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141.
Physicochemical approach to the theory of foam drainage 总被引:1,自引:0,他引:1
We have investigated theoretically the effect of surface viscoelasticity on the drainage of an aqueous foam. Former theories
consider that the flow in Plateau borders is either Poiseuille flow or plug-flow. In the last case, the dissipation is attributed
to flow in the nodes connecting Plateau borders. Although we do not include this dissipation in our model, we obtain a drainage
equation that includes terms equivalent to those of the earlier models. We show that when the water solubility of the surfactant
stabilizing the foam is low, the control parameter M for the transition between the two regimes is the ratio , where μ is the bulk viscosity, D
s the surface diffusion coefficient, R the radius of curvature of the Plateau border and ɛ the surface elasticity. When the surfactant is more soluble M is rather related to the bulk diffusion coefficient. Within the frame of this approach and in view of the estimated M values, we show that the flow in Plateau borders is Poiseuille-like.
Received 26 June 2001 相似文献
142.
O. Almanza M. A. Rodríguez‐Prez J. A. De Saja 《Journal of Polymer Science.Polymer Physics》2004,42(7):1226-1234
The thermal conductivity at constant pressure of a collection of crosslinked, closed‐cell polyethylene foams were measured at room temperature with the transient plane source (TPS) method. The experimental results were compared with those determined by a standard steady‐state technique. The results showed that the values measured by the TPS method follow the same trends as those measured by a heat‐flow meter. Therefore, with the TPS technique it is possible to observe the influence of structural characteristics such as cell size, black carbon content in foams, density, and so forth on thermal conductivity. However, the values obtained by the transient method were approximately 20% higher than those given by the standard method. Possible reasons for these variations are discussed. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 1226–1234, 2004 相似文献
143.
Douglas M. Ackermann Jr. David N. Jewell Matthew L. Stedman Vorakan Burapatana Prabhani V. Atukorale Michelle L. Pinson Alison E. Wardle Wenyan Zhu Robert D. Tanner 《Applied biochemistry and biotechnology》2003,107(1-3):659-671
Protein foams can be used to extinguish fires. If foams are to be used to extinguish fires where people are present, such
as in high-rise buildings or ships, then a method for allowing people to breathe in a foam-filled environment is needed. It
is proposed that the air, used to create the foam be used for breathing. A canister that will break incoming air-filled foam
has been designed for attachment to a standard gas mask, in order to provide breathable air to a trapped person. Preliminary
results for the modified mask indicate feasibility of breathing air from air-filled protein foam. 相似文献
144.
TiH2颗粒可以作为多孔铝的发泡剂[1,2]. Al2O3包覆TiH2颗粒与未包覆的TiH2颗粒相比, 可以起到控制(延迟)其发泡的作用, 提高泡沫铝材料的孔隙均匀性. 然而, 目前采用的包覆方法是将细小Al2O3粉通过机械研磨包覆在TiH2表面[3].本文尝试采用化学法制备Al2O3/TiH2包覆颗粒, 并研究其包覆的效果. 用化学法制备Al2O3/TiH2包覆颗粒, 并用其作为多孔铝制备中的发泡剂, 此项研究在国内外尚未见报道. 相似文献
145.
Djalma Batista Dias Leonardo Gondim de Andrade e Silva 《Radiation Physics and Chemistry》2007,76(11-12):1696-1697
Cross-linking of low-density polyethylene by electron beam irradiation was studied in this work with the aim of foam production by thermal expansion. Mechanical and thermal properties of the obtained foams were studied and it was found that relatively low doses up to 40 kGy could be used leading to a product with excellent surface appearance. 相似文献
146.
BaoHuaLIU LiBanCHEN MinZHANG AiFangYU 《中国化学快报》2003,14(7):752-754
CO2-copolymer based polyurethane foams were synthesized and characterized in this paper. The foams were found to have higher strength and lower heat of combustion than the conventional polyether polyurethane foams. They may find wide applications in many fields. 相似文献
147.
Andrea Labouriau Dean Taylor Moshe Pasternak 《Polymer Degradation and Stability》2006,91(8):1896-1902
We have investigated hydrolysis and oxidation effects on tin octoate and on tin-octoate residues in RTV polysiloxane foams by means of Nuclear Magnetic Resonance (NMR) and Mössbauer spectroscopy (MS). 119Sn NMR showed the presence of various tin species whereas 119Sn MS detected the presence of two oxidation states: Sn(II) and Sn(IV). The relative abundance of Sn(IV) increased as both the tin octoate and the foam aged. Foams were also solvent extracted and no selective extraction of one tin oxidation state was observed; both oxidation states were detected. 13C NMR indicated that octanoic acid is present in the tin octoate and in the foams as a residue. MS data showed that aging treatments of the foams and of the neat catalyst have a great effect on the tin oxidation state. The two spectroscopic methods complement each other in following the effects of hydrolysis and oxidation. 相似文献
148.
Xinhong Song Yiying Chen Mingcong Rong Prof. Dr. Zhaoxiong Xie Tingting Zhao Prof. Yiru Wang Prof. Dr. Xi Chen Prof. Dr. Otto S. Wolfbeis 《Angewandte Chemie (International ed. in English)》2016,55(12):3936-3941
Surfaces with super‐amphiphilicity have attracted tremendous interest for fundamental and applied research owing to their special affinity to both oil and water. It is generally believed that 3D graphenes are monoliths with strongly hydrophobic surfaces. Herein, we demonstrate the preparation of a 3D super‐amphiphilic (that is, highly hydrophilic and oleophilic) graphene‐based assembly in a single‐step using phytic acid acting as both a gelator and as a dopant. The product shows both hydrophilic and oleophilic intelligence, and this overcomes the drawbacks of presently known hydrophobic 3D graphene assemblies. It can absorb water and oils alike. The utility of the new material was demonstrated by designing a heterogeneous catalytic system through incorporation of a zeolite into its amphiphilic 3D scaffold. The resulting bulk network was shown to enable efficient epoxidation of alkenes without prior addition of a co‐solvent or stirring. This catalyst also can be recovered and re‐used, thereby providing a clean catalytic process with simplified work‐up. 相似文献
149.
A. A. R. de Oliveira V. Ciminelli M. S. S. Dantas H. S. Mansur M. M. Pereira 《Journal of Sol-Gel Science and Technology》2008,47(3):335-346
Bioactive glass/polymer hybrids are promising materials for biomedical applications because they combine the bioactivity of
bioceramics with the flexibility of polymers. In previous work hybrid foams with 80% bioactive glass and 20% polyvinyl alcohol
were prepared by the sol–gel method. The produced hybrids presented a high acidic character due to the catalysts added. In
this work different methods to control the acidity and toxicity of the hybrids were also evaluated, through changes in the
synthesis pH and use of different neutralization solutions. The hybrids were prepared with inorganic phase composition of
70%SiO2–30%CaO and PVA fractions of 20–60% by the sol–gel method. The characterization of the obtained foams was done by FTIR, SEM,
Raman Spectroscopy, Helium Picnometry and TGA. The immersion of hybrids in a calcium acetate solution was the most adequate
neutralization method. The foams presented porosity of 60–85% and pore diameters of 100–500 μm with interconnected structure. 相似文献
150.
M.W. Blair R.E. Muenchausen A. Labouriau T.S. Stephens 《Polymer Degradation and Stability》2008,93(8):1585-1589
We have used electron paramagnetic resonance (EPR) and 57Fe Mössbauer spectroscopies to investigate potential aging mechanisms in filled RTV polysiloxane foams, diatomaceous earth, and their other constituents. Intense, broad EPR resonances in the RTV foams were recorded at room temperature as a function of microwave power. These signals were shown to come from the diatomaceous earth filler (Celite® 350) in the RTV foams. 57Fe Mössbauer measurements for neat Celite® 350 showed the presence of iron compounds in the form of lepidocrocite. Further EPR measurements showed that the intense, broad signals from Celite® 350 and the RTV foams were due to lepidocrocite that has been annealed to 175 °C and is in an excited state. EPR measurements of annealed samples of Celite® 350 also indicated that structural (chemisorbed) water is not easily released by the lepidocrocite. Therefore, the presence of intermediate forms of iron oxides in Celite® 350 and RTV foams indicates that water is not active in these materials. 相似文献