Environmental aging of the Ti-6Al-4V/FM-5 polyimide. adhesive bonded system: implications of physical and chemical aging on durability

Ti-6A1-4V/FM-5 polyimide adhesively bonded double cantilever beam (DCB) specimens were aged for 12 months at elevated temperatures (177°C and 204°C) in one of three different environments: ambient atmospheric air pressure and reduced air pressures of 2 psi (13.8 kPa) and 0.2 psi (1.38 kPa), to assess bond durability. The FM-5 polyimide adhesive (Tg~ 250°C) is based on a polyimide developed by NASA Langley Research Center and is produced by Cytec Industries, Inc. Bonds aged for different times were tested to measure the critical strain energy release rate as a function of the temperature and environment. The greatest loss in bond strength occurred after aging in air at 204°C. Following thermal rejuvenation of the aged bonds at 300°C for 2 h, part of the strength loss could be recovered. This strength recovery was attributed to the reversal of physical aging in the adhesive resin. Further evidence for physical aging, which is a thermo-reversible phenomenon, was obtained from tests conducted on neat resin specimens using DMA (dynamic mechanical analysis) and DSC (differential scanning calorimetry). The unrecovered portion of the loss in bond strength following longer-term aging was attributed to chemical aging/degradation of the bonded 'system'. The 'system' in this study includes the adherends, the adhesive, the surface pretreatment (chromic acid anodization, CAA), and their respective interphase/interface regions. Evidence for chemical aging was also seen from weight loss, and Soxhlet extraction data on neat resin specimens.     

Mechanics of the indentation test and its use to assess the adhesion of polymeric coatings

The indentation test provides a simple means by which the adhesion of coatings can be qualitatively assessed. On the way to establishing a quantitative measurement of the adhesion strength of coatings and films, it is important that the mechanics of this test are clearly understood. To investigate the influence of factors such as the coating thickness, the indenter radius, and friction during the test, numerical simulations of the indentation of a typical polymeric coating, polymethylmethacrylate (PMMA), bonded to a rigid substrate were conducted by using the finite element method. The stress generated during the indentation test were obtained by employing an accurate constitutive model of the elastic-viscoplastic behaviour of the polymeric coating under consideration. The results of this analysis illustrate the effects of the factors mentioned above on the deformation of the coating during indentation, its confinement, and interfacial shear, and the normal, shear, and hoop stress distributions occurring during indentation. These results provide insight into the possible failure mechanisms operative during the indentation of thin coatings and the important effects of the coating thickness during such tests.     

加成型有机硅反应过程的实时监测

用实时傅里叶变换红外光谱仪（FTIR）对乙烯基硅橡胶和含氢硅油的加成聚合过程进行了表征，得到了基团浓度消耗比反应时间变化的曲线，结果表明，在反应过程中，硅氢基与乙烯基的浓度减少呈非线性关系，这可能是硅氢基在反应过程中与空气中的物质进行了反应，从而在消耗量上较乙烯基多的缘故。     

Oxidation of benzothiazole, 2‐mercaptobenzothiazole and 2‐hydroxybenzothiazole in aqueous solution by means of H2O2/UV or photoassisted Fenton systems

Oxidative treatments of benzothiazole and benzothiazole derivatives (2‐mercaptobenzothiazole, 2‐hydroxybenzothiazole) in aqueous solution have been studied by using H₂O₂/UV and iron(III) photoassisted Fenton techniques. Experimental runs have been carried out in the pH range 3.0 –8.0 by means of annular reactors and proper UV lamps. The effect of pH, the initial concentration of hydrogen peroxide, the substrate, and the iron(III) concentrations have been investigated. A suitable model has been developed and used for the best estimation of kinetic constants for HO radical attack on the target molecules with the H₂O₂/UV system. The values obtained with this model are consistent with those reported in the literature for other heterocyclic compounds. © 2001 Society of Chemical Industry     

H_2S焚烧炉酸性气、空气配比燃烧的自动控制

分析了酸性气制酸工艺硫化氢与空气配比燃烧必须解决的问题 ,比较了不同的控制方案对工艺所造成的影响 ,提出了采用先进控制解决问题的具体方案 ,并给出了该系统中燃烧空气的具体计算方法     

The stability of monochlorotriazinyl reactive dyes on cellulose films in aqueous alkaline solutions containing peroxide bleaching agents

The stability of seven reactive (one difluoromonochloropyrimidinyl and six monochlorotriazinyl) dyes on cellulose immersed in sodium peroxoborate (PB) solution (UK–TO solution) containing tetraacetylethylenediamine (TAED) was examined using cellulosic films at 60 °C. The extent of dye loss that occurred from the dyed cellulosic films which were immersed in the UK–TO solution without detergent correlated closely to the ratings obtained using the BS 1006 UK–TO wash test. The dye loss that occurred from the dyed cellophane films was attributed to three contributions, namely, alkaline hydrolysis of dye–fibre bonds, oxidative fading of the dye chromophore by peroxides and cellulose degradation accelerated by PB and TAED. The alkaline hydrolysis of the dye–fibre bond and the extent of cellulose degradation in the UK–TO solution were the main contributions to the dye loss; dye oxidation was a minor factor in the dye loss mechanism. The physical bonding of the dye molecules reinforced the covalent dye–fibre bond stability towards the UK–TO solution.     

Antioxidant effects of reduced water produced by electrolysis of sodium chloride solutions

Antioxidant vitamins and enzymes such as superoxide dismutase, catalase and glutathione peroxidase are considered to function as scavengers against reactive oxygen species and to provide protection against reactive oxygen species, including free radicals. Although antioxidants such as L-ascorbic acid, d-catechin and quercetin dehydrate show superoxide dismutation activity, using reduced water produced in the cathode side by electrolysis as a solvent instead of 2 mM NaC1 solution of the same pH level as the reduced water increased the superoxide dismutation activity of these antioxidants. Moreover, neither the reduced water nor its electrolyte solution showed any superoxide dismutation activity by itself. On the other hand, the reduced water was able to decrease hydrogen peroxide levels. It has been found that the behaviour of H₂ in reduced water, which was activated by a platinum electrode, differed from that of H₂ introduced by bubbling of hydrogen gas. The former decreased H₂O₂, whereas the latter did not. These results suggest strongly that the increase in superoxide dismutation activity, with a proton donor such as L-ascorbic acid, is due to an increase in the dissociation activity of water while the scavenging activity for H₂O₂ is due to activated dissolved H₂ in the reduced water.     

聚醚／氨基硅油的制备及其应用

以含氢硅油，烯基环氧化合物和烯基聚醚为原料，在铂催化剂存在下，通过硅氢加成反应，制成了聚醚／环氧硅油，所得产物再与有机胺反应，制得了聚醚／氨基硅油。研究了含氢硅油粘度，聚醚／氨基硅油的氨基结构，硅质量分数,pH值以及残留Si－H基对聚醚／氨基硅油性能的 影响，结果表明，与聚醚／环氧硅油柔软剂CGF相比，硅质量分数为25．95％，粘度大于10000mPa.s的哌嗪基聚醚硅油能赋予织物更好的柔软，平滑手感及白度，织物静态吸湿性为1″81。     

Synergistic effect between Laves phase and Zr Ni phases in Zr(MnVNi)_2 hydrogen storage alloys

１　ＩＮＴＲＯＤＵＣＴＩＯＮＴｈｅＡＢ２ｔｙｐｅＺｒｂａｓｅｄＬａｖｅｓｐｈａｓｅｈｙｄｒｏｇｅｎｓｔｏｒａｇｅａｌｌｏｙｓｈａｖｅｂｅｅｎｓｔｕｄｉｅｄｅｘｔｅｎｓｉｖｅｌｙｄｕｅｔｏｔｈｅｉｒｈｉｇｈｃａｐａｃｉｔｙ，ｌｏｎｇｃｙｃｌｅｌｉｆｅｔｉｍｅａｎｄｔｈｅｐｏｔｅｎｔｉａｌｔｏｂｅｃｏｍｅａｐｒｏｍｉｓｉｎｇｃａｎｄｉｄａｔｅｆｏｒＡＢ５ｔｙｐｅａｌｌｏｙｓｉｎＮｉＭＨｂａｔｔｅｒｉｅｓ［１，２］．ＵｎｌｉｋｅｔｈｅｃｏｍｍｏｎＡＢ５ｔｙｐｅｈｙｄｒｏｇｅｎｓｔｏｒａｇ…     

运输溜矿井疏堵爆破

井下采矿的运输溜矿井在溜矿过程中常会被卡堵，中断生产，常用书堵爆破的专用工具将炸药送至卡堵处引爆松卡。现介绍溜矿井疏堵爆破输送炸药包的专用工具－传统火箭弹，改进的安全火箭弹以及新开发准确度高的浮球炸药包。