Epoxy resin

Epoxy resin emerged in 1936 when Swiss chemist Pierre Castan sought an alkali-resistant binder for coatings. Working at a dental products manufacturer in Geneva, he reacted bisphenol A with epichlorohydrin to create an amber-colored, low-melting solid that could be hardened by adding phthalic anhydride. The material had remarkable properties: exceptional adhesion, chemical resistance, and dimensional stability after curing.

The convergent evolution of epoxy development demonstrates the adjacent possible aligning simultaneously across multiple locations. While Castan worked in Switzerland, German chemist Paul Schlack at IG Farben independently developed similar materials. In the United States, Sylvan Greenlee at Devoe & Raynolds patented bisphenol A-epichlorohydrin resins in 1939. Each researcher arrived at the same fundamental chemistry through different application paths—coatings, adhesives, and electrical insulation.

Castan initially tried to market his discovery for dental applications—castings and fixtures—but commercial interest was limited. He filed for patent protection in 1938, with grants following around 1940. Unable to commercialize directly, Castan licensed his patents to CIBA AG of Basel, a decision that would shape the global epoxy industry.

CIBA proved the crucial commercializing force. At the Swiss Industries Fair in 1946, they launched an epoxy resin adhesive and four electrical casting resins—the beginning of industrial-scale epoxy production. The material found immediate applications in aircraft construction, where its strength-to-weight ratio and bonding properties offered advantages over riveting. The post-war era's demand for lightweight, strong materials created the market that the pre-war inventors had lacked.

The path dependence established by Castan and CIBA's early dominance shaped the industry for decades. CIBA (later merged into what became BASF) remained a major producer, while the fundamental chemistry—the reaction of bisphenol A with epichlorohydrin—became the standard that competitors copied. Today, epoxy resins form the matrix of carbon fiber composites, the encapsulation of electronics, the coatings on food cans, and countless adhesive applications—all descendants of Castan's amber-colored solid.