Epoxy adhesives composition

An important term that is used in formulating epoxy adhesive compositions is epoxy equivalent weight (EEW). This is defined as the weight of resin in grams that contains one equivalent of epoxy. As the resin s molecular weight increases, the EEW will also increase. 

Baldwin, J. M. and Robins, J., Epoxy Adhesive Composition Comprising a Calcium Salt and Mannich Base, U.S. Patent No. 5,629,380, 1997. 

Oh HJ, Kim HY, Kim SS. Effect of the core/ shell structured meta-aramid/epoxy nanofiher on the mechanical and thermal properties in epoxy adhesive composites by electrospinning. J Adhesion 2013. 

C (75%) corresponds to the amount of silver loaded into the epoxy adhesive composition. 

The commercial possibiUties for epoxy resins were first recognized by DeTrey Emres in Switzerland and DeVoe and Raynolds in the United States (1,2). In 1936, DeTrey Emres produced a low melting bisphenol A-based epoxy resin that gave a thermoset composition with phthaUc anhydride. Apphcation of the hardened composition was foreseen in dental products, but initial attempts to market the resin were unsuccessful. The patents were hcensed to CIBA AG of Basel, Switzerland (now CIBA-GEIGY), and in 1946 the first epoxy adhesive was shown at the Swiss Industries Eair and samples of casting resin were offered to the electrical industry. 

Even the earliest reports discuss the use of components such as polymer syrups bearing carboxylic acid functionality as a minor component to improve adhesion [21]. Later, methacrylic acid was specifically added to adhesive compositions to increase the rate of cure [22]. Maleic acid (or dibasic acids capable of cyclic tautomerism) have also been reported to increase both cure rate and bond strength [23]. Maleic acid has also been reported to improve adhesion to polymeric substrates such as Nylon and epoxies [24]. Adducts of 2-hydroxyethyl methacrylate and various anhydrides (such as phthalic) have also been reported as acid-bearing monomers [25]. Organic acids have a specific role in the cure of some blocked organoboranes, as will be discussed later. 

Although the acrylate adhesives are readily available and studies have shown that they can produce reasonable bonding properties, they have the disadvantages of having high shrinkage, high fluid absorption, and low service temperatures. Acrylate adhesive applications would be limited. The development of EB-curable epoxy adhesives would have applications in the aerospace and automotive industry and potential wider uses. The most immediate application for these resin systems is composite repair of commercial and military aircraft. 

There has been very little work done on the development of EB-curable epoxy adhesives. When undertaking this development work the authors had two objectives. The first objective was to develop a series of adhesives for bonding aluminum-to-aluminum (Al-Al) and composite-to-composite (C-C) with lap shear strengths of 30 MPa or greater at room temperature. The second objective was that the... 

We have also looked at the lap shear strength of selected EB-ciirable epoxy adhesives. Because the adhesives being developed were being used for both aluminum-to-aluminum and composite-to-composite applications the lap shear strengths for both adherends was measured. Aluminum adherends were T2024 phosphoric acid anodized according to ASTM 3933. The composite adherends... 

Effects on lap shear strength of EB-cured epoxy adhesives from different surface preparations on aluminum and composite adherends... 

As soon as the Ar s were determined and the values of r s are found, the values of the adhesion coefficient A may be readily defined by using relation (27). The values of A s for the different inclusion-volume contents studied are given in Table I for iron-epoxy particulate composites with different amounts of fillers, up to 25 percent l4>. 

Fig. 15. The variation of the adhesion coefficient A = (ri, — t 2) for the three-term unfolding model and the exponent 2r for the two-term model of a series of E-glass-epoxy fiber composites, versus the fiber-volume content uf...

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

Mode I and Mode II interlaminar fracture toughness values, G),. and Ofij, of carbon tiber-epoxy matrix composites containing various interleaved adhesive layers."... 

Title Novel Sulfur-containing Phenolic Resin, Process for Preparing the Same, Phenol Derivatives Having Thioether Structure or Disulfide Structure, Process for Preparing the Same and Epoxy Resin Composition Adhesive... 

The primer chosen for this investigation consisted of an equimolar mixture of phenyl- and amino-functional silanes, suggested as a potential superior primer for aluminum/epoxy adhesive joints [7], The amino-functional silane is known to be effective as an adhesion promoter for fiber-reinforced composite materials [1, 2] as well as for epoxy/metal adhesive joints [8, 9] and provides for strong chemical interaction between the adhesive and primer, while the phenyl functional silane should reduce the overall concentration of polar, hydrophilic functional groups in the interphase region and at the same time maintain or improve the ability of the resin and primer to interpenetrate due to its structural similarity to the adhesive resin. 

Epoxy adhesives are commercially available as liquids, pastes, films, and solids. Epoxy adhesives are generally supplied as 100 percent solids (no solvents or other volatiles), but some are available as sprayable solvent systems or water emulsions. Epoxy adhesives are also available in a wide range of chemical compositions, which allows for variations in how... 

Construction. Polymeric materials such as adhesives, sealants, and composites have been used considerably in the last several decades for the construction, repair, and rehabilitation of our transportation infrastructures. Even though most processes were experimental until recently, they have evolved to the point where many are now standardized and well accepted. Table 1.6 hsts several common applications for advanced polymeric materials (as well as the polymeric resins that are most commonly employed). In the construction or repair of roads and bridges, epoxy adhesives have primarily been used for bonding concrete and for bonding stiffening members or repair structures to degrading concrete facilities. 

A carrier or reinforcement is usually a thin fabric, cloth, or paper used to support the semicured adhesive composition to provide a tape or film. In tapes, the carrier is the backing on which the adhesive is applied. The backing may be used for functional or decorative purposes. In epoxy films or structural tape, the carrier is usually porous and the adhesive saturates the carrier. Glass, polyester, and nylon fabric are common carriers for supported B-staged epoxy adhesive films. In these cases, the carrier provides for a method of applying the adhesive and also may act as reinforcement and a internal shim to control the thickness of the adhesive. 

Smith, R., The U.S. Epoxy Adhesives Business, Composites News, June 30, 2004. 

Inorganic fillers may be added to the adhesive composition to reduce the concentration of epoxy resin in the formulation as the degree of polymeric shrinkage is dependent on the volume of epoxy in the joint (Chap. 9). 

EMI cured epoxy adhesive formulations are claimed to have outstanding adhesion to metals, and for this reason it is added as a co-curing agent in many compositions. It is an excellent anhydride accelerator providing higher thermal resistance than typical tertiary amine accelerators. 

TABLE 7.4 Epoxy -Phenolic Adhesive Compositions of Commercially Available Types5... 

Hopper, F. C., and Naps, M., Epoxy Resin Adhesive Compositions, Their Preparation, and Tape Containing the Same, U.S. Patent 2,915,490, 1959. 

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