The cholesteric nature of cellulose triacetate solutions

Solutions of cellulose triacetate (CTA) in trifluoroacetic acid (TFA) become liquid crystalline above a certain critical concentration. Using the techniques of spectrophotometry, wide-angle light scattering and circular dichroism we have shown that the mesophase formed is cholesteric. We have measured its pitch, which depends on polymer concentration, and shown that the cholesteric structure is right-handed. Measurements of optical activity and the optical effects of shear and magnetic fields are also described and discussed.     

Rapid expansion of cellulose triacetate from ethyl acetate solutions

Rapid‐expansion‐of‐supercritical‐solution (RESS) experiments were performed for solutions of cellulose triacetate [CTA; weight‐average molecular weight = 145,700, polydisperity = 2.07] in ethyl acetate [EA] over a range of concentrations and conditions of polymer–solvent phase behavior. Solid‐solubility experiments were carried out beforehand and identified hot and compressed liquid EA at approximately 175°C as a good solvent for CTA. Cloud‐point measurements were then used to locate the region of liquid–liquid equilibrium (LLE) for this system. The RESS results indicate that the phase state of the pre‐expansion mixture determines the product size, and the overall concentration of the pre‐expansion mixture determines the product morphology. However, we have also discovered a new constraint: for the production of well‐formed fibers and particles, the rapid‐expansion path must include penetration into a region of LLE, which must exist over a sufficient pressure range so that a separate, polymer‐rich liquid phase has time to develop before the onset of vapor–liquid equilibrium (VLE). If rapid expansions are carried out at temperatures near or below the lower critical end point, the expansion path leads directly into a region of VLE, and a disruptive vapor expansion occurs within the continuous liquid phase. In this case, hollow particles, hollow structures, and even foams are produced. By the proper choice of operating conditions, we were able to produce continuous CTA fiber from a 5 wt % solution in EA at 250°C and 69 bar. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 95: 290–299, 2005     

Gel formation and liquid crystalline order in cellulose triacetate solutions

The formation of a liquid crystalline state of cellulose triacetate solution in trifluoroacetic acid was studied using optical microscopy, polarimetry and circular dichroism measurements. Below a critical concentration of $\text{34}\text{g}\text{100}\text{ml}$ a clear isotropic solution was formed. Solutions more concentrated than this were in the cholesteric liquid crystalline state. If water was added to the solution, a gel phase was formed if the polymer concentration was above a critical value. We interpret our observations in terms of the Pincus-de Gennes theory and show that the formation of liquid crystalline order involves both inter-and intramolecular forces.     

木质素基离子变换树脂在放射性核素分离上的应用

离子交换是铀及其他放射性核素水冶过程中从浸出液实现浓缩分离的重要工艺之一,离子交换树脂是此过程应用的最主要材料.探讨并展望了木质素基离子交换树脂作为新型放射性核素吸附材料在核工业水冶系统中的应用前景,指出其将成为木质素高值化利用的一个新领域.     

The condensate polishing performance of powdered ion-exchange resins

The coating properties and ion-exchange performance of powdered ion-exchange resins were examined in a small test facility. Satisfactory resin coatings were obtained with cation : anion resin ratios in the range 1 : 1 to 3 : 1, but a 9 : 1 resin ratio resulted in a high pressure drop across the coating. The “settled resin volume” proved to be a reliable guide to the coating performance of resin slurries. The ion-exchange capacity of the cation resin increased from 2.5 to 2.8 equiv./kg as the sodium concentration in the influent decreased from 49 to 0.5 mg 1^?1. Within the ranges examined, resin ratio, resin loading and flowrate had no significant effect on cation capacity. The ion-exchange capacity of the anion resin for chloride ions was 2.2 to 2.3 equiv/kg at ambient temperature but exposure of the resin for four days at 80 °C reduced the capacity to 1.6 equiv./kg; four days at 90 °C reduced the capacity to less than 1 equiv./kg. The thermal stability of the powdered anion resin was markedly less than that quoted elsewhere for anion bead resin. The stability of the floc was also investigated.     

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.     

氨基膦酸型含氟螯合树脂用于离子膜二次盐水精制

对D-412氨基膦酸型螯合树脂进行共聚改性,在聚合中引入含氟单体,在树脂骨架上引入氟元素制得氨基膦酸型含氟螯合树脂。最佳反应条件为:聚合配方中含氟单体选用甲基丙烯酸八氟戊酯(质量分数为0.8%),再经过氯甲基化、胺化、膦酸化反应。试验证明:该改性螯合树脂用于离子膜法烧碱盐水的二次精制,吸附性能得到提高,力学性能也得到提高,树脂破碎率远低于未处理的D-412螯合树脂。     

Infra-red absorption spectra of ion-exchange resins

Infra-red absorption spectra have been obtained by the KBr disc technique for some fifty commercial ion-exchange resins with quaternary ammonium, tertiary and mixed amine, sulphonic, phosphonic, secondary phosphate, and carboxylic groups, as well as for a number of experimental resins, including some of the solvent-modified type. The use of the technique in structural characterisation of ion-exchange resins is discussed.     

离子交换树脂电再生技术的研究进展

离子交换树脂的电再生法，只消耗电能，无需酸碱化学药剂，对环境无污染，使用方便，具有良好的环境效益。本文阐述了混床和复床电再生机理，并介绍了目前国内在电再生方面的研究进展。     

A comparative study of the thermal decomposition of cellulose and cellulose triacetate

Conclusions A comparative study has been made of the thermal decomposition of cellulose and of cellulose acetates having various degrees of polymerization, and also of specimens regenerated from nonaqueous solutions.The effect of the solvent on reducing the effective energy of activation of thermal decomposition on transition from the starting samples of cellulose and its derivatives to specimens regenerated from nonaqueous solutions has been revealed.It has been found that the degree of polymerization exerts no significant effect on the temperature of thermal decomposition.Translated from Khimicheskie Volokna, No. 4, pp. 28–29, July–August, 1986.     

Curing characteristics of epoxy resins filled with cellulose and oxidized cellulose

Gel time and Brookfield viscosity studies of epoxy resins containing varying concentrations of cellulose, periodate oxidized cellulose, chromic acid oxidized cellulose, and ethylene glycol were carried out at 120°C using the tertiary amine hexamethylene tetramine as catalyst. It was found that the hydroxyl groups of cellulose and oxidized cellulose did not only act as accelerators for the tertiary amine catalyzed polymerization of the epoxy resin, but evidence was also found which pointed to the actual participation of the cellulosic fillers in the crosslinking reaction leading to the thermoset epoxy polymer. The gel times of the epoxy curing reaction decreased as the concentrations of the cellulosic fillers increased. The change in viscosity with time (curing characteristics) curves for 40 parts of cellulose or oxidized cellulose per hundred parts of resin (phr) were similar to that of 10 phr ethylene glycol, while the curve for 20 phr cellulose-filled epoxy resin was almost identical to the curve for 10 phr periodatefilled resin. These differences are explained on the basis of the percentage of hydroxyl groups in the various filler molecules that are available for their role as accelerators. The possibility of greater participation of oxidized cellulose in the network formation with the epoxy resin than ordinary cellulose has also been surmised on the basis of its increased viscosity build-up after the gel time is achieved.     

Drying cellulose triacetate in a dryer with a vibrational fluidized bed

Conclusions The process of drying cellulose triacetate in a vibrating bed has been studied.For final drying of cellulose triacetate before solution, it is recommended to use an industrial specimen of a unit with a vibrating bed having a capacity of 2700 kg/h.This assembly can be used to dry other fibre-forming disperse polymeric materials containing strongly bound moisture.Translated from Khimicheskie Volokna, No. 3, pp. 49–51, May–June, 1984.     

Transesterification of brazilian vegetable oils with methanol over ion-exchange resins

The transesterification of several Brazilian vegetable oils with methanol was carried out at 60°C in the presence of several ion-exchange resins having different structures. The vegetable oils used were from Babassu coconut, corn, palm, palm kernel, and soybean. The effect of the methanol/oil mole ratio and the influences of the structure of the ion-exchange resin and the type of vegetable oil used on the catalytic activity of the ionexchange resins were investigated. The resins used were Amberlyst 15, Amberlyst 31, Amberlyst 35, and Amberlyst 36. Amberlyst 15 produced the best results for the transesterification of vegetable oils. The methyl ester yield is higher for palm kernel oil and Babassu coconut oil than for soybean oil, probably owing to their higher content of shorter-chain FA. Therefore, it was shown that the catalytic activity of the resin depends on the FA composition of the vegetable oil employed.     

Adsorptive separations of alkylphenols using ion-exchange resins

Separation of close boiling point mixtures of alkylphenols, such as p-cresol/2,6-xylenol, m-cresol/2,6-xylenol and p-cresol/m-cresol has been attempted using commercially available ion-exchange resins. The basic resins selectively adsorb the cresol isomers from their mixtures with 2,6-xylenol. The separation seems to be decided by the thermodynamic selectivity in the ion-exchange resin framework with diffusional selectivity also contributing to the separation.     

Fibers from a mixture of cellulose triacetate and polystyrene

Conclusions The introduction of a nonfiber-forming substance — polystyrene — into cellulose triacetate does not cause the formation of long microfibers in the polymer matrix; the polystyrene is distributed along the fiber axis in the form of stretched-out regions.The addition of polystyrene helps increase the strength figures for triacetate fibers by more than 20%.Translated from Khimicheskie Volokna, No. 4, pp. 37–38, July–August, 1983.