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991.
This paper shows the wide application range (such as electrical self‐heating and electromagnetic shielding effectiveness) of composites consisting of conductive carbon black/aluminum flakes (CBA) filler and epoxy insulative matrix. The effect of CBA content on the network structure of epoxy matrix was investigated in detail. Static electrical conductivity increases linearly with the increase of filler concentration at the interface in epoxy composites. The large decrease of the conductivity as a function of the temperature is analyzed in terms of the negative temperature coefficient of conductivity (NTCC) effect. The influence of viscosity, surface energy and barrier highest energy on the NTCC behaviour in the composite is also considered. Based on these results, a new interpretation is proposed to explain the NTCC phenomena by computing the swelling force among conductive phases. The correlations of conductivity during the temperature cycling and activation energy were analyzed. The effects of dynamic ageing at various temperatures on the resistivity are reported. Current–voltage–temperature characteristics for epoxy with different contents of CBA were examined in detail. A model based on the law of energy conservation is proposed to calculate the specific heat and amount of heat dissipation. The static charge of the epoxy–CBA composites was estimated. The correlation between electromagnetic wave‐shielding effectiveness (EMS), conductivity and frequency of epoxy composites with different filler contents is also discussed. Furthermore, the effect of annealing on EMS of epoxy composites was examined. © 2002 Society of Chemical Industry 相似文献
992.
湿法磷酸生产中,均以水为介质冲洗倾覆盘式真空过滤机的滤盘,为实现系统的污水零排放,提高倾覆盘式真空过滤机的生产能力,提出以回磷酸和硫酸配制成混酸去冲洗滤盘的方法。分析了采用该方法的诸多优点及注意事项,指出安全生产问题须认真落实。 相似文献
993.
Blending a crosslinked high‐density polyethylene (xHDPE) enhances melt strength and strain hardening behavior in elongational viscosity of high‐density polyethylene (HDPE) to a great degree. Gel fraction of xHDPE has a stronger effect on the strain hardening than sol fraction, although sol fraction also enhances the strain hardening to some degree. Further, the xHDPE crosslinked by peroxide in a compression mold exhibits more pronounced effect than xHDPE by radiation, which is attributed to the difference in the amount of the gel fraction. The xHDPE, which enhances the strain hardening, has sparse crosslink points in the network. Moreover, it was found from linear viscoelastic measurements, such as oscillatory modulus and relaxation modulus, that the xHDPE is characterized as a critical gel, which was also supported by the result of tensile testing. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 73–78, 2002 相似文献
994.
Jui‐Ming Yeh Chi‐Lun Chen Yen‐Chen Chen Chin‐Yi Ma Hsi‐Ya Huang Yuan‐Hsiang Yu 《应用聚合物科学杂志》2004,92(1):631-637
A series of polymer–clay nanocomposite (PCN) materials containing polysulfone (PSF) and layered MMT clay were successfully prepared by effectively dispersing inorganic nanolayers of MMT clay in an organic PSF matrix via a solution dispersion technique. The synthesized PCN materials were subsequently investigated with a series of characterization techniques, including Fourier transform infrared (FTIR) spectroscopy, wide‐angle powder X‐ray diffraction (XRD) and transmission electron microscopy (TEM). The prepared PCN coatings with low clay loading (1 wt %) on cold‐rolled steel (CRS) were found to be superior in corrosion prevention to those of bulk PSF, based on a series of electrochemical measurements of corrosion potential, polarization resistance, corrosion current and electrochemical impedance spectroscopy (EIS) in a 5 wt % aqueous NaCl electrolyte. The effects of material composition on the molecular barrier, mechanical strength and optical clarity of PSF and PCN materials, in the form of membranes, was also studied by molecular permeability analysis (GPA), dynamic mechanical analysis (DMA) and UV‐Visible transmission spectra, respectively. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 631–637, 2004 相似文献
995.
Polyamide/epoxysilane (coupling agent) composites were reacted with poly(dimethylsiloxane) (PDMS), a condensation product of diethoxydimethylsilane (DEDMS), by a sol–gel process. Polyamide–PDMS nanocomposites were obtained. The existence of the condensation product of DEDMS and the reaction between the epoxy group and the polyamide were confirmed with Fourier transform infrared, attenuated total reflection, and wide‐scanning X‐ray photoelectron spectroscopy. Atomic force microscopy and contact‐angle measurements showed that the surface properties of polyamide were greatly improved by the addition of PDMS. The pyrolysis temperature of polyamide with PDMS was approximately 400°C, and the pyrolysis temperature was similar to that of pure polyamide. Also, the char contents increased with the addition of PDMS. The glass‐transition temperature of polyamide with or without PDMS was approximately 140°C according to differential scanning calorimetry. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 1947–1955, 2004 相似文献
996.
997.
介绍了BA/Py,BA/Ph和PHBA三种具有三芳基甲烷结构B阶树脂的合成方法及分子链的单元结构形式。对用紫外光和激光照射法进行脱氢反应的实验条件及脱氢化后树脂的磁性能(磁滞现象,矫顽力和磁化强度)进行考查。 相似文献
998.
The gel effect will bring a violent increase of conversion for methyl methacrylate (MMA) polymerization in a short time. It will be very dangerous for the reactor, as it causes an increase of molecular weight and broadens the molecular weight distribution. To unify the kinetics, molecular weight, and its distribution, on the basis of the mathematical models for semibatch polymerization of MMA, three controlled objectives that are the heat load distribution index, the change in molecular weight, and molecular weight distribution index are presented. Three materials (monomer, solvent, and chain transfer agent) and their flow rate and feeding mode are analyzed for the open control of kinetics, molecular weight, and its distribution. The optimum flow rate and mode are obtained. The heat load distribution index and molecular weight distribution index are even less than 2.0 and 2.2, respectively. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 4399–4405, 2006 相似文献
999.
Chu‐Ping C. Vijverberg 《时间序列分析杂志》2006,27(6):811-829
Abstract. A continuous Euler model has time‐varying coefficients. Through a logarithmic time transformation, a continuous Euler model can be transformed to a continuous autoregressive (AR) model. By using the continuous Kalman filtering through the Laplace method, this article explores the data application of a continuous Euler process. This time deformation of an Euler process deforms specific time‐variant (non‐stationary) behaviour to time‐invariant (stationary) data on the deformed time scale. With these time‐invariant data on the transformed time scale, one may use traditional tools to conduct parameter estimation and forecasts. The obtained results can then be transformed back to the original time scale. Simulated data and actual data such as bat echolocation and the US residential investment growth are used to demonstrate the usefulness of time deformation in forecasting. The results indicate that fitting a traditional autoregressive moving‐average (ARMA) model on an Euler data set without imposing time transformation leads to forecasts that are out of phase while the forecasts of an Euler model stay mostly in phase. 相似文献
1000.