Adhesive - What is an adhesive?

Definition of ADHESIVE:

This term can refer both to a property of materials that makes them capable of adhesion (i.e. an adhesive material is able to create a bond with another material) and to any material that is capable of holding two surfaces together by surface attachment (i.e. an adhesive is the substance that is used to create a bond between two materials). Adhesives can also be referred to using the terms “glue”, “cement”, “mucilage”, or “paste”.

Compared to other techniques used to join two surfaces or materials together (e.g. sewing, mechanical fastening, thermal bonding etc), adhesives can be used to join a much wider range of materials together, can distribute stress across the joint more efficiently (reducing the chances of joint failure), offer a more aesthetic design and provide opportunities for greater flexibility of design, and tend to be much more cost effective (and time efficient) than other methods.             

There are many, many, many different types of adhesives, although they are typically categorised in one of two ways. They may be grouped by origin into “natural adhesives” (made from organic sources, such as vegetable starch, natural resins, or animals – sometimes known as “bioadhesives”) and “synthetic adhesives” (made from man-made materials, such as polymers – this group includes emulsion adhesives, thermoplastic adhesives, and thermosetting adhesives).

More commonly, adhesives are grouped by their method of adhesion and then organised into “reactive adhesives” (require a chemical reaction to form an adhesive bond) and “non-reactive adhesives” (don’t require a physical change to form an adhesive bond, although they may undergo a physical change in order to form a bond).

Reactive adhesives are further divided into “multi-part adhesives” (where the chemical reaction takes place between two or more components (usually a base resin and a hardener/curing agent) that are mixed together to create an adhesive bond) and “one-part adhesives” (where the chemical reaction takes place between the adhesive and an external energy source, such as radiation (e.g. UV Light), heat, or moisture).

Examples of non-reactive adhesives include drying adhesives, contact adhesives, hot melt adhesives, and pressure sensitive adhesives. Drying adhesives create an adhesive bond via evaporation and can be either solvent-based adhesives (components of an adhesive are dissolved in a solvent, which evaporates and leaves the components behind) or emulsion adhesives (the components of an adhesive are dispersed throughout a liquid, such as water, which evaporates and leaves the components behind). Contact adhesives are similar but must be applied to both of the surfaces that are to be stuck together and time allowed for the adhesive to dry (via evaporation), before the two surfaces are pushed together to form an instant adhesive bond. Hot melt adhesives are thermoplastics that are heated and applied in molten form so that an adhesive bond is formed as they cool down and solidify. While other adhesives (sometimes known collectively as “structural adhesives”) create an adhesive bond once they have hardened via chemical or physical processes (e.g. via chemical reaction, evaporation, or cooling), pressure sensitive adhesives are “tacky” under normal conditions and require only the pressure of a finger or hand to form an adhesive bond (through intermolecular interactions between the adhesive and the adherend).

At Label Planet, all of our products are self-adhesive labels, which means that they are all made with pressure sensitive adhesives.

Here is the Harvard-style citation to use if you would like to reference this definition of the word adhesive:
Label Planet (2016) What is an adhesive? | Adhesive Definition. Available at: https://www.labelplanet.co.uk/glossary/adhesive/ (Accessed: January 1, 2024).