphates

The thermal degradation of cellulose, cellulose phosphates, and cellulose thiophosphates was studied by differential thermal analysis, dynamic thermogravimetry, and derivative thermogravimetry from ambient temperature up to 750°C. Various thermodynamic parameters for different stages of thermal degradation of cellulose and its derivatives have been obtained following the methods of Broido, and Freeman and Carroll. Infrared spectra of thermally degraded samples were obtained. The data were analyzed in an effort to obtain more information concerning the flame-retardant mechanisms of cellulose phosphates and cellulose thiophosphates. Lower values of decomposition temperatures and activation energies of decomposition and higher char yields of cellulose phosphates as compared to cellulose lead to the conclusion that cellulose phosphorus esters are good flame retardants, and this property is retained even when these esters were subjected to ion exchange by Na⁺ and K⁺ ions. However, with the introduction of sulphur atoms, there was some decrease in this property.     

Studies on thermal degradation of cellulose and cellulose phosphoramides

Reaction of cellulose with hexamethylphosphoric acid triamide has been investigated under various physical conditions. Dimethylamine hydrochloride was found to be an efficient catalyst for the system. The thermal degradation of cellulose and its phosphoramide products in air was studied by DTA, TG, and DTG techniques from ambient temperature to 500°C. The data were processed for the various thermodynamic parameters following the methods of Freeman and Carroll, of Broido, and of Dave and Chopra. The energies of activation, E_a, for the degradation for various cellulose phosphoramide samples were found to be in the range of 92–136 kJ mol^?1. These values were found to decrease with increase in the degree of substitution. A mechanism for the thermal degradation of cellulose phosphoramide has been proposed. The IR spectra of char residues of cellulose phosphoramide gave an indication of the formation of compounds containing C?O and P?O groups.     

Preparation of cellulose triacetate and cellulose tricarbanilate by nondegradative methods

A method for obtaining triacetate having a D.S. of 3.0 has been obtained by acetylating the cellulose with acetic anhydride–pyridine reagent containing a catalytic amount of acetyl chloride. The process is rapid and nondegradative. Cellulose tricarbanilate can be prepared without recourse to pyridine solutions by using dimethylformamide (DMF) as solvent and triethylenediamine (1,4-diazobicyclo[2.2.2]octane) as catalyst. The DMF solution of the cellulose tricarbanilate can be cast directly into films or the polymer easily recovered owing to the solubility of the reaction solvent and impurities in water.