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31.
A study of modified carbon paste electrode employing Nile blue (NB) adsorbed on silica gel modified with niobium oxide (SN) for electrocatalytic oxidation of reduced nicotinamide adenine dinucleotide (NADH) is described. The adsorbed organic dye on SN was used to prepare a modified carbon paste electrode to investigate its electrochemical properties. The formal potential (E°′) of the adsorbed NB (−230 mV vs. saturated calomel electrode, SCE) showed a shift of 70 mV towards a more positive potential value, compared to NB dissolved in aqueous solution. In solutions with pH between 6.0 and 8.0 did stability and E°′ remained almost constant. However, for a solution pH lower than 6.0 the E°′ was affected by the acidity of the contacting solution, shifting the E°′ towards more positive values. For the solution pHs between 6.0 and 8.0 the electrocatalytic activity remained almost constant. A linear response range for NADH between 1.0×10−5 and 5.2×10−4 mol l−1, at pH 7.0, was observed for the electrode, with an applied potential of −200 mV versus SCE. The formation of an intermediate charge transfer (CT) complex was proposed to the CT reaction between NADH and adsorbed NB. The heterogeneous electron transfer rate, kobs, was 1400 M−1 s−1 and the apparent Michaelis-Menten constant, was 0.21 mM at pH 7.0 evaluated from rotating disk electrode (RDE) experiments with an electrode coverage of about 5.2×10−9 mol cm−2. The increase in the reaction rate between NADH and the immobilized NB compared to those obtained with dissolved NB was assigned to the shift of the E°′ towards more positive values. 相似文献
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33.
淀粉丙烯酸接枝共聚吸水性树脂的研究进展 总被引:4,自引:0,他引:4
基于淀粉丙烯酸接枝共聚作为吸水性树脂具有环保和可生物降解的优良特性 ,目前 ,人们普遍关注的是如何提高其吸水性 ,抗温性 ,控制水份释放 ,压力下保水 ,以及电解液的吸收等。这些特性的改进将使产品的用途更为广泛 ,可以预见 ,淀粉丙烯酸接枝共聚作为吸水性树脂具有广阔的应用和发展前景。 相似文献
34.
Siby VargheseJ. Karger-Kocsis 《Polymer》2003,44(17):4921-4927
Natural rubber (NR) based nanocomposites with 10 wt% natural and synthetic layered silicates were produced via the latex compounding method. As layered silicates, sodium bentonite (natural) and sodium fluorohectorite (synthetic) were selected in addition to a non-layered inert filler (English India clay or commercial clay) as reference material. The nanocomposites were prepared by compounding the dispersions of clays and other latex chemicals necessary for vulcanization. The vulcanized nanocomposites were subjected to mechanical, thermal and swelling tests. The silicate dispersion was studied by transmission electron microscopy. Layered silicates outperformed the reference material (commercial clay) in all aspects. This was attributed to the intercalation/exfoliation of the silicates and to the formation of a skeleton ‘(house of cards)’ silicate network in the NR matrix. 相似文献
35.
试验发现:一种阴离子型兼具非离子性的乳化剂A用于羧基丁苯胶乳聚合体系,可显著提高胶乳的质量,其质量分数即使下降到原配方乳化剂标准用量的25%,也能制备出合格的胶乳;与使用SDS的聚合体系相比,使用乳化剂A的聚合体系的聚合反应及产物质量重复性好,胶乳的钙离子稳定性显著提高。分析发现,乳化剂用量的大小会导致聚合反应机理的差异,从而影响聚合反应及产物质量;在酸性条件下,乳化剂本 身的稳定性也是造成这种差异的原因之一。应用试验结果表明:用乳化剂A代替SDS并在一定范围内改变其用量,不会影响胶乳的应用性能。 相似文献
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38.
采用物理掺和法,在苯丙乳液中加入锐钛型纳米TiO2,制成内墙涂料,进行抑菌试验和甲醛降解实验研究,分析了纳米TiO2的光催化原理和抗菌机理。结果表明,随着TiO2含量增加,甲醛降解能力和抗菌性能增强,当TiO2含量为4%时效果最好。 相似文献
39.
Hydrophobically modified alkali-soluble emulsion (HASE) polymers are an important class of rheology modifiers for waterborne
coatings applications. They are typically prepared as terpolymers by emulsion polymerization of ethyl acrylate (EA), methacrylic
acid (MAA), and an associative macromonomer. The viscosity development and shear responses of HASE solutions depend on a number
of factors. This article presents rheological data reflecting the impacts of three key variables: hydrophobe size, acid content,
and molecular weight, on model HASE thickening and rheological performance. The relative contributions of hydrophobic association,
chain expansion, and polymer chain length are discussed.
In steady shear flow, all thickener solutions approached some constant low-shear viscosity at small deformation rates. At
the same molar composition, larger hydrophobe size resulted in higher viscosity development and greater shear thinning behavior.
The amount of acid monomer in HASE polymers can influence the balance between hydrophobic attraction and electrostatic repulsion
forces. It was found that a minimum of 15 wt% MAA was required to effect dissolution and thickening of the model HASE polymers.
Increasing the MAA level yielded higher zero-shear viscosity and storage modulus G’ with maximal values being obtained at
40% MAA.
The molecular weight of the model thickeners was controlled by the amount of chain transfer agent (CTA) added during polymerization.
When the CTA level was below 0.1 wt% based on total monomers, the polymer solutions displayed shear-thinning behavior. A small
increase in CTA concentration beyond 0.1% resulted in a dramatic change to Newtonian flow, and the solution viscosity was
nearly two orders of magnitude lower.
The model thickeners were also tested in a vinyl acrylic architectural paint formulation. The effects of each individual factor
on paint thickener efficiency, high-shear, and low-shear properties are discussed and compared with solution rheology for
predictive relationships.
Presented at the 81st Annual Meeting of the Federation of Societies for Coatings Technology, November 11–12, 2003, in Philadelphia,
PA. 相似文献
40.
讨论了现用计算公式的缺陷及原因,提出4个修正公式,并举例说明了修正后公式对确定合理的模具公差和保证注塑件顺利生产的重要经济意义。 相似文献