Axisymmetric drop shape analysis profile

Contact Angle Measurements. Axisymmetric drop shape analysis - profile (ADSA-P) The hydrophobicity/ hydrophilicity of a solid surface is usually expressed in terms of wettability, which can be quantified by contact angle measurements. ADSA-P is a technique to determine liquid-fluid interfacial tensions and contact angles... 

For even better results, drop profile analysis can be applied instead of measuring the contact angle directly (axisymmetric drop shape analysis, ASDA Fig. 4.20). This technique extracts experimental drop profiles from video images while slowly increasing or decreasing the droplet volume [42, 43]. The best fit of experimental data with theoretical assumptions based on the Laplace equation of capillarity allows one to calculate the surface/inter-facial tension and subsequently the contact angle. Also droplet radius, droplet volume, and the contact area are computed. ADSA can therefore reveal... 

Cheng, P. and Neuman, A. W., Computational evaluation of axisymmetric drop shape analysis-profile (ADSA-P), Colloids Surf., 62, 297-305 (1992). 

Axisymmetric Drop Shape Analysis-Profile The technique of Axisymmetric Drop Shape Analysis-Profile (ADSA-P), as practiced by the present authors, is a powerful method for determining contact angles and liquid-fluid interfacial tensions from the profile of liquid drops. Besides these two parameters, the drop volume and the drop surface area, as well as the drop radius, all with their corresponding 95% confidence limits, or other statistical information are also output. 

Axisymmetric Drop Shape Analysis-Diameter As discussed earlier, a drop shape method, such as ADSA-P, utilizes the meridian profile of a sessile drop to calculate the contact angle and the interfacial tension. Despite its versatility, this technique does suffer from some limitations. In cases of very low contact angles (less than 20°), it may be difficult to measure contact angles accurately by using profile techniques, e.g. ADSA-P. In order to avoid this difficulty, an alternate method called ADSA-(C)D (contact diameter) has been developed by utilizing the drop contact diameter (see Figure 14.6(b)... 

It is usually called axisymmetric drop shape analysis.The interfacial tension and contact angles are determined from the shape of the axisymmetric menisci of both sessile and pendant drops. The employed strategy is to fit the shape of an experimental drop to the theoretical drop profile according to the Laplace equation, using surface tension as adjustable parameter. Details of the methodology together with a program to implement it can be found elsewhere. ... 

The surface tension of polystyrene in supercritical carbon dioxide is determined experimentally by Axisymmetric Drop Shape Analysis-Profile (ADSA-PX where a high pressure and temperature cell is designed and constructed to facilitate the formation of a pendant drop of polystyrene melt. As pressures and temperatures increase, the surface tension of polystyrene decreases. A linear relationship is found between surface tension and temperature, and between surface tension and pressure. The slope of surface tension change with temperature is dependent on pressure. 

The technique of Axisymmetric Drop Shape Analysis-Profile ADSA-P) [10,11] was used for image analysis and experimental parameters. Surface or interfacial tensions were obtained by fitting the Laplace equation of capillarity from the shape and dimensions of the acquired axisymmetric menisci [12]. The value of surface tension was generated as a fitting parameter after a least square algorithm was employed to minimize the difference between experimental drop profiles and theoretical ones [13]. During this procedure, the density difference between polystyrene and carbon dioxide was an input parameter [14, 15, 16], which was determined by the Sanchez and Lacombe (S-L) equation of state (EOS). 

Surface tensions of poljuneric fluids or melts may be measured by a variety of direct techniques, with those based upon analysis of the shape of axisymmetric fluid drop profiles (3,72) the most versatile and popular. Discussions of the relative advantages and disadvantages of each technique are presented in Reference 3. Several drop geometries are possible as shown in Figure 18. The shape of these drops is governed by the Bashforth-Adams equation... 

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