Applications adhesion tension

This application has only a limited scope in connection with adhesion tension studies, because of the need for an independent approach to the solid-vacuum and solid-liquid interfacial tensions. There exists, however, one case where an application of this approach is of considerable use the glassy fluorocarbon solid surface studied by Fowkes... 

The two-liquid adhesion tension data are of particular value in the event that the one-liquid values for each of the liquids are also available. From Table III it is seen that this is the case for both liquids on polytetrafluoroethylene and for isopropylbiphenyl alone on polyethylene. Application of the modified Bartell-Osterhof relation, Equation 18, gives values for the film pressure, which are recorded in Table in. 

Hybrid anchors (not to be confused with hybrid adhesives as discussed in 4.3.2) combine the working principles of adhesive anchors with expansion or undercut mechanisms. Torque-controlled adhesive anchors (Figure 4.7) transfer tension loads via friction. Because of their ability to re-expand upon the application of tension loads, they are particularly suited for use in concrete that may crack over the anchor life, and may be used in a variety of applications where the flexibility of an adhesive anchor system is required. They are also less sensitive to hole cleaning procedures than ordinary adhesive anchors. Grouted undercut anchors, like standard undercut anchors, transfer tension loads via bearing. The grout improves the form-fit between the anchor and the concrete thereby reducing initial anchor movement under load. 

At present there is only one commercially available tissue adhesive with approved on-label indications for skin closure. 2-Octyl-cyanoacrylate (Dermabond, Ethicon, Inc., Somerville, NJ) is presently indicated for skin closure in wounds which are not under extreme tension. This tissue adhesive is approved for topical skin application only. It is not indicated for internal use. The material is useful in closing traumatic skin lacerations [4,5] after wounds have been thoroughly cleaned as well as for minimally invasive surgical incisions and even larger surgical incisions in elective cases. The cyanoacrylate is applied while the skin... 

Industrially, silicone surfactants are used in a variety of processes including foam, textile, concrete and thermoplastic production, and applications include use as foam stabilisers, defoamers, emulsifiers, dispersants, wetters, adhesives, lubricants and release agents [1]. The ability of silicone surfactants to also function in organic media creates a unique niche for their use, such as in polyurethane foam manufacture and as additives to paints and oil-based formulations, whilst the ability to lower surface tension in aqueous solutions provides useful superwetting properties. The low biological risk associated with these compounds has also led to their use in cosmetics and personal care products [2]. 

Nitrile latices are used in a wide variety of applications, including production of dipped nitrile mbber products. In the principle use of paper saturation, adhesives and fiber bonding, small particle size and optimum surface tension is desirable to achieve rapid penetration and setup or drying. 

When sodium silicate solutions of intermediate ratios are concentrated to a thick gum. they become very sticky and tacky. This property is important to many of the adhesive applications. It is related to high cohesion and low surface tension rather than primarily to viscosity. 

Zisman discovered that there is a critical surface tension characteristic of low-energy solids, such as plastics and waxes. Liquids ihat have a lower surface tension than the solid will spread on that solid, while liquids with a higher surface tension will not spread. Examples of critical surface tension values for plastic solids in dynes per cm are "Teflon/ 18 polyethylene, 31 polyethylene terephthalate, 43 and nylon, 42-46. As one indication of the way this information can be used in practical applications, one can consider the bonding of nylon to polyethylene. If nylon were applied as a melt to polyethylene, it would not wet the lower-energy polyethylene surface and adhesion would be poor. However, molten polyethylene would spread readily over solid nylon to provide a strong bond. 

Specifications and Standards. Borax stability is an important property in adhesives, paper, and textile applications. Ollier emulsion properties tabulated by manufacturers include tolerance to specific solvents, surface tension, minimum film-forming temperature, dilution stability, freeze-thaw stability, percent soluble polymer, and molecular weight. 

The adsorption of surfactants at the liquid/air interface, which results in surface tension reduction, is important for many applications in industry such as wetting, spraying, impaction, and adhesion of droplets. Adsorption at the liquid/liquid interface is important in emulsification and subsequent stabilization of the emulsion. Adsorption at the solid/liquid interface is important in wetting phenomena, preparation of solid/liquid dispersions, and stabilization of suspensions. Below a brief description of the various adsorption phenomena is given. 

Surfactants act as wetting agents by lowering the surface tension of the waterborne epoxy. Silanes can be used to increase adhesion to certain substrates and fillers, as shown in Table 14.4, formulation C. Water-compatible thickeners and protective colloids such as polyvinyl alcohol, substituted cellulosics and sugars, and some acrylics improve application properties and offset viscosity decrease seen with water dilution. 

Mohandas and co-workers (18), confirming previous findings of Weiss and Blumenson (19), have also shown that cells in an environment free of adsorbable proteins (which rapidly modify the surface properties of polymeric or inorganic substrates) will exhibit a similar direct relationship between their adhesion and the critical surface tension of the surface they contacted. DiflFerential adhesion of red blood cells was measured by determining the fraction of cells retained on a surface after the application of well-calibrated shear stresses (IS). In protein-free experiments, the red cells (themselves dominated in adhesive interactions by their protein membranes) had greatest adhesion to glass, intermediate adhesion to polyethylene and siliconized glass, and least adhesion to Teflon. 

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