The substance used to bind/glue two surfaces. Adhesives can have natural or synthetic origin and be thermoplastic or thermosetting. Adhesives are typically defined by the kind of adhesion. They can be reactive and non-reactive adhesives. The reactive adhesives chemically reacts to harden: one-part adhesives (light curing materials, e.g. acrylic based adhesives; heat curing materials, e.g. cyanoacrylates and urethanes); multi-part adhesives (acrylics, urethanes and epoxies). The non-reactive adhesive are: drying adhesives (solvent based, e.g rubber cement; polymer dispersion based, e.g. PVAc), pressure sensitives adhesives (e.g acrylate polymers), contact adhesives (e.g natural rubber and neoprene), hot adhesives (hot melt thermoplastic adhesives).
