Papers by Keyword: Contact Angle (CA)

Abstract: Research on polymers has grown exponentially in the purpose of oil spill removal from the water surface. It is very important to take immediate action to remove the oil from the water surface to reduce worldwide oil pollution. Materials with high porosity and mostly, superhydrophobic and oleophilic natures are the best candidates for this purpose. In this research, the electrospinning method was used to synthesize the polystyrene (PS), polysulfone (PSF), and polyvinylidene fluoride (PVDF) for the application of oil-spill removal. Different concentrations were used to produce electrospun fiber using N, N-Dimethylformamide (DMF). Contact angle (CA) measurement was applied to justify the hydrophobicity of all the polymers. Based on the CA results, only one sample, 24%concentrations of polystyrene (PS-5) showed the highest water contact angle (WCA) and the value was above 150°. This means PS-5 is superhydrophobic. ASTM F726-12 standard and low viscous motor oil were used for the oil sorption test. Moreover, the oil sorption results were compared within all the polymers to identify the best polymer, and solvent concentration that can absorb oil the most. The highest oil absorption efficiency is 20.99g/g using 24% concentrations of PS (PS-5) electrospun fiber.

Abstract: Membrane distillation (MD) is a thermally driven membrane separation process. In recent years, MD is considered as a key technology for desalination applications. It has been proven that it has numerous advantages compared to other desalination processes such as reverse osmosis. The thermal driving force, no osmotic pressure effect on membrane fluxes are among the advantages of this MD process. Membranes fabricated from hydrophobic polymers such as polyvinylidene fluoride (PVDF) can be a great choice for MD for the desalination process. However, MD membranes are still held back by some problems, most notably due to pore wetting effects, thereby limiting their use in treating seawater for desalination propose. This study proposes the use of carboxylic acid to modify the PVDF membrane to increase its hydrophobicity as a solution to avoid wetting in MD for water desalination. As a first step, membrane produced using PVDF pellets under the phase inversion method. Then the membrane underwent modification using 5wt%, 10wt% and 15wt% of formic acid via immersion technique. The characteristics of membrane produced observed by the contact angle, Fourier-transform infrared spectroscopy (FTIR) and membrane performance test. The impact of the concentration of formic acid solution and feed temperature on the membrane was evaluated. The result showed that by modifying the membrane with formic acid resulted in the increase in contact angle from unmodified PVDF membrane, 83.03° to 100.88° when the membrane modified with formic acid with concentration was 10 wt%. It was subsequently shown through FTIR peaks that formic acid successfully modified the PVDF membranes. Highest salt rejection percentage was also obtained with 68.9% when the feed temperature is 60 °C.

Abstract: The Super-hydrophobic surface can be obtained easily by pollution accumulation on room temperature vulcanized (RTV) silicone rubber coating surface. The photos taken by digital camera show that the amount of pollution on the RTV coating surface was increased with time, and after one year, the RTV coating surface nearly could hardly be seen. The water state contact angle (CA) measurement, which was investigated by the static contact angle instrument, reveals that the CA value of RTV coating surface is increased with increasing the pollution accumulation, and in suitable amount of pollution accumulation, the super-hydrophobic surface (water contact angle of 152^o and roll-off angle smaller than 5 ^o) was obtained. The scanning electric microscope (SEM) of RTV coating with different pollution accumulation was investigated. It shows that the continuous micro-nanobinary structure can be formed with enough dust particles on the RTV surface. The mechanism of the effect of pollution accumulation on the wetting property was analyzed, the migration of hydrophobic molecular in RTV coating onto the pollution surface and the formation of micro-nanobinary structure on the RTV coating surface have synergistic effect on the super-hydrophobic surface formation caused by the pollution accumulation.

Abstract: We study the preparation of thin film on the glass substrate with the method of dip coating, which is based on methanol and MTMS as raw materials, making them form silica aerogel by sol-gel method. Scanning electron micrographs (SEM) show that such a film possesses a porous three-dimensional network structure. The high porosity and low refractive index determine that the transmittance rate can reach 90%. The prepared film also exhibited apparent hydrophobic effect, with the contact angle of 156.3°and rolling angle of less than 10°. The transparency and superhydrophobic of the film make it suitable as multifunctional coatings for many application fields including solar cells, cellphones and a variety of electron device.

Abstract: At the present time bonding has spread into almost all sectors of practice and it would be very difficult to find an industry in which there is no need to use this technology of joining a wide range of materials. In comparison with conventional joining methods (riveting, welding and screwing) provides bonding new combination of options and allows obtaining special shapes and properties which cannot be created by conventional methods of coupling. For the formation of quality bonded joint it is important that the adhesive bonding surface is well wetting. Wettability is characterized by the contact angle of wetting. The liquid must have a lower surface tension than the solid in order to be able to wetting the solid substance. This article describes the effect of beta irradiation on the contact angle of wetting, on the surface energy and on the final strength of bonded joints of HDPE.

Abstract: The surface free energy of the asphalt was determined using the Owen-Wendt method by determining the contact angles between asphalt and different probe liquids. The effect of rock asphalt on the surface free energy of asphalt was measured. The results indicate that the rock asphalt increase the surface free energy of asphalt, which enhances the moisture damage resistance of asphalt.

Abstract: The purpose of this study is to measure contact angle and surface tension of liquid Fe-Si-B alloys at high temperature using sessile drop method. The surface tension and contact angle result is based on sessile drop method by use of a digital camera to take the drop profile and fit the profile by Youngs-Laplace equation. The surface tension of liquid Fe-Si-B alloy and its dependence on temperature has been studied. Contact angles of this liquid alloy on various refractories substrate have been determined using this instrument. The result showed that the contact angles and surface tension of Fe-4Si-3B alloy liquid drop on Al₂O₃ substrate have value of 134 to 127and 1575-1350 mN/m respectively. The result indicated also that increasing temperature can decrease contact angle and surface tension in Fe-Si-B alloy.

Abstract: Flax fibres surface were treated by different treatment in order to enhance the interfacial bonding force between flax natural fibres and vinyl resin matrix. The experiment of contact angle and mechanical property were done to characterize the surface topography and bonding force and choose the best modification. What’s more, the morphology behaviour of the flax fibre surface were charact- erized using SEM.

Abstract: The micro/nanocomposite structure on silicon surface was formed by a simple 2-step chemical etching with a potassium hydroxide anisotropic etching and a stain etching in order to obtain a superhydrophobic silicon surface. Micro-sized pyramids structure was formed in a mixture of 3 wt.% potassium hydroxide with 8 vol.% isopropyl alcohol solution at 80C for 60 min. The formation of the nanosized structure was performed by stain etching at room temperature using nitric acid (HNO₃) / hydrofluoric acid (HF) aqueous solutions. The silicon surface had the superhydrophobic surface. The contact angle was measured and the maximum value was 167^o for the condition of second etching with HF : HNO₃ : H₂O = 11 : 1 : 3.

Abstract: This study investigates the use of nanoscale bilayers assembly film for hydrophilic modification on stainless steel plate and observed its effect on the plates evaporation behavior in acetone. This study first establishes the technique of nanoscale bilayers assembly, then performs surface hydrophilic modification on stainless steel plate by changing the surface structure, which produces different contact angles. The relationship between layers (0, 5, 10, 15 bilayers) of surface modified and the contact angle is empirically determined, and results show that, similar to findings stated in the literature [, after surface modification the contact angle decreases from 70° (layer 0) to 24° (layers 15); in addition, the results from this study have demonstrated a certain level of technical capability. This study was investigated the evaporation test in a modified surface , also is the first time reported in previous literature. Evaporation tests show that under the best contact angle evaporation rate can be increased by 50%, indicating the high potential of surface hydrophilic modification on stainless steel plate for improving evaporation behavior.