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81.
Tsuneki Ichikawa Ken-ichi Oyama Tatsu Kondoh Hiroshi Yoshida 《Journal of polymer science. Part A, Polymer chemistry》1994,32(13):2487-2492
Effect of irradiation temperature on the main-chain scission of poly (methyl methacrylate) (PMMA) caused by γ-irradiation was studied by means of gel permeation chromatography and ESR spectroscopy. Although no temperature dependency was observed on the scission efficiency for purified PMMA, the efficiency for crude or monomer-doped purified PMMA was decreased by decreasing the temperature below ca. 200 K. Above 200 K the efficiency was constant and did not depend on the purity of PMMA. ESR study of the irradiated PMMA revealed that the suppression of the scission below 200 K is induced by the addition of methyl methacrylate monomer to primary radical species, which otherwise cause the main-chain scission by warming the polymer above 200 K. The primary radical generated above 200 K immediately converts to the scission-type ? CH2 ? ?(CH3) COOCH3 radical through the β-scission of the polymer main chain, so that the efficiency of the scission does not depend on both the impurity and the irradiation temperature. © 1994 John Wiley & Sons, Inc. 相似文献
82.
On the self-association of the normal alcohols and the glass transition in alcohol-alcohol solutions
Arnold V. Lesikar 《Journal of solution chemistry》1977,6(2):81-93
The glass-transition temperature (Tg) in mutual binary mixtures of the primary alkanols from methanol throughn-octanol has been measured as a function of composition. For mixtures of the alkanols heavier than ethanol,T
g is found to be a linear function of the number-average molecular length. Methanol and ethanol mixtures show higherT
g values than indicated by this relation. These results are found to be consistent with association of the heavier alkanols into chains of very great length in the supercooled liquid, while ethanol and methanol must form networks with a moderate degree of crosslinking between chains. 相似文献
83.
A high-powered, microwave-induced nitrogen–oxygen plasma (N2–O2–MIP) generated by using an Okamoto cavity at atmospheric pressure was investigated when the observation height, the flow rate of carrier gas, and the oxygen content were varied as the experimental parameters. The emission characteristics of the plasma were evaluated with regard to the excitation temperature and the intensity ratio of atomic line to ionic line. The excitation temperature of the N2–O2–MIP was in the range of 5100–5700 K when the oxygen content was varied from 0 to 30% at the observation height of 7 mm and the carrier gas flow rate of 0.6 l/min. The intensity ratio of atomic line to ionic line was elevated with an increase in the oxygen content. 相似文献
84.
Jean Pascal Eloundou 《European Polymer Journal》2002,38(3):431-438
Dipolar relaxations in a reactive epoxy-amine system based on diglycidyl ether of bisphenol A with 4,4′-diaminodiphenylsulfone were studied with the Havriliak-Negami function. The system was cured isothermally at 140 °C using simultaneous kinetic and microdielectric studies.The relaxation time was calculated from the frequency fmax of the peak of the loss factor ε′′ versus frequency f. A linear relation exists between the logarithm of the relaxation time τ and the glass transition temperature Tg. Then, logτ follows the Di Benedetto equation revisited by Pascault and Williams allowing the prediction of the relaxation time τ during cure.The unrelaxed permittivity at high frequency εu, the relaxed or static permittivity εs and the skewness parameter β were found independent on the conversion or the curing time. The distribution parameter α decreases as curing time t increases. The difficulty of orientation of dipoles in the electric field due to vitrification is responsible of these behaviours. 相似文献
85.
Shingo KomatsuYouichi Sakamoto Toshiyasu Suzuki Shizuo Tokito 《Journal of solid state chemistry》2002,168(2):470-473
Perfluoro-1,3,5-tris(p-quaterphenyl)benzene (PF-13Y) and perfluoro-1,3,5-tris(p-quinquephenyl)benzene (PF-16Y) have been synthesized and characterized. They showed higher glass transition temperatures compared with perfluoro-1,3,5-tris(p-terphenyl)benzene (PF-10Y). Organic light-emitting diodes were fabricated using these materials as the electron-transport layers. PF-13Y and -16Y are better electron transporters than PF-10Y. The electron mobilities of PF-10Y and Alq3 were measured by the time-of-flight technique. PF-10Y showed higher electron mobilities (10−4 cm2/V s) and weaker electric field dependence compared with Alq3. 相似文献
86.
Possible use of room temperature ionic liquids (RTILs) as chelate extraction solvent was evaluated by using 1-butyl-3-methylimidazolium hexafluorophosphate ([bmim][PF6]), 1-hexyl-3-methylimidazolium hexafluorophosphate ([hmim][PF6]) and 1-octyl-3-methylimidazolium hexafluorophosphate ([omim][PF6]). These RTILs showed high extraction performance for divalent metal cations with 4,4,4-trifluoro-1-(2-thienyl)-1,3-butanedione (Htta). The extracted metals were back-extracted into 1 mol dm−3 nitric acid quantitatively. Furthermore, the extracted species were estimated as neutral hydrated complexes M(tta)2(H2O)n (n= 1 or 2) for M = Ni, Cu and Pb and anionic complexes M(tta)3− for M = Mn, Co, Zn and Cd. 相似文献
87.
Quan Zheng 《European Polymer Journal》2006,42(4):807-814
Two dendritic reversible addition-fragmentation transfer (RAFT) agents with 8 and 16 terminal dithiobenzoate (DTB) groups on the surface of poly(propylene imine) (PPI) dendrimers (generation 2.0 and 3.0, respectively) were successively prepared, and they were used in the RAFT polymerization of N-isopropylacrylamide (NIPAAM). The polymerization kinetics was confirmed to pseudo-first-order behavior. The 1H NMR and GPC analyses show that the dendrimer-star den (NIPAAM)x (x = 8 or 16) prepared by RAFT method has well-defined structure, controlled molecular weight and low polydispersities (PDI < 1.3). The aqueous solution prepared from dendrimer-star PNIPAAM showed reversible changes in optical properties: transparent below a lower critical solution temperature (LCST) and opaque above the LCST. 相似文献
88.
89.
基于参考光栅的光纤光栅应变传感器温度补偿 总被引:6,自引:8,他引:6
为解决光纤布拉格光栅(FBG)应变测量时的应变、温度交叉敏感问题,利用FBG便于构成传感网络的优点,将温度补偿参考FBG与应变测量FBG串联在一路光纤上,根据2只FBG布拉格波长相对漂移获得被测结构应变。双FBG波长相对漂移对温度的灵敏度仅为0.12pm/℃,较好地实现FBG应变测量的温度补偿。参考FBG法原理简单,可操作性强,为FBG应变传感器的实际工程应用奠定了基础。 相似文献
90.