Chain extenders for polyesters. I. Addition-type chain extenders reactive with carboxyl end groups of polyesters

Effective chain extenders for linear polyesters were investigated among some bis-heterocycles, which were capable of coupling carboxyl terminals of the polyesters through addition reaction. Consequently, 2,2′-bis(2-oxazoline), 2,2′-bis(5,6-dihydro-4H-1,3-oxazine) and N,N′-hexamethylenebis(carbamoyl-2- oxazoline) were found to be the most effective chain extenders. Starting from a poly(ethylene terephthalate) (PET) having intrinsic viscosity ([η]) of 0.66 and carboxyl content (CV) of 46 eq/10⁶ g, one could obtain polyesters with [η] of above 1.0 and CV of below 5 eq/10⁶ g in the presence of the chain extenders. Typical reaction condition for the coupling of PET was heating PET under atmospheric nitrogen above its melting temperature with 0.5 mol % of a chain extenders only for several minutes. Bis-2-thiazolines showed no effect under the condition investigated, while in case of bis-2-imidazolines definite degradation was observed. Bis-N-acylaziridines and bisiminocarbonates resulted in some gell formation, indicative of side reactions.     

Quantitative methyl esterification of carboxyl end groups of polyethylene terephthalate

Summary For esterification of its carboxyl end groups in heterogeneous phase, polyethylene terephthalate was treated with boron trifluoride/methanol and with diazomethane in chlorobenzene, respectively. Whereas treatment with boron trifluoride/ methanol in some cases was accompanied by polymer degradation, reacting the polyester with diazomethane resulted in complete methyl esterification without any detectable side reaction.33. Communication in the series Synthetic fibers in the Wool Industry; 32. Communication see V. Rossbach, F. P.Schmitz u. J. Föhles, Angew. Makromol. Chem., submitted for publication     

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.     

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。     

Crystallization behavior and morphology of polylactide and PLA/clay nanocomposites in the presence of chain extenders

The effect of clay and chain extender on the nonisothermal, isothermal crystallization kinetics, and morphology of polylactide (PLA) was investigated in this study. PLA and PLA‐based nanocomposites containing 2 wt% organoclay were prepared via melt compounding. Three commercially available chain extenders were used: polycarbodiimide (PCDI), tris(nonylphenyl) phosphite (TNPP), and Joncryl ADR4368F. The nanoclay particles were found to act as nucleating agents. Chain extender incorporation, however, had diverse effects on both crystallization rate and degree of crystallinity. Nonisothermal DSC results revealed that the addition of PCDI increased the cold‐crystallization temperature (T_c) from 106 to 114°C, reduced the degree of crystallinity from 6.3 to 5.3%, and resulted in the formation of bimodal melting peaks in PLA. On the other hand, the reduction of chain ends in the presence of TNPP resulted in a significant increase of the crystallization rate and degree of crystallinity from 6.3 to 15.2%. In the case of Joncryl, its incorporation led to the formation of a long‐chain branching structure, which disrupted the chain packing. Therefore, the degree of crystallinity (from 6.3 to 1.6%) and the rate of crystallization decreased, while T_c was increased from 106 to 122°C in the presence of Joncryl. POLYM. ENG. SCI., 2013. © Society of Plastics Engineers     

Effect of chemical modification of carboxyl groups in apple residues on metal ion binding

AR (apple residue) was used as an alternative and cheap material for binding metal ions due to the presence of carboxyl and phenolic functional groups. The binding capacity of copper, lead, and cadmium by AR was pH dependent. Carboxyl groups of AR were esterified by acidic methanol to determine the contribution of carboxyl groups to metal ions binding. The extent of esterification was determined by analyzing the amount of methanol released in the sample hydrolysates by gas chromatography. The effect of esterification on binding metal ions was investigated in batch experiments by unmodified and modified AR. All esterified AR showed significant decreases in binding copper, lead and cadmium. The loss in the capacity of metal ion binding was proportional to the extent of esterification. The capacity of metal binding decreased with increase in the concentration of methanol in the respective hydrolysates or the modified AR. The data indicate that carboxyl groups on AR play an important role in the metal ion binding.     

Study of the inhibition of certain trophic levels by the presence of metal cations in water

Bioassays and biological tools have been developed for the evaluation of the toxicity of water. A protocol of short-term tests allowed the examination of the influence of temperature, salinity, hardness and effect of complexation on the toxicity of Cd²⁺, Cu²⁺, Ni²⁺ and Zn²⁺ by means of a test daphnia (Daphnia magna). The development of an experimental installation functioning continuously, where the trophic level is represented by the daphnia, led to the development of a system of bio-indication. The survival of the daphnia is examined under conditions of disturbances produced by Cd²⁺, Cu²⁺, Ni²⁺ and Zn²⁺. The application of the chronic test (21 d) allowed the folow-up of the inhibition of the survival and the reproduction of D. magna by Cd²⁺, Cu²⁺ and Ni²⁺. A methodology with the help of the phototactic effect of D. magna was proposed. This one aims at developing a phototactic biosensor subjected to the toxicity of cadmium. Bioassays, using the purifying activity of the activated sludge, were considered and enabled understanding of the phenomena of inhibition and adaptation of these muds in the presence of trivalent chromium. In addition, two watery freshwater plants, Lemna minor and Salvinia natans, were exposed to Cd²⁺, Cu²⁺ and Zn²⁺ in order to test their sensitivity. We consequently carried out a histological study on leaves of S. natans contaminated by metal toxicity independently of the test.     

光度法测定PET切片端羧基含量的方法及其研究

论述采用光度法测定聚酯切片的端羧基 ,对称样量、滴定剂的浓度、溶剂的空白等测试条件和参数进行优化选择     

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.     

增容剂存在下高乙烯基聚丁二烯增韧聚乳酸（英文）

通过在钼系催化制备L-丙交酯聚合体系中加入环氧化高乙烯基聚丁二烯橡胶(HVBR)(EHVBR)原位制备环氧化高乙烯基聚丁二烯接枝聚乳酸(PLLA-g-EHVBR),并作为增容剂改善非极性橡胶HVBR与聚乳酸(PLA)的相容性。结果表明,相比于PLA/HVBR,环氧度为30%的PLLA-g-EHVBR能显著提高PLA/HVBR的扯断伸长率,且对拉伸强度影响较小。扫描电子显微镜结果表明,PLLA-g-EHVBR有助于PLA与HVBR相容性的提高。     

聚丁二酸丁二醇酯切片端羧基滴定方法优化

采用化学试剂滴定的方法测定聚丁二酸丁二醇酯切片的端羧基值,对溶剂的配比、滴定溶剂选择、指示剂的选择等影响因素进行条件试验。研究发现,用氯仿作为溶剂,以0.05 mol/L的NaOH-乙醇溶液作为滴定剂,以百里香酚蓝作指示剂,滴定终点颜色由黄色变为蓝色,颜色变化明显,平行性和准确性都很好。     

Oxygen-permselectivity in new type polyorganosiloxanes with carboxyl group on the side chain

Summary Oxygen-permselectivity through polyorganosiloxanes with carboxyl group on the side chain is discussed in terms of the differences between the O₂, N₂ diffusion coefficients or their solubility coefficients. The oxygen-selectivity increases from 2 to 5 with the increase in the carboxyl component of the side chain. Especially the selectivity in the diffusion coefficient is found to more contribute to the oxygenpermselectivity in comparison with that of the solubility coefficient. But the permeation coefficient decreases with the permselectivity.This work was partially supported by a Grand-in-Aid from the Ministry of Education, Science and Culture, Japan.     

Synthesis and properties of new crosslinkable telechelics with benzoxazine moiety at the chain end

New crosslinkable telechelics containing benzoxazine moiety at the chain end have been synthesized using oligomeric bisphenols with aromatic ether structure. The chain length of the oligomer is estimated from the size exclusion chromatography and proton nuclear magnetic resonance spectroscopy (¹H NMR). The degree of end-capping by benzoxazine moieties, that is estimated from ¹H NMR spectrum, increases during 24 h of the reaction. The telechelic is used to cast polybenzoxazine films with excellent thermal stability. Mechanical and chemical properties of these films are studied as a function of the degree of end-capping.     

PBT端羧基含量测定方法的优化

采用全自动电位滴定仪测定PBT切片的端羧基含量,对称样量、溶剂的配比、滴定剂的浓度等进行了正交优化。得到最佳条件为称样量2g,溶剂配比1:1,氢氧化钾-乙醇溶液浓度0.05mol/L,经验证实验,平行性和准确性都很好,相对偏差为1％,符合GB/T 14190—1993相对偏差应小于5％的要求。     

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     

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PET中端羧基的不确定度评定

通过光度滴定法测定PET中端羧基含量的分析,找出影响不确定度的因素,对各因素的不确定度进行评估,从而得出端羧基测定主要受到测定使用的标准滴定溶液的浓度和方法的重复性等方面的不确定度因素影响。     

Role of polymer chain end groups in plasma modification for surface metallization of polymeric materials

How to improve adhesion between poly(oxybenzoate‐co‐oxynaphthoate) (Vecstar OC and FA films) and copper metal by Ar, O₂, N₂ and NH₃ plasma modification was investigated. The mechanism of adhesion improvement is discussed from the viewpoint of chemical and physical interactions at the interface between the Vecstar film and copper metal layer. The adhesion between Vecstar OC film and copper metal was improved by chemical rather than physical interactions. Polymer chain end groups that occur at Vecstar OC film surfaces contribute effectively to adhesion. This improvement in adhesion is due to interactions between copper metal and O?C groups formed by plasma modification. Aggregation of the O?C groups to the copper metal/Vecstar OC film interface is a key factor for good adhesion. From this aspect, heat treatment of plasma‐modified Vecstar OC films on glass plates is effective in the aggregation, and the peel strength for the copper metal/Vecstar OC film system reached 1.21 N (5 mm)^?1. Copyright © 2009 Society of Chemical Industry     

氧化降解法制备羧基封端的液体氟橡胶

以偏氟乙烯-六氟丙烯共聚物(VDF-HFP)为原料,采用氧化降解法合成了羧基封端的液体氟橡胶,通过傅里叶变换红外光谱法、凝胶渗透色谱法、乌氏黏度计和电位滴定仪表征了产物.结果表明,产物在1 766 em-1处出现羧基基团的特征峰,其重均分子量比VDF-HFP有较大程度的降低,这与特性黏数的结果一致;产物的羧基质量分数为...