Adhesive and cohesive properties

The performance of a product where adhesion plays a role is determined both by its adhesive and cohesive properties. In the case of silicones, the promotion of adhesion and cohesion follows different mechanisms [37]. In this context, adhesion promotion deals with the bonding of a silicone phase to the substrate and reinforcement of the interphase region formed at the silicone-substrate interphase. The thickness and clear definition of this interphase is not well known, and in fact depends on many parameters including the surface physico-chemistry of... 

Standard-grade PSAs are usually made from styrene-butadiene rubber (SBR), natural rubber, or blends thereof in solution. In addition to rubbers, polyacrylates, polymethylacrylates, polyfvinyl ethers), polychloroprene, and polyisobutenes are often components of the system ([198], pp. 25-39). These are often modified with phenolic resins, or resins based on rosin esters, coumarones, or hydrocarbons. Phenolic resins improve temperature resistance, solvent resistance, and cohesive strength of PSA ([196], pp. 276-278). Antioxidants and tackifiers are also essential components. Sometimes the tackifier will be a lower molecular weight component of the high polymer system. The phenolic resins may be standard resoles, alkyl phenolics, or terpene-phenolic systems ([198], pp. 25-39 and 80-81). Pressure-sensitive dispersions are normally comprised of special acrylic ester copolymers with resin modifiers. The high polymer base used determines adhesive and cohesive properties of the PSA. 

An EB-curable struetural adhesive formulation usually eonsists of one or more crosslinkable oligomeric resins or prepolymers, along with such additives as reactive diluents, plasticizers, and wetting agents. The oligomer is an important component in terms of the development of mechanical properties. The adhesive and cohesive properties depend on the crosslink density, chemical group substitution, and molecular organization within the polymer matrix. Adhesion is achieved... 

The addition of silica fume to dry-mix shotcrete in proportions of 10-15% by mass of Portland cement substantially improves the adhesive and cohesive properties of the freshly applied shotcrete. Silica fume creates a very dense and sticky mix with an almost complete lack of bleeding. These characteristics of the material are attributed to the extreme densification achieved by packing of the ultrafine silica fume particles between the cement particles in the plastic (fresh) shotcrete. Practical ramifications of these characteristics include the observations which follow [107, 117-119]. 

Gluten is used in many other foods where its adhesive and cohesive properties provide beneficial value (29). In breakfast... 

High molecular weight and random coil structure of protein result in more associations and thereby enhance adhesive and cohesive properties. Although these characteristics are inherent in native gluten proteins, functional properties of other proteins may be improved by chemical or thermal processing. 

Fibronectin is present in plasma, subendothelium and platelet alpha granules. Despite containing the RGD sequence, the role of fibronectin in adhesive and cohesive properties of platelets seems less important. It has been suggested that plasma fibronectin would not be required for platelets to adhere on vascular extracellular matrices [45]. However, studies with plasma depleted of fibronectin seem to indicate that this adhesive protein could play a role in mediating adhesion of platelet and thrombus formation on collagen rich surfaces [46]. As will be commented on later, the mote recent studies suggest that vascular fibronectin would mediate platelet adhesion under certain experimental conditions [47]. 

Sealant A material that has the necessary adhesive and cohesive properties to form a seal. 

ISO 9046 1987 Building construction sealants - determination of adhesion and cohesion properties at constant temperature. 

Polyester polyols are used widely in urethane adhesives because of their excellent adhesive and cohesive properties. Compared to polyether-based polyols, polyester-based polyol adhesives have higher tensile strengths and improved heat resistance. These benefits come at the sacrifice of hydrolytic resistance, low-temperature performance, and chemical resistance. One of the more important application areas for these products is in the solvent-borne thermoplastic adhesives used in shoe sole binding. These products are typically made from adipic acid and various glycols (see Fig. 15). 

Product technologies that have high adhesion include elastomeric adhesives and sealants (see Silicone adhesion and Rubber-based adhesives). Their adhesive strength reflects both adhesion and cohesion properties (see Peel tests and Rheological theory). In each of these product technologies, the unique physico-chemical properties of silicones, in general, and in adhesion, in particular, originate from the atomic and chemical bond structures of the PDMS backbone. 

Cement n. A material or a mixture of materials (without aggregate) which, when in a plastic state, possesses adhesive and cohesive properties and hardens in place. Frequently, the term is used incorrectly for concrete, e.g., a cement block for concrete block (n) See adhesive, (v) See bond. 

Its intrinsically polar nature assures good adhesion and cohesion properties among active material particles. 

A. Carr6 and J. Schultz, Polymer-aluminium adhesion. II. Role of the adhesive and cohesive properties of the polymer, J. Adhes. 17, 135-156 (1984). 

Oxidation stability Other properties Fair to good Good Poor Good Good inherent EP properties Good Poor Good adhesive and cohesive properties Excellent Good... 

Reaction of two or more monomers by free radical polymerization is an effective way of altering the balance of properties of commercial products. Addition of the polar monomer acrylonitrile to styrene (or methyl acrylate to ethylene) produces a polymer that combines the strength of the base homopolymer with much improved oil and grease resistance. The adhesive and cohesive properties of coatings resins are balanced by controlling the mix and relative proportions of monomers in the recipe. 

Polyurethanes, by virtue of their considerable variability, have become very valuable to the adhesives industry over recent decades. They generally show above-average adhesion and cohesion properties. Low molecular mass reaction products of hydroxyl... 

In the first paper, Petke reviews the current literature for developments in structure-property relationships of adhesives. He illustrates how chemical and physical structure affect both the adhesive and cohesive properties of polymers. In his review, he shows how the balance of adhesive and cohesive properties determine the ultimate bond strength of an adhesive. Relationships are cited for several types of adhesives. 

The chemistry and structure of the tackifying terpene resins are developed by E. Ruckel al. These resins, produced commercially from pine turpentine, since the mid-Thirties, are formulated with natural rubber to produce pressure sensitive adhesives. More recently, the scope of their use has been broadened by formulation with elastomers and waxes for hot melt applications. Empirical application tests have developed a broad knowledge of utility but little science or predictability. By use of sophisticated high polymer techniques, polymerization mechanisms are used to explain how the minor structural differences between the beta-pinene and dipentene resins suit these resins respectively for pressure sensitive and hot melt adhesive usage. Again for use application the critical aspects of the formulation are its adhesive and cohesive properties as demonstrated by tack, shear and peel properties. 

Bulk material characteristics such as particle and bulk densities, hardness, flowability, adhesion and cohesion properties, and rate of material flow. 

In van Ooij s model, brass develops a high bond strength to rubber because the sulfide not only has good adhesive and cohesive properties, but is also very porous so that the rubber molecules become entangled in this film during vulcanization. This phenomena is depicted in Fig. 20. 

Peel tests for sealants are usually carried out to determine adhesion and cohesion properties of the material. 

Adhesives can be classified according to their areas of application, the nature of the materials that need bonding or the physical state at the time of application. However, none of these classifications allow commercial products to be adapted to specific applications or studies, nor do they enable us to determine the optimum conditions or limitations when using these products. To achieve these additional stages, we need to understand the physical and chemical behavior of the raw materials used as base components of these adhesives and to take an active interest in major developments regarding their formulation. Indeed, the raw materials are responsible for the general adhesive and cohesive properties of the bonded joints, while the art of adhesive formulation helps to find the most diverse potential applications possible for products prepared using these raw materials. 

The philosophy behind a description of adhesives via their raw polymer materials differs according to whether the area of interest is AIPPs or AICPs. For the first category, the polymer is present within the adhesive formulation, and the adhesive and cohesive properties must be acquired before being dissolved, being made into an emulsion, or being melted. In that case, research and development is aimed at the development of linear macromolecular compounds. 

Where tensile shear strength refers to the strength of a lap joint under tension and comprises both adhesive and cohesive properties of the adhesive, in concentric assemblies it is the resistance to deformation of the solid polymer trapped in the gap between the surfaces that determines the strength. 

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