Adhesives are natural or synthetic substances primarily used as glue. The first natural adhesives date back thousands of years and were made from a variety of trees, plants, starches, flour, and certain animal skins. In ancient times, these organic materials were mixed with water to create a sticky paste substance. Since then, adhesive production has become a more varied and complex process. The development of synthetic, thermoplastic, and pressure sensitive adhesives has improved the durability and range of use for this product. Adhesives now play a vital industrial role, whether they are used in complex mechanical processes or to close simple machine fractures.
Similarly, sealants are sticky materials that become solid when applied to a surface and block any air or matter from entering a gap. They are typically made from chemical liquids, paints, and malleable substances. In addition, specialized types of sealant can be produced from silicone and Polyurethane. In some industries, sealants are applied via pipe systems to create a coat around a sensitive assembly. Like adhesives, sealants can be used to repair fractured work pieces or to fasten up surfaces.