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991.
本文采用正交设计及方差分析法,确定了 SO_3磺化法合成 PNTS 新工艺的最佳工艺条件;并从技术及经济方面将新工艺同国内现有的生产老工艺进行了分析对比。 相似文献
992.
Two series of polypropylenes with different molecular weight distribution and tacticity characteristics were injection molded into flexural test specimens by varying cylinder temperature and the effects of the molecular weight distribution and tacticity on the structure and properties of the moldings were studied. Measured propertied were flexural modulus, flexural strength, heat distortion temperature, Izod impact strength, and mold shrinkage and structures studied were crystallinity, the thickness of skin layer, a*‐axis‐oriented component fraction and crystalline orientation functions. The relations between the structures and properties were also studied. It was found that the molecular weight distribution and tacticity characteristics affect the properties mainly through the molecular orientation and crystallinity, respectively. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 2142–2156, 2002 相似文献
993.
994.
The syntheses of polyenynes as model compounds for poly(diacetylene)s (PDAs) are described. Variation of properties (UV–VIS, Raman, NMR and bond geometries) as a function of the chain length was investigated. After extrapolation to infinite chain length these data were compared to those for PDAs. From UV–VIS spectra a value of λ = 551 nm (2.25 eV) was calculated corresponding to the electronic transition of a single polyenyne chain. This energy is located at the low energy end of a yellow PDA solution spectrum. From Raman scattering v(C?C) = 2108–2128 cm?1 and v(C?C) = 1505–1532 cm?1 were calculated after extrapolation. Similarly sp-C13C NMR data yielded a shift of δ = 100 ppm. These data are almost identical to data known for yellow PDA solutions. Bond geometries are almost identical to those of poly(diacetylene)s and theoretical data. 相似文献
995.
The large-deformation three-dimensional glass-rubber constitutive model for isotropic, amorphous, linear polymers near the glass transition, previously proposed, has been extended to include a spectrum of network relaxations. In addition, an experimental programme of uniaxial tension and compression tests was carried out on high molecular weight cast sheets of poly(methyl methacrylate) (PMMA), with varying strain-rate and temperature across the range from 114 to 190 °C, encompassing the thermoforming range of practical importance. The extended model was found to fit successfully the data for PMMA, provided a doublet network relaxation spectrum was employed. The original model, with only a single network relaxation, was found to be grossly inadequate when there was significant network relaxation by entanglement slippage. Parameters of the model for PMMA, obtained by fitting to the new data, were compared with values obtained by other routes. 相似文献
996.
Ionomeric composites based on sepiolite and hydrogenated poly(styrene butadiene) block copolymer were obtained and characterized from a microstructural and electrical point of view. Before blending, because of the high silanol group concentration in the sepiolite, the latter could be organophilized with suitable coupling agents. The resulting materials were easily processed into thin films or membranes 0.2–0.4 mm thick, their conductivity in some cases approaching 10?1 S/cm. Their suitability for film formation and good electrical properties indicate potential applications as electrolytes in polymer fuel cells. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 3512–3519, 2002 相似文献
997.
未来十年综合航电系统的发展趋向 总被引:4,自引:4,他引:0
本文主要阐述未来十年国外综合航电系统的总的发展趋向,重点介绍了在开放式系统结构的研究与应用、采用COTS技术、模块化、多传感器综合技术等方面的发展趋向。 相似文献
998.
SynthesisandSpectralPropertiesofMixedLigandComplexesofLanthanidePerchloratewithBis(phenylsulfinyl)ethaneandOrganicLewisBase... 相似文献
999.
空气中^131I的取样和测量方法的研究 总被引:5,自引:2,他引:3
本文介绍一种气态和气载~(131)I 取样器。着重介绍了一种指数分布源的效率刻度方法,讨论了与取样有关的一些问题。 相似文献
1000.
Novel hydrogen-bonded acidic fluorinated poly(amide-imide-silica) hybrid materials, FPAI-SiO2 (6E and 6F) series, were synthesized by a sol-gel process. The structures and spin relaxation of the hybrids were characterized by infrared (IR), and 29Si and 13C nuclear magnetic resonance (NMR) spectroscopy. The abundant Q4 structures implied that in free catalyst the degree of condensation of tetramethoxysilane was enhanced by hydrogen-bonded acidic fluorinated poly(amide-imide). The dynamics on the local mobility of the hybrids was investigated by the time constant for energy exchange between 1H and 29Si spin system (TSiH) and spin-diffusion path length (L) measurements. It was found that the faster TSiH of 6E and 6F hybrids compared with the previous study of similar 6C and 6D hybrids implied that 6E and 6F hybrids had more aggregated structures even though the organic terminal segment changed from rigid imide to more flexible amide. The interactions of the charge transfer between donor and acceptor molecules or π-π aromatic stacking may be the dominant factors to affect the structures of 6E and 6F hybrids. Moreover, M1 and D2 segments of 6F hybrids had the same level mobility and the mobility of the 6F hybrids was little improved as the soft and flexible 1,3-bis(3-aminopropyl)-tetramethyl-disiloxane segment was incorporated in the dense structures of 6F hybrids. All of the L values of 6E and 6F hybrids were on the scale of 3.5-4.0 nm. The result also suggested that 6E and 6F hybrids had similar denser structures as 6D hybrids. 相似文献