Plastisol adhesives, which have been used widely in the bodywork construction for automobiles, represent another group of physically setting adhesives. A plastisol adhesive is formed by the dispersion of a polymer, mostly polyvinyl chloride (PVC), in a plasticizer. During the curing process, when the dispersion is heated, the polymer dissolves irreversibly in the plasticizer that acts as a solvent, transforming into soft PVC. When the cured adhesive coat is in the thermoplastic state its resistance to heat and its creep strength are poorer than those of chemically setting systems. An improved resistance to heat can be obtained by adding chemical setting components to the plastisol adhesives, such as epoxy systems. The advantages of plastisol adhesives are that they are relatively cheap, and high adhesion and durability are obtained even on nonpretreated steel surfaces or on body sheets that have been oiled for the purpose of corrosion protection.
4.2.3