Unsaturated Polyester Resin (Fibreglass)

Carleton Ellis, one of the most prolific American inventors of his time, found that a polyester made with maleic acid - which leaves a reactive double bond in every repeat - could be dissolved in a liquid monomer such as styrene and then cured with a catalyst into a hard solid, with no pressure and no by-product. That made it possible to soak glass fibre in a liquid and let it harden in shape: fibreglass boats, car bodies and radomes followed within a decade. **US 2,255,313**, "Ethylenic-alpha-beta synthetic resins and process of making same", Ellis, filed 6. August 1937, granted 9. September 1941: a maleic-polyhydric-alcohol ester, "a polymerizable alpha-substituted ethylene body and a curing catalyst", with a fibrous filler. **Hazardous: the resin gives off styrene and the catalyst (MEKP) burns eyes and skin.** Work outdoors or with strong ventilation. You lay up a two-layer fibreglass tray and weigh how much of it is glass.