High-performance adhesives

Adhesives consumer and craftsmen adhesives (pastes and adhesives for home use) industrial and packaging adhesives engineering adhesives (high-performance sealants and systems) ... 

Eccobond . [Emerson Cuming] Epoxy, urethane, or acrylic adhesives high performance conductive adhesives for ii strial and electronic ai lics. 

Yaroch, E.J., Water-based adhesives. High Performance Adhesive Bonding, Society of Automotive Engineers (SAE), pp. 138-152,1983. 

Small amounts of polymer-grade terephthaHc acid and dimethyl terephthalate are used as polymer raw materials for a variety of appHcations, eg, adhesives and coatings. They are also used to make high performance polymers or engineering resins. Poly(ethylene terephthalate) is itself an engineering resin, although one more widely used is poly (butylene) terephthalate, formed by reaction with 1,4-butanediol as the comonomer. 

Primers for Metal. If reasonably high performance is required ia the end product and unless cost is of paramount importance, a minimum of two coats, usually a primer and a top coat, should be appHed to metal. For highest performance, primer vehicles should provide good wet adhesion, be saponification resistant, and have low viscosity to permit penetration of the vehicle iato microsurface irregularities ia the substrate. Color, color retention, exterior durabiHty, and other such properties are generally not important ia primers. Resia systems such as those including bisphenol A epoxy resias which provide superior wet adhesion can thus be used ia spite of their poor exterior durabiHty. 

Vinyls. Vinyl resins are thermoplastic polymers made principally from vinyl chloride other monomers such as vinyl acetate or maleic anhydride are copolymerized to add solubUity, adhesion, or other desirable properties (see Maleic anhydride, maleic acid, and fumaric acid). Because of the high, from 4,000 to 35,000, molecular weights large proportions of strong solvents are needed to achieve appHcation viscosities. Whereas vinyls are one of the finest high performance systems for steel, many vinyl coatings do not conform to VOC requirements (see Vinyl polymers). 

Adhesives. Because of exceUent adhesion to many substrates, epoxy resins are extensively used for high performance adhesives. These can be categorized into high temperature curing systems (soHds and Hquids) and room temperature curing systems (Hquids). 

Depending on the characteristics and performance requirements, adhesives systems are frequendy modified with diluents (reactive and nonreactive) and polyfunctional high performance resins, as weU as with fillers of various types. 

This enormous hardness is exploited in grinding wheels which are made from small particles of a high-performance engineering ceramic (Table 15.3) bonded with an adhesive or a cement. In design with ceramics it is never necessary to consider plastic collapse of the component fracture always intervenes first. The reasons for this are as follows. 

Pure PDMS networks are mechanically weak and do not satisfy the adhesive and cohesive requirements needed for most applications in which the silicone adhesive joint is subjected to various stresses. For crosslinked silicones to become high performing adhesives, they need to be strengthened. 

For many bonding applications a variety of adhesives can perform adequately. Hot melt adhesives are normally chosen where process speed is critical. Since hot melts have no carrier vehicle (solvent or water), and thicken rapidly as they cool, they are limited in their ability to (1) penetrate low porosity substrates or wet out very rough surfaces (2) cut through or imbibe surface contaminants and (3) wet out high thermal conductivity substrates (e.g. metals). Nonetheless, hot melts are increasingly the adhesive of choice in automated production environments because of their fast set speed. 

Poly(tetramethylene oxide) polyols (PTMEG) are high performance polyethers that are crystalline waxes at molecular weights above 650 and liquids at lower molecular weights. They are only available as diols, but they produce adhesives with good hydrolysis resistance and moisture resistance, which is why these adhesives are even used in medical devices, blood bags, catheters, and heart-assist devices [25]. Certain thermoplastic polyurethane adhesives and solvent-borne adhesives are also based on PTMEG s. 

Most moisture-curing liquid adhesives utilize poly(oxypropylene) (PPG) polyols, as shown above. These raw materials produce among the lowest-viscosity prepolymers but may not have sufficient modulus at higher temperatures for some applications. A certain percentage of polyester polyols may also be utilized to boost performance, but these may cause a large increase in viscosity, and so they are more often used in conjunction with polyether polyols to provide a high-performance adhesive with workable viscosities. Poly(butadiene) polyols may be utilized for specific adhesion characteristics. 

Polyurethane dispersions (PUD s) are usually high-performance adhesives based on crystalline, hydrophobic polyester polyols, such as hexamethylene adipate, and aliphatic diisocyanates, such as methylene bis(cyclohexyl isocyanate) (H12MDI) or isophorone diisocyanate (IPDI). These PUD s are at the more expensive end of the waterborne adhesive market but provide excellent performance. 

Campbell, F.J. and Brenner, W., Curing high performance structural adhesives by electron-beam radiation. Nav. Eng. J., June, p. 160 (1982). 

Lopata, V.J., Chung, M., McDougall, TE. and Weinberg, V.A., Electron-curable adhesives for high-performance structures. 39 Int. SAMPE Symp., Apr. 11-14, 1994. 

The full-prepolymer, quasi-prepolymer, and one-shot techniques may appear to be quite similar, but they each have important bearing on equipment requirements and physical properties. The full-prepolymer method, for example, is die process of choice for making high-performance cast elastomers with superb dynamic properties, such as industrial bumpers and bushings. Quasi-prepolymers are used in less demanding applications like shoe soles, adhesives, and spray elastomers. One-shots make up the rest, including most foams and elastomers. 

Aqueous, removable, pressure-sensitive adhesive compositions, useful for high-performance applications, comprise a mixture of a copolymer of alkyl (meth)acrylate and N-substituted (poly)amide of (meth)acrylic acid and a copolymer of alkyl (meth)acrylate and ethylenically unsaturated carboxylic acid, where at least one of the copolymers is an emulsion copolymer. Polyoxyalkyl-enes and phosphate esters may be used as surfactants [234]. 

Proper reinforcement of rubber matrix using hllers can be achieved only if there exists adequate adhesion between the hller and the mbber. Rubber-mbber adhesion and rubber-hller adhesion both without and with adhesion promoters have been studied extensively [125-127]. Fiber-matrix adhesion in short fiber-rubber composites is always a field of extensive research. If the fibers are not bonded properly with the rubber matrix, fibers will shde past each other under tension deforming the matrix, thereby reducing the strength properties. In the case of short fiber-reinforced rubber composites, loads are not directly applied to the fibers, but are apphed to the matrix. To obtain a high-performance composite, the load must be effectively transferred to the fibers, which is possible only when the fiber-matrix interphase is sufficiently strong. In addition, the adhesion between the fiber and the matrix should be such that the failure occurs in the matrix rather than at the interphase [92]. 

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