Some Properties of Polycaprolactone Composites with Cellulose Nanocrystals

Russian Journal of General Chemistry - Composites of polycaprolactone with cellulose nanocrystals were produced, and their morphological, thermal, and strength characteristics were examined. It was...     

Study of the Structure and Sorption Properties of Some Types of Cellulose

The pulsed NMR, isopiestic and pycnometric methods are applied to investigate the physicochemical properties of softwood [GOST (State Standard) 9571-89] and hardwood [GOST 28172-89] celluloses, as well as flax cellulose [GOST 10330-76, 9394-76], both in the initial state and subjected to chemical treatment. Possible changes occurring in the supramolecular structure of a polymer are analyzed. The structural and sorption characteristics of the investigated samples are calculated. Their water absorption capacities are determined.     

Properties and Applications of Cellulose Acetate

Cellulose acetate is one of the most important esters of cellulose. Depending on the way it has been processed cellulose acetate can be used for great varies of applications (e.g. for films, membranes or fibers). The properties of the applied cellulose acetates are very important for these applications. A special field for using cellulose acetate is the synthesis of porous, spherical particles, so called cellulose beads. Different types of technical cellulose acetates were used and their ability to form such cellulose beads was characterized. First the different types of cellulose acetates were characterized by means of solubility; turbidity and degree of substitution. In addition the molar mass and the distribution of substituents along the polymeric chain were analyzed. Next, the cellulose beads were synthesized within an emulsion process using these different cellulose acetates. Then the properties (particle size, porosity, morphology) of the cellulose beads were determined. Finally, the relationship between the characteristic of cellulose acetates and properties of cellulose beads was investigated.     

Properties of Aqueous Solutions of Mixtures of Methyl Cellulose and Hydroxypropyl Cellulose

Rheological properties of dilute and moderately concentrated aqueous solutions of mixtures of methyl cellulose and hydroxypropyl cellulose and gelation in these solutions were studied. Using the solvent vapor sorption, the compatibility of the polymer pair was examined and the composition range in which the thermodynamic compatibility is realized was determined.     

Carboxymethyl Cellulose Amides and Their Properties

Single-stage synthesis of carboxymethyl cellulose amides was studied. The influence exerted by introduction of amide groups with bulky alkyl radicals on the thermodynamic affinity of mixed cellulose ethers for a solvent and their solubility in water was evaluated.     

Alteration of Bacterial Cellulose Properties by Diacetylglycerol

Bacterial cellulose (BC) was altered by means of 0.5-2.5% w/v diacetylglycerol in acetone-water through impregnation process provided DGBC composites. Results from the scanning electron microscope images, revealed that diacetylglycerol filled the pores of BC, leads to the significant enhanced in hydrophilicity and caused a smoother BC morphology. The addition of diacetylglycerol into BC caused a slightly changed in crystallinity indexes and bring about the reduction in tensile strength and Young's modulus but increased in elongation at break and toughness. The significant reduction of tensile strength and Young's modulus was achieved for DGBC 2.5% as well as for elongation at break and hydrophylicity improvement. Through the impregnation method, diacetylglycerol serves as biodegrada–ble and safe plasticizer, resulted in less rigid and higher ductility DGBC composites.     

Sorption Properties of Gel Films of Bacterial Cellulose

The structure and sorption properties of gel films of bacterial cellulose were studied in its interaction with polyvinylpyrrolidone and silver nanoparticles stabilized by this compound.     

Mechanical Properties of Regenerated Cellulose Fibres for Composites

Summary: A broad variety of regenerated cellulose fibres was subjected to single fibre tensile tests in order to determine the modulus of elasticity, tensile strength, and failure strain. The results were compared to glass fibres and flax fibres, which are considered the most important technical and natural fibres, respectively. With regard to their modulus of elasticity and tensile strength, regenerated cellulose fibres showed clearly lower values than glass fibres, even when their low density was taken into account. The average modulus of elasticity and tensile strength of regenerated cellulose fibres was also lower than the values measured for flax fibres, but when variability was considered, both fibres performed similarly. In terms of interfacial shear strength with polypropylene, lyocell fibres performed significantly less well than sized glass fibre and ramie fibre. The most important difference between regenerated cellulose fibres and both glass and flax fibres is their high failure strain and thus high work to fracture. The high work to fracture of regenerated cellulose fibres makes them particularly useful for composite applications where high fracture toughness is required.     

纤维素混合醚酯的制备与静电纺丝性能

研究了几种纤维素混合醚酯的制备及其高压静电场纺丝性能,分析了溶剂组成、溶液浓度、分子量、酯化基团对成纤性和纤维直径的影响。结果表明:在非均相条件下,经过碱化、醚化与酯化,得到不同结构的纤维素混合醚酯HPMCP、HPMCT与HPMCAS,均可实现静电纺丝;在甲醇/二氯甲烷=1∶4的溶剂体系中易得到表面光滑纤维;在溶剂组成一定条件下,溶液仅在一定浓度范围可纺,且浓度越低、纺丝电压越高,纺丝平均直径越小;当溶剂组成、溶液浓度一定时,分子量对其溶液纺丝的可纺性有直接影响,HPMCAS仅重均分子量达到7.2×104才能获得表面光滑纺丝纤维;在溶剂组成、溶液浓度和分子量一定的条件下,相邻酰基间距离越小,酸性越强,溶液电导率越大,丝越细。     

醋酸纤维素/PET接枝共聚物的制备及性能

以低数均分子量的聚对苯二甲酸乙二醇酯(PET)、二醋酸纤维素(CDA)为原料,异孚尔酮二异氰酸酯(IPDI)为接枝剂,二月桂酸二丁基锡(DBTDL)和离子液体1-丁基-3-甲基咪唑氯盐为催化剂制备得到新型的接枝共聚物CDA-g-PET。对接枝过程进行了优化,研究了催化剂种类与接枝剂用量对接枝过程的影响,利用红外分析和广角X射线衍射分析探究了接枝机理。同时对CDA-g-PET膜进行力学性能测试,探讨了PET的加入量对CDA-g-PET膜力学性能的影响。结果表明:PET通过化学键连接接枝到CDA上,接入的PET降低了CDA的结晶性;采用DBTDL与离子液体作为联合催化剂,接枝时间由7d缩短至8h;当接枝剂IPDI的加入量,即n(IPDI)/n(PET)为1.05~1.10时CDA-g-PET无交联;随着PET含量的增加,CDA-g-PET膜与CDA膜相比拉伸强度仅降低6.55%~27.24%,断裂伸长率增加149.89%~177.81%。     

Synthesis and Opto-Electronic Properties of Cholesteric Cellulose Esters

Cholesteric materials display unique optical properties which can be exploited in opto-electronic applications such as light emitting diodes. The key feature is the position of the wavelength of the emitted light relative to the one of the selective reflection band. We have synthesized a set of cellulose derivatives displaying the cholesteric phase with the aim to investigate the correlation between chemical structure and properties. Phase transition temperatures, the chain packing, the wavelength of selective reflection but also absorption and fluorescence spectra were investigated as a function of the degree of substitution (DS), the nature of lateral substituents, the composition of doped systems and blends of different cellulose derivatives. Investigated were furthermore the degree of circular polarization of the emitted light for guest–host systems and for cellulose systems with chromophores linked by covalent bonds to the cellulose backbone as well as their performance in light emitting diodes. The conclusion is that the optical properties can be accounted for on the basis of the model of a one-dimensional photonic crystal. The limiting factor with respect to opto-electronic applications is the poor control of the uniformity of the helix formation and orientation.     

多胺型稻草纤维素球的制备及其对水体中Zn2+的吸附性能

多胺型稻草纤维素球的制备及其对水体中Zn2+的吸附性能;农副产品;稻草;多胺型稻草纤维素球;锌     

醋酸纤维素衍生物的合成及包衣性质

用苯酐、四氢苯酐和甲基四氢苯酐对醋酸纤维素进行修饰,对醋酸纤维素邻苯二甲酸酯(CAP)、醋酸纤维素四氢邻苯二甲酸酯(CATH)和醋酸纤维素甲基四氢邻苯二甲酸酯(CAMT)的性质如酸值、膜透湿性、抗张强度、黏度和玻璃化转变温度进行了初步探讨,并选用盐酸青藤碱为模型药物进行包衣片剂的体外释放实验.结果表明,两类高分子材料的成膜性能良好,符合药剂学薄膜包衣材料的有关要求.包衣片的体外释放实验表明,CAMT和CATH作为薄膜材料在纯化水中释放药物的速度比醋酸纤维素薄膜材料释放药物的速度明显减慢.CAMT和CATH可以用作长效释药的包衣材料.     

纤维素/壳聚糖共混透明膜的制备及阻隔抗菌性能研究

利用壳聚糖溶液包覆法制备了具有高气体阻隔性及抗菌性的透明纤维素膜,其扫描电镜照片证明壳聚糖厚度在1.31 ～4.07 μm之间.通过红外光谱、紫外光谱、热重分析仪、电子万能试验机和接触角测试仪对纤维素/壳聚糖共混膜的结构和性能进行了详细研究,结果表明由于壳聚糖和纤维素之间具有一定的氢键相互作用,使得纤维素/壳聚糖共混膜较好地保持了纯纤维素膜的机械强度,其拉伸强度都大于110 MPa.此外,壳聚糖的包覆对纤维素膜的透明性没有影响,它在600 ～ 800 nm处的透光率仍维持在80％左右,并且提高了纤维素膜的疏水性,其水接触角从纤维素膜的70°提高到了100°.利用气体渗透仪进一步研究了纤维素/壳聚糖共混膜的氧气阻隔性,结果表明该膜具有很好的氧气阻隔性,其氧气渗透系数甚至低于市场上理想的氧气阻隔材料乙烯-乙烯醇共聚物(EVA).金黄色葡萄球菌抗菌测试表明,通过壳聚糖包覆法改性纤维素能够明显提高纤维素膜的抗菌性.     

Flow Properties of Moderately Concentrated Solutions of Cellulose Acetate Polymer

Calculations [1] of rheological properties of polymeric solutions have usually been restricted to very dilute o r to very concentrated solutions. In either case, one starts with a model for the micro- structure. Between these two conceptual extremes lies the broad class of moderately concentrated solutions. To cover this region theoretically, two approaches have been used; 1) network theories focusing attention on entanglement junctions, and 2) single-molecule theories focusing attention on single molecules but including inter- molecular interactions. Williams, Wang, and Zimm introduced a double model; one for a particular macromolecule and another for solutions containing like molecules in which the chosen macro- molecule is suspended. This approach has turned out to be quite successful because spheres immersed in a suspension of like spheres behave as i f suspended in a Newtonian fluid, and the resulting ex- pression for viscosity is quite simple in form and qualitatively correct for moderate concentrations.     

Structure and Transport Properties of Films of Mixed Cellulose Esters

Cellulose acetomyristates of varied composition were studied. The sample volume abnormally increases in high-temperature stretching and after swelling in benzene. Cellulose acetomyristates can be used as membranes for separating aromatic and aliphatic hydrocarbons.     

高取代氰乙基纤维素膜材料的合成及其性能

本文针对采用高取代氰乙基纤维素(HCEC)作为膜材料进行一系列合成条件试验,对产物的取代度、特性粘度及膜的反渗透性能进行测试,并用红外光谱图及X-射线衍射表征,实验表明HCEC是一种较理想的膜材料,它能很好地溶于丙酮,易成膜,用它制成的反渗透膜除具有较好的反渗透性能外,还具有耐酸、碱水解和抗微生物分解性能。此外,可以按一定比例与CA共混,制成除具有优良的反渗透性能外,抗微生物分解性能以及透水量都比CA膜较好的膜。三种不同膜的横截面电镜图显示其内部结构有明显差别。     

纤维素苯甲酸酯接枝二乙二醇十六烷基醚的制备及性能

分别以1-烯丙基-3-甲基咪唑氯盐([Amim]Cl)和1-乙基-3-甲基咪唑醋酸盐([Emim]Ac)/N,N-二甲基乙酰胺(DMAc)为溶剂体系,以微晶纤维素(聚合度为220)和苯甲酰氯(BC)为原料制备纤维素苯甲酸酯(CB).探索了溶剂体系、反应温度和投料比对产物取代度、溶解性和熔融性能的影响.结果表明,以[Amim]Cl为溶剂时,随着反应温度的升高(60~80℃)或体系中苯甲酰氯与葡萄糖单元环(AGU)投料量的增加(3∶1~9∶1),产物的溶解性和熔融性能均提高,取代度也随之升高(0.13~2.98);以[Emim]Ac/DMAc为溶剂时,产物中苯甲酰基的接枝度较低,且共聚物中引入乙酰基不适合制备纤维素-g-苯甲酰氯.初步探讨了在[Amim]Cl中合成纤维素苯甲酸酯接枝二乙二醇十六烷基醚(CB-g-E_2C_(16))固-固相变材料的性能,研究结果表明,CB-g-E_2C_(16)相变材料的相变温度为12.7~29.1℃,相变焓为12~24 J/g,在294℃仍能保持热稳定性,为该类纤维素基固-固相变材料的可熔融加工奠定了理论基础.     

Rheological Properties of Aqueous H-Carboxymethyl Cellulose Solutions with Various Additives

Rheological properties of moderately concentrated aqueous solutions of carboxymethyl cellulose in the H form with various additives were studied.     

Preparation and Properties of Cellulose/Waste Leather Buff Biocomposites

The aim of the present work was to utilize waste leather buff (WLB) as filler in cellulose and make biocomposites for packaging applications such as wrappers. Cellulose was dissolved in the environmentally friendly ionic liquid 1-allyl-3-methylimidazolium chloride (AmimCl). To this solution, WLB was added in amounts of 5 to 25 wt.% of cellulose. The cellulose and cellulose/WLB composite films were prepared by regenerating the corresponding cast solutions in a water coagulation bath followed by washing and drying. These films were tested for their tensile properties, thermal stability, and morphology. The tensile modulus and strength of the composite films were lower than those of the matrix. The lowering of the tensile modulus and strength with increasing WLB loading was attributed to the random orientation of the leather fibers of WLB in the composites. However, the % elongation at break of the composite films was found to be higher than that of the matrix and increased with increasing WLB content. The possible interaction between the matrix and WLB filler was probed using FT-IR analysis. The thermal stability of the composite films was higher than that of the matrix. The increase in thermal stability of the composite films was attributed to cross-linked collagen protein leather fibers in WLB. The fractographs of the composite films indicated good interfacial bonding between cellulose and leather fibers of WLB. These composite films may be considered for packaging and wrapping applications.