The performance of solvent-based adhesives is largely determined by the polymer system in the formulation. The choice of adhesive type depends on the specific substrates and environmental resistance needed – temperature resistance, oil and plasticizer resistance, etc. Most solvent based adhesives contain flammable solvents which require proper precautions for safe handling. In addition, many organic solvents are regulated due to environmental concerns with emissions.
Within each type of solvent based adhesive, formulations are available to match the application requirements of the process – brush, roll, bead or ribbon, spray. Once the adhesive is applied, solvent evaporates relatively quickly causing an increase in viscosity of the adhesive film. Bonds can be made immediately after adhesive application or after some solvent has evaporated but before the adhesive has dried to the point where it will no longer wet (open time). Waiting for some evaporation prior to bonding (set time) increases the initial strength of the adhesive bond and allows assemblies to be processed more quickly.
The time window for proper bonding is specified by the adhesive manufacturer. Coating both substrates and waiting until the adhesive sets before bonding typically provides the best initial bond strength with longest open time. If assembly and processing requires extending open time or very high initial strength, the adhesive can be coated and dried then activated by spraying, brushing, or rolling with a light coat of solvent to develop surface tack on the adhesive. Solvent based adhesives remain soluble in organic solvent after drying. This reduces the need for equipment maintenance and facilitates clean-up. Care must be taken to follow manufacturers’ recommendations for safe handling of solvents.