Produced primarily from synthetic materials, glue or adhesive is, simply put, a bonding agent designed to join various materials together. Glue comes in several states including liquid, semi-solid and solid. Almost anything is bondable with the right type of glue. Glue functions by being applied to one or both of the joining surfaces and given time to harden or cure, thereby creating the bond.
Glue can be categorized as a pressure-sensitive, contact, hot melt, drying, multi-part or synthetic adhesive. Pressure-sensitive glues include many common glues found in homes and schools. They can form permanent or temporary bonds. Contact glues such as neoprene or cyanoacrylate work by chemically bonding upon contact with materials. Hot melt glues start in solid form. When heat is added, the glue quickly turns into a semi-solid state for application, and set time is very fast. Drying glues include solvent-based and emulsion adhesives. Mixing one or more solvents with some type of polymer, solvent-based glues harden as the solvent evaporates. Rubber cement and white glue are examples of this type.
Glue is identified by its ingredients and manner of hardening. Certain multi-part glues such as epoxies, acrylics and polyurethane chemically react with other components to form their bond. One-part adhesives require something external to cure the glue such as high heat, moisture or light radiation. Ultraviolet light is used to cure certain glues, mainly acrylics. Heat exposure cures epoxies, helping to make those bonds incredibly resilient against later heat and/or chemical exposure.
Glue is found everywhere, from homes, schools and offices to workplaces and all manner of industrial facilities. Used to bond paper, make arts and crafts, upholstery and furniture, other kinds of glue are used to make automobiles, boats, bicycles, skis and countless other consumer goods. Plywood, particleboard, books, electronics and thousands of other products feature some type of glue as a component. Whether used as an ingredient or on its own, without glue an untold number of products would not be possible.