California Department of Transportation
 

11. ADHESIVES & SEALANTS

11.1 Adhesives

11.1.1 Design of Joint

The joint shall be designed to minimize concentrations of stress. The basic stress shall be in shear. The weakest design is where the basic stress is in cleavage or peel and non-axial loading in tension produces cleavage.

11.1.2 Harmful effects

The user shall ascertain that the formulation of the adhesive selected shall have no harmful effects on the bonded assembly or nearby items when bonded assembly is in storage, transit or use under the environmental conditions for which it was designed. Harmful effects may be caused by the slow release of trapped solvents which can damage many types of rubber and plastic, or cause other harmful results degrading operation of the equipment. All manufacturer’s application instructions shall be followed.

11.1.3 Structural compatibility

Adhesives which are not compatible structurally shall be avoided. For example, a brittle adhesive shall not be used for glass bonding because excessive shrinkage during setting or curing shall load the glass in tension. For assemblies which may be flexed or subject to impact, a brittle adhesive shall not be used. All manufacturer’s application instructions shall be followed.

11.2 Sealants

If a sealant is necessary to seal electrical items a polyurethane sealant is the preferred choice. There are also specialty sealants made for electrical work (e.g., liquid tape, electrical by Plastic Dip, E6000 by Eletric Products). If a silicone is used it shall be one for use around electronics (#748 RTV silicon by Dow Corning). All manufacturer’s application instructions shall be followed.

Last updated 01/14/04