Epoxy adhesives resin manufacture

Formulators in the adhesives industry do not normally manufacture epoxy resins. Generally, formulators buy epoxy resins, modify them with other materials, do similar compounding to the curative, and then package the product as a complete adhesive system ready for the end user. There are many excellent textbooks6-8 available giving information about the preparation, chemistry, and use of epoxy resins in general applications. It is not the intention here to go into such detail but to focus only on epoxy adhesive systems. 

Properties often used by epoxy resin manufacturers to specify particular grades of resin include the epoxy content, viscosity or softening point, and color. In addition, properties such as density, vapor pressure, flash point, refractive index, solubility characteristics, and hydroxyl content are often reported. The important properties of uncured epoxy formulations with regard to most adhesive applications are... 

The vapor pressure of an epoxy resin system will have an indirect effect on the final properties of the cured adhesive. However, vapor pressure of the epoxy adhesive and its components may have a direct effect on the health and safety of those who manufacture or apply these products. 

Solid epoxy resins are usually formulated as solvent solutions and blends with lower-MW resins for the production of liquid adhesive systems. However, solid epoxy resins are also often employed in the manufacture of adhesive systems having solid form. There are several forms of solid epoxy adhesives that find application. The most common are supported or unsupported film, powder, and solder stick. Formulations for these adhesives are detailed in Chap. 13. 

Epoxy adhesives can be manufactured into a film form. This is most conveniently done with solid epoxy resins in solution. Epoxy film adhesives can be thermoplastic (e.g., linear ultrahigh molecular weight phenoxy resin) hot melts, but more commonly they are formulated, thermosetting materials. 

TRADE NAMES AND MANUFACTURERS EPOXY ADHESIVES, EPOXY RESINS, CURING AGENTS AND CATALYSTS, ADDITIVES AND MODIFIERS... 

Manufacture of glycerol and unmodified epoxy resins manufacture of elastomers, water-treatment resins, surfactants, ion exchange resins, plasticizers, dyestuffs, pharmaceutical products, oil emulsifiers, lubricants, and adhesives 3511,3513, 3529, 354, 38, 4... 

The adhesive is manufactured in tape form by a hot-melt process. It is a tacky solid at room temperature. The integrity is maintained by using a finely woven glass fabric scrim as the carrier. This process is an excellent example of the compromises required in the technology of formulation. Some of the high-temperature performance that is expected from the phenolic resole is sacrificed for the improved bond strength and toughness afforded from the epoxy resin. The filler is added to make the thermal coefficient of expansion of the cured adhesive more metallic in nature. Dicyandiamide is the... 

Bolger JC (1983) Structural adhesives today s state of the art. In Schneberger GL(ed) Adhesives in manufacturing. Marcel Dekker Inc, New York, pp 133-194 Boom BW, van Driel LMJ (1985) Allergic contact dermatitis to epoxy resin in infusion sets of an insulin pump. Contact Dermatitis 12 280... 

Historically, copper-clad laminates with acrylic or epoxy adhesives have been the major materials for flexible circuits. Each manufacturer has developed a special resin grade or special additives to ensure reliable flexibility and bond strength. Other adhesive materials such as phenol resin or silicon resin have been developed however, they have not become standard adhesive materials in flexible circuits. 

Usually the same films are chosen for the coverlay films as are used for the substrate layers. The films are coated with semicured acrylic or epoxy resin, which is used as an adhesive layer. The surfaces of the adhesive layers are covered with release films when the materials are delivered to circuit manufacturers. Semicured adhesive resins are unstable at room temperature, so film coverlay must be kept in refrigerators. The adhesive resins of the coverlay usually have only weeks of pot life even when they are kept in low-temperature environments, and exact conditioning is required for processing. 

Epoxy based adhesives also work well with Celanex reinforced resins. Some suggested epoxy adhesives are Scotch-Weld 2214 and 2216, manufactured by the 3M Co., St. Paul, MN. Scotch-Weld 2214 is a one-part epoxy which can be cured in 40 min at 120°C (250°F). Scotch-Weld 2216 is a two-part system which cures in 24 h at room temperature. Both of these adhesives gpve tensile shear strengths in excess of 500 psi and are resistant to such environments as fuels, salt spray, and air up to 93° C (200° F) continuous and (250°-300° F) short-term. Many other epoxy-based adhesives are also suitable for use with Celanex Another method of joining Celanex is with adhesive bonding tape. One such tape, Bostik... 

Adhinarayanan [1201 describes the adhesive properties of epoxy—imide resins obtained through the reaction of epoxy resins, namely, Araldite GY250 (di-glycidylether of bisphenol A and epichlorohydrin difunctional) and Araldite EPN1138 (novolac epoxy resin polyfunctional), both manufactured by Hidustan Ciba-Geigy India Ltd (Calcutta), with bis(carboxyphthalimide)s. The chemical structures of these epoxy resins and bis(carboxyphthalimide) are... 

The first adhesive was FM350NA which is an aluminium-filled epoxy resin manufactured by Cyanamid and formulated especially for use over a wide range of temperatures. The stress-strain data are shown in Fig. 2. 

Phenolic resins are used to manufacture the most durable of plywood ( marine plj ood ) and are used in repair operations. Epoxy adhesives are widely used to make laminate structures of marine plywood and plywood/polyester. 

Polyimide resins are inherently lower in chlorides than epoxies. For this reason, many IC manufacturers have chosen to use conductive polyimides, rather than epoxies, for high rel assembly operations, even though polyimides are more expensive, give lower bond strengths, and are more difficult to cure and to process than epoxy adhesives. 

Recently, the major U.S. and Japanese resin manufacturers have made available new, highly purified epoxy resins which contain much less extractable and hydrolyzable chlorides than the best epoxy resins prior to 1980. Adhesive for-mulators now use these high purity epoxy resins to produce conductive adhesives, coatings, and encapsulants which yield chloride levels of 10 ppm or less and sodium levels of 5 ppm or less. 

Aerospace adhesive manufacturers were quick to exploit epoxy resins. Starting in the early 1950s, a succession of epoxy and modified epoxy adhesives were developed and conuner-cialized. The major advantage of epoxy based adhesives was that crosslinking occurs via an addition reaction. As previously stated this made low pressure bonding possible and permitted the use of nonperforated honeycomb. 

The earliest epoxy adhesives were based on difiinctional bisphenol resins. As the epoxy manufacturers introduced more functional resins, first the epoxy novolacs and then a series of high functionality specialty resins, aero-... 

---