Epoxy is a high performance thermosetting resin, which is the product of a one-way chemical reaction. The reaction takes place between a resin and hardener, and is triggered by the mixing process, or as is the case with one-part systems, the reaction is accelerated with heat.

It is a diverse family, including adhesives, coatings, casting resins and laminating resins. On top of this, there are many different types of hardener and a wide range of additive available, which creates the opportunity to tailor the resin to a range of applications. Key properties include high strength, low shrinkage, excellent wet-out and adhesion with other materials, insulating, and resistance to solvents and chemicals.

One downside of epoxy is that it uses some nasty ingredients that are harmful to people and the environment, in particular bisphenol A (BPA) monomer. BPA is a key ingredient of epoxy resin, alongside epichlorohydrin (ECH) – most epoxy systems are derived from reacting these two ingredients. Bisphenol A (BPA) has been at the centre of numerous studies, because it poses a risk to people and the environment (it is an endocrine disruptor and oestrogen-mimicker). The concern is that small amounts of the chemicals present in food packaging materials migrate into the contents.

Even so, certain grades of epoxy are certified as food safe and considered non-toxic by organisations such as the US Food and Drug Administration (FDA) and the European Food Safety Authority (EFSA). As a result, they can be utilised in food contact applications. Examples include coatings on steel water storage tanks and steel food packaging (tin cans), chocolate moulds and table tops.

Another downside is that as a thermosetting resin, it is not recyclable. Bio-based alternatives are emerging that attempt to reduce the negative impacts of this versatile resin by replacing a portion of the petrochemical derived ingredients with potentially renewable ones.