Interface rheological properties

Interface Surface film properties Interface rheological properties Interface tension... 

The properties of t have been studied quite extensively. It is an interface rheological property which manifests many of the characteristics of the bulk shear yield stress although the numerical values of t are significantly less than the bulk analogue. Thus to a first order... 

The dry adhesive films on the two substrates to be joined must be placed in contact to develop adequate autoadhesion, i.e. diffusion of polymer rubber chains must be achieved across the interface between the two films to produce intimate adhesion at molecular level. The application of pressure and/or temperature for a given time allows the desired level of intimate contact (coalescence) between the two adhesive film surfaces. Obviously, the rheological and mechanical properties of the rubber adhesives will determine the degree of intimacy at the interface. These properties can be optimized by selecting the adequate rubber grade, the nature and amount of tackifier and the amount of filler, among other factors. 

Investigation of Oil-Water Interfaces by Spectroscopic Methods. Relations with Rheological Properties of Multiphasic Systems... 

Rheological measurements were carried out to investigate the rheological properties of emulsions stabilized by different fat-water interfaces and the influence of fat droplets on the formation of the protein networks during a process of gelation. 

The dynamic behavior of fluid interfaces is usually described in terms of surface rheology. Monolayer-covered interfaces may display dramatically different rheological behavior from that of the clean liquid interface. These time-dependent properties vary with the extent of intermolecular association within the monolayer at a given thermodynamic state, which in turn may be related directly to molecular size, shape, and charge (Manheimer and Schechter, 1970). Two of these time-dependent rheological properties are discussed here surface shear viscosity and dynamic surface tension. 

The rheological properties of a fluid interface may be characterized by four parameters surface shear viscosity and elasticity, and surface dilational viscosity and elasticity. When polymer monolayers are present at such interfaces, viscoelastic behavior has been observed (1,2), but theoretical progress has been slow. The adsorption of amphiphilic polymers at the interface in liquid emulsions stabilizes the particles mainly through osmotic pressure developed upon close approach. This has become known as steric stabilization (3,4.5). In this paper, the dynamic behavior of amphiphilic, hydrophobically modified hydroxyethyl celluloses (HM-HEC), was studied. In previous studies HM-HEC s were found to greatly reduce liquid/liquid interfacial tensions even at very low polymer concentrations, and were extremely effective emulsifiers for organic liquids in water (6). 

For a specific resin, the shear stress at the interface depends on the temperature of the interface, pressure, and the sliding velocity, it also depends on resin type, additives and additive levels, and the rheological properties of the resin. Stresses at the interface and the coefficients of friction for numerous resins have been published previously from two sources, and the data can be found in the references [15-31]. Additional stress data are provided in Appendix A4 and in several of the case studies in Chapter 12. 

T.D. Dimitrova and F. Leal Calderon Rheological Properties of Highly Concentrated Protein-Stabilized Emulsions. Adv. Colloid Interface Sci. 108-109, 49 (2004). 

Smith,T.L Bruce, C.A. (1979) Intrinsic viscosities and other rheological properties of flocculated suspensions of non magnetic and magnetic ferric oxides. J. Colloid Interface Sci. 72 13-25... 

Bos, M.A., van Vliet, T. (2001). Interfacial rheological properties of adsorbed protein layers and surfactants. Advances in Colloid and Interface Science, 91, 437-471. 

A similar technique can be used to study the rheological properties of liquid films. Figure 4 shows the formation of a W/O/W emulsion film with two, identical aqueous phases (such as in water-in-oil emulsions) at the tip of the capillary. A pre-requisite of the experiment is that the surface of the capillary must be well wetted by the film phase, i.e., it should be hydrophobic in this case. First, an aqueous drop is formed inside the oil (film liquid) and the aqueous phase is in the bottom of the cuvette. Then, the level of the aqueous phase is slowly increased. As the oil/water interface passes the drop, a cap shaped oil film, bordered by a circular meniscus, covers the drop. This film can be studied in equilibrium and in dynamic conditions, similar to the single interfaces (See above). The technique can be used to study films from oil or aqueous phase which can be sandwiched between identical or different liquid or gas phases. 

The surface rheological properties of the /3-lg/Tween 20 system at the macroscopic a/w interface were examined by a third method, namely surface dilation [40]. Sample data obtained are presented in Figure 24. The surface dilational modulus, (E) of a liquid is the ratio between the small change in surface tension (Ay) and the small change in surface area (AlnA). The surface dilational modulus is a complex quantity. The real part of the modulus is the storage modulus, e (often referred to as the surface dilational elasticity, Ed). The imaginary part is the loss modulus, e , which is related to the product of the surface dilational viscosity and the radial frequency ( jdu). 

Electrorheological (ER) fluids are materials whose rheological properties (viscosity, yield stress, shear modulus, etc.) can be readily controlled using an external electric field. For example, in some cases, they can switch from a liquid-like material to a solid-like material within a millisecond with the aid of an electric field, by means of the so-called ER effect.1617 The unique feature of the ER effect is that ER fluids can reversibly and continuously change from a liquid state to a solid state. ER fluid research is focused mainly on the automotive and robotics industry as electrical and mechanical interfaces for applications such as clutches, brakes, damping devices, fuel injection, and hydraulic valves. However, more recently, there is growing... 

A surfactant at low concentration in aqueous solution exists as monomers (free or unassociated surfactant molecules). These monomers pack together at the interface, form monolayer and contribute to surface and interfacial tension lowering. Although this phenomenon is highly dynamic (surfactant molecules arrive and leave the interface on a very rapid timescale), molecules at the interface interact with the neighbouring molecules very strongly which enables measurement of the rheological properties of the monolayer. 

D. E. Tambe and M. M. Sharma, Hydrodynamics of thin liquid-films bounded by viscoelastic interfaces, J. Colloid Interface Sci. 147, 137-151 (1991) Factors controlling the stability of colloid-stabilized emulsions. 1. An experimental investigation, J. Colloid Interface Sci. 157, 244-253 (1993) Factors controlling the stability of colloid-stabilized emulsions. 2. A model for the rheological properties of colloid-laden interfaces, J. Colloid Interface Sci. 162, 1-10 (1994) Factors controlling the stability of colloid-stabilized emulsions. 3. Measurement of the rheological properties of colloid-laden interfaces, J. Colloid Interface Sci. 171, 456-462 (1995). 

An intermediate layer to enhance the physical properties of the joint and improve bond strength (e.g., adjustment of the rheological properties at the interface or strengthening weak substrate regions)... 

Sherman, P. 1967a. Changes in the rheological properties of emulsions on aging. II. Viscosity changes in w/o emulsions at rates of shear from 0.133 sec-1 to 10.77 sec-1. J. Coll. Interface Sci. 24, 97-106. 

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