Dielectric relaxation studies of heterogeneously substituted cellulose acetate and its plasticization by dibutyl phthalate

Dielectric relaxation measurements are reported on plasticized commercial and heterogeneously substituted cellulose acetate. Differences in the observed behaviour are attributed to the retention of a degree of crystallinity and microscopic structure in the original substituted cellulose samples. A comparison of dynamic mechanical and dielectric relaxation data further emphasizes the influence of the nature of the original morphology on the micro dynamics.     

Pyroelectric behaviour of solution-grown cellulose acetate polymer films

The pyroelectric behaviour of cellulose acetate polymer films was studied in a vacuum of 10^?3 torr under a polarizing field strength range of 6.25 × 10⁵–50 × 10⁵ V/m and a polarizing temperature range of 304–406 K. The pyroelectric coefficient exhibited abnormal behaviour, starting initially on the negative side and then changing sign from negative to positive. Negative coefficients are believed to be due to dipolar orientation, whereas space charge polarization is responsible for positive pyroelectric coefficients.     

纤维素乙酸酯的现状及发展前景

从生产工艺流程及应用方面,介绍了乙酯纤维和纤维素乙酯膜的现状及发展。对纤维素乙酸酯的发展提出了几点建议。指出目前是国内开发乙酯产品的较佳时机。     

Electrical conduction behaviour of diphenylthiocarbazone doped cellulose acetate

Current–voltage (I–V) characteristics of diphenylthiocarbazone (DPh)-doped cellulose acetate grown from solution have been studied as a function of temperature, thickness and voltage in a metal–polymer–metal sandwich con-figuration. The role of the dopant molecular concentration in the polymer matrix and the modification of the conduction characteristics are studied. Initially, the conductivity increases as a function of dopant concentration, but at higher concentrations, it begins to decrease. The dopant molecules act as additional trapping centres at lower concentration, while at optimum concentration they provide a link between polymer molecules, leading to the formation of a charge transfer complex. The decrease in conductivity with higher concentration of doping is due to the onset of the increase in heterogeneity, which can increase the trapping sites for charge carriers. The variation of current for doped films with temperature shows different regions with different activation energies. This behaviour is explained in terms of the type of conduction mechanism operating in the material. At low voltages, Ohm’s law is followed, while at higher voltages space charge limited current is observed. It was also noted that a Richardson–Schottky emission is responsible to some extent for the transport of charge carriers. Quantitative information about the transport parameters is derived. ©1998 Society of Chemical Industry     

LiClO4 doped cellulose acetate as biodegradable polymer electrolyte for supercapacitors

The possibility of producing a biodegradable polymer electrolyte based on cellulose acetate (CA) with varied concentration of LiClO₄ for use in supercapacitors has been investigated. The successful doping of the CA films has been analyzed by FTIR and DSC measurements of the LiClO₄ doped CA films. The ionic conductivity of the films increased with increase in salt content and the maximum ionic conductivity obtained for the solid polymer electrolyte at room temperature was 4.9 × 10^?3 Ω^?1 for CA with 16% LiClO₄. The biodegradation of the solid polymer electrolyte films have been tested by soil burial, degradation in activated sludge, and degradation in buffer medium methods. The extent of biodegradation in the films has been measured by AC Impedance spectroscopy and weight loss calculations. The study indicated sufficient biodegradability of the materials. A p/p polypyrrole supercapacitor has been fabricated and its electrochemical characteristics and performance have been studied. The supercapacitor showed a fairly good specific capacitance of 90 F g^?1 and a time constant of 1 s. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Effect of nanoscale confinement on molecular mobility and drug release properties of cellulose acetate/sulindac nanofibers

Polymers confined in the nanoscale exhibit various unusual properties that are not seen in bulk polymers. Here, the effect of nanoscale confinement on the drug release properties of polymer nanofibers is investigated by analyzing the molecular mobility and drug release kinetics of cellulose acetate/sulindac nanofibers (CNs). It is observed that the activation energy, E_a, for molecular motion of both the main chain and side chain tended to increase as the diameter of the CNs decreased from 850 to 260 nm. The increased E_a indicates that the chains confined in ultrathin CNs are closely packed, resulting in a low molecular mobility. With decreasing diameter from 620 to 260 nm, the diffusion coefficient of drug is significantly decreased from 85.3 to 10.3 nm² min⁻¹. Such correlation between E_a and drug diffusion rate indicates that the confinement-induced suppression of the molecular motion could significantly affect the drug release properties of polymer nanofibers. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47863.     

Synthesis and characterization of fluorinated polyacrylate–cellulose acetate butyrate interpenetrating polymer networks

Fluorinated polyacrylates are highly hydrophobic and oleophobic. However, their poor mechanical properties prevent their development in many applications. Combination of a fluorinated polyacrylate network with a rigid cellulose acetate butyrate (CAB) network in an interpenetrating polymer network (IPN) architecture is an effective method for improving the mechanical properties of fluorinated polyacrylates. IPNs combining poly(3,3,4,4,5,5,6,6,7,7,8,8,8‐tridecafluorooctyl acrylate) (polyAcRf6) with CAB were prepared according to an in situ polymerization/crosslinking synthesis. CAB was crosslinked by addition between unmodified hydroxyl groups and the isocyanate of a pluri‐isocyanate crosslinker. The fluorinated network was obtained through free‐radical copolymerization of 3,3,4,4,5,5,6,6,7,7,8,8,8‐tridecafluorooctyl acrylate with poly(ethylene glycol dimethacrylate). The rates of formation of both networks were followed using Fourier transform infrared spectroscopy. Differential scanning calorimetry (DSC) and dynamic mechanical thermal analysis (DMTA) of IPNs show a single glass transition temperature and a single mechanical relaxation temperature, which are characteristic of a high degree of interpenetration between the partner networks. The mechanical properties of IPNs are greatly improved compared with those of the single fluorinated network. CAB/polyAcRf6 IPNs were prepared, and characterized using DSC and DMTA as well as contact angle measurements for their surface properties. As hoped, the mechanical properties of such materials are much improved compared with those of the fluorinated partner alone. Copyright © 2010 Society of Chemical Industry     

脂肪酶改性醋酸纤维的性能研究

采用脂肪酶Lipex 100L对醋酸纤维进行脱乙酰化处理,改善纤维的吸湿、染色等性能;通过脂肪酶处理残液的紫外光谱分析、反应液pH值变化以及染料对纤维的吸附量、回潮率、取代度测试等方法,分析酶处理后反应液中水解产物的产生和纤维表面官能团的变化.结果表明:脂肪酶处理醋酸纤维后,反应液中有水解产物乙酸存在,醋酸纤维的回潮率...     

Grafting of cellulose fibers latex by atom transfer radical polymerization

ABSTRACT

This study reported the synthesis of macro-initiator based on microfibers cellulose (MFC) from empty bunches (EFB), which was Ethyl α-bromoisobutyrate. The availability of the hydroxyl group on MFC offered a facile functionalization with Ethyl α-bromoisobutyrate to produce Bromo-ester group on MFC surface (MFC-BiB) that are known to be the excellent initiator for atom transfer radical polymerization (ATRP). As MFC provides only three hydroxyl groups per each unit of glucose with low reactivity, it is crucial to modify MFC with bromide functional groups having reactivity about 10.000 times greater than the hydroxyl group in the MFC. An MFC-BiB macro-initiator was successfully synthesized by homogeneous acetylation of cellulose with Ethyl α-bromoisobutyrate (EBiB) at 40°C. To confirm the performance MFC-BiB as macroinitiator, copolymerization between latex and MFC-BiB was conducted to produce Cellulose-g-latex by ATRP method with bipyridine/CuCl/CuCl₂ ligand as a complex catalyst and toluene/water as a mixed solvent. The degree of MFC-BiB substitution was measured by the FTIR method. The grafting copolymers were characterized by H-NMR and FTIR. The results indicated that the degree of substitution of macro-initiator at the ratio of MFC/EBiB of 1:3 and 1:6 were 1.27 and 1.28, respectively. The grafting efficiency of cellulose backbone with latex via ATRP showed a well-controlled grafting reaction at 44.5%.     

秸秆醋酸纤维素的制备

农作物秸秆是自然界中数量极大的可再生资源,本研究以农作物秸秆为反应原料,采用无污染蒸汽爆破技术活化预处理,然后进行乙酰化反应,通过溶剂萃取分离并制备出高附加值的醋酸纤维素。实验结果表明：秸秆汽爆后明显增加了反应活性,制备醋酸纤维素的适宜条件是123℃,2 h,催化剂用量为7％,汽爆秸秆中性洗涤剂处理后的乙酰化结果效果最好,不同汽爆秸秆中小麦秸秆乙酰化效果最佳,优化实验条件下,秸秆醋酸纤维素聚合度均在120以上,取代度2.80以上,并且用红外图谱、1H NMR进行了表征。与目前工业上采用α-纤维素含量较高的高级浆为反应原料相比,不仅原料和预处理成本大大降低,而且工艺流程简单。     

Effect of cellulose acetate/cellulose triacetate ratio on reverse osmosis blend membrane performance

Surface functionalization and modification including the grafting process are effective approaches to improve and enhance the reverse osmosis (RO) membrane performance. This work is aimed to synthesize grafted/crosslinked cellulose acetate (CA)/cellulose triacetate (CTA) blend RO membranes using N-isopropylacrylamide (N-IPAAm) as a monomer and N,N-methylene bisacrylamide (MBAAm) as a crosslinker. The morphology of these membranes was analyzed by scanning electron microscopy and their surface roughness was characterized by atomic force microscopy. The performance of these membranes was evaluated through measuring two major parameters of salt rejection and water flux using RO unit at variable operating pressures. It was noted that the surface average roughness obviously decreased from 148 nm for the pure CA/CTA blend membrane with 2.5% CTA to 110 nm and 87 nm for the grafted N-IPAAm and grafted/crosslinked N-IPAAM/MBAAm/CA/CTA-RO membranes, respectively. Moreover, the contact angle decreased from 51.98° to 47.6° and 43.8° after the grafting and crosslinking process. The salt rejection of the grafted CA/CTA-RO membrane by 0.1% N-IPAAm produced the highest value of 98.12% and the water flux was 3.29 L/m²h at 10 bar.     

Photodegradation of cellulose acetate film in the presence of benzophenone as a photosensitizer

To study the effectiveness of photosensitizers to accelerate the degradation of cellulose acetate (CA) under ambient environment, CA (degree of substitution = 2.45) films containing benzophenone, which is one of the typical photosensitizers, were prepared and their degradative behavior by photoirradiation was examined. Decrease in molecular weight of CA and generation of carbon dioxide, carbon monoxide, and acetic acid from the CA films were observed by the irradiation of xenon arc lamp light, which was passed through a filter for cutting off the wavelength shorter than 275 nm. With increasing the concentration of benzophenone, the molecular weight of CA decreased and the generation of the degradation products from the CA films increased. These results may suggest that radical reactions of CA films proceed by photoirradiation and lead to oxidation and random cleavage of CA, and that benzophenone is an effective additive to accelerate the degradation of CA under ambient environment. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

纤维素乙酸酯装置顺序控制系统的组态设计和实施

介绍了纤维素乙酸酯装置中的顺序控制功能,以及在YOKOGAWA CS-3000系统上实现该顺序控制的过程。实际运行证明该控制方案可行,并具有稳定、可靠的优点。     

醋酸纤维素的降解性研究进展

介绍了醋酸纤维素的生物降解、水解、光解的降解机理与研究现状,并对影响醋酸纤维素降解速率的因素进行了探究。从现有研究中可知,影响醋酸纤维素降解速率的主要因素为醋酸纤维素自身的分子结构（如取代度、取代度分布及结晶性等）,物理改性、化学改性及增塑改性会通过改变醋酸纤维素的分子结构,进而影响醋酸纤维素的降解性能。最后,总结了醋酸纤维的应用领域,并做出了展望。     

乙酸纤维素的应用及改性研究现状

随着污染问题及资源短缺问题的日益严重,乙酸纤维素作为纤维素的重要衍生物之一,具有良好的加工性能及可生物降解性能,近年来一直备受关注。本文系统介绍了乙酸纤维素在服装纺织、烟用滤嘴及膜材料等方面的应用,分析了目前乙酸纤维素应用中存在的问题。同时从共混改性、纳米及纳米复合改性、表面改性等方面对乙酸纤维素的改性技术的研究进展进行了综述,最后展望了乙酸纤维素的发展前景,指出开发简单易行能够工业化的改性技术及制备出可再生的生物降解材料研究是乙酸纤维素改性今后的主要发展方向。     

Electrospun progesterone-loaded cellulose acetate nanofibers and their drug sustained-release profiles

Novel cellulose acetate (CA) nanofibers incorporated with hormone progesterone (P₄) were prepared by electrospinning and its potential as a controlled release system for medicine and veterinary was evaluated by controlled release essay. The morphology, thermal behavior, and structure of P₄-loaded CA nanofibers were characterized by scanning electron microscopy, differential scanning calorimetry, and Fourier-transform infrared spectroscopy. The analyses revealed that the incorporation of P₄ increased nanofibers' diameter from around 340 to 892 nm to 8% w/w P₄-loaded CA nanofibers. Furthermore, P₄ has demonstrated high interaction with CA affecting its crystalline structure, since pure CA nanofibers presented 67.23% of crystallinity while P₄-loaded CA nanofibers where amorphous. Ultimately, the drug release essay demonstrated a two-stage profile, and regarding release kinetics, the samples evidenced a diffusion mechanism depending on P₄ concentration in the nanofiber.     

醋酸纤维素纤维干法纺丝成形模拟

建立了基于Maxwell粘弹性本构方程的干法纺丝动力学模型,对醋酸纤维素纤维干法纺丝过程进行了模拟,预测了纤维成形过程中丝条的溶剂浓度、温度、速度、张力等沿纺程的变化关系。结果表明:纤维固化成形发生在闪蒸结束后离喷丝口不远处,此后丝条溶剂含量变化很小;丝条温度在闪蒸时略低于热吹风温度,闪蒸结束后迅速上升到热吹风温度;丝条张力主要来源于空气的摩擦阻力和卷绕张力,在纺程下半段以摩擦阻力为主;提高泵供量后溶剂蒸发速率变慢,丝条温度达到热吹风温度所需时间变长,丝条固化点离喷丝头越远;闪蒸速率随纺丝液溶剂含量增高而减小,同时丝条温度升到甬道温度的时间也越长。     

Adsorption properties of cyclic compounds on cellulose acetate

The interaction between solutes and semipermeable membranes is an important factor for the membrane‐separation process. As an extension to previous works, we studied the adsorption properties of cyclic compounds on cellulose acetate, a material commonly used for semipermeable membranes, in aqueous solution systems by high‐performance liquid chromatography (HPLC). Cycloalcohols, cycloethers, amino acids, heterocyclic aromatic compounds, and nucleosides were used in this study. The logarithm of the capacity factor (log k′) for these compounds was linearly correlated with the logarithm of 1‐octanol/water partition coefficients (log K_o/w) as well as noncyclic compounds. Cyclic compounds were relatively retained more than were noncyclic compounds in spite of their hydrophilic properties, which indicates the structural effects of the solute molecule on the adsorption. Although noncyclic compounds were retained mainly by hydrophobic interaction, the retention of cyclic compounds was suggested to be controlled by their inclusion within the micropore in cellulose acetate. The adsorption of heterocyclic aromatic compounds was not influenced only by ionic dissociation but also by tautomerism. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 1657–1663, 1999     

氨基磺酸盐型水性醋酸纤维乳液的制备与性能

采用乙二胺基乙磺酸钠(AAS)作为亲水剂,在二月桂酸二丁基锡(DBTDL)的催化下,通过异佛尔酮二异氰酸酯(IPDI)将亲水基引入二醋酸纤维(CA)分子中,制得了一种氨基磺酸盐型水性醋酸纤维乳液(SWCA)。利用FTIR、DLS、黏度计、TEM、SEM、接触角测量仪、XRD、TGA,对SWCA结构及涂膜性能进行表征。考察了IPDI与AAS物质的量比对SWCA乳液粒径、黏度、涂膜表观形貌及耐水性的影响。结果表明:当n(IPDI)∶n(AAS)=1.1∶1时,乳液最稳定,微观形态呈水包油型(O/W)核壳结构,乳液粒径和分散系数(PDI)最小,分别为128nm和0.112,此时乳液表观黏度最大,为73.5m Pa·s,所成涂膜致密平整,接触角可达110.2°±2°,表现出明显的疏水性;此外,与二醋酸纤维相比,SWCA涂膜结晶性减弱,呈微晶态或次晶态结构,且具有较好的耐热性。