水性聚酰亚胺的研究进展与应用

阐述了水性聚酰亚胺(PI)的国内外研究现状,着重分析了其合成原理和合成路线,介绍了水性PI在粘合剂、光刻胶、涂料、漆包线漆等方面的应用。     

Iron(III)‐Catalyzed Halogenations by Substitution of Sulfonate Esters

A novel halogenation reaction from sulfonates catalyzed by iron(III) is described. The reaction can be performed as a stoichiometric or a catalytic version. This reaction provides a convenient strategy for the efficient access to structurally diverse secondary chlorides, bromides and iodides. The stereochemical course of the reaction is governed by the substrate and the experimental conditions. Secondary alcohols modified as quisylates or pysylates are substantially more reactive. Aliphatic quisylates proceed with overall inversion of configuration under catalytic conditions. Chemoselectivity in bismesylates was observed in favour of the secondary mesylate. Additionally, based on the experimental results, a possible catalytic cycle for the halogenation has been proposed.     

兴仁换流站交流滤波器组开断方案

以贵广Ⅱ回直流模型为基础,应用PSCAD／EMTDC仿真分析了滤波器小组断路器在不同的分断方式、不同的分闸时间下断口间过电压及容性电流的大小。结果显示,滤波器分闸时在断口之间的最大暂态过电压与电流基本呈一个反比关系;最佳分断角度为在电压角度为1000～1100或者280°～290°。     

Dependency of Doppler Factors on Resonance Self-Shielding Factors for Gold and Silver

A simple model was developed to evaluate the effect of the radial power profile on the thermo-hydraulics in the core during reflood phase of loss-of-coolant accident in PWRs. It was incorporated into REFLA code, a reflood analysis code.

The model assumes that the fluid mixes completely among subchannels and additionally that the fuel temperature is not affected each other among fuels. This model is featuring no three-dimensional treatment for the evaluation on effect of the radial power profile.

The model improved the predictability of clad temperature and gave a better prediction than a method which is generally used in the safety analysis. The model predicted a poorer core cooling in high radial power region than data. The error of the prediction increased with the increase in radial power ratio. These indicates the conservativeness of the model on the maximum clad temperature prediction. The reason of the conservativeness is due to the neglection of the heat transfer enhancement by two-dimensional effect in high power region.     

OH and COOH functionalized single walled carbon nanotubes-reinforced alumina ceramic nanocomposites

Alumina ceramics reinforced with 1 wt.% single-walled carbon nanotube (SWCNT) were fabricated via spark plasma sintering (SPS) of composite powders containing carboxyl (COOH) or hydroxyl (OH) group functionalized single-walled carbon nanotubes. The samples were SPS’ed at 1600 °C under 50 MPa pressure for holding time of 5 min and at a heating rate of 4 °C/s. The effects of CNT addition having different surface functional groups on microstructure, conductivity, density and hardness were reported. It was shown that nanotube addition decreased the grain sizeof alumina from 3.17 μm to 2.11 μm for COOH-SWCNT reinforcement and to 2.28 μm for COOH-SWCNT reinforcement. The hardness values of the composites are similar for all samples but there is 4.5 and 7.5 times increase in electrical conductivity with respect to monolithic alumina for COOH-SWCNT and OH-SWCNT, respectively. It was also shown by TEM and FEG SEM observations that transgranular fracture behaviour of alumina was changed to mostly intergranular fracture mode by the addition of both types of CNTs which may be due to location of CNTs along the grain boundaries. A significant grain size reduction in alumina is considered toresult fromthe suppressing effect of CNTs during sintering.     

双螺杆挤出机湿热法处理聚全氟乙丙烯不稳定端基

介绍了聚全氟乙丙烯（FEP）树脂不稳定端基的产生机理,一般处理方法及其优缺点。采用双螺杆挤出机湿热处理FEP粉料,分析了FEP树脂挤出造料前后端基数量。结果表明,—COOH数量减少最显著,平均减少55%;—CF=CF₂基团平均减少9%,—COF基团基本不变。将脱羧与挤出造粒工艺作为一个操作单元,操作工艺简单、安全环保,设备投资少。     

基于灰色动态模型群的济宁市需水量预测

针对以往单一GM(1,1)模型建立过程中难以克服不稳定因素对预测结果的影响,提出根据不同时间段建立多个GM(1,1)模型,基于济宁市2001~2011年用水量数据,采用灰色动态模型群对济宁市2011~2020年需水量进行预测。结果表明,济宁市2011年用水量为26.76×108 m3,到2015年需水量增至29.9×108 m3,2020年增至33.9×108 m3,呈增长趋势,这与济宁市社会经济发展态势相吻合,可见灰色动态模型群用于需水量预测可行、有效。     

Amphoteric ion exchange membrane synthesized by direct polymerization for vanadium redox flow battery application

Novel sulfonated poly (fluorenyl ether ketone) with pendant quaternary ammonium groups (SPFEKA) was successfully synthesized by one-pot copolymerization of bis(4-fluoro-3-sulfophenyl)sulfone disodium salt, 4,4′-difluorobenzophenone, bisphenol fluorene and 2,2′-dimethylaminemethylene-9,9′-bis(4-hydroxyphenyl) fluorene (DABPF). The chemical structures were confirmed by FT-IR, and ¹H NMR. The thermal properties were fully investigated by TGA. The synthesized copolymers SPFEKAs are soluble in aprotic solvents, and can be cast into membranes on a glass plate from their N,N′-dimethylacetamide (DMAc) solution. A new kind of amphoteric ion exchange membrane (AIEM) was obtained by immersed SPFEKA into 1 M sulfuric acid. The proton conductivities of these membranes are comparable to the most reported sulfonated polymers under the same conditions. The permeability of vanadium ions in vanadium redox flow battery (VRB) was effectively suppressed by introducing quaternary ammonium groups for Donnan exclusion effect. AIEM-20% possess a only 4.4% vanadium ion permeability of Nafion 115. Cell performance tests showed that the VRB assembled with AIEM-20% shows the highest coulombic efficiency (CE) at the current density of 50 mA/cm², because of its lowest VO²⁺ permeability. In conclusion, these ionomers could be promising candidates for ion-exchange membranes for VRB applications.     

Surface modification of ethylene copolymers molded against different mold surfaces. Part 2. Changes at the outermost surface

The influence of the mold surface on the surface composition of thermoplastics has been investigated. Two different random copolymers, poly(ethylene-co-acrylic acid) (EAA) and poly(ethylene-co-vinyl acetate) (EVA), with varying comonomer contents were used. Specimens were prepared in molds coated with films of perfluorinated ethylene-propylene copolymer (FEP) and of poly(ethylene terephthalate) (PET). Samples were also molded against air and vacuum. Changes in the concentration and arrangement of the functional groups at the outermost surface were studied using X-ray photoelectron spectroscopy (XPS or ESCA), Fourier transform infra-red techniques (FTIR), and contact angle measurements. The concentration of functional groups at the outermost copolymer surface depended on the nature of the surface against which the random copolymers were molded. Results are interpreted in terms of differences in surface energy between the mold surface and the copolymer. The polar acrylic acid groups in EAA increased when molded against the polar PET mold surface and decreased when molded against nonpolar mold surfaces. Air exposure affected the EAA copolymer surface so that the nonpolar parts migrated to the outermost polymer surface, which resulted in a decreased content of acrylic acid groups. Acetate groups in EVA were found to be in excess at the surface when molded against both polar PET and nonpolar FEP. The signal of O 1s in the XPS spectra depended on the mold surface and the time in the XPS vacuum environment. This can be explained in terms of preferential arrangement of the acrylic acid and the vinyl acetate groups.     

Comparison of Sample Preparation Methods for NIR Analysis of Carbohydrate Content of Unbleached Eucalyptus Pulps

Abstract

The formation of hexenuronic acid groups during kraft pulping via demethylation of the 4‐O‐methylglucuronic acid groups attached to the wood xylan backbone was discovered a long time ago. In recent years, the formation of hexenuronic acid groups has attracted new interest and it has been stated that they represent the majority of the uronic acid groups in kraft pulps. However, the values reported in the literature are scattered. Furthermore, the data reported recently are partly in conflict with the earlier observations, which are based on analytical methods of a different type. It is obvious that more reliable and quantitative methods are needed for the determination of hexenuronic acids in pulps in order to assess their influence on factors associated with the bleaching process and pulp quality.