Epoxies have been revolutionising industries worldwide since the 1930s.
From everyday products to cutting-edge industrial machinery, their adaptability knows no bounds. With over 50 different substances known as epoxy resins and a multitude of hardeners, the possibilities are endless. By blending different types of epoxy resins and incorporating additives, plasticisers, or fillers, the final properties can be tailored to fulfil specific applications.
The Chemistry Basics
Epoxy resins are a diverse class of prepolymers and polymers featuring multiple epoxy groups, also known as glycidyl or oxirane groups. Derived from petroleum or organic feedstock through a reactive process involving epoxide units, these resins can vary in chain lengths and purity grades, allowing for a wide range of uses.
Epoxy resins are quantified by their epoxide content, indicating the number of epoxide equivalents in 1kg of resin. Another crucial parameter is the molecular weight, defining the state of the resin – liquid or solid – and opening up opportunities for applications like coatings, glues, and paints.
The Birth of BADGE
One of the most common epoxy resins is formed by reacting epichlorohydrin with Bisphenol A, producing Bisphenol A diglycidyl ether, affectionately known as BADGE or DGEBA. These low-molecular resins have become a staple in the world of epoxy commercialisation.
The Art of Curing
The magic behind epoxies lies in the curing process – an exothermic reaction achieved either by epoxy resins reacting with themselves (catalytic homo-polymerization) or by cross-linking with a hardener. This results in epoxy thermoset polymers boasting unparalleled adhesion, durability, resistance, and versatility.
Epoxy resins are brought to life with the help of various hardeners, each offering unique characteristics. Amines, anhydrides, phenols, and thiols are among the popular choices, enabling epoxy resins to cater to diverse temperature ranges and applications.
The Origins of the ‘Epoxy’ Name
‘Epoxy’ originates from the Greek words ‘epi’ (over) and ‘oxi’ (oxygen). Today, this term encompasses both the fundamental component and the end product of epoxy resins.