Characterization of acidic groups in oxycelluloses III. Effect of cation freeing and blocking on estimation of carboxyl groups and lactones by the idometric method

A differentiation between free carboxyl and various lactone groups in different types of oxycelluloses was carried out based on the variation in their reaction rate with KI/KIO₃ solution. For oxycelluloses prepared under acidic conditions, a large proportion of carboxyl groups are present in free form. Each oxycellulose was also studied after cation freeing as well as after blocking the free carboxyl groups by treatment with sodium chloride. Cation freeing was found to cause considerable lactonization of carboxyl groups; sodium chloride treatment blocked them only partially.     

Characterization of acidic groups in oxycelluloses IV. Effect of accelerated aging on yellowing as well as carboxyl groups and lactones in pulp

Bleached bamboo pulp as well as two oxypulps were subjected to accelerated aging by heating as well as steaming, and the yellowing or color reversion was studied. The yellowing is increased by the presence of free carboxyl and the reducing groups in oxycelluloses. The again treatments were found to cause an increase in free carboxyl groups accompanied by a reduction in copper number. A differentiation between free carboxyl and various lactone groups in oxidized and also aged samples was carried out based on the variation in their reaction rates with KI/KIO₃ solution, and the characteristic acidic group spectrum showed that on steam again the fastreacting lactones are lost.     

Characterization of acidic groups in oxycelluloses. I. Identification of various functional groups

A large number of oxycelluloses were prepared and modified further by treatment with sodium borohydride as well as chlorous acid, and qualitative color tests were carried out to detect the presence of various functional groups. Uronic acid groups were found to be present in most of the samples. Enediol groups were not detected in any of the samples, although the samples after sodium carbonate treatment gave distinct color tests for enediols, indicating the presence of α-hydroxymonoketo groups. Characteristic color tests for lactones were observed for most of the samples. The intensity of color developed in the lactone test was, however, found to decrease progressively on contact with a KI–KIO₃ mixture for various periods. The difference in the values of carboxyl content between the methylene blue method and the iodometric method is thus mainly caused by the opening of lactones in the latter method.     

碘量法测定液体石油产品中硫化氢含量

通过酸化-吹气-吸收装置来提取液体石油产品中的硫化氢,在酸性条件下,硫化物与过量的碘作用,剩余的碘用硫代硫酸钠滴定,由硫代硫酸钠溶液所消耗的量,间接求出硫化氢的含量。经过一系列实验发现：该分析方法加标回收率在94．48％-97．36％,标准偏差0．0159,变异系数2．05％,分析结果表明数据的准确度和精密度较好,取得了满意的效果。     

Role of carboxyl groups in water absorption by keratin

The contribution of carboxyl groups to the water sorbing properties of keratin has been investigated over the complete water vapour pressure range. A series of partially methylated wools were studied: below 80% R.H. there is a reduction in water content linear with the reduction in the number of carboxyl groups, but at humidities above 80% R.H. extra water is absorbed because of disruption of the structural network under the acid conditions of treatment. Extrapolation of the plot of equilibrium water content vs. free carboxyl group content of partially methylated wool samples at a particular humidity. made at several humidity values, enables an isotherm to be deduced for wool containing no ? COO? groups. The reduction of water content for wool of zero carboxyl group content, as a function of relative humidity, represents the isotherm attributable to the free carboxyl groups in keratin; this is a simple Langmuir isotherm at low humidities. The reduction of water content is proportionately greater at lower humidities—at 5% R.H., 36% of the total water and at 65% R.H., 22% of the total water absorbed by keratin is associated with free carboxyl groups. The number of water molecules associated with each carboxyl group is greater than previous literature values.     

Determination of carboxyl groups in low-rank coals

The determination of carboxyl groups in low-rank coals by exchange with barium chloride-triethanolamine reagent is re-examined. The difference in carboxyl contents calculated from the barium content of the exchanged coal, and the amount of acid used to extract the barium, is discussed. Reliable carboxyl contents are obtained providing the latter procedure is used.     

Physical aging of thin 6FDA-based polyimide membranes containing carboxyl acid groups. Part II. Optical properties

The change in refractive index with time for thin films (∼350 nm) formed from glassy 6FDA-based polyimides was monitored by ellipsometry to quantitatively track the physical aging process. The refractive index increased linearly, attributed to the densification of the glassy polyimide, with respect to aging time, on a logarithmic scale; this result is consistent with the decrease in gas permeability during physical aging reported in part I of this series. An excellent correlation was formed between the volumetric aging rate r, computed from the refractive index change by the Lorentz-Lorenz equation, and the permeability reduction rate, ; this relationship depends on the type of gas but appears to be the same for all polymer structures examined. The change in fractional free volume was examined from the refractive index data using parameters determined by group contribution methods. The free volume versus aging time results are well-described by the self-retarding relaxation model of Struik; however, this model does not explain the strong effect of thickness on aging rate. The change in free volume correlates well with the change in gas permeability of these thin films.     

降低聚酯切片端羧基措施的探讨

分析原料性质及生产工艺条件对聚酯切片端羧基的影响,提高酯化段最终酯化率及EG物质的量比、提高缩聚系统真空度、适当降低缩聚反应温度,可以降低切片端羧基。     

碘量法测定二氧化氯要点分析

二氧化氯是一种安全高效的消毒剂。采用国家行业标准中有效二氧化氯含量的测定方法的测量结果差异较大，用碘量法测定稳定态二氧化氯溶液中的有效二氧化氯含量时，活化反应的速度对测定有效二氧化氯的含量有一定影响。通过条件实验确定了碘量法测定有效二氧化氯含量的最佳测试条件，即：活化时间13min，盐酸稀释至与水体积比1：4，参考电压140V，可确保实验结果的平行性和再现性。     

Distribution of carboxyl groups in carboxymethylated cotton fibers

Cotton cellulose was partially carboxymethylated by a one‐bath method using monochloroacetic acid and sodium hydroxide. A method was developed to study the extent of the carboxymethylation of cellulose within the cotton fibers using scanning electron microscopy (SEM) and energy‐dispersive X‐ray analysis (EDX). Uranyl nitrate was used as a stain. Scanning electron photomicrographs revealed that the carboxymethylation of cellulose occurred throughout the cotton fiber cross section. However, the X‐ray microanalysis data indicated a variation in the extent of the reaction among the morphological regions that have different chemical accessibility. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 72: 203–207, 1999     

Adhesive monomers to dental ceramics. II. Methacrylamide derivatives containing carboxyl and phenyl groups for effective adhesion of calcium metaphosphate ceramic

Twelve methacrylamide derivatives containing carboxyl and phenyl groups have been evaluated as adhesives for calcium metaphosphate ceramic, a promising but hard-to-adhere cast ceramic restoration material. Although methacrylamide monomers having a carboxyl group showed low adhesive tensile strength for the ceramic, contrary to the glycidyl methacrylate derivatives, the monomer having neighboring two carboxyl groups at the phenyl ring exhibited quite high adhesion. Moreover, the monomer proved to retain high adhesion strength for the surface-etched ceramic for a long period of time even in water and would thus be suitable for practical clinical applications. © 1994 John Wiley & Sons, Inc.     

Pyrolysis of brown coals. 1. Decomposition of acid groups in coals containing carboxyl groups in the acid and cation forms

The effect of low-temperature pyrolysis (up to 300 °C) on the acid groups of two low-rank coals (a brown coal from Victoria, Australia, and a lignite from Texas, U.S.A.) has been studied for samples in both the acid and cation forms. A preliminary study at temperatures above 300 °C was made on the brown coal. The carboxyl groups of coals in the acid form decompose to give one mole of carbon dioxide for each equivalent of carboxyl content. Cation-form coals yield more carbon dioxide on pyrolysis than can be accounted for by the carboxyl groups present. Water is evolved in proportion to the carbon dioxide evolved from both acid- and cation-form coals, but the ratios differ. Findings have been interpreted as indicating that some other oxygen-containing group is associated with the carboxyl group. In the case of the acid-form coal this group decomposes to give water. When the carboxyl group is in the cation form, decomposition of the associated groups gives carbon dioxide as well as water. Phenolic groups appear to be stable, at least to 300 °C.     

Conductimetric titration of polyelectrolytes having sulfate and carboxyl groups

Summary Conductimetric titration of polyelectrolyte solutions was carried out to determine the contents of sulfate and carboxyl groups. In the mixtures of poly(acrylic acid) and poly(vinyl sulfate), and of alginic acid and dextran sulfate, the contents of sulfate and carboxyl groups observed by the conductimetric titration were in agreement with those derived from the concentration of the original homopolymers. This method was applied to a viscous polysaccharide from red algae, funoran, which contains both the sulfate and carboxyl groups. These results suggested that this method is applicable to either the samples consisting of the mixture of homopolymers or those of copolymers containing both ionic species.     

电导滴定法测定桉木浆中酚羟基和羧基

两相含水有机介质中电导滴定法测定接木浆中酚羟基和羟基的方法是可行的。较好的滴定条件是：滴定介质为丙酮：吡啶：乙醇：水（40：10：1：1,体积比）;样品浓度为2g/L,滴定剂KOH-异丙醇浓度为0．01mol/L。     

Synthesis and characterization of fluorescent PEG-polyurethane with free carboxyl groups

An innovative spherical poly(vinyl alcohol)(PVA)/peat/clay porous composite bead was prepared and shown to be suitable for use as an adsorbent. The mass transport process for the adsorption of metal ions onto this composite bead in an aqueous system was investigated. In the external mass transport process, the diffusion coefficient (D₁) of Cu⁺² and Zn⁺² ions increased with increasing initial metal ion concentration and the increasing effect was more pronounced in the initial metal ion concentrations range of 18?×?10^-3 to 22?×?10^-3?M. The diffusion rate of Zn⁺² ions was faster than that of Cu⁺² ions. In the intraparticle diffusion process, the diffusion coefficient (D₂) decreased with increasing initial metal ion concentration in the initial concentration range of 1?×?10^-3 to 4?×?10^-3?M, and the value of D₂ maintained an almost constant value in the initial concentration range of 8?×?10^-3 to 22?×?10^-3?M. The rate of ion diffusion within the adsorbent for Cu⁺² ions was faster than that for Zn⁺² ions. The adsorption mechanism was controlled by the intraparticle diffusion process. The adsorption followed the Langmuir adsorption isotherm model. The maximum amount of adsorbed metal ions for Cu⁺² and Zn⁺² ions were 22.57 and 13.62?mg/g composite bead, respectively.     

光度法测定聚酯切片端羧基含量的方法条件优化

容量法测定有色聚酯的端羧基时存在滴定终点无法判断的困扰,本论文使用光度法从溶液搅拌速度、空白溶剂测定、混合溶剂选择、标准滴定液稳定性等方面对聚酯切片端羧基测试结果的准确性展开研究,并探讨了在有色聚酯端羧基测定中的应用。光度法测定结果的准确度较好,解决了容量法无法测定有色聚酯端羧基的困扰,也避免容量法因人为因素导致的分析误差。     

具有不同取代基数量铁酞菁衍生物改性双极膜的性能研究

分别用具有不同取代基数量铁酞菁衍生物加入羧甲基纤维素钠(CMC)阳离子交换膜中,制备改性的CMC/CS双极膜(BPM,CS∶壳聚糖)。结果表明,经铁酞菁改性后,阳膜的离子交换容量、亲水性和双极膜的机械性能均获得提高,双极膜的溶胀度下降。此外,改性后,铁酞菁衍生物可在双极膜中间界面层形成高荷电区,促进水解离,降低膜阻抗和槽电压。当电流密度为60 mA/cm2时,Fe2Pc2(COONa)12-CMC/CS BPM,FePc(COONa)8-C MC/CS BPM,FePc(COONa)4-CMC/CS BPM和CMC/CS BPM的膜电压分别为5.6,6.2,6.5,8.9 V。     

Selective alkylation of acidic hydroxyl groups in coal

The organic molecules which make up coal are held together not only by covalent bonds, but also by a substantial network of hydrogen bonds as well as certain other weak intermolecular associations, which together are called the secondary structure. It is believed that acidic hydroxyl groups are responsible for most of the secondary structure. These attractive forces have been diminished traditionally by solvent swelling the coal, then permanently removed by selective silylation or acetylation of the polar functionalities. A new selective alkylation procedure has been developed which converts polar hydroxyls into relatively non-polar ethers and esters, and has been successfully tested on a bituminous and sub-bituminous coal. This selective O-alkylation proceeds rapidly under very mild conditions and renders the coal essentially free from its secondary structure.     

Hydrogenation of 1,3-butadiene and isoprene prepolymers having carboxyl end groups

The hydrogenations of butadiene and isoprene prepolymers having carboxyl and cyano end groups were investigated by two methods: Heterogenous hydrogenations were carried out at 45°C and 50 psi of hydrogen pressure with palladium on carbonate as catalyst. The best degree of saturation and carboxyl retention were 95 and 79% for butadiene prepolymers and 84 and 95% for an isoprene prepolymers, respectively. Dimide reduction was made in xylene at 130–140°C and normal pressure with p-toluenesulfonylhydrazide (TSH) as the diimide source. A nearly 100% degree of saturation for butadiene prepolymers and 91% for isoprene prepolymers were achieved. The effects of reaction conditions on the degree of saturation and the carboxyl retention, calculation of molecular weight before and after hydrogenation based on H-NMR spectral data, and diimide reduction with TSH are discussed. © 1995 John Wiley & Sons, Inc.     

含羧基团聚丙烯酸硅氧烷的制备及性能

1 引言 为了防止各种基材表面受到损伤或污染,已开发了可剥离的保护膜产品(以下简称保护膜).但是,一般市售的可剥离保护膜都比较厚,而且其应用仅限于简单的二元平面,对于含有三元曲面的构件则难以使用.虽然丙烯酸系或松香树脂类胶膜能够用碱性化学试剂脱膜,但是丙烯酸类胶膜经户外曝露后,用碱性化学试剂很难使被保护表面恢复原状.