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Agrega??o de cadeias de acetatos de celulose em LiCl/DMAc: avalia??o via viscosimetria
Morgado, Daniella L.;Martins, Virginia da C. A.;Plepis, Ana M. de G.;Frollini, Elisabete;
Polímeros , 2011, DOI: 10.1590/S0104-14282011005000019
Abstract: linters cellulose was acetylated to obtain cellulose acetates with different degrees of substitution (ds) in homogeneous medium, using lithium chloride/n,n-dimethylacetamide (licl/dmac) as solvent system, and acetic anhydride as acetylating agent. the aggregation among chains of cellulose or cellulose acetates (ds 0.8, 1.5 and 2.0) in solution was studied through viscometric measurements. the results showed that aggregation in licl/dmac is different for cellulose and acetates, and depends on the temperature and ds in the case of acetates. this study corresponds to the first step of a project, which aims at to prepare cellulose acetates films, as well as acetates films reinforced with cellulose, by casting directly from these solutions in licl/dmac. the results presented here allow for an optimized choice of concentration range for preparing films from licl/dmac solutions of acetates and cellulose.
纤维素LiCl/DMAc溶液法制备纤维素薄膜  [PDF]
纺织学报 , 2011,
Abstract: 以LiCl/DMAc为溶剂溶解棉浆粕,得到均匀透明的纤维素LiCl/DMAc溶液后,采用湿法工艺制备了纤维素薄膜。用红外光谱和X射线衍射等分析方法对薄膜结构进行了表征。考察了凝固浴种类、制膜液纤维素浓度、凝固浴中LiCl/DMAc浓度及凝固浴温度对薄膜力学性能的影响,得到了纤维素LiCl/DMAc溶液法制备纤维素薄膜的最佳工艺条件:配制纤维素质量分数为6-7%的纤维素LiCl/DMAc溶液,选用含有质量分数为10-15%的LiCl/DMAc的水溶液作凝固浴,固化温度为20℃时,可得到具一定强度的均匀透明的纤维素薄膜。
SYNTHESIS AND CHARACTERIZATION OF CELLULOSE-SILICA COMPOSITE FIBER IN ETHANOL/WATER MIXED SOLVENTS
Ning Jia,Shu-Ming Li,Ming-Guo Ma,Jie-Fang Zhu
BioResources , 2011,
Abstract: Cellulose-silica composite fiber samples have been successfully synthesized using cellulose solution, tetraethoxysilane, and NH3 H2O in ethanol/water mixed solvents at room temperature for 24 h. The cellulose solution was previously prepared by the dissolution of microcrystalline cellulose in a solvent mixture of N,N-dimethylacetamide (DMAc)/lithium chloride (LiCl). The effect of the tetraethoxysilane concentration on the product was investigated. The products were characterized by X-ray powder diffraction (XRD), thermogravimetric analysis (TG), differential scanning calorimetric analysis (DSC), scanning electron microscopy (SEM), Fourier transform infrared spectrometry (FT-IR), energy-dispersive X-ray spectrum (EDS), and cross polarization magic angle spinning (CP/MAS) solid state 13C-NMR. The morphology of the cellulose-silica composite fiber was investigated by SEM, while their composition was established from EDS measurements combined with the results of FT-IR spectral analysis and XRD patterns. The XRD, FT-IR and EDS results indicated that the obtained product was cellulose-silica composite fiber. The SEM micrographs showed that the silica particles were homogeneously dispersed in the cellulose fiber. The CP/MAS solid state 13C-NMR results indicated that the silica concentration had an influence on the crystallinity of the cellulose. This method is simple for preparation of cellulose-based composites.
LiCl/DMAc体系对蔗渣的溶解性  [PDF]
李状,石锦志,廖兵,庞浩
化工进展 , 2010,
Abstract: LiCl/DMAc体系是近年来日益受到重视的纤维素非水溶剂,但其溶解植物生物质,如蔗渣的情况却鲜有报道。本文从活化时间、固液比、LiCl浓度、加热时间及加热温度5个方面对LiCl/DMAc体系溶解蔗渣的行为进行研究。结果表明最佳溶解条件为蔗渣160℃活化1h,烘干后取400mg与10%LiCl/DMAc溶液20mL按固液比1∶50g/mL混合,160℃加热3h后,蔗渣溶解率可达81.8%。这为均相条件下利用蔗渣进行高效衍生化提供了有前景的发展方向。
纤维素LiCl/DMAc溶液的制备及溶液稳定性  [PDF]
纺织学报 , 2010,
Abstract: 研究了制备纤维素LiCl/DMAc(氯化锂/N,N-二甲基乙酰胺)溶液的制备工艺及溶液稳定性。结果表明:将活化处理的纤维素加入到LiCl溶解在DMAc形成的LiCl/DMAc体系中,在100℃下搅拌一定时间后冷却到室温搅拌数小时,可得到均匀透明的纤维素LiCl/DMAc溶液。配制该溶液,纤维素浓度越大,所需加热搅拌和室温搅拌时间越长;同样,纤维素聚合度越大,其溶解效果越差;LiCl含有结晶水,纤维素只溶胀不溶解,而且只当LiCl质量分数超过6%时,纤维素才能完全溶解,LiCl含量随纤维素浓度而提高。另外,通过研究纤维素LiCl/DMAc溶液在不同温度下的粘度随时间的变化率,得出了在低于50℃下,该溶液在30天内很稳定;溶液加热至100℃后,可稳定存在15小时的结论。
天然彩色棉纤维素LiCl/DMAc溶液流变性能的研究  [PDF]
纺织学报 , 2010,
Abstract: 为进行天然彩色棉纤维素的静电纺丝,研究了天然彩色棉和白棉纤维素LiCl/DMAc(N,N-二甲基乙酰胺)溶液的流变性能。结果表明:棕棉纤维素LiCl/DMAc溶液的非牛顿指数较高,最接近1;3种纤维素溶液的非牛顿指数随溶液温度的升高而增高,棕棉、绿棉纤维素LiCl/DMAc溶液分别在30、35℃以上具有较稳定的流变特性;3种纤维素溶液的非牛顿指数随溶液质量分数的增加而减小,棕棉、绿棉纤维素溶液质量分数在1.2%、1.1%以下均具有较稳定的非牛顿指数。通过棕棉纤维素LiCl/DMAc溶液的静电纺丝实验,证实了棕棉纤维素质量分数必须在1.2%以下才可能形成稳定的射流,制得直径为200nm以下的静纺纤维。
DMAc / LiCl 体系下纤维素 / 聚醚砜共混膜的制备与表征  [PDF]
孙中华,陈夫山
包装工程 , 2013,
Abstract: 采用 N,N-二甲基乙酰胺(DMAc) / 氯化锂(LiCl)体系作为纤维素溶剂,制备了纤维素 / 聚醚砜共混膜。探讨了共混比对膜的断裂强度、断裂伸长率和纯水通量等膜性能的影响,并确定了纤维素 / 聚醚砜最佳共混比为 1 : 16。 对共混膜进行了 SEM 和 DSC 分析,确认了纤维素 / 聚醚砜共混膜是一个相容的聚合物共混体系。
DMAc / LiCl 体系下均相接枝纤维素的制备与表征  [PDF]
陈萍莉,孙中华
包装工程 , 2014,
Abstract: 目的 研究均相条件下纤维素接枝甲基丙烯酸甲酯的较佳制备条件。 方法 用 DMAc / LiCl 体系作为纤维素溶剂,过硫酸铵作为引发剂,将纤维素与甲基丙烯酸甲酯进行均相接枝聚合。 结果 最终确定了纤维素均相接枝甲基丙烯酸甲酯的较佳条件, 反应时间为 2 h, 单体与纤维素的质量比为1 : 1 ,引发剂与纤维素质量比为 6 : 50 ,反应温度为 80 益 。 结论 在此接枝条件下,纤维素均相接枝甲基丙烯酸甲酯的接枝率为 76% ,通过 FTIR,SEM 和 TG-DTA 表征,确认了均相接枝产物的存在。
Bamboo Fibers Elaborating Cellulose Hydrogel Films for Medical Applications  [PDF]
Karla Lizette Tovar-Carrillo, Motohiro Tagaya, Takaomi Kobayashi
Journal of Materials Science and Chemical Engineering (MSCE) , 2013, DOI: 10.4236/msce.2013.17002
Abstract:

Bamboo fibers were used as source to prepare cellulose hydrogel films for cell cultivation scaffold. The preparation of cellulose solutions was carried out by three different dissolving methods with NaOH-based and NaOH/urea aqueous solutions and DMAc/LiCl solution. Several hydrogel films were elaborated and their properties were compared to evaluate the effect of the dissolving method. It was found that tensile strength of the resultant hydrogel films increased from 21 to 66 N/mm2 when DMAc/LiCl was used instead of the NaOH/urea solution. The same tendency was observed in the obtained elongation values. Moreover, a remarkable difference in fibroblast cell cultivation was observed in higher cell density, when DMAc/LiCl method was used. The obtained results with DMAc/LiCl also were seen to be higher than the results for PS dish used as control. However, low cytocompatibility was observed when NaOH and NaOH/urea methods were used. The obtained results showed that hydrogel films elaborated with cellulose solution prepared with DMAc/LiCl method exhibited good cytocompatibility for the cell cultivation scaffold.

Bio-based Films from Linter Cellulose and Its Acetates: Formation and Properties  [PDF]
Daniella L. Morgado,Bruno V. M. Rodrigues,Erika V. R. Almeida,Omar A. El Seoud,Elisabete Frollini
Materials , 2013, DOI: 10.3390/ma6062410
Abstract: This paper describes the results obtained on the preparation of films composed of linter cellulose and the corresponding acetates. The acetylation was carried out in the LiCl/DMAc solvent system. Films were prepared from a LiCl/DMAc solution of cellulose acetates (degree of substitution, DS 0.8–2.9) mixed with linter cellulose (5, 10 and 15 wt %). Detailed characterization of the films revealed the following: (i) they exhibited fibrous structures on their surfaces. The strong tendency of the linter cellulose chains to aggregate in LiCl/DMAc suggests that these fibrous elements consist of cellulose chains, as can be deduced from SEM images of the film of cellulose proper; (ii) the cellulose acetate films obtained from samples with DS 2.1 and 2.9 exhibited microspheres on the surface, whose formation seems to be favored for acetates with higher DS; (iii) AFM analysis showed that, in general, the presence of cellulose increased both the asperity thickness and the surface roughness of the analyzed films, indicating that cellulose chains are at least partially organized in domains and not molecularly dispersed between acetate chains; and (iv) the films prepared from cellulose and acetates exhibited lower hygroscopicity than the acetate films, also suggesting that the cellulose chains are organized into domains, probably due to strong intermolecular interactions. The linter and sisal acetates (the latter from a prior study), and their respective films, were prepared using the same processes; however, the two sets of films presented more differences (as in humidity absorption, optical, and tensile properties) than similarities (as in some morphological aspects), most likely due to the different properties of the starting materials. Potential applications of the films prepared in tissue engineering scaffold coatings and/or drug delivery are mentioned.
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