Laminating nitrile rubbers

Laminating. Nitrile rubbers blended with various epoxy resins and activated by suitable amines and/or acidic agents have been employed to bond elastomers, plastics, fabrics, wood, and metals to themselves and each other. Normally good bond strength can be developed at or near room temperature. Any information must be adapted to the substrate being bonded but Table 26 gives a starting formulation. The triethylenetetramine is added as a 50% solution in methyl ethyl ketone just prior to use. Such a cement will cure in 4-24 hours at room temperature and less than 30 minutes at 150°F. 

Nitrile rubber adhesives. The main application corresponds to laminating adhesives. PVC, polyvinyl acetate and other polymeric films can be laminated to several metals, including aluminium and brass, by using NBR adhesives. NBR adhesives can also be used to join medium-to-high polarity rubbers to polyamide substrates. The adhesive properties of NBR rubbers can be further improved by chemical modification using polyisocyanate or by grafting with methyl methacrylate. 

Chiou and Bradley [81] conducted hydraulic burst and stress rupture tests on 1.28mm thick (58v/o 87/ 35/87° hoop filament wound) tubes made from E-glass fibre/Brunswick LRF-571 DGEBA epoxy resin. There were 6% voids in the laminate. A co-cured nitrile rubber liner was employed, partly to keep the inner surface dry and partly to ensure that pressure could still be maintained if the GRP cracked during the tests. The tests followed 6 months immersion in static simulated sea water (Aquarium Systems Instant Ocean, p = 1023 kgm, pH = 8.2). The tubes had a high (1.5%) moisture uptake, although some of this might have been free water in the voids, but saturation was not reached. 

Hazardous Decomp. Prods. CO, CO2, acrid fumes NFPA Health 2, Flammability 3, Reactivity 2 Uses Monomer for synthesis of nitrile rubber, PVAc emulsions, PVOH, EVA copolymers, vinyl chloride-vinyl acetate copolymers, PVBI, and vinyl acetate-acrylonitrile copolymers in polymerized form for plastic masses, films, lacquers, latex paints, adhesives, textile finishing, safety glass interlayers textile hand modifier binder for paper coatings esterification for food starch modified film-former in cosmetics food pkg. adhesives resinous/polymeric food-contact coatings for polyolefin films food-contact paper/paperboard, ionomeric resins, copolymers, laminates, resin-bonded filters, textiles... 

Nitrile rubber adhesives The main application corresponds to the laminating adhesives. PVC, polyvinyl acetate and other polymeric films can be laminated to several metals... 

NBR latices can be also used in adhesive applications. The use of latex has the advantage of avoiding the previous solution of the polymer before application and has favourable environmental treats. Compounding with a resorcinol-formaldehyde solution allows to bond nitrile rubber to cotton or rayon fabric. Nitrile latex can be mixed with PVC latex to give excellent adhesion of polypropylene carpet and plywood backings. Combinations of nitrile latices and styrene-butadiene latices provides good laminating bonds for saturated paper and woven fabrics. 

Nitrile rubber/phenolic resin produces one of the most durable and toughest elastomeric materials developed in the adhesive industry. Further, its resistance to water as to organic solvents is excellent. For these reasons, the nitrile rubber/phenolic resin laminates are used in printed circuit board manufacturing, to bond metallic substrates between themselves (aluminium, steel) and to bond rubber to magnesium. Films of nitrile rubber/phenolic blends have also been used in the aircraft industry for bonding metal-to-metal surfaces in both plain and honeycomb sandwich constructions. 

Laminating Adhesives. Nitrile rubbers have found a large number of applications in the area of laminating adhesives. Table 5 lists the varied applications for these adhesive systems. Several of these specific application areas will then be covered in more detail. Polyvinyl chloride, polyvinyl acetate, and other polymeric films have been laminated to a wide variety of metals including aluminum and brass. 

Table 5. Applications for Laminating Adhesives of Nitrile Rubber.

The adhesive properties of nitrile rubber can be further improved by chemical modification. Nitrile rubber treated with isocyanate was mixed with a polyisocyanate and found to be an excellent adhesive for rubber to sailcoth laminates. In other work, methyl methacrylate was grafted onto nitrile rubber to give a material with good adhesive strength. 

Nitrile rubber/phenolic adhesives are also quite useful in adhering rubber to various met-als, " e.g., in the manufacture of rubber covered metal rollers. Huber reported that a nitrile/phenolic adhesive composition provided excellent bonding of rubber to a magnesium roll (Table 20). Other metal bonding applications with nitrile rubber/phenolic adhesives include laminating aluminum foil to paper and then to wood, bonding abrasives to metal, and bonding polyamide to metal. 

Automotive trim and clips have been bonded with nitrile rubber/phenolic adhesives and polyamide has been bonded to rubbei and to pavement in a road marking application. Plastic/paper laminates for printing blankets have been prepared. Finally, grit tiles have been bonded to paperboard and other substrates to produce prefabricated tile structures which are stable on application to buildings. 

Miscellaneous - Polyvinyl butyral is used as a olear adhesive film to laminate two sheets of glass to form safety glass for car windshields. Phenol formaldehyde resins are used to make brake lining composites, and blends of nitrile rubber and phenolic resin are used to bond brake linings to brake shoes. 

NBR adhesives have excellent shelf stability and high temperature properties. They are used in aircraft, automobile, paper, and electronics applications. Blended with phenolic resins, they have been used to laminate aluminum and stainless steel, fabricate airplane structures, bond abrasives to metal, brake linings to brake shoes, laminate leather, attach soles in shoe manufacturing and bond cardboard, polymeric films, masonite, wood and metal to each other and themselves. Nitrile rubber-phenohc resin blends are poor adhesives for non polar elastomers such as natural rubber, butyl rubber, polyethylene unless their surfaces have been activated to improve adhesion. 

Usual adherends Rubber (particularly nitrile), metal, vinyl plastics Fabrics, foils, plastic film laminate, rubber and sponge rubber, wood Plastics, metals, rubber... 

After the release agent/coagulant dip is applied, Ae formers are preferably conveyed to the next station in the production line where the laminate layer is applied to the formers. The laminate layer may be comprised of an elastomeric or liquid resin dip, such as natural rubber latex. Alternatively, the laminate layer may be a natural or synthetic rubber, such as S5mthetic latex, polyiuethane, nitrile or polychloroprene. By varying the content of the latex material, the laminate layer may be varied to provide different degrees of strength, comfort, and flexibility. In any event, the content of the latex applied to the former will preferably be adjusted to provide the desired gripability, protection from cuts and abrasions, and liquid repellency. ... 

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