Adhesives are substances used to connect together two objects or surfaces by adhesion mechanisms, such as chemical bonding, or intermolecular interactions.
Adhesives may be divided according to the number of their components used for forming and curing the adhesive layer:
- one-component adhesives – they get hardened through chemical reaction induced by an external agent e.g. heat, moisture or UV radiation.
- multi-component adhesives – they get hardened by mixing two or more components that react together and form the joint. The adhesive components separately do not have adhesive properties.
The mechanical strength of the glued surfaces is influenced by several factors, including:
- size and shape of surfaces glued – the joint formed over a large area with an irregular shape is more durable and stronger than that created through joining small, smooth materials,
- the depth of adhesive penetration into the substrate – the rougher the surface, the more durable the joint.
- impact of the adhesive on surfaces glued – the joint formed by chemical bonding between the components of the adhesive and the material of the area glued, it is more resistant than that created through chemical interaction between the components.
Many types of synthetic adhesives are available on the market, including epoxy, phthalic, polyurethane, poly-acrylic or silicone adhesives, which are used e.g. to join metal, ceramics, paper, wood, plastics or leather.
