Epoxy based adhesive

Epoxy-based adhesives, 10 458-459 Epoxy-based composites, 26 763 Epoxy-based powder coatings, 10 439-442 Epoxy-based thermoplastics, 10 365... 

Commonly used adhesives include epoxy, rubber, acrylic or vinyl emulsions, and urethanes. Epoxies are high-priced, but they have better chemical resistance and durability than the others, and they have dominated the market in outdoor applications. Significant advantages of the epoxy-based adhesives are that they have no solvents and, therefore, exhibit little shrinkage. They cure relatively fast and, therefore, are not as exposed to inclement... 

Over the past several decades, significant advances have been made in developing epoxy-based adhesives having improved performance over these early adhesive systems. These improvements were made possible by (1) the incorporation of toughening additives into epoxy resin formulations and (2) the use of multifunctional epoxy resins primarily for high-temperature applications. These innovations are discussed in later chapters. 

Estes, R. H., The Suitability of Epoxy Based Adhesive for Use in Medical Devices, Technical Paper GB-63, Epoxy Technology, Pembroke, MS, 1999. 

It should also be emphasized that the epoxy resins are only building blocks in the development of epoxy-based adhesives. The formulation will ultimately involve one or more epoxy resins curing agents modifiers, such as plasticizers, flexibilizers, accelerators, stabilizers, and flow control agents and fillers. In general, flexibility can be controlled by the parameters shown in Table 3.8. 

One of the most popular uses of radiant curing is the advancement (viscosity increase) or crosslinking of pressure-sensitive adhesives. These applications have been satisfied mostly with acrylate-based adhesive systems. With epoxy-based adhesives, the main applications are electrical and electronic components, the bonding of large aerospace structures such as composites, and the bonding of transparent substrates such as glass and plastic. 

There are several claims in the literature regarding the maximum speed of microwave curing of epoxy adhesives. Claims have been made of ten- to twenty fold cure time reduction when compared to conventional thermal heating. A more practical estimate, however, is that microwave joining using epoxy-based adhesive will significantly reduce the curing time... 

The above analysis applies to degradation processes that relate to the bulk adhesive. Interfacial degradation processes such as corrosion can be similarly determined. Thermal and oxidative stability, as well as corrosion and water resistance, depends on the adherend surface as well as on the adhesive itself. Epoxy-based adhesives degrade less rapidly at elevated temperatures when in contact with glass or aluminum than when in contact with copper, nickel, magnesium, or zinc. The divalent metals have a more basic oxide surface than the higher-valence metal oxides and hence serve to promote dehydrogenation reactions, which lead to anion formation and chain scission.7... 

For elevated-temperature cures, however, dicyandiamide and melamine curing reactions have been shown to be beneficial in epoxy-based adhesives when used on copper substrates. These epoxy adhesives perform about as well in copper joints as in aluminum or steel joints. The formulations show significantly increased time to adhesive failure on either bare or alkaline permanganate-treated copper.30... 

Next to viscosity, epoxy content and hydroxyl content are the prime properties of importance in formulating epoxy-based adhesive systems. Epoxy content allows one to determine the correct amount of curing agent to use. With certain curing agents it may also be important to know the hydroxyl content. These values determine the reactivity of the system. 

Cyanoacrylates are not appropriate for the bonding of the steel parts of an automobile, because of the environments that the car will be exposed to. Those environments include such things as rain, variations in temperatnre, exposure to solvents (such as gasoline, oil, and windshield washer solntion), ozone, acid rain, salt spray, and ultraviolet light from the Sun. (A more appropriate adhesive for car parts would be an epoxy-based adhesive.) Another example of a special adhesive would be the one used to attach a new rearview mirror in an antomobile. Because the cured adhesive in this case will be exposed to wide variations in temperature and to an extremely large amonnt of nltraviolet fight from the Snn for prolonged periods of time, an adhesive formnlated specifically for these conditions should be used. 

Epoxy-based adhesives, hot or cold curing, as one- or two-component pastes or as adhesive films for structural bonding with significant loads... 

Requirements of the adhesive. A full compliance spectrum for steel/concrete bonding has been published by the authors(18) and is reproduced as an Appendix at the end of the book. The purpose of the adhesive is to produce a continuous bond between steel and concrete to ensure that full composite action is developed by the transfer of shear stress across the thickness of the adhesive layer. Experience has shown that the best chance of success is likely to be achieved by using cold-cure epoxy based adhesives which have been specially developed for use in the construction industry. Provided that the surfaces have been prepared properly, these bond well to both steel and concrete and do not suffer shrinkage and cracking problems such as may occur with other systems like polyesters. For these purposes a cold-cure adhesive is defined as one which is capable of curing to the required strength between the... 

D.J. Crabtree, "Dynamic Mechanical Analysis (DMA) for Quality Assurance of Epoxy-Based Adhesives and Composite Materials," 12th National SAMPE Tech. Conf., 10/7-9/1980. 

Fillers and thixotropic agents are used widely throughout the various acrylic sealant and adhesive products. Fillers also form a significant component of epoxy-based adhesives. For example, if it is necessary to identify the filler used in the hardener component of an epoxy product, the isolation sequence involves initial centrifugation of the product to isolate the crude filler component. The latter is then washed repeatedly with acetone and dried thoroughly. The fine dry powder may then be used to prepare a standard KBr disk for IR analysis. 

Epoxy adhesives are also easy to modify for special purposes. For example, they can be filled with carbon, silver, or gold to provide electrical conductivity. Other additives can enhance thermal conductivity, while maintaining electrical insulation. Additional performance properties of epoxy-based adhesives that can be modified include impact resistance, shrinkage, glass transition temperature, high-temperature strength, surface specific adhesion characteristics, and chemical or moisture resistance. 

Epoxy-based adhesive systems offer the advantages of relatively low cure temperatures, no volatiles formed during cure, low cost, and a variety of formulating and application possibilities. The higher-temperature-resistant... 

Nitrile-phenolic adhesives are more resistant to radiation damage than epoxy-based adhesives. 

Figure 2.10 Effect of bond line thickness on the peel strength of a toughened epoxy-based adhesive. Although not directly proportional, the effect is substantial and of considerable practical importance because bond line thickness is often difficult to control. In most cases the overall result of an increase in bond line thickness is beneficial, even though the shear strength may fall most joints fail because they cannot meet peel and cleavage overloads. Generally shear overloads are rare.

The ECV 3 is probably one of the most innovative cars ever built. A significant and unique feature is its aluminium monocoque body which relies entirely on a toughened epoxy-based adhesive for its structural integrity. (Photograph courtesy BL Technology Ltd adhesive supplied by Permabond Adhesives Ltd.)... 

Plastic composite bridges are very successful examples of on-site production pultruded parts can be easily carried to the application site and processed (GFR resin - polyester thin-walled cellular modules were quickly assembled and bonded by epoxy-based adhesives on-site in a very short time in the Aberfeldy foot bridge). 

Extensive information on the durability of bonded aluminum joints is available in the reviews of Minford. " Figure 4 illustrates some typical results, showing the effect of adhesive variation on joint durability for a marine exposure. Vinyl-phenolics and nitrile-phenolics have an excellent history of joint durability and rank among the most resistant to environmental deterioration. In spite of this, however, the current trend is to use epoxy-based adhesives, which provide easier processing and higher peel... 

Solid sheet linings can also be applied either as an adhesive-bonded lining or a loose-fitting lining. Adhesive-bonded sheet linings on steel substrates consist of fabric backed sheets bonded to steel vessel walls with neoprene or epoxy based adhesive. Linings may be applied in the field or in the shop. Joints are heat welded using a rod of the same polymer as the sheets. 

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