The Epoxide group of resins finds a wide range of uses in surface coatings due to certain outstanding properties.

The resins are formed from a condensation between epichlorhydrin and bisphenol. The reaction is an extremely complex one from which resin structures for a variety of end uses may be obtained.

Epoxide resins are characterised by the following film properties:

-          Good chemical resistance, including caustic alkalis.

-          Excellent adhesion.

-          Good hardness and flexibility.

They are soluble in esters, ketones and aromatic hydrocarbons. In industrial stoving enamels (for white goods), cross-linking with a melamine resin produces tough, resistant, high gloss finishes.

For use as air dry coatings, they are cross-linked with polyamides and supplied as two pack-paints.

Low Chalk resistance limits usage as exterior topcoats, but main outlets are as anti-corrosive primers and undercoats for aircraft and road transport. Their low molecular weight (and low viscosity) enables them to be used in high solids coatings. When blended with coal tar pitch, they form thick coatings for marine structures and ship bottoms.

Among other important applications there are:

-          Powder coatings, in which the solid resin, in pigmented form, is electrostatically applied, then sintered at high temperature.

-          Water-borne coatings, in which the resin is emulsified along with a reactive amino resin to form Electrocoat primers for vehicle application.

These are popular and recognised with labels, such as cathodic electrocoat or anodic electrocoat, where the paint is electro-deposited onto the car body. This process making sure that all surfaces, even the inside of tubes and box sections, are evenly coated to the required film thickness.