Interfacial properties, importance

Poly(phenylene sulfide) (PPS) is another semicrystalline polymer used in the composites industry. PPS-based composites are generally processed at 330°C and subsequently cooled rapidly in order to avoid excessive crystallisation and reduced toughness. The superior fire-retardant characteristics of PPS-based composites result in appHcations where fire resistance is an important design consideration. Laminated composites based on this material have shown poor resistance to transverse impact as a result of the poor adhesion of the fibers to the semicrystalline matrix. A PPS material more recently developed by Phillips Petroleum, AVTEL, has improved fiber—matrix interfacial properties, and promises, therefore, an enhanced resistance to transverse impact (see PoLYAffiRS containing sulfur). 

The traditional view of emulsion stability (1,2) was concerned with systems of two isotropic, Newtonian Hquids of which one is dispersed in the other in the form of spherical droplets. The stabilization of such a system was achieved by adsorbed amphiphiles, which modify interfacial properties and to some extent the colloidal forces across a thin Hquid film, after the hydrodynamic conditions of the latter had been taken into consideration. However, a large number of emulsions, in fact, contain more than two phases. The importance of the third phase was recognized early (3) and the lUPAC definition of an emulsion included a third phase (4). With this relation in mind, this article deals with two-phase emulsions as an introduction. These systems are useful in discussing the details of formation and destabilization, because of their relative simplicity. The subsequent treatment focuses on three-phase emulsions, outlining three special cases. The presence of the third phase is shown in order to monitor the properties of the emulsion in a significant manner. 

It has been also shown that when a thin polymer film is directly coated onto a substrate with a low modulus ( < 10 MPa), if the contact radius to layer thickness ratio is large (afh> 20), the surface layer will make a negligible contribution to the stiffness of the system and the layered solid system acts as a homogeneous half-space of substrate material while the surface and interfacial properties are governed by those of the layer [32,33]. The extension of the JKR theory to such layered bodies has two important implications. Firstly, hard and opaque materials can be coated on soft and clear substrates which deform more readily by small surface forces. Secondly, viscoelastic materials can be coated on soft elastic substrates, thereby reducing their time-dependent effects. 

The recovery of petroleum from sandstone and the release of kerogen from oil shale and tar sands both depend strongly on the microstmcture and surface properties of these porous media. The interfacial properties of complex liquid agents—mixtures of polymers and surfactants—are critical to viscosity control in tertiary oil recovery and to the comminution of minerals and coal. The corrosion and wear of mechanical parts are influenced by the composition and stmcture of metal surfaces, as well as by the interaction of lubricants with these surfaces. Microstmcture and surface properties are vitally important to both the performance of electrodes in electrochemical processes and the effectiveness of catalysts. Advances in synthetic chemistry are opening the door to the design of zeolites and layered compounds with tightly specified properties to provide the desired catalytic activity and separation selectivity. 

Mechanisms and Interfacial Properties of Molecules of Biological Importance (F. A. Schultz and I. Taniguchi, eds.) The Electrochemical Society, Pennington, 1993, pp. 423-434. (c) K Nakano, S Uchida, Y. Mitsuhashi, Y. Fujita, H. Taira, M. Maeda, and M. Takagi, in ACS Symposium Series 690 Polymers in Sensors. Theory and Practice (N. Akmal and A. M. Usmani, eds.), American Chemical Society, Washington DC, 1996, pp. 34-4-5. 

Our goal is to develop a property-performance relationship for different types of demulsifiers. The important interfacial properties governing water-in-oil emulsion stability are shear viscosity, dynamic tension and dilational elasticity. We have studied the relative importance of these parameters in demulsification. In this paper, some of the results of our study are presented. In particular, we have found that to be effective, a demulsifier must lower the dynamic interfacial tension gradient and its ability to do so depends on the rate of unclustering of the ethylene oxide groups at the oil-water interface. 

The authors propose that a major difficulty in interpreting kinetic current flow at the semiconductor-solution interface lies in the inability of experimentalists to prepare interfaces with ideal and measurable properties. In support of this hypothesis, the importance of ideal interfacial properties to metal electrode kinetic studies is briefly reviewed and a set of criteria for ideality of semiconductor-solution interfaces is developed. Finally, the use of semiconducting metal dichalcogenide electrodes as ideal interfaces for subsequent kinetic studies is explored. 

Yoneyama H, Tsuda R, Nishida K, Kuwabata S (1993) Proceedings of the 5th International Symposium on Redox Mechanisms and Interfacial Properties of Molecules of Biological Importance, Schultz E, Taniguchi I (eds), The Electrochemical Society, Pennington NJ, USA... 

The grafting of polymers to substrates has been studied for over fifty years and remains an important goal in polymer science. Recent work has focused on the synthesis of so-called polymer brushes whereby the polymer chains stretch out away from the substrate or interface [1-5]. This contemporary topic is a direct descendent of earlier work on organic graft copolymers in industry and academia. Research in this area is driven by the need to control the interfacial properties of films and the compatibility of blends. 

This is not the only proof that the metal properties are important in the interfacial properties. We have already studied the capacitance curves and found that it is difficult to find a model that would describe the curves properly (Section 6.6.5). Would it be possible then, to think that the metal also contributes to the capacity of the interface and that it could, at least to some extent, explain the shape and asymmetry of the capacitance curves ... 

So far we have established in a qualitative way the importance of the metal properties on the characteristics of the interfacial region through two properties, the relation of Omvs. pzc and the capacitance of the double layer. What is next At this point it would be good to obtain a detailed model of the metal region and then determine—now in a quantitative way—the influence of the metal on the interfacial properties, similarly to the procedure followed when studying the solution region (Section 6.6.1). 

Through the jellium model of the metal we have explained the effect of the metal electrons on the interfacial properties. We also know that the spillover of electrons creates a separation of charges at the metal edge, and consequently, a surface potential. However, what is the magnitude of this surface potential How important is its contribution to the total potential drop in the interfacial region ... 

In considering the impact of thermodynamically favourable interactions between biopolymers on the formation and stabilization of food colloids, a number of regular trends can be identified. One of the most important aspects is the effect of complexation on interfacial properties, including rates of adsorption and surface rheological behaviour. 

Key Concepts of Interfacial Properties in Food Chemistry CASE STUDY LIPID OXIDATION OF EMULSIONS The case of lipid oxidation in an emulsified system is a perfect example to illustrate the importance of interfacial properties in food chemistry. The goal of this case study is not to completely describe the very complex mechanisms of lipid oxidation in emulsions. Indeed, many investigators over the past years have focused on this research area. Instead, the key interfacial parameters that influence lipid oxidation in emulsions are emphasized. 

Particles can either be produced by bottom-up processes (e.g. precipitation) or top-down approaches (e.g. wet milling). In these processes particle-particle interactions become relevant when the particle size is below 1 pm. Engineering macroscopic product properties is then only possible through tailored surface and interfacial properties, no matter whether a bottom-up process like precipitation [11] or a top-down process such as milling in stirred media mills [12] is studied. Aggregation is an important aspect in both processes which are studied in the following. 

In colloidal dispersions, a thin intermediate region or boundary, known as the interface, lies between the dispersed and continuous phases. Each of emulsions, foams, and suspensions represent colloidal systems in which interfacial properties are very important because droplets, bubbles, and particles can have very large interfacial areas. 

Example. An emulsion is a dispersion of one immiscible liquid in another. In most cases one of the liquids is aqueous and the other is in some sense, an oil. Emulsions are another kind of colloidal system in which interfacial properties are very important because emulsified droplets have a large interfacial area. Even a modest interfacial energy per unit area can become a considerable total interfacial energy to be reckoned with. 

Of course, interfacial tension lowering alone may not be sufficient to stabilize an emulsion, in which case other interfacial properties must be adjusted as well. These simple calculations do, however, show how important the interfacial properties can become when colloidal-sized species are involved, as in the case of emulsions. 

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