Some Reflections on Acid–Base Solid Surface Free Energy Theories

1997 ◽  
Vol 195 (1) ◽  
pp. 121-136 ◽  
Author(s):  
C.Della Volpe ◽  
S. Siboni
Keyword(s):  
Free Energy ◽  
Surface Free Energy ◽  
Solid Surface ◽  
Acid Base

Linear Stability of Thin Liquid Film on Solid Surface Under Effect of Apolar and Polar Forces

2012 ◽  
Author(s):  
El–Harbawi M. ◽  
Mustapha S. ◽  
Idris A. ◽  
Jameel A.T. ◽  
T.G. Chuah
Keyword(s):  
Thin Film ◽  
Growth Rate ◽  
Free Energy ◽  
Solid Surface ◽  
Unit Area ◽  
Excess Free Energy ◽  
Navier Stokes ◽  
Two Dimensional ◽  
Acid Base ◽  
Navier Stokes Equation

Tenaga lebihan bebas Gibb per unit luas (ΔG) bagi suatu saput nipis yang tulen, tanpa cas pada satu sokongan hanya diterbitkan daripada interaksi antara molekul apolar (Lifshitz - van der Waals) dan polar (acid-bes). Interaksi polar dapat dinyatakan secara berasingan sebagai tekanan penghidratan, interaksi hidrofobik dan intekrasi asid-bes. Jumlah tenaga lebihan bebas Gibb per unit luas (ΔG) bagi satu saput nipis pada satu lapisan bergantung kepada ketebalan saput, dan angkali penyebaran apolar dan polar untuk sistem tersebut. Saput dimodelkan sebagai cecair Newtonian 2-dimensi dengan ketumpatan tetap, ρ, dan kelikatan, μ, mengalir di atas satu permukaan mengufuk. Ketebalan purata saput cecair, h0, dianggapkan cukup nipis supaya kesan graviti boleh diabaikan dan melambung atas oleh gas pasif dan menyambung secara lateral hingga infiniti (Model dua-dimensi). Daya badan yang disebut dalam persamaan Navier-Stokes adalah diubahsuaikan oleh kandungan interaksi antara molekul lebihan (daya apolar dan polar) antara saput bendalir dan permukaan pepejal bergantung kepada daya-daya apolar dan polar. Persamaan Navier-Stokes telah diubahsuai dengan keadaan sempadan berkaitan diselesaikan bawah kaedah pendekatan gelombong panjang untuk memperolehi persamaan perkembangan tak-linear bagi saput antara permukaan. Daya apolar dan polar telah didapati memainkan peranan pencirian atas saput nipis dan kesan utama pada sifat tenaga lebihan bebas, kadar penubuhan, kadar penubuhan maksimum, gelombong neutral, nombor gelombang yang dominan, jarak gelombong dominan dan masa memecah. Oleh demikian, teori linear adalah kurang sesuai untuk menyatakan kestabilan pencirian selaput. Kata kunci: Daya apolar, daya polar, kestabilan linear, kadar pertumbuhan, masa memecah The total excess free energy per unit area (ΔG) of a pure, uncharged thin film on a support is solely derived from the apolar (Lifshitz - van der Waals) and polar (acid-base) intermolecular interactions. Polar interactions are variously described as the hydration pressure, hydrophobic interaction and acid base interaction. The total free excess energy (per unit area) of a thin film on a substrate depends on the film thickness, and the apolar and polar spreading coefficients for the system. The film is modelled as a two-dimensional Newtonian liquid of constant density, ρ and viscosity, μ, flowing on a horizontal plane. The liquid film of mean thickness, h0, is assumed to be thin enough to neglect the gravity effect and bounded above by a passive gas and laterally extends to infinity (two-dimensional model). The body force term in the Navier-Stokes equation is modified by the inclusion of excess intermolecular interactions (apolar and polar forces) between fluid film and the solid surface owing to apolar and polar forces. The modified Navier-Stokes equation with associated boundary conditions is solved under long wave approximation method to obtain a nonlinear equation of evolution of the film interface. The apolar and polar forces were found to play the dominant role in characteristic of thin films and the main effect on the behavior of the excess free energy, growth rate, maximum growth rate, neutral wave, dominant wavenumber, dominant wavelength and rupture time. Hence, the linear theory is inadequate to describe the stability characteristics of films. Key words: Apolar force, polar force, linear stability, growth rate, rupture time

Surface Free Energy Change of UV Exposed Composites and Coatings via Acid-Base Interactions

2011 ◽  
Author(s):  
R. Asmatulu ◽  
M. Ghaddar
Keyword(s):  
Free Energy ◽  
Service Life ◽  
Surface Energy ◽  
Surface Free Energy ◽  
Uv Light ◽  
Free Energy Change ◽  
Energy Change ◽  
Acid Base ◽  
Coating Materials ◽  
Base Interaction

Surface free energy of composite and coatings are critically important for the performance of the materials since the change in surface free energies can drastically affect the physical, chemical and physicochemical properties, and hence the service life of them. The characterization of the surface free energy is the key issue to understand the mechanisms of the surface degradation. Acid-base interaction is one way of determining the surface free energy change on these surfaces. In the present study, we exposed composite and coating surfaces to UV light, and then measured the contact angle values using various liquids (e.g., DI water, diiodomethane and glycerol). Using the van Oss approach, we calculated the surface energy changes of the surfaces exposed to the UV light. We found that the surface energy, acidity and basicity of the composite and coating materials were drastically changed as a function of UV exposure time. This study can be useful for the moisture uptake of composites, composite degradation, aging and service life of these products.

Effect of temperature on the surface free energy and acid–base properties of Gabapentin and Pregabalin drugs − a comparative study

RSC Advances ◽  
2015 ◽  
Vol 5 (60) ◽  
pp. 48712-48719 ◽  
Author(s):  
S. Ramanaiah ◽  
Vikram Karde ◽  
P. Venkateswarlu ◽  
Chinmay Ghoroi
Keyword(s):  
Free Energy ◽  
Surface Energy ◽  
Comparative Study ◽  
Surface Free Energy ◽  
Effect Of Temperature ◽  
Temperature Dependent ◽  
Acid Base ◽  
Base Properties

Temperature dependent surface energy variations observed in Gabapentin and Pregabalin drugs.

scholarly journals Some problems of characterization of a solid surface via the surface free energy changes

2017 ◽  
Vol 35 (7-8) ◽  
pp. 647-659 ◽  
Author(s):  
Emil Chibowski
Keyword(s):  
Contact Angle ◽  
Free Energy ◽  
Experimental Determination ◽  
Surface Free Energy ◽  
Solid Surface ◽  
Contact Angles ◽  
Absolute Value ◽  
Receding Contact

During the processes occurring at a solid surface, the changes in the surface free energy take place. The knowledge about surface free energy is very helpful for understanding the processes taking place on the surface. However, experimental determination of solid surface free energy is still not a fully solved problem. In this paper, some problems dealing with calculation of solid surface free energy from contact angle are discussed based on literature values of advancing and receding contact angles measured on four different fluoropolymers surface. The four approaches most often used for the calculation are described and especial focus on the approach in which both the advancing and receding contact angles is paid. It is concluded that using probing liquids the absolute value of solid surface free energy cannot be determined. However, the determined apparent values of the energy are very helpful to understand the conditions necessary for a given process to occur.

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