Kinetics of reactions of blocked isocyanates

Blocked isocyanates are widely used in many kinds of one-package coatings, powder coatings and adhesives. They have also been used in water-borne polyurethane. The kinetics and mechanism of the reactions of blocked isocyanates are reviewed and two urethane forming reaction mechanisms by which a blocked isocyanate can react with a nucleophile are provided. Furthermore, effects of isocyanate structure, reaction medium, catalyst and functionality on kinetics of blocked isocyanate are discussed in detail.

封闭异氰酸酯几种反应的动力学

封闭异氰酸酯广泛地应用于各种单组分涂料、粉末涂料和胶粘剂中。近年来 ,随着人们对水性聚氨酯的重视和开发 ,封闭异氰酸酯的重视和使用程度进一步加大。本文对封闭异氰酸酯的相关反应的动力学进行了综述 ,对两种不同的反应机理及其动力学的影响因素作了介绍

Determination of ultra-trace rare-earth elements in human plasma by inductively coupled plasma mass spectrometry

Inductively coupled plasma mass spectrometry (ICP-MS),a highly sensitive inorgnic analytic technique,fits to determine ultra-nace rare-earth elements in human plasma. Under the optimized conditions detection limits for 15 rare-earth elements are in the range of 0.7 (for Eu)-5.4 (for Gd) ng.L-1. Indium as an internal standard element is used to compensate for matrix suppression effect and sensitivity drift. Three kinds of preparation methods, diluted with 1% HNO3, digested with HNO3-H2O2 and with HNO3-HClO4, are checked and compared,and the former is the simplest way to be measured. The samples diluted with 1% HNO3, stored in 4 degrees C, are very steady for 16 days. With the method, 11 healthy plasma samples in Changchun area of China are analysed.

人体血浆中15种超痕量稀土元素的电感耦合等离子体质谱法测定

本文用电感耦合等离子体质谱法测定了人体血浆中的稀土元素。在优化的条件下 ,以内标法测得的各种纯水溶液的检测限在 0 .7(Eu)～ 5 .4(Gd) ng·L- 1范围内。研究了 K,Na,Ca,Fe等基体元素对稀土测定的影响。以 In为内标元素补偿样品基体效应以及灵敏度飘移。比较了直接稀释、HNO3- H2 O2 消解及 HNO3-HCl O4消解 3种样品处理方法 ,用 1% HNO3直接稀释样品可满足轻稀土元素的定量分析要求 ,方法的定量测定下限≤ 1μg·L- 1。

Fabrication and characterization of heteropolyanion Langmuir-Blodgett films

The possibility of the formation of Langmuir-Blodgett (LB) films with dimethyldioctadecylammonium (DODA) after the addition of cobalt(II)-substituted Dawson-type tungstodiphosphate anion (briefed as (H2O)(CoP2W17O618-)-P-11) in the subphase has been explored. Marked modifications of the compression isotherms are observed when this anion is dissolved in the subphase, which demonstrates that the polyanions interact with the monolayers. LB films have been readily obtained from this system. The adsorption Fourier transform IR (FT IR) spectroscopy, atomic force microscopy (AFM), X-ray diffraction (XRD) and cyclic voltammetry (CV) have been used to investigate the morphological and molecular structure of the deposited film. The FT IR results showed the presence of the polyanion within the LB films, and the shift for its characteristic bands may be related to the presence of positively charged DODA. AFM measurement reveals that the LB films of DODA/(H2O)(CoP2W17O618)-P-II are regularly and uniformly deposited on the substrate. XRD experiments prove that the lamellar structure of the LB films of DODA/(H2O)(CoP2W17O618-)-P-II is well-defined. The LB films of DODA/(H2O)(CoP2W17O618-)-P-II immobilized onto an indium-oxide (ITO) glass, in aqueous solutions of pH 2.0-5.0, show quite facile redox reactions even for multilayers. All the experiments carried out in the present study suggest that the new materials of heteropolyanions can be formed by LB techniques and beneficial physicochemical properties of heteropolyanions can be maintained/enhanced through molecular-level design. (C) 1999 Elsevier Science S.A. All rights reserved.

SYNTHESIS AND CHARACTERIZATION OF TRISUBSTITUTED HETEROPOLYTUNGSTOGERMANATES CONTAINING GROUP 3A ELEMENTS

Six new compounds, alpha,beta-KaHb[GeW(9)M(3)(H2O)(3)O-37]. xH(2)O(M = Al, Ga, In; a + b = 7) and alpha-K9H5[Ge2W18Ga6(H2O)(3)O-74]. 20H(2)O, were synthesized from the lacunary precursors a and beta-GeW9O3410- and characterized by elemental analysis, spectroscopy and electrochemistry. Tungsten-183 NMR spectra of the title complexes consist of two lines with intensity ratio 2:1 as expected for trisubstituted heteropoly anions. The intensity ratio of alpha-Ga compound is 1:2, which is different from others(a:1). With the help of FAB mass spectrum, we concluded that it is a dimer with D-3h structure in aqueous, and the others exist by monomers with C-3v structures.

Synthesis and properties of thermotropic liquid crystalline copolyesters containing bis(4-hydroxyphenyl)methanone(IV)

A series of thermotropic liquid crystalline copolyesters were synthesized by thermal polycondensation of p-hydroxybenzoic acid, terephthalic acid, bis (4-hydroxyphenyl) methanone and diols. The resulting copolyesters were characterized by WAXD,DSC and PLM. All the copolyesters formed a nematic phase.

冠醚的空腔及其与希土硝酸盐配合物结构的关系

本文计算了五十多种希土硝酸盐冠醚配合物中冠醚的空腔直径Ｄｃ及希土离子直径（Ｄｉ）与Ｄｃ之比值（Ｄｉ／Ｄｃ）．冠醚的空腔受许多因素影响．诸如希土元素的离子半径，希土离子与冠醚之间的结合力，冠醚环上的取代基等．Ｄｉ／Ｄｃ数值所处的范围与所形成的配合物结构类型密切相关，遵循下列四个近似规则：（１）如Ｄｉ／Ｄｃ＞１．４，所形成的配合物结构中三个阴离子占据冠醚的同一侧（结构类型Ⅰ）；（２）若０．８＜Ｄｉ／Ｄｃ＜０．９，配合物中金属离子被包围在冠醚空腔中．三个阴离子占据冠醚环的两侧（结构类型Ⅱ）；（３）如Ｄｉ／Ｄｃ＜１．４，配合物一般为结构类型Ⅲ，在某些情况下也可为结构类型Ⅳ，它由几个配位阴离子及一个多硝酸根配阴离子形成．

AN INFRARED SPECTROSCOPIC STUDY ON THE STRUCTURAL PHASE-TRANSITIONS OF LAURYLAMMONIUM CHLORIDE

Infrared spectroscopy was used to study the structural phase, transitions of laurylammonium chloride in the temperature range from 290 to 365K. It was shown that there is a solid-solid phase transition at 339 K with a pre-transition at 327 K. The infrared spectra indicated that virgin crystals at room temperature form a well-ordered phase with all-trans hydrocarbon chains, and the lengths of N-H...Cl hydrogen bonds are different. The spectra suggested that the gauche conformers begin to appear at temperature above 327 K. The spectra at high temperature over 339 K demonstrated that the interaction between the chains decreases, the partial ''melting'' of the chains is obvious, and the hydrogen bonds (N-H...Cl) have the same lengths. The main transition and pre-transition are mainly assigned to the intramolecular and intermolecular order-disorder changes, respectively.

AN INFRARED SPECTROSCOPIC CHARACTERIZATION OF THE SOLID SOLID BEHAVIOR OF DODECYLAMMONIUM CHLORIDE

The infrared spectra of the bilayer system dodecylammonium chloride has been studied as a function of temperature. Unusual splitting of some vibrational modes helps us to characterize the structure of different solid states. This study provided the evidence for the occurrence of an order-disorder phase transition whose onset occurs at 327 K and its completion ends at 339 K. In the low temperature phase below 327 K, the virgin crystals form a well-ordered phase with all-transhydrocarbon chains. In the intermediate state between 327 and 339 K, the data demonstrate the introduction of intramolecular as well as intermolecular disorder. The coexistence of solid and liquid-crystal-like states is shown by the persistence of factor group splittings together with the existence of defect bands in the wide intermediate temperature range. In the high temperature phase over 339 K the crystals convert to a liquid-crystal-like system with extensive motional and conformational disorder, but still show characteristics in their infrared spectra which indicate the presence of ordered segments in the hexagonal solid phase.

MOSSBAUER-EFFECT STUDIES OF THE DIMER OF A BIMETALLIC EU-AL COMPLEX

Mossbauer spectra of the dimer of a bimetallic Eu-Al complex, [(CF3COO)3EuHAl(C2H5)2 . 2 THF]2 are measured at different temperatures (81 to 166 K) and some Mossbauer parameters, such as isomer shift, electric quadrupole splitting and asymmetric parameter, are derived from the experimental spectra. The Debye temperature of the compound determined by a Debye model is 128 K. The results indicate that europium in the organo-europium compound is trivalent and that a bridging hydrogen atom between two europium atoms exists in the dimer. The low Debye temperature implies that the weaker binding force between the europium atom and the lattice may be related to the structure and the chemical bonding in the organometallic compound of europium.

THE COMPOSITIONS AND STRUCTURES OF SOME COMPOUNDS IN THE SYSTEM CA-SR-CU-O

The system of Ca-Sr-Cu-O have been investigated. Two new compounds with compositions Sr3Cu5O8+alpha and CaSrCu3O5+alpha have been discovered. Both are orthorhombic with a = 6.489, b = 11.280, c = 12.240 angstrom for CaSrCu3O5+alpha and a = 3.950, b = 11.479, c = 13.420 angstrom for Sr3Cu5O8+alpha. The X-ray powder data for CaSrCu3O5+alpha, Sr3Cu5O8+alpha, Sr2CuO3 and SrCuO2 are presented. The oxidation state of Cu ion and oxygen contents are analyzed by iodometric titration. Sr0.5Ca0.5CuO2 that has a similar structure with SrCuO2 has been found and its X-ray data are presented also.

固体ASm_2I_5的d-f跃迁荧光和反射光谱(A=K,Rb,Cs,T1)

本文系统地研究了化合物ASm_2I_5(A=K,Rb,Cs,T1)固体粉末的荧光光谱和反射光谱.讨论了Sm~(2+)在立方晶体场中的分裂能随着碱金属离子半径的增大而减小和f-d激发能随着A-I(A=Rb,T1)键的共价性增加而明显降低的现象.并从晶场效应和化学键性质两个方面解释了ASm_2I_5(A=K,Rb,Cs)和ASm_2I_5(A=Rb,T1)中的Sm~(2+)荧光光谱分别发生蓝移和红移的现象.

Ca-Sr-Cu-O系中若干化合物的组成和结构的研究

研究了Ca-Sr-Cu-O三元金属复合氧化物体系,发现了两个新化合物Sr_3Cu_5O_(8+x)和CaSrCu_3·O_(5+x),两者都属正交晶系,前者a=3.950,b=11479,c=13.420 A.后者a=6.489,b=11.280,c=12.240A.文中给出了这两个化合物和SrCuO_2、Sr_2CuO_3的XRD谱.用碘量法测定了化合物中的氧含量.此外还发现了结构与SrCuO_2相似的固溶体Sr_(0.5)Ca_(0.5)CuO_2,也测定了它的XRD谱.

高1,2-聚丁二烯及通用橡胶的流变性质

采用多速粘度计和Monsanto试验机联用,在表观剪切速率为3×10~(-8)—2.5×10~8s~(-1)时观察了高1,2-聚丁二烯(PB)生胶与顺式1,4-PB,EPDM,SBR 1500在流变性质上的差异。高1,2-PB虽在中等剪切速率下有较高的粘度,但在低、高剪切速率时的粘度均较低,这一特性有利于它的加工。高1,2-PB在低剪切速率下的流动活化能较其他橡胶高,故抗冷流性能优越,易于存放。