Epoxy in adhesives

Behm, D. T., and Gannon, J., Epoxies in Adhesives and Sealants, vol. 3, Engineered Materials Handbook, ASM International, Materials Park, OH, 1990. 

DGEBA is the most commonly used epoxy in adhesive formulations. Although they may range from very simple, low molecular weight, primarily aliphatic resins to more complex, multifunctional, primarily aromatic materials. A wide choice of curing agents is available, in common with other applications. Schmidt and... 

The most often used epoxies in adhesives are based on the diglycidyl ether of bisphenol-A (DGEBA) as seen in Equation 2.9 ... 

Epoxy stmctural adhesives are used in an extraordinarily wide range of appHcations. They are available in essentially all of the forms discussed above, except for primer—Hquid combinations or as room temperature curing Hquids. The highest technology appHcation for epoxies is in aerospace stmctural... 

Pentaerythritol in rosin ester form is used in hot-melt adhesive formulations, especially ethylene—vinyl acetate (EVA) copolymers, as a tackifier. Polyethers of pentaerythritol or trim ethyl ol eth an e are also used in EVA and polyurethane adhesives, which exhibit excellent bond strength and water resistance. The adhesives maybe available as EVA melts or dispersions (90,91) or as thixotropic, one-package, curable polyurethanes (92). Pentaerythritol spko ortho esters have been used in epoxy resin adhesives (93). The EVA adhesives are especially suitable for cellulose (paper, etc) bonding. 

Because of the bulky neo stmcture in the middle of the molecule, this compound has enhanced hydrolytic stabiUty in addition to low volatihty. It is useful in many types of flexible foam, as well as in adhesives and epoxy- or phenoHc-based laminates. 

High purity 4-dodecylphenol is used to produce specialty surfactants by its reaction with ethylene oxide. The low color of high purity 4-dodecylphenol is important in this appHcation from a standpoint of aesthetics. 4-Dodecylphenol is also used to produce phenoHc resins which are used in adhesive appHcations and printing inks. 4-Dodecylphenol is also used as an epoxy curing catalyst where the addition of 4-dodecylphenol accelerates curing of the epoxy resin to a hard, nontacky soHd. 

Isopropa.nola.mines. Reaction of propylene oxide with ammonia yields mono-, di-, and triisopropanolamines. These products find use as soluble oils and solvents, emulsifiers, waterless hand cleaners, cosmetics, cleaners, and detergents. In industrial apphcations isopropanolamines are used in adhesives, agricultural products, corrosion inhibitors, coatings, epoxy resins, metalworking, and others (51). 

The thermal stabiUty of epoxy phenol—novolak resins is useful in adhesives, stmctural and electrical laminates, coatings, castings, and encapsulations for elevated temperature service (Table 3). Filament-wound pipe and storage tanks, liners for pumps and other chemical process equipment, and corrosion-resistant coatings are typical appHcations using the chemically resistant properties of epoxy novolak resins. 

Corrosion-inhibiting primers based on this technology have been in continuous service since they were first utilized with nitrile epoxies in the late 1960s. These inhibitors function by passivating the aluminum. In this process, water permeating the adhesive bondline carries a certain amount of inhibitor to the oxide surface. 

In addition to epoxy-phenolic adhesives three-part epoxy-phenolic-nitrile rubber systems are used in metal-metal edge joints and honeycomb constructions [208], These add toughness not available in most EP systems and improve peel strengths. When used on honeycomb, the NR-P is normally applied to the aluminum skin and the EP to the honeycomb for assembly. Service temperature limitations are those imposed by the NR-P part. 

Antimonious acid H3Sb03 and its salts are less well characterized but a few meta-antimonites and polyantimonites are known, e.g. NaSb02, NaSb305.H20 and Na2Sb407. The oxide itself finds extensive use as a flame retardant in fabrics, paper, paints, plastics, epoxy resins, adhesives and rubbers. The scale of industrial use can be gauged from the US statistics which indicate an annual consumption of Sb203 of some 10000 tonnes in that country. 

Materials. The single films and multilayered materials examined are listed in Tables I and II, respectively. The adhesive (10thick) between any two layers was a two-component curing, epoxy—polyester adhesive, Adcote 503A, Morton Chemical Co. Pouches (11.5 X 17.8 cm) were made from the multilayered materials by heat sealing the sides and bottom under the optimum heat sealing conditions (3). 

Aromatic amines formed from the reduction of azo colorants in toy products were analysed by means of HPLC-PDA [703], Drews et al. [704] have applied HPLC/ELSD and UV/VIS detection for quantifying SFE and ASE extracts of butyl stearate finish on various commercial yarns. From the calibrated ELSD response the total extract (finish and polyester trimer) is obtained and from the UV/VIS response the trimer only. Representative SFE-ELSD/UV finish analysis data compare satisfactorily to their corresponding SFE gravimetric weight recovery results. GC, HPLC and SEC are also used for characterisation of low-MW compounds (e.g. curing agents, plasticisers, by-products of curing reactions) in epoxy resin adhesives. 

Materials. The adhesives and primers used in this study were model and commercial materials that were cured according to conditions appropriate for the specific adhesive chemistry. Adhesives A and B were conventional epoxy/Versamid and epoxy/dlcyandiamlde adhesives, respectively. Adhesives C and D were commercial urethane and epoxy/polyamlde adhesives, respectively. Adhesive E was a conventional two-part epoxy/amldoamlne adhesive. Adhesive F was a vinyl plastlsol adhesive. The adhesive primers used in this study were a urethane crosslinked epoxy electrocoat primer and spray primers based on tall oil modified epoxy ester, and polyesterpolyol/isocyan-ate chemistry. Dicyandlamlde was obtained from Aldrich Chemical Company. Epon 828 was obtained from Shell Chemical Company. 

Such a variety of effects suggests that (1) Further analytical study would be required to understand them theoretically, but (2) Broader practical study would pinpoint formulations which would permit the recycler to optimize critical end-use properties. This would be useful primarily in epoxy moldings and castings, and in adhesive formulations. 

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