Surface energy contact angle

The fundamentals upon which most of these operations are based are surface phenomena. Surfaces are attracted to each other by van der Waals forces surfaces are repelled by the electrochemical double layer or by steric hindrance. Surface energies, contact angles, and wetting are important. 

Application of the PS-PDMS coating onto the PS base polymer was carried out by solution-blending base PS with small amounts of PS-PDMS products in THE Solutions were cast onto glass slides for surface energy (contact angle) measurements. These measurements were done in order to calculate surface free energy quantities, based on various model equations (Cai, 1997). Static contact angles were obtained from video capture methods with the aid of software for pixel-based calculations. Results of these measurements have been qualitatively consistent, and typically shown in Fig. 4.6.4. 

Table 1 provides an overview of a small sampling of liquids of the relevant properties for a few common optofluidic liquids. Note that this represents a non-comprehensive list, other parameters of particular interest include fluid-fluid surface tension, fluid-solid surface energy, contact angle, fluid-solid electroosmotic mobility, compatibility with soft elastomers (or other materials of interest), and numerous others. 

Keywords fibre, surface, organosilane, titanate, zirconate, chrome complex, surface energy, contact angle, interface, mechanical properties, adhesion, maleic anhydride. 

In 2002 year, Li and Zhu reported a new model for simulation of coupled heat and moisture transfer processes, considering the capillary liquid diffusion process in textile [15], which developed the liquid diffusion coefficient as a function of fiber surface energy, contact angle, and fabric pore size distribution. Based on this new model, Wang et al. [16] considered more the radiative heat transfer and moisture sorption and condensation in the porous textile, achieving more accurate simulation for the reaUstic situation. The governing equations of the model are shown as follows ... 

Keywords Solid surface tension Solid surface energy Contact angle Work of adhesion Zisman method Surface tension component mefliod Fowkes method Owais-Wendt-Rabel-Kaelble mefliod Extended Fowkes mefliod Equation of state... 

When the solid substrate is a nonpolar, low-energy surface, the contact angle can be used to determine the surface (excess) concentration of the surfactant at the solid-liquid interface rS . 

Aqueous solutions of certain trisiloxane surfactants wet rapidly low-energy surfaces (water contact angle > 90°) [1]. The spreading rate of a superspreader solution significantly exceeds that expected for a purely liquid diffusion controlled process [2, 3]. 

In summary, this chapter presents the basic thermodynamic principles and the work of adhesion that quantitatively characterize surfaces of materials. Laboratory techniques for surface characterization have been described, which allow an understanding of the chemical and physical properties of material surfaces. Empirical equations have been described for calculating surface tension (energy) of solid polymeric surfaces using contact angle and other parameters. 

Superhydrophobic surfaces (water contact angles higher than 150°) can only be achieved by a combination of hydrophobicity (low surface energy materials) with appropriate surface texture. In nature one can find an array of impressive and elegant examples of superhydrophobic surfaces. For example, on a lotus leaf rain drops bounce off after impact, then entirely roil off the lotus leaf and drag along any dirt particles, without leaving residues. 

In coating, the coating fluid should spread out on the support. For this to occur the surface tension of the fluid should be low and the surface energy of the support should be high. The contact angle in a drop of fluid on the surface, between the surface of the support and the surface of the fluid measured through the fluid, is a measure of the ability of the fluid to wet the surface. This contact angle should be low. 

The poly(MPC) brush gave a quite wettable surface. The contact angle of the water droplet (2.0 pL) on poly(MPC) brush surface was very low (below 5°). The contact angles of methylene iodide and hexadecane were 45° and <5°, respectively. Using the Owens-Wendt equation [49], the surface free energy of the poly(MPC) brush surface was estimated to be 73 mJ/m, which is quite similar to that of water. Therefore, water plays the role of a good solvent, resulting in low friction of the poly(MPC) brush. Ho et al. [50] prepared a low-friction surface on polyurethane... 

FIGURE 4.58 Orientations of oblong particle with aspectratio 1.4 at air-water surface with contact angle 0 = 70° by surface energy minimization using Surface Evolver software (with... 

So in the present paper, I have attempted to juxtapose the various surface - chemical criteria — thermodynamic work of adhesion, interfacial free energy, contact angle, spreading coefficient, penetration and solubility compatibility — and have expressed the conditions which optimize these criteria. In the determination of these conditions, the values of Tgv sl " Iv required. 

From Tables 2 and 3, an epoxide adhesive (surface tension 45 dynes/cm) would not be expected to wet and effectively bond a low energy surface such as polyethylene (critical surface tension 31 dynes/cm). When the polyethylene surface was etched for increasing times in a sulfuric acid-dichromate solution, bond strengths markedly increased and the surface s contact angle with water (increasing polarity) similarly decreased (Fig. 4). ... 

A modification to the nudeation barrier to accoimt for heterogeneous nudeation developed by Volmer simply multiplies the energy barrier in Equation 11.15 hy f 6), the ratio of the volume of a spherical cap sitting a surface with contact angle 9 as shown in Figure 11.10, to the volume of a sphere with the same radius. 

While a well-defined equilibrium situation allows a clear characterization of fleq. the displacement of the contact line (which evidently implies a velocity of displacement) requires a deviation from this value, resulting in a dynamic contact angle (see O Fig. 5.4). In fact, whenever on ideal surfaces the contact angle deviates from 0eq (which represents the absolute minimum in free energy of the system) the contact line will show the tendency to move in order to try to reestablish equilibrium. In general, the stronger deviates from ( eq> the faster will be the movement of the contact line (see Fig. 5.5). Thus, for fldyn 0eq> instead of a perfect balance of interfacial tensions at equilibrium, a net force F (per unit length of the contact hne) remains ... 

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