In aqueous systems, partially hydrophobic particles are known to stabilize foams even in the absence of any added surfactant. This paper shows that the same principle can be applied to polymeric systems: particles that are partially wetted by a polymer melt can stabilize a foam of that polymer. The foam stability is attributable to the adsorption of the particles at the air/polymer interface. Remarkably, stable foams are realized even from polymers that are liquid at room temperature, and hence are otherwise unfoamable. The implications of this result to practical foaming operations are discussed.
The influence of oxygen plasma treatment on surface properties of poly(p-phenylene benzobisoxazole) (PBO) fibers and aging effect of the oxygen plasma modified PBO fiber surfaces were investigated by X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM) and dynamic contact angle analysis (DCAA), respectively. The results indicated that the oxygen plasma treatment introduced some polar groups to PBO fiber surfaces, enhanced surface roughness and changed surface morphologies of PBO fibers by plasma etching and oxidative reactions. Surface wettability of PBO fibers may be significantly improved by increasing surface free energy of the fibers via oxygen plasma treatment. Aging effect of the oxygen plasma treated PBO fibers showed that the fiber surface wettability degraded in the first several days after the plasma treatment, and it was found to be changeless as the aging time continued as long as 30 days. 相似文献
The photo-induced change in wettability of hydrophobized TiO2 films has been investigated for steel coated with acidic TiO2 nanosols containing varying concentrations of dispersed nanocrystalline titania, such as Degussa P25. The photo-induced change in wettability was evaluated by measuring the time-dependent drop of water contact angle (WCA) after samples had been soaked in either n-octyltriethoxysilane (OTS) or decanoic acid (DA). TiO2 films treated in this way exhibit superhydrophobic behaviour, with WCA greater than 160°. After radiation with UV (black light), the superhydrophobic properties are transformed into superhydrophilic properties, with WCA of almost 0°. As P25 content and layer thickness increase, high rates of photo-induced change are found, but a moderate calcination regime is required. On the other hand, hardness and E modulus pass through a maximum at 25 wt% P25, so that a P25 content between 25 and 50 wt% is the optimum for practical uses. With such stable coatings, wettability can be controlled over a wide range, and the switch between hydrophobic and hydrophilic states can be carried out repeatedly when DA is used as the hydrophobizing agent. Use of a low calcination temperature (450 °C) for the intermediate annealing of the single layers in multilayer coatings and a short final sintering step at a relatively high temperature (e.g. 630 °C for 10 min) allow the preparation of relatively thin TiO2 films on steel with a high photoactivity. 相似文献
Bio-template method has recently attracted much attention because of its prominent advantages in obtai-ning morphology controlled materials with structural specificity, complexity and their unique functions. The bio-template method combining with electrochemical deposition was employed to synthesize spirulina/hematite composite microstructures using native spirulina as template. A great amount of hematite(α-Fe2O3) nanoparticles can be formed and deposited onto the spirulina, resulting in a robust and pseudo-homogeneous surface. And the spirulina/α-Fe2O3 composite exhibits an improved surface wettability due to its helical morphology. This facile strategy may open new horizons in the field of replicating specific biological structures for functional materials in other potential applications. 相似文献
Crystallization process of molten Ba(B0.9Al0.1)2O4 from supercooled pendant drop was investigated on a viewpoint of a supercooling and a solid phase formation. Molten pendant drop was crystallized by a rod touching at an crystallization temperature under an adequate degree of supercooling. Three kinds of rods were used. Each rod was made of Pt, hBN and graphite which had different wettability to the molten drop. There were three kinds of phases on a solid Ba(B0.9Al0.1)2O4, such as a high temperature crystal phase, a low temperature crystal phase and a glass phase. All phases could be formed by the present method. 相似文献