Epoxy coatings for chemical resistance are used to protect metals, concrete and a wide variety of other materials from chemical damage. These coatings are often formulated for specific environments and applications. When selecting an epoxy system for chemical resistance, a number of factors must be considered, including the chemistry and network structure of the coating. The most important factor is the crosslinking density of the final epoxy coating, which is influenced by the curing agent, resin and diluent used.
Epoxies are polymers that are composed of long molecules with repeating subunits. These structures give them a wide range of properties, from toughness and elasticity to the ability to absorb many different chemicals. Epoxies contain epoxide groups that harden (or cure) through chemical reactions with other substances or by heating them to a high temperature. This is how epoxy resins and epoxy paints become cured.
Mastering the Elements: A Deep Dive into Epoxy Coatings for Unrivaled Chemical Resistance
The main diluents of epoxy are aliphatic alcohols and polyols. They are reacted with epichlorohydrin to form glycidyl ethers or epoxides, which form epoxy resins. Other ingredients can be added to the epoxides and diluents to modify their characteristics, such as flame resistance through brominated bisphenol A or electrical properties through dielectric additives.
Typical chemical-resistant epoxy coatings include carbon fiber composite, glass fiber, and other reinforcement materials, as well as harder nano-fillers like graphene. Some systems also use a combination of these to achieve the desired characteristics. Latent hardeners, which show only limited reactivity at ambient temperatures but react rapidly when heated, are available. These enable one-component (1K) products to be produced, where the resin and hardener are supplied pre-mixed and only need heat to initiate the curing reaction.