Page 502 - Handbook of Adhesives and Sealants

434 Chapter Eleven

strength to most elastomers. Surface treatment consists of washing
with a solvent, abrading, or acid cyclizing as described in Appendix
C-3.
Elastomers vary greatly in their formulation from one manufacturer
to another. Fillers, plasticizers, antioxidants, and other components
may affect the adhesive bond. Adhesives should be thoroughly tested
with a specific elastomer and then reevaluated if the elastomer man-
ufacturer or formulation is changed even though the physical property
specification may remain unchanged. Table 11.4 shows common types
of adhesives used for bonding elastomers.

11.4.3.2 Unvulcanized elastomers. Uncured or unvulcanized elasto-
mers may be bonded to metals and other rigid adherends as part of
their curing process by first priming the adherend with a suitable air-
or heat-drying adhesive. The liquid elastomer is then injected or
poured around the substrate surface, and then it is vulcanized or
cured. Bonding of rubber to metal hubs or inserts is commonly accom-
plished this way. The elastomers that can be bonded in this manner
include nitrile, neoprene, urethane, natural rubber, SBR, and butyl
rubber. Less common unvulcanized elastomers, such as the silicones,
fluorocarbons, chlorosulfonated polyethylene, and polyacrylate, are

TABLE 11.4 Common Adhesives for Bonding Rubber
Chlorinated rubber—used to some extent for bonding natural rubber
Epoxy—used to bond some rubbers
Epoxy-polyamide—used to bond some rubbers
Natural rubber solution—for bonding natural rubber
Natural rubber latex—for bonding sponge rubber
Neoprene synthetic rubber—for bonding natural and synthetic rubbers, especially
neoprene
Nitrile synthetic rubber—for bonding natural and synthetic rubbers
Phenolic-neoprene—for most types of rubber
Phenolic-nitrile—for most types of rubber
Phenolic-vinyl—cycled rubbers, i.e., those surface treated with sulfuric acid
Polyurethanes—used to some extent for rubbers especially urethane
Reclaimed rubbers—for most types of rubber
Resin-rubber blends—numerous formulations are available for bonding most types
of rubber
Resorcinol formaldehyde—has been used to some extent for bonding rubbers
Silicones—for bonding silicone rubbers