Prevention of Hydrosilation Cure Inhibition in a Polysiloxane Adhesive by Surface Oxidation

For a variety of reasons epichlorohydrin-ethylene oxide (ECO)-based compounds, in the form of rain erosion boots or sleeves, are bonded to aircraft radomes using a hydrosilation-cured RTV polysiloxane adhesive. Unfortunately, cure of the adhesive can be completely inhibited by unreacted vulcanizing agent and/or ECO cure by-products. We have earlier shown that this inhibition can be prevented by treating the ECO surface with hydrogen peroxide to oxidize the hydrosilation catalyst poisons to a harmless state. In this study we have used spectroscopic techniques to monitor the hydrosilation reaction kinetics and in turn to identify the poison, define the poisoning level and monitor the poison removal by hydrogen peroxide treatment. The degree of poison removal is also correlated with adhesive bond strength using a 180°; peel test. The critical poison in the system was excess ECO vulcanizing agent which can be completely removed from the surface using a 30 vol. % H₂O₂ treatment for 30 minutes as long as the initial vulcanizing agent concentration is 1 p.p.h. or less.     

助硫化剂对过氧化物共硫化NBR／CM的影响

研究了不同助硫化剂对过氧化物共硫化NBR／CM的影响。实验结果表明,助硫化剂S、PDM和Zn（MMA）。均能有效地提高共混物的拉伸强度和撕裂强度;助硫化剂S和TCY均能降低共混物的DIN磨耗体积。     

Fe/Al_2O_3催化剂催化氧化兰炭废水

采用浸渍法制备Fe/Al_2O_3催化剂,采用BET、XRD和穆斯堡尔谱等进行结构和性能表征。以自制Fe/Al_2O_3为催化剂,应用催化湿式过氧化氢氧化技术处理COD为6 742 mg·L-1的兰炭废水,通过建立正交实验确定最佳实验条件,结果表明,在p H=4、过氧化氢添加量9.6 m L、反应时间150 min和反应温度80℃条件下,兰炭废水COD去除率达66.30%。对催化氧化后的废水进行GC-MS分析,确定最终氧化产物主要为乙酸。表明自制Fe/Al_2O_3催化剂具有优良的催化效果,并使大分子难降解有机污染物分解为易生化的小分子污染物,甚至被完全分解矿化。     

冷法H_2O_2氧化制备马铃薯淀粉粘合剂及改性研究

在室温下,以马铃薯淀粉为原料,双氧水为氧化剂,制备出了马铃薯淀粉粘合剂.探讨了氧化剂用量、催化剂用量、糊化剂用量、氧化时间、糊化时间、粉水比、络合剂用量对粘合剂性能的影响,以粘度和初粘力为评价指标,通过L18(37)正交试验确定制备淀粉粘合剂的最佳条件为:m(水)∶m(马铃薯淀粉)=5∶1,双氧水1.3 mL,硫酸亚铁0.2 g,NaOH为3.0 g,氧化时间90 min,糊化时间30 min,硼砂0.3 g.并以添加聚乙烯醇进行接枝改性,提高其干燥时间和初粘力,实验得到添加量为5%时效果最好.     

相转移催化氧化体系在燃料油脱硫中的应用

介绍了以过氧化氢为氧化荆的相转移催化氧化脱硫研究现状.对过氧化氢/有机酸/季铵盐体系、过氧化氢/杂多酸/季铵盐体系和过氧化氢/合成相转移催化剂体系在脱除燃料油中噻吩、苯并噻吩、二苯并噻吩等方面的应用作了综述.指出了过氧化氢/合成相转移催化剂体系是燃料油深度脱硫的一个重要研究方向.     

Silicone acrylates through the hydrosilation of polyacryloyloxy functional monomers with copolymers of dimethyl and hydrogen methylsiloxanes

Silicone acrylates, as possible electron beam (EB) curable release coatings for paper, were prepared by the platinum-catalyzed hydrosilation of polyacryloyloxy functional monomers with copolymers of dimethylsiloxane and hydrogen methylsiloxane (PDMHMS). The hydrosilation of either 1,6-hexanediol diacrylate (HDDA) or trimethylolpropane triacrylate (TMPTA) with PDMHMS occurs to only one of the 2 or 3 available olefinic groups, respectively, as long as excess monomer is present. The amount of excess monomer needed to prevent gelation during hydrosilation or subsequent storage in excess of 1 month appears to be dependent on the hydrogen methylsiloxane content of the PDMHMS. A release coating having excellent cohesive and adhesive strength on paper was obtained by the EB curing of the product of hydrosilation of TMPTA with a PDMHMS containing 4 mol % hydrogen methylsiloxane at a dose-to-cure of 2 Mrad, but the aged release force was excessively high. The poor aged-release performance was likely due to dilution of the dimethylsiloxane content of the coating with excess monomer required to stabilize the silicone acrylate. © 1993 John Wiley & Sons, Inc.     

过氧化氢溶液中痕量离子吸附分离用氨基功能化SBA-15的制备及性能

通过后接枝法制备了氨基功能化SBA-15介孔氧化硅(S-N),用于吸附过氧化氢溶液中的金属和阴离子及有机杂质制高纯过氧化氢.研究了接枝量对吸附剂结构和性能的影响并发现S-N中的氮含量随接枝剂用量增加而增加,最高为1.83％.S-N保留了高度有序的六方孔道结构,但比表面积和孔体积均随接枝量增加而下降.在过氧化氢溶液中,各...     

Hydrogen‐containing silicone resin as the crosslinking agent of heat‐curable silicone rubber

The hydrosilation‐cured vulcanizates (HCV) of silicone rubber were prepared by using hydrogen‐containing silicone resin (HSR) as the crosslinking agent. The influences of both the amount and structure of HSR on hydrosilation‐curing silicone rubber (HCSR) were discussed. The results indicate that HSR is a good crosslinking agent for HCSR. The tensile strength, tearing strength, elongation at break, and hardness of the vulcanizates can reach 9.6 MPa, 37.8 kN/m, 870% and 56 SHA, respectively. The aging stability of the vulcanizates can be improved greatly. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 3066–3069, 2003     

过氧化物硫化体系对AEM/三元尼龙TPV性能的影响

采用过氧化物F40和DCP两种类型的硫化体系,同比改变过氧化物硫化体系中助硫化剂和硫化剂的用量,探究硫化剂添加量对AEM/PAM15动态硫化体系的影响。结果表明,随硫化剂添加量的增加,硫化程度先增加后减小;F40与DCP相比,对材料的性能影响相似,但DCP硫化过程中伴有刺激性气味且速率过快;动态硫化后的TPV[1]与硫化前相比,多了一个界面玻璃化温度,显示了两种基料良好的结合性能。     

Fe-exchanged Y zeolite as catalyst for wet peroxide oxidation of reactive azo dye Procion Marine H-EXL

This paper evaluates the degradation of a reactive azo dye, Procion Marine H-EXL, by catalytic wet hydrogen peroxide oxidation (CWHPO). The catalyst was prepared by ion-exchange, starting from a commercially available ultrastable Y zeolite. All experiments were performed on a laboratory scale set-up. The effects of different reaction parameters such as initial pH, catalyst and hydrogen peroxide concentrations on the oxidation of the dye aqueous solution were assessed. Apart from the conventional parameters, the toxic potential of the dye’s degradation products was investigated using the bioluminescence test. HPICE analysis was also performed to obtain detailed information on the resulting oxidation products (organic and inorganic anions). The results indicate that after only 10 min at 50 °C, 20 mmol/l H₂O₂ and 1g/l FeY_11.5 the color removal was as high as of 97% at pH=3 and 53% at pH=5. More than 96% removal of the dye could be attained in 30 min at pH=5, t=50 °C, 20 mmol/l H₂O₂ and 1 g/l FeY_11.5 which corresponds to about 76% reduction of the initial COD and 37% removal of the initial TOC. A preliminary study of catalytic oxidation with hydrogen peroxide of the synthetic textile wastewater containing the specific dye is also presented. Leaching tests indicate that the activity of the catalyst is not due to leached iron ions, although an amount of 0.1–4.0 ppm of iron ions was found in aqueous solution. The catalyst allows almost total elimination of the dye and a significant removal of COD and TOC without the significant leaching of Fe ions. It was also observed that by using this catalyst, it is possible to extend the range of pH values for which Fenton-type oxidation can occur and no iron hydroxide sludge is formed.     

Catalytic wet peroxide oxidation of phenolic solutions over a LaTi1−xCuxO3 perovskite catalyst

LaTi_1−xCu_xO₃ perovskites are efficient catalysts for the oxidation of aqueous solutions of phenol using hydrogen peroxide as precursor of free radicals. The catalytic results have shown that under mild reaction conditions and oxidant contents lower than stoichiometric, phenol was rapidly removed with a final total organic carbon (TOC) conversion of ca. 90%. Initial rate of TOC removal depends dramatically on temperature, catalyst loading and peroxide concentration. Perovskite catalyst after reaction is completely regenerated by calcination and retains a similar catalytic performance. Finally, the catalytic results demonstrate that leaching of active species during the catalytic oxidation seems to proceed by a complex mechanism in which the presence of hydrogen peroxide in combination with phenol plays an essential role.     

Surface modification of UHMWPE fibers

Ultrahigh molecular weight polyethylene (UHMWPE) fibers have a high specific strength, high specific modulus, and outstanding toughness, but their poor adhesive properties has limited their use for composite material applications. In this research, the effects of chemical etching on the surface chemistry and topography have been explored using chromic acid, potassium permanganate, and hydrogen peroxide etching. The smooth surface observed on the as-received fiber was rich in ether and/or hydroxyl oxygen. This smooth surface resulted from the presence of an outer layer, a weak boundary layer, that was removed by all the etchants. A fibrillar structural hierarchy was revealed beneath this outer layer and the fiber was relatively unchanged by further etching. Chromic acid, the strongest etchant studied, produced a rough and oxidized UHMWPE surface with both ether and carbonyl oxygen. The combination of outer layer removal, roughness, and changes in oxygen bonding helps explain the improved adhesion on chromic acid etching in spite of the reduction in surface oxygen. Neither hydrogen peroxide nor potassium permanganate etching roughened or oxidized the surface to a great extent and neither yielded improved adhesion. © 1994 John Wiley & Sons, Inc.     

混炼硅橡胶的配合技术(九)

介绍了用2，4-二氯过氧化苯甲酰作硫化剂的挤出成形用混炼硅橡胶（包括低硬度混炼硅橡胶、不粘连芯线的混炼硅橡胶、高电气强度电线用混炼硅橡胶）的配制方法及改进其加工和表面性能的方法；同时，还介绍了用甲基苯甲酰类过氧化物作硫化剂时改进混炼硅橡胶表面性能的方法（包括添加含氢硅油、硅藻土、二烷基过氧化物或过氧化苯甲酰以及细化硫化剂粒子）。     

甲基咪唑盐酸盐/草酸型低共熔溶剂的制备及其在模拟油中氧化脱硫中的应用

通过简单加热并搅拌甲基咪唑盐酸盐和草酸的混合物合成了甲基咪唑盐酸盐/草酸（[HMIM]Cl/H₂C₂O₄）型酸性低共熔溶剂,以[HMIM]Cl/H₂C₂O₄为萃取剂和催化剂、H₂O₂为氧化剂催化氧化法脱除模拟油中的二苯并噻吩,考察不同的脱硫体系、反应温度、催化剂加入量、氧硫比、模拟油中含硫化合物类型对脱硫率的影响。实验表明,在反应温度为40℃、模拟油量为5 ml、[HMIM]Cl/H₂C₂O₄加入量为1.25 ml、O/S 12、反应时间为140 min的最佳反应条件下二苯并噻吩的脱除率可以达到92.2%。动力学分析表明,该氧化脱硫体系符合一级反应动力学方程。循环使用7次后催化剂的活性没有明显降低。     

双氧水法脱硫副产稀硫酸浓度的探讨

介绍了双氧水脱硫的基本原理,阐述了维持H2O2一定浓度的必要性,分析了稀硫酸浓度对SO2脱除率、气相中硫酸雾含量的影响,提出了适宜的控制浓度.双氧水法脱硫的稀硫酸w(H2SO4)一般不宜超过30％,w(H2O2)控制在0.3％～0.5％,硫磺制酸企业稀硫酸w(H2SO4)可适当降低至20％～25％.     

Comparison of supports for the direct synthesis of hydrogen peroxide from H2 and O2 using Au–Pd catalysts

The direct synthesis of hydrogen peroxide from H₂ and O₂ using a range of supported Au–Pd alloy catalysts is compared for different supports using conditions previously identified as being optimal for hydrogen peroxide synthesis, i.e. low temperature (2 °C) using a water–methanol solvent mixture and short reaction time. Five supports are compared and contrasted, namely Al₂O₃, -Fe₂O₃, TiO₂, SiO₂ and carbon. For all catalysts the addition of Pd to the Au only catalyst increases the rate of hydrogen peroxide synthesis as well as the concentration of hydrogen peroxide formed. Of the materials evaluated, the carbon-supported Au–Pd alloy catalysts give the highest reactivity. The results show that the support can have an important influence on the synthesis of hydrogen peroxide from the direct reaction. The effect of the methanol–water solvent is studied in detail for the 2.5 wt% Au–2.5 wt% Pd/TiO₂ catalyst and the ratio of methanol to water is found to have a major effect on the rate of hydrogen peroxide synthesis. The optimum mixture for this solvent system is 80 vol.% methanol with 20 vol.% water. However, the use of water alone is still effective albeit at a decreased rate. The effect of catalyst mass was therefore also investigated for the water and water–methanol solvents and the observed effect on the hydrogen peroxide productivity using water as a solvent is not considered to be due to mass transfer limitations. These results are of importance with respect to the industrial application of these Au–Pd catalysts.     

Degradation of Rubber-to-Metal Bonds During Simulated Cathodic Delamination

Cathodic delamination of neoprene-to-steel adhesive bonds prepared using a proprietary vulcanizing adhesive and primer was investigated using Fourier-transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). Chlorinated rubber in the adhesive and primer was stable during immersion in NaOH solutions simulating the high pH conditions obtained at the bondline during cathodic delamination. However, methylene groups linking phenol moieties in phenolic resins in the primer were rapidly oxidized during immersion in NaOH solutions to form benzophenone linkages which were oxidized further to carboxylic acids and quinones. Chlorine produced by dehydrohalogenation of chlorinated rubber in the adhesive and primer during curing of the neoprene reacted with ZnO in the primer to form ZnCl₂ in the bondline. Failure of adhesive bonds between neoprene and steel during cathodic delamination is probably related to oxidation of the phenolic resins in the primer and to osmotic effects related to the high solubility of ZnCl₂.     

氧化石墨烯负载纳米Fe3O4类芬顿处理制药废水

采用改进Hummer法制备了氧化石墨烯(GO)负载纳米Fe₃O₄磁性催化剂(Fe₃O₄/GO),对其进行了X射线衍射仪、扫描电子显微镜和能量-色散光谱表征,并将其应用于多相类芬顿处理高浓化学原料药生产废水。结果表明,Fe₃O₄颗粒成功负载在GO表面,且没有出现明显的团聚现象。当废水的pH为3,双氧水(H₂O₂的质量分数30%)投加量10 mL/L,催化剂投加量2 g/L,反应120 min后COD去除率达78%,UV254去除率高达81%。三维荧光光(3D-EEM)分析可知,芳香类和富里酸类物质在催化降解过程中得到有效去除。     

A型铸造粘合剂的研究

以聚乙烯醇为主要原料,采用化学改性的方法成功制备了A型铸造粘合剂。研究了甲醛、双氧水和交联剂对铸件性能的影响。结果表明,该粘合剂完全能满足铸造生产,其性能优于合脂油,是节能环保型产品。该粘合剂最大特点是能回用旧砂,回用的比例可达50%。     

The Role of Lignin in Surface-Activated Bonding of Lignocellulose—Characterized by Differential Scanning Calorimetryt

The study of surface modification to prepare an optimum surface for bonding is of practical importance for the production of glued materials. Lignocellulosic materials contain many chemical groupings such as phenolic and alcoholic hydroxyls, carbonyl groups, etc., capable of being readily activated by physical or chemical methods. These active sites can then react under heat and pressure, either with active sites from another surface, or through a crosslinking agent to form a glued product.

This paper reports the role of lignin in the reactions between lignocellulosic materials and hydrogen peroxide studied by a differential scanning calorimetry method. The results showed that lignin is much more reactive toward hydrogen peroxide than is cellulose, and that the lignin-hydrogen peroxide reaction yields the highest enthalpy. Correlation between lignin and enthalpy, and enthalpy and bonding will also be discussed.