Interfacial acid-base properties

In this chapter, the relationship of geological origins and interfacial properties of bentonite clay will be reviewed first. Then we will discuss the migration of water-soluble substances in rocks and soil, and the effect of sorption on the migration. A linear model will be derived by which the quantity of ion sorbed on rocks can be estimated when the mineral composition and sorption parameters of the mineral components are known. Surface acid-base properties of soils will be discussed, and the sorption of an anion (cyanide ion) will be shown on different soils and sediments. 

Bentonite rocks have many uses in the chemical and oil industries and also in agriculture and environmental protection. The usefulness of bentonite for each of these applications is based on its interfacial properties. These properties are determined by geological origin, chemical and mineral composition (especially montmorillonite content), and particle size distribution, and they include the specific surface area (internal and external), cation-exchange capacity (CEC), acid-base properties of the edge sites, viscosity, swelling, water permeability, adsorption of different substances, and migration rate of soluble substances in bentonite clay. 

This equation was used to estimate the interfacial adhesion in comparison with the acid-base properties of glass fibers in LDPE. The effect of surface treatment of glass beads on their interfacial adhesion to PET was also estimated from a mechanical property measurement. A mathematical model describing the adsorption of polymers on filler surfaces related coupling density to the average area available for coupling between rubber and filler surface. ... 

For example, little is known about acid-base interactions at solid/solid interfaces. It has long been recognized that molecular interactions across the interface between condensed phases may be split into physical and chemical terms. Physical interactions (vander Waals forces) contribute to the non-ideality of fluids and have been traditionally considered for interfaces. However, modern theories explain interfacial phenomena on solid surfaces, such as adhesion or wetting, in terms of chemical interactions. Moreover, the Lewis definition of acidity is so comprehensive that it can easily be accepted that most chemical interactions at solid surfaces may be effectively described as acid-base interactions [15]. continuously growing literature reinterprets interactions at solid/solid interfaces in terms of acid-base properties. For example, their role was shown in relation to solid/solid adhesion in film-substrate or fber-matrix systems as well as in wood and paper processing,... 

IGC as a tool to characterize dispersive and acid-base properties of the surface of fibers and powders, in Interfacial Phenomena in Chromatography (ed. E. Pefferkom), Marcel Dekker, New York, pp. 41-124. 

F.M. Fowkes, Quantitative characterization of the acid-base properties of solvents, polymers, and inorganic surfaces, in Acid-Base Interactions—Relevance to Adhesion Science and Technology ed. by K.L. Mittal, H.R.J. Anderson (VSP, Utrecht, 1991), pp. 93-115 M.K. Chaudhury, Interfacial interaction between low-energy surfaces. Mater. Sci. Eng. R Rep. 16(3), 97-159 (1996). doi 10.1016/0927-796X(95)00185-9... 

Adsorption of third particles other than water molecules on metal electrodes influences the microstructure and the electrochemical activity of the electrode interface. For example, the interface of metal electrodes usually acts as a Lewis add in the adsorption of water molecules, but its Lewis add-base property is altered by the adsorption of third partides. Electronegative particles such as oi en molecules, if adsorbed, increase the local Lewis acidity of interfacial metal atoms around the adsorption sites whereas, electropositive particles such as sodium atoms, if adsorbed, increase the local Lewis basicity around their adsorption sites. Furthermore, the adsorption energy of water molecules is altered by the coadsorption of third partides on metal electrodes. 

The concept of acid/base interactions constitutes an interesting, if not universal, approach to a better understanding of the interfacial properties of composite materials and could constitute a basis for a better choice of surface treatments applied to the fibres. 

IGC can be used to determine various properties of the stationary phase, such as the transition temperatures, polymer—polymer interaction parameters, acid-base characteristics, solubility parameters, crystallinity, surface tension, and surface area. IGC can also be used to determine properties of the vapor-solid system, such as adsorption properties, heat of adsorption, interaction parameters, interfacial energy, and diffusion coefficients. The advantages of IGC are simplicity and speed of data collection, accuracy and precision of the data, relatively low capital investment, and dependability and low operating cost of the equipment. 

Electrochemical processes at the ITIES involve two basic types of elementary reactions ion transfer and electron tunneling across the liquid liquid boundary. Depending on the properties of the ionic species and the solvents, these two processes can be accompanied by a variety of phenomena such as solvent exchange, interfacial complexation, adsorption, photoexcitation, acid-base dissociation, etc. There are conceptual as well as practical... 

A correlation has been developed between the residual adhesion of bonded assemblies following accelerated ageing and the magnitude of acid-base interfacial interactions. The strength of interactions needed to avoid property loss under the chosen ageing conditions can be estimated. This capability represents a guideline to the selection of preferred silane additives for the adhesion of PU adhesives to substrates with known acid-base interaction potentials. 

The forces controlling surfactant interactions with polymers are identical to those involved in other solution or interfacial properties, namely, van der Waals or dispersion forces, the hydrophobic effect, dipolar and acid-base interactions, and electrostatic interactions. The relative importance of each type of interaction will vary with the natures of the polymer and surfactant so that the exact characters of the complexes formed may be almost as varied as the types of material available for study. 

Characterization and interfacial properties of solid surfaces, solid-fluid interfaces, acid-base interactions, and colloidal dispersions... 

ABSTRACT. The paper examines the influence of interactions at polymer surfaces and interfaces on the properties of polymer systems, with emphasis on acid/base interactions. The method of inverse gas chromatography is used to evaluate the donor-acceptor interaction potential of components in polymer systems. The usefulness of the interaction parameters is established by their ability to rationalize diverse properties of polymer systems, including the adsorption of polymers on pigments, and the effectiveness of thermal stabilizers in pigmented polymers. Various strategies for controlling surface and interfacial interactions in polymer systems are reviewed, with emphasis placed on the ability of polymers to adopt various surface orientations and compositions. TTiese inherent surface modification effects are attributed to thermodynamic driving forces, and are shown to influence polymer adhesion, barrier and other properties dependent on surface and interfacial forces. 

More recently, it has been shown, in particular by Fowkes and co-workers [2,6,7], that electron acceptor and donor interactions, according to the generalized Lewis acid-base concept, could be a major type of interfacial forces between two materials. This approach is able to take into account hydrogen bonds which are often involved in adhesive joints. Inverse gas chromatography at infinite dilution for example is a well adapted technique [8-10] for determining the acid-base characteristics of fibres and matrices. Retention data of probes of known properties, in particular their electron acceptor (AN) and donor (DN) numbers according to Gutmann s semi-empirical scale [11], allow the determination of acid-base parameters, and Kj), of fibre and matrix surfaces. It becomes then possible to define a "specific interactions parameter" A at the fibre-matrix interface, as the cross-product of the coefficients and Kq of both materials [10,11] ... 

Such a strong correlation illustrates the importance acid-base interactions for a better understanding of interfacial properties of composites. It is clear that the intercept at the origin should be different from zero, since disp sive interactions (W ) still exists when A = 0. It also seems that the magnitude of this intercept depends on the mechanical properties of the matrix [14]. 

A tentative model has been proposed to relate the interfacial shear strength at the fibre-matrix interface, measured by a fragmentation test on single fibre composites, to the level of adhesion between both materials. This last quantity has been estimated from the surface properties of both the fibre and the matrix and was defined as the sum of dispersive and acid-base interactions. This new model clearly indicates that the micromechanical properties of a composites are mainly determined by the level of physical interactions established at the fibre-matrix interface and, in particular, by electron acceptor-donor interactions. Moreover, to a first approximation, our model is able to explain the stress transfer phenomenon through interfacial layers, such as crystalline interphases in semi-crystalline matrices and interphases of reduced mobility in elastomeric matrices. An estimation of the elastic moduli of these interphases can also be proposed. Furthermore, recent work [21] has shown that the level of interfacial adhesion plays a major role on the final performances (tensile, transverse and compressive strengths and strains) of unidirectional carbon fibre-PEEK composites. 

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