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排序方式: 共有292条查询结果,搜索用时 218 毫秒
1.
John Comyn 《The Journal of Adhesion》1989,29(1):121-130
Single lap joints of aluminium alloy, bonded with a number of structural adhesives, have been aged at 100% or 50% relative humidity (r.h.) at 50°C for up to 10000 hours. The adhesives used have included a simple epoxide and some modified phenolics and epoxides. Whilst joints are not significantly weakened on exposure at 50% r.h., significant weakening occurs at 100% rh. There is an initial fall in strength in the early stages of exposure, but after this period joints remain fairly stable, retaining approximately 40-60% of the strengths they had before exposure. Water diffusion coefficients in the adhesives have been obtained from experiments on the mass uptake of water by films of the adhesives. Water concentration profiles and overall levels of water in adhesive joints have been calculated from diffusion coefficients, and these show that the initial fall in strength is controlled by water diffusing through the adhesive layer. Joint strengths recover significantly when they are dried out. The behaviour of joints can be interpreted by there being ion-pairs at the interface. Water reduces the interionic force by raising the permittivity of the surroundings, and this is reversed when the water is removed. 相似文献
2.
根据树脂传递模塑(RTM)模具对基体树脂的基本要求,选用双酚A环氧乙烯基酯树脂为基体,聚乙酸乙烯酯为低收缩添加剂,玻璃纤维经编织物为增强材料,并加入相应的助剂,制备了复合材料RTM模具。该模具具有成本较低、开发周期短、精度较高等优点,但表面强度和热效率较低。 相似文献
3.
环氧有机硅阳离子型光敏预聚物的合成及其光敏性能的研究 总被引:7,自引:0,他引:7
合成了环氧有机硅光敏预聚物及阳离子光引发剂甲苯茂铁四氟硼酸盐,研究光引发剂种类、预聚物与单体配比、增感剂结构等因素对固化速度的影响,发现预聚物体系的感度较高,最小感度值为165mJ/cm^2;并讨论了甲苯茂铁四氟硼酸盐的暗聚合能力。 相似文献
4.
Small-angle neutron scattering experiments in the range of q2 from 0.01 to 25 nm−2 have been carried out on branched epoxide resins based on bisphenol-A at the Institute Laue—Langevin (I.L.L) in Grenoble (q=(4π/λ) sin(θ/2)). Measurements were made with six samples in the range of MW from 1500 to 19 000 and four concentrations between 1.3 and 10% (w/w) in deuterated diglyme. The results are as follows: (i) The mean square radius of gyration follows a relationship S2z=4.69×10−4M1.20W (nm2). (ii) In all cases fairly large second virial coefficients A2 are obtained which, however, decrease strongly with molecular weight. Above MW=2500, the virial coefficient follows the relationship A2=1.6M−0.85W (mol cm3g−2). (ii) The reciprocal particle scattering factor as a function of q2 exhibits only a slight upturn and otherwise shows the behaviour of a randomly branched polycondensate. The slight upturn is discussed as being caused by the finite volume of the monomeric unit. Possible reasons for the high exponent in the S2z versus MW dependence are briefly discussed. 相似文献
5.
6.
将乙二醇二缩水甘油醚分散在水中制成环氧化合物乳液,并以其为交联剂,用以对丙烯酸系单体/胺基单体乳液共聚物的改性,制成了双组分室温固化乳液涂料。研究了乳化剂种类和胺基单体用量对聚合稳定性的影响,结果表明,若采用p 壬基酚聚氧化乙烯醚硫酸钠为乳化剂,且胺基单体用量低于单体总量2 5%时,可以制得稳定的带胺基的共聚物乳液。将丙烯酸系共聚物乳液和环氧乳液复合并在室温下干燥成膜,通过对聚合物膜的DSC和力学性能测试均表明,双组分体系在成膜过程中发生了交朕反应,而未加环氧化合物的单组分聚合物乳液成膜时则不发生交联。 相似文献
7.
4-乙烯基环己烯环氧化反应研究 总被引:2,自引:0,他引:2
分别以单过氧马来酸、单过氧邻苯二甲酸、过氧三氯乙酸以及过氧乙酸作环氧化试剂,对4-乙烯基环己烯环氧化反应作了研究,并从分子结构的角度,阐明了4-乙烯基环己烯在环氧化反应中所表现出的选择性 相似文献
8.
Deepa Jonnalagadda Debin Wan Jerold Chun Bruce D. Hammock Yasuyuki Kihara 《International journal of molecular sciences》2021,22(9)
Polyunsaturated fatty acids (PUFAs) are essential FAs for human health. Cytochrome P450 oxygenates PUFAs to produce anti-inflammatory and pain-resolving epoxy fatty acids (EpFAs) and other oxylipins whose epoxide ring is opened by the soluble epoxide hydrolase (sEH/Ephx2), resulting in the formation of toxic and pro-inflammatory vicinal diols (dihydroxy-FAs). Pharmacological inhibition of sEH is a promising strategy for the treatment of pain, inflammation, cardiovascular diseases, and other conditions. We tested the efficacy of a potent, selective sEH inhibitor, 1-trifluoromethoxyphenyl-3-(1-propionylpiperidin-4-yl) urea (TPPU), in an animal model of multiple sclerosis (MS), experimental autoimmune encephalomyelitis (EAE). Prophylactic TPPU treatment significantly ameliorated EAE without affecting circulating white blood cell counts. TPPU accumulated in the spinal cords (SCs), which was correlated with plasma TPPU concentration. Targeted lipidomics in EAE SCs and plasma identified that TPPU blocked production of dihydroxy-FAs efficiently and increased some EpFA species including 12(13)-epoxy-octadecenoic acid (12(13)-EpOME) and 17(18)-epoxy-eicosatrienoic acid (17(18)-EpETE). TPPU did not alter levels of cyclooxygenase (COX-1/2) metabolites, while it increased 12-hydroxyeicosatetraenoic acid (12-HETE) and other 12/15-lipoxygenase metabolites. These analytical results are consistent with sEH inhibitors that reduce neuroinflammation and accelerate anti-inflammatory responses, providing the possibility that sEH inhibitors could be used as a disease modifying therapy, as well as for MS-associated pain relief. 相似文献
9.
Erkan Ertürk Mustaf Ali Tezeren Tahir Tilki Tuba Erdogan Ahmet C Gren 《Polymer International》2012,61(5):795-799
The readily available mixed‐valent iron trifluoroacetate complex [Fe2IIIFeII(µ3‐O)(O2CCF3)6(H2O)3] is an effective catalyst for the polymerization of epoxides. A very small amount of the catalyst (1.0–0.01 mol%) could initiate the polymerization of cyclohexene oxide, cyclopentene oxide and epichlorohydrin. Based on quantitative end‐group analysis by 19F NMR spectroscopy, a Lewis acid (LA⊕) catalyzed anionic reaction mechanism is proposed. Copyright © 2012 Society of Chemical Industry 相似文献
10.
菜豆环氧化物水解酶1和2(PvEH1、PvEH2)能够动力学拆分外消旋邻甲基苯基缩水甘油醚(rac-oMGE),从而保留(R)-oMGE。基于对PvEH1和PvEH2结构的同源模拟和分析,发现二者分子中的盖子环差异较大,故本文选择盖子环作为研究目标。经融合聚合酶链式反应(FPCR),获得了PvEH2的盖子环区域被PvEH1对应区域替换的杂合酶Pv2Pv1。用全细胞酶E. coli/pv2pv1催化rac-oMGE,当(S)-oMGE刚好水解完全时,产物(S)-3-邻甲苯基-1,2-丙二醇((S)-oTPD)的eep由PvEH2的58.3%提高至75.5%。为进一步提高酶的性质,在Pv2Pv1中选取11个氨基酸位点进行丙氨酸(A)突变,获得最优突变子E. coli/pv2pv1K176A,活性为E. coli/pv2pv1(4.2U/g)的2.1倍,且当S构型的底物刚好完全水解时,(S)-oTPD的eep进一步提高为80.3%。分子对接分析发现,盖子环替换和K176位点突变为A,均使(R)-oMGE环氧环中的Cα更易受到酶中D101位点的攻击。利用E. coli/pv2pv1K176A催化150mmol/L rac-oMGE水解制备(R)-oMGE(ees>99%)和(S)-oTPD(eep=80.4%),二者的产率YS和YP分别为32.7%和60.1%,时空产率STYS和STYP为1.6g/(L·h)和3.3g/(L·h)。本实验为改善EH的催化性质提供了一种有效策略。 相似文献