Natural rubber adhesives are commonly used in bonding non-metallic materials such as leather, fabrics, paper, and other rubber products. Natural rubber has good resistance to water, but poor resistance to organic solvents, and chemical oxidizing agents. The natural rubber molecule crystallizes at about -35°C and water latex emulsion must be protected from freezing.
Often chlorinated natural rubber is used in adhesive formulations. outstanding property of chlorinated rubber is its resistance to water, some oils, salt spray, and acids and alkalis. Resistance to organic solvents in general is poor, and the practical temperature limit is 140°C. In adhesive formulations, chlorinated rubber has been used to bond natural and synthetic rubbers to metals. Such adhesives have been used to prime metal surfaces prior to bonding with neoprene or nitrile based adhesives.
Other methods of processing natural rubber for use in adhesive formulations are: by cyclizing (treating with acids or metal salts) to form hard, tough adhesives for metal surfaces; and by reacting with hydrogen chloride (rubber hydrochloride adhesives) to form thin, transparent adhesives used in the packaging industry.