How epoxy is made
Epoxy is sold as two liquids that are harmless apart, and it only turns solid when you mix them.
- stations
- 6
- things upstream
- 17
- raw sources
- 7
- steps from the ground
- 6
The short version
Epoxy is sold in two parts. The resin is made by reacting bisphenol A with epichlorohydrin and caustic soda, then washing out the salt. The hardener, usually an amine, is made separately. Nothing happens until the two are mixed at the point of use, and then the molecules cross-link into a thermoset solid.
-
Make bisphenol A
Phenol and acetone, both derived from propylene and benzene, are condensed into bisphenol A. It is the backbone of most epoxy resin.
-
Make epichlorohydrin
Propylene is reacted with chlorine to make the reactive three-carbon compound epichlorohydrin. It supplies the epoxide groups that give the resin its name.
-
React the two with lye
Bisphenol A meets an excess of epichlorohydrin and sodium hydroxide in a reactor. Salt forms as a byproduct, and a thick, honey-like liquid resin is left.
Goes in -
Wash and strip the resin
The salt is washed out with water and the extra epichlorohydrin is distilled off and reused. The finished resin is a clear liquid.
-
Package resin and hardener
Resin goes into one container and a hardener, typically a polyfunctional amine, into another. Splitting them lets the product sit in a store for months.
-
Mix and cure on site
When the customer combines the parts, the hardener links the resin molecules into a rigid three-dimensional network. The result is a thermosetting plastic that heat will not melt.
Worth repeating
- Paul Schlack of Germany patented the condensation of epoxides and amines in 1934.
- Claims of discovery of bisphenol-A epoxy resins include Pierre Castan in 1943, and Ciba licensed his work.
- Between 25 and 30% of all bisphenol A goes into making epoxy and vinyl ester resins.
Back to the ground
Follow every input upstream and epoxy starts as these 7 raw sources.
Where it goes next
Epoxy feeds 16 lines directly and reaches 182 things in total.
Further down the line
Keep walking
Sources
Cite this page: "How epoxy is made." Assembly Line, 2026-11-03. https://assemblyline.org/make/epoxy