航空导管弯曲试验的疲劳裂纹萌生寿命

飞行器液压导管受接头和卡箍等约束，在使用的振动环境中，会因弯曲应力而导致破裂，影响到飞行安全．本文对飞行器液压系统通用的不锈钢导管的裂纹萌生寿命进行了试验研究．首先在对8 mm、12 mm 无缺陷导管和含U 型缺口8 mm 导管的疲劳试验和有限元分析的基础上，得到了导管的最大拉应变-裂纹萌生寿命数据．然后采用基于强度极限和弹性模量估算法的Manson-Coffin 公式来预测导管裂纹萌生寿命．最后引入加载类型修正系数、表面质量修正系数、试样尺寸修正系数、应力集中敏感系数和有效应力集中系数，使修正后的公式对三种类型的导管均有较好的裂纹萌生寿命预测精度．     

Synthesis of functional polymers—Vinylidene fluoride based fluorinated copolymers and terpolymers bearing bromoaromatic side‐group

The radical co‐ and terpolymerization of 4‐[(α,β,β‐trifluorovinyl)oxy]bromo benzene (TFVOBB) with 1,1‐difluoroethylene (or vinylidene fluoride, VDF, or VF₂), hexafluoropropene (HFP), perfluoromethyl vinyl ether (PMVE), and chlorotrifluroroethylene (CTFE) is presented. Although TFVOBB could be thermocyclodimerized, it could not homopolymerize under radical initiation. TFVOBB could be copolymerized in solution under a radical initiator with VDF or CTFE comonomers, while its copolymerization with HFP or PMVE were unsuccessful. The terpolymerization of TFVOBB with VDF and HFP, or VDF and PMVE, or VDF and CTFE also led to original fluorinated terpolymers bearing bromoaromatic side‐groups. The conditions of co‐ and terpolymerization were optimized in terms of the nature of the radical initiators, and of the nature of solvents (fluorinated or nonhalogenated). Various monomer concentrations in the co‐ and terpolymers were assessed by ¹⁹F and ¹H‐NMR spectroscopy. The thermal and physico chemical properties were also studied. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 5077–5097, 2004     

含吡咯烷酮基丙烯酸酯类单体的合成及聚合

轻度交联的聚甲基丙烯酸2-羟乙酯(HEMA)是众所周知的医用水凝胶,即所谓的“Hvdron”。但其吸水率一般在59%(EWC为37%),并不尽人意。近年来,为了提高这类水凝胶的亲水性及生物相容性,常用一些亲水性的烯类单体进行表面改性或通过共聚以达到此目的,N-乙烯基吡咯烷酮是较为常用的这类单体之一。本文合成了含吡咯烷酮基丙烯酸酯类的单体,即丙烯酸2-N-吡咯烷酮基乙酯(PyEA),甲基丙烯酸2-N-吡咯烷酮基乙醋(PyEMA),并研究了这两种单体在甲基丙烯酸二甲氨乙酯(DMAEMA)与过硫酸钾(KPS)所组成的氧化还原引发体系下的聚合。     

Addition of secondary phosphines to N-vinylpyrroles

Secondary phosphines 1-3 react readily with N-vinylpyrroles 4 and 5 under radical initiation to give regiospecifically anti-Markovnikov adducts, diorganyl-2-(1-pyrrolyl)ethylphosphines 6a-d, highly reactive building blocks for organic synthesis, in 88-91% yields.     

Initiation of cationic polymerization of n-butyl vinyl ether by stable cation radicals of substituted phenothiazines

3,7-Diethyl- 10-phenylphenothiazine (DEPPT), a phenothiazine derivative whose 3,7- and 10-positions are blocked, was synthesized. Potentiostatic electrolysis of DEPPT in acetonitrile (ACN) in the presence of 0.1M of LiClO₄ at 0.7 V (vs. Ag/Ag/Cl) yielded the stable cation radical of DEPPT (DEPPT^+·) which was characterized by cyclic voltammetry, UV-visible spectroscopy, and ESR spectrometry. Stable cation radicals of 10-phenylphenothiazine and 3,7-diethyl-10-methylphenothiazine were also prepared. The cationic polymerization of n-butyl vinyl ether was initiated by these cation radicals, including DEPPT^·+. The electron transfer mechanism for the initiation step, which we proposed previously, was supported by the fact that DEPPT^·+ was capable of initiating the polymerization; dimerization of DEPPT^·+ by releasing protons is precluded because 3,7- and 10-positions are all blocked. © 1994 John Wiley & Sons, Inc.     

PHOTOSENSITIVITY OF Ce (Ⅳ) INITIATED METHYL ACRYLATE POLYMERIZATION

The influences of UV light irradiation (313 nm) and diffused daylight on the polymerization of methyl acrylate initiated by the ceric ammonium nitrate without any reducing agent have been studied both in aqueous nitric acid and in pure water. The rate of polymerization was found to be accelerated and the overall activation energy and the induction time were found to be decreased sharply by the UV light irradiation. Under UV light, the rate of polymerization is 8 times as high as the rate in dark. The rate of polymerization was found to attain a maximum with the increase of nitric acid concentration and the rate of polymerization became less sensitive to UV light in the presence of nitric acid whereas the induction period reduced outstandingly. Based on the experimental results, the mechanism is proposed.     

铈离子与氨基甲酸酯类化合物引发丙烯酰胺聚合的研究

本文对铈离子与苯基氨基甲酸酯类化合物在H_2O-CH_3CN(3∶1,V/V)及H_2O-HCONH_2(1∶2,V/V)两种介质中引发丙烯酰胺的聚合进行了研究。考察了不同结构的苯基氨基甲酸酯对聚合的影响。苯基氨基甲酸酯类化合物对铈离子引发聚合均有促进作用,其中对-甲苯基氨基甲酸酯的促进作用最为显著。测定了聚合反应表现活化能及聚合动力学方程,并提出了聚合反应机理。     

Gas-phase Reaction of 2-Chlorothiophene with Hydrogen Sulfide in the Presence of Alcohols

The effect of methanol and ethanol on the route of the gas-phase reaction of 2-chlorothiophene with hydrogen sulfide, leading to 2-thiophenethiol and to bis(2-thienyl) sulfide, has been investigated. It was found that methanol significantly enhances this reaction and increases its selectivity for the thiol at higher temperatures than without the initiator. The optimal conditions were achieved at 570°C in the presence of 10 mole % of methanol when the conversion of the 2-chlorothiophene in the reaction with hydrogen sulfide reaches 98% and the yield of the thiophenethiol (43%) exceeds that of the bis(2-thienyl)sulfide (31%). In the absence of methanol the 2-thiophenethiol is formed only at 510-540°C in just 17% yield, the basic reaction product being the indicated sulfide (52% yield); the conversion of the 2-chlorothiophene does not exceed 54%.     

Redox polymerization of 2-hydroxyethyl methacrylate (HEMA). I. Influence of surfactants on polymerization kinetics

Oxidation of ferrous orthophenanthroline (FeP) by peroxydiphosphate (PP) in aqueous medium at pH 1 was followed spectrophotometrically. Kinetic analysis has shown that oxidation occurs via the formation of an intermediate complex between FeP and PP. Equi-librium and rate constants were calculated. Influence of surfactants on the oxidation of FeP by PP was also Investigated. The equilibrium constant for complex formation was found to be higher in the presence of surfactants. The enhanced complex formation has been attributed to the ionic interactions between the charged surfactant and the ionic species in the reaction medium. Polymerization of HEMA initiated by the redox system,FeP/PP, was carried out in aqueous medium, under the conditions of excess reductant over oxidant and excess oxidant over reductant. The polymerization followed different mech-anisms under these conditions; with excess oxidant, the growing polymer radicals underwent oxidative termination, while with excess reductant, primary radical termination was pre-ferred. The effect of surfactants on the aqueous polymerization of HEMA using the redox system FeP/PP was also investigated. In addition to the decrease in rate, the polymerization followed a different mechanism in the presence of surfactants, the growing radicals ter-minated by mutual interaction. © 1995 John Wiley & Sons, Inc.     

REVERSE ATOM TRANSFER RADICAL POLYMERIZATION OF STYRENE WITH COPPER-BASED CATALYST

 "Living"/controlled radical polymerization of styrene was carried out with diethyl 2,3-dicyano-2,3-diphenylsuccinate (DCDPS)/CuCl₂/bipyridine (bipy) initiation system at 120℃. The molecular weights of resultant PSt increased with the monomer conversion and the polydispersities were in the range of 1.37 ～ 1.52. A linear ln([M]o/[M])versus time plot was also obtained indicating the constant concentration of growing radicals during the polymerization with this initiation system. End group analysis by ¹H-NMR spectroscopic studies showed that the end groups of the polymer obtained is cω-functionalized by a chlorine group from the catalyst and a-functionalized by a (carbethoxy-cyano-phenyl)methyl group from the fragments of the initiator. Having C1 atom at the chain end, the PSt obtained can be used as a macroinitiator to promote a chain-extension reaction with fresh St and block copolymerization reaction with a second monomer, such as methyl methacrylate, in the presence of CuC1/bipy catalyst via a conventional ATRP process.