Metals recommended adhesives

SR-9016 is a metallic diacrylate adhesion promoter for UV/EB cure applications. SR-9016 is water soluble up to 20 wt%. This product promotes adhesion to metals, including steel, tin-free steel, brass, and aluminum. Usage levels up to 5% are recommended... 

Zinc surfaces may be involved either by the use of galvanized steel or of zinc die castings. Again, anhydride-cured epoxies should be avoided as also should adhesives which contain tackifiers based on rosin derivatives. These rosin materials tend to form soaps with zinc and to form them at the interface between metal and adhesive thus creating a weak boundary layer. Polychloroprene adhesives are recommended for use with zinc as the tackifier used is normally a tcrt-butyl phenolic resin which is perfectly safe, although some products may contain other, less satisfactory, tackifier. 

CO/ECO/GECO compounds can be successfully compression, transfer, injection, or injection/transfer molded. Injection molding may be the most commonly used method. When molding with metal inserts, Ty-Ply BN, Chemlok 250, and Chemlok 855 are some of the recommended adhesives for bonding ECO to metal. 

Zinc is used in multiple applications. It is widely employed for galvanizing steel and iron against rust. It is also used for die casting and forming alloys including brass and bronze. This lustrous blue-white metal is hard/brittle at ambient temperatures. It is malleable at 100—150°C, conducts electricity and heat, is anticorrosive, and has a relatively low melting point (419.5°C). Zinc is the fourth most common metal today. Adhesives recommended include nitrile-epoxies, epoxies, silicones, cyanoacrylates, and rubber-based adhesives [21]. 

The other problem that can occur with metals is the presence of various machine oils on the surface, such as might be used in the automotive area. Oil serves as a low surface energy barrier to adhesion, in most instances. Abrading and solvent wipe are recommended or else degreasing. Removing the surface oil is... 

A critical problem with adhesion layers arises from grain boundary diffusion. Deposited films tend to be polycrystalline and granular. The electrochemistry of the adhesion film is frequently much less desirable than the electrochemistry of the primary film. Moreover, minute contamination of the primary metal film surface by adhesion components can dramatically degrade the electron transfer properties (e.g., electrochemical reversibility, as evidenced by cyclic voltammetric peak potential separation) of the film [58], Thus it is essential that the adhesion layer is not exposed to solution. While the rate of diffusion of adhesion metals through the bulk of the primary layer is quite slow, grain boundary diffusion along the surfaces of grains is much faster. In many cases, the adhesion layer can seriously compromise the performance of the electrode. This is particularly a problem for chromium underlayers. Recently a codeposited Ti/W adhesion layer has been recommended as an alternative to chromium, with reportedly better adhesion and fewer interferences than Cr. A procedure was also described to recondition these electrodes to minimize interference by adhesion layer metals [58]. 

Silanes have also been employed to improve adhesion to metal substrates. For example, Toray Chemicals of Japan has observed adhesion improvement for Mo by employing an organosilane (isopropanol solution) and for Al, Ti, Ni, and Pd by employing an organotitanate spun from toluene. Results for other silanes to Au and Al are reviewed later. Similarly, Dynamit Nobel recommended employing glycidoxypropyltrimethoxysilane to improve positive photoresist image adhesion to Ta, W, Al, and Nb. 

Mercaptosilane has long been recommended for use in crosslinkable rubber compositions [10], i.e. NBR, SBR, etc., both as an adhesion promoter to aid bonding between rubber adherends (or rubber to metal) and to enhance bonding... 

Titanates have been instrumental in the bonding of fluorinated resins to packaging films, poly(hydantoin)—polyester to polyester wire enamel, polysulfide sealant to polyurethane (a phosphated titanate is recommended), polyethylene to cellophane using a titanated polyethylenimine, and silicone mbber sealant to metal or plastic support using polysilane (Si—H) plus polysiloxane (Si—OR) and titanate as the adhesive ingredients (450—454). Polyester film coated first with a titanium alkoxide, then with a poly(vinyl alcohol)—polyethylenimine blend, becomes impermeable to gases (455). 

The actual metal surface that takes part in the bonding is illustrated in Fig. 16.1. Adhesives recommended for metal bonding are in reality used for metal-oxide bonding. They must be compatible with the firmly bound layer of water attached to surface metal-oxide crystals. Even materials such as stainless steel and nickel or chromium are coated with transparent metal oxides that tenaciously bind at least one layer of water. 

As with metal substrates, the effects of plastic surface treatments decrease with time, so it is important to carry out the priming or bonding as soon as possible after surface preparation. The surface preparation methods suggested in App. F are recommended for conventional adhesive bonding. Greater care must be taken in cleaning thermoplastics than... 

The width of the lap shear specimen is generally 1 in. The recommended length of overlap, for metal substrates of 0.064-in thickness, is 0.5 + 0.05 in however, it is recommended that the overlap length be chosen so that the yield point of the substrate is not exceeded. In lap shear specimens, an optimum adhesive thickness exists. For maximum bond strengths, the optimum thickness varies with adhesives of different moduli (from about 2 mils for high-modulus adhesives to about 6 mils for low-modulus adhesives).5... 

Recommended Practice for Metal to Metal Overlap Shear Strength Test for Automotive Type Adhesives... 

Other workers, who have had occasion to repeat the work of Kalmus report considerable difficulty in obtaining thick deposits of cobalt consistent with a high quality of adhesion. The solutions recommended by Kalmus yield quite satisfactory results for very thin deposits, but the case is otherwise where deposits are required ranging in thickness from 3 to 5 thousandths of an inch and upwards. In these eases the deposited metal is found to separate very readily from its base.3 Furthermore, in view of more recent research on the rapid deposition... 

The metallic catalyst most widely employed is some form of tin. However, some specialized uses of titanium, mercury, and even lead exist in industry. Based on my industrial experience I do not recommend the use of tin in a coating or adhesive that is designed for long ageing or wearing. 

Letterpress, Flatbed, Sheet Fed This is one of the oldest printing methods wherein direct contact is made between raised type, usually metal, and the facestock. The quality of the printing would be rated as fair to good since control of the ink is not as positive as some of the other methods. It should be considered for very short run paper stock where copy is fairly simple. The label stock usually used is a standard Crack/Peel type with very little selection of the adhesive. This type of factory-cut liner is more difficult to remove than other t5q)es, particularly for a large label. Not recommended for vinyls or other exterior grade use. 

As intended by the adhesive formulation, no parasitic side reactions such as formation of urea, new uretdione, isocyanurate, biuret, or allophanate are detected for the bulk and for thick films on Al, Cu, and Au (dpu>l pm cf Figs. 6.3, 6.7). Even ultrathin PU films on Au correspond to bulk properties to a very good approximation (Fig. 6.8), which is a recommendation for films on Au as references with respect to effects in the interphase on different metals. 

Unfilled poly(amide imide) powder for adhesive applications High-strength grades perform more like metals at elevated temperature cmd are recommended for repetitively-used precision mechanical and load-bearing parts... 

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