Called thermoset polyesters, these materials are glass fiber-reinforced unsaturated polyesters. They are also often referred to as “sheet molding compounds” (SMCs), “fiber-reinforced plastics” (FRPs), or simply “fiberglass.”
Urethane adhesives are the clear market leader in this area. Particularly in the transportation industry, urethanes’ resilience and resistance to peel, fatigue, and impact have made them the first choice for large-area panel bonding, although primers are sometimes needed. Toughened epoxies are also quite useful for bonding fiberglass components; they are used where more load-bearing capability is needed.
Reactive acrylics have been shown to be versatile adhesives for these materials. They can be used without primers and have an excellent combination of rapid curing, resilience, and load-bearing properties. Reactive acrylics have had particular success in the marine industry for the assembly of recreational boats. Tough acrylics have the unique ability to control bond open times, followed by rapid strength development. Cyanoacrylate adhesives also perform well in small gap situations where “instant” cure is the dominant requirement.