Solvent based rubber adhesives have been the mainstay of the shoe and leather industry. Epoxies are adhesive systems made by a complex chemical reaction. Various resins are made synthetically by reacting two or more chemicals. The resultant resin can then be reacted or cured by the addition of another chemical called a hardener, or catalyst. The basic epoxy resin systems are further modified to change their physical properties by the addition of such things as flexibilizers for impact resistance and flexibility, diluents or solvents to reduce the viscosity fillers and reinforcements like glass fiber, alumina, silica sand, clay, metal powders and flakes to change properties such as heat and electrical resistance, fire retardance, strength and adhesion to certain substrates or materials.
Epoxy adhesives can bond a wide variety of substrates with high strength particularly metals.
They have been used to replace some traditional metalworking methods of joining like nuts and bolts, rivets, welding, crimping, brazing and soldering. High strength epoxies are used to construct rotor blades of helicopters, attach aluminum skins to the struts of aircraft wings and tail sections. Those of you who ski may know that your skis are laminates of plastics, wood, and metal joined with an epoxy. If you are a golfer, the heads of your clubs are bonded with an epoxy. Hot melt adhesives are thermoplastic polymers that are tough and solid at room temperature, but are very liquid at elevated temperatures.