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Abstract North Vietnamese NR latexes were successfully epoxidized using peracetic acid at moderate temperature and pH range. The epoxide contents of pure epoxidized natural rubber (ENR) are from 5 to 70 mol%. The ENR products were characterized and determined by spectral and thermal analysis besides the chemical titration. Conditions of longlasting or excessive temperature, or high acidic pH led to side ring opened products, proved easily by IR, 1H-NMR, and DSC analysis. The ENR were vulcanized using a semiefficient system. The epoxidation increased the adhesion between rubber and tire cord and metal. This effect becomes stronger beyond 25 mol% and tends to be limited at over 60 mol%. The ENRs were used to formulate special-purpose adhesives. The shear strength of the adhesive ranges from 32 to 45 kg/cm2 for bonding rubber to nylon and rubber to metal, respectively. 相似文献
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A simple and efficient aerobic oxidative dehydrogenation reaction method for the conversion of 2-(alkylthio)-1,4-dihydropyrimidines to 2-(alkylthio)pyrimidines using copper catalyst with no additives, such as an oxidant, acid, or base, has been developed. The reaction was successful with a wide range of 2-(alkylthio)-1,4-dihydropyrimidine substrates. 相似文献
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A. P. Molchanov T. Q. Tran A. V. Stepakov G. L. Starova R. R. Kostikov 《Russian Journal of Organic Chemistry》2014,50(1):78-82
N-Aryl-C-(arylcarbamoyl)nitrones regioselectively add to methyl 2-(2-phenylcyclopropylidene)-acetate and methyl 2-methylidene-3-phenylcyclopropanecarboxylate to give in each case two diastereoisomeric 5-oxa-6-azaspiro[2.4]heptane-4-carboxylates. 相似文献
48.
Let denote a Hermite process of order and self-similarity parameter . This process is -self-similar, has stationary increments and exhibits long-range dependence. When , it corresponds to the fractional Brownian motion, whereas it is not Gaussian as soon as . In this paper, we deal with a Vasicek-type model driven by , of the form . Here, and are considered as unknown drift parameters. We provide estimators for and based on continuous-time observations. For all possible values of and , we prove strong consistency and we analyze the asymptotic fluctuations. 相似文献
49.
Mohanad A. Hussein Dr. Uyen P. N. Tran Dr. Vien T. Huynh Dr. Junming Ho Dr. Mohan Bhadbhade Prof. Dr. Herbert Mayr Dr. Thanh V. Nguyen 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(4):1471-1475
Tropylium bromide undergoes noncatalyzed, regioselective additions to a large variety of Michael acceptors. In this way, acrylic esters are converted into β-bromo-α-cycloheptatrienylpropionic esters. The reactions are interpreted as nucleophilic attack of bromide ions at the electron-deficient olefins and the approach of the tropylium ion to the incipient carbanion. Quantum chemical calculations were performed to elucidate the analogy to the amine- or phosphine-catalyzed Rauhut–Currier reactions. Subsequent synthetic transformations of the bromo-cycloheptatrienylated adducts are reported. 相似文献
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Bui Dac Dung Trinh Van Giap Tibor Kovacs Tran Ngoc Toan Le Dinh Cuong Tran Khanh Minh Nguyen Huu Quyet Nguyen Van Khanh 《Journal of Radioanalytical and Nuclear Chemistry》2014,299(3):1943-1948
Mineral sands are mined in several countries to supply to the titanium and zircon producing industries. Coastal black mineral sands usually contain, besides ilmenite (FeTiO3) and rutile (TiO2), radioactive minerals such as zircon (ZrSiO4) and monazite (RePO4). Radon and thoron activity concentration originated from natural radioactive contents of the black mineral sand was monitored at the extraction and processing for black minerals in the coastal areas of Ha Tinh Province, one of the around 40 coastal mineral sand deposits in Vietnam. The survey was carried out with the Raduet chambers made by Radosys Ltd—Hungary. The obtained results for 25 investigated points show that the measured values are not high in the residential houses and in case of the sand extraction site as well. At the titanium processing plant the measured values were higher than outside the facility (Radon: 18–55 Bq/m3 with average of 34 Bq/3 and Thoron 33–118 Bq/m3 with average of 58 Bq/m3) but still comparable to the average concentration of the world published by UNSCEAR. The typical outdoor levels of radon and thoron gas are each of the order of 10 Bq/m3. Although the radon concentrations were low in the zircon and titanium processing plants, the thoron concentrations in the houses for separating rutile and zircon were very high. At zircon processing factory, the thoron concentration could reach 2,931 Bq/m3 and the estimated annual effective dose would be 21.4 mSv/a. Intervention has to be taken in order to reduce the thoron level in this factory since the level of thoron and its progenies corresponding to an annual occupational effective dose is beyond the action level of 6 mSv/a. 相似文献