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Coal Dust
Published in S. Komar Kawatra, Advanced Coal Preparation and Beyond, 2020
The contact angle is a measure of the resultant interfacial tensions between the liquid droplet, the solid surface, and the air. The contact angle tends to be large if the surfaces are dissimilar, while the contact angle is small if liquid completely wets the surface. Chemical additives which improve wetting characteristics tend to alter the balance of these forces to encourage wetting of the surface. There are two primary methods for measuring contact angles. The first method is the sessile drop method in which a liquid droplet is placed on the solid surface. The second technique is known as the captive bubble method in which a vapor bubble is attached to a submerged solid surface. In each test method, the lower the contact angle is, the more hydrophilic the solid surface behaves. In general, if the measured contact angle is less than 90°, the solid behaves as a hydrophilic surface. The two primary contact angle measurement methods are demonstrated in Figure 18.1.
Formation damage remediation with novel blend of anionic-cationic surfactants in high temperature and low permeability sandstone reservoirs
Published in Petroleum Science and Technology, 2023
Yingcheng Li, Q. Li, W. Zhang, J. Jin, X. Bao, Y. Meng, X. Zhang, X. Wu, L. Zhang, R. Guo, X. He, Z. Shen, L. Cui, O. Sha
The wettability of the cores was evaluated by the contact angle measurements with Krüss DSA100 by the captive bubble method. A clean reservoir core was firstly cut into slices with 3 mm thickness and polished to minimize measurement errors. These slices were assembled in a core holder, evacuated, and saturated with formation brine, consequently displaced by force with crude oil. The plugs were aged inside the holder at reservoir temperature for 7 days to obtain the oil-saturated slice samples. Slices from disassembled holder were individually immersed in brine and surfactant solution, respectively. The crude oil was dispensed under the slices using a crooked capillary needle. The oil drops attached to the slices slowly and formed an angle, which would be measured by the enhanced video-image digitalization technique.
Studies of polypropylene surface modified with novel beta-thiopropionate-based zwitterionic polymeric brush: synthesis, surface characterization, and significantly reduced fouling characteristics evaluation
Published in Journal of Biomaterials Science, Polymer Edition, 2020
Chia-Sheng Hung, Kun-Ting Hsieh, Chi-Hui Cheng, Jui-Che Lin
The decreased water contact angle of PP-OH could be mainly attributed to the hydroxyl groups formed after the oxygen plasma treatment. Since the BIBB initiator is fairly hydrophobic, the PP-Br would become hydrophobic as compared to the PP-OH, either by sessile drop or captive bubble method. After surface-initiated grafting of the zwitterionic polyDPAMA onto the PP surface, the PP-DPAMA became hydrophilic, either determining in the air or under the water. This is likely due to the hydrophilic nature of the zwitterionic material having a strong affinity towards water molecules and, even forming a hydration layer after immersed within the water. Such hydrophilic characteristics are more pronounced when contact angle was determined within the water, in which the contact angle value is statistically much less than the other hydrophilic PP-OH (47 ± 2 vs. 38 ± 2; p < 0.05). On the other hand, the hydrophilic nature of the zwitterionic PP-DPAMA is statistically similar to the oxygen plasma-treated PP (PP-OH) when determined in the air (49 ± 7 vs. 53 ± 3; p = 0.2).
Studies of zwitterionic sulfobetaine functionalized polypropylene surface with or without polyethylene glycol spacer: surface characterization, antibacterial adhesion, and platelet compatibility evaluation
Published in Journal of Biomaterials Science, Polymer Edition, 2020
Chi-Hui Cheng, Guan-Fu Chen, Jui-Che Lin
The surface hydrophilicity of these surface-modified PP substrates was determined by the captive bubble method, in which an air bubble was placed onto the substrate that was immersed within the water. Instead of using the sessile drop method commonly reported in the literature, the use of the captive bubble method in determining the surface hydrophilicity is aiming to simulate the clinical condition, in which the biomaterials were placed within the aqueous physiological milieu. The measurement was performed on at least 5 different spots for each sample.