Is Resin Flammable? Epoxy, Polyester, and UV Resin Explained

Resin is a broad category that covers dozens of different materials: epoxy resin, polyester resin, UV resin, alkyd resin, and more. Their fire properties vary, but there’s one consistent theme. In liquid form, resins present a more significant fire hazard than after curing.

Most resins in liquid form are flammable. Polyester resin has a flash point of around 90°F (32°C), making it highly flammable and a fire risk even at room temperature. Epoxy resin has a flash point around 300–400°F (149–204°C); it is combustible but less immediately hazardous. UV resin varies but is generally in a similar range to epoxy resin. Once cured, all of these become significantly less hazardous, though they’ll still burn in a fire.

Polyester Resin: The Most Dangerous

Polyester resin (the kind used in fiberglass boat construction and automotive body repair) is the most fire hazardous of the common resins. Its flash point of around 90°F is below typical summer ambient temperatures, meaning it can produce ignitable vapor at room temperature. The styrene solvent used in polyester resin is both flammable and toxic. Working with polyester resin requires serious ventilation, no open flames nearby, and preferably a non sparking work environment.

UV Resin for Crafting

UV curing resin, popular in jewelry making and crafting, is generally based on acrylate or epoxy chemistry. It’s combustible in liquid form but less immediately hazardous than polyester resin. Keep it away from heat sources and flames while working. The UV lamp used to cure it is not a fire risk in normal use.

Cured Resin Storage and Disposal

Dispose of resin properly. Don’t pour liquid resin down drains or into regular trash. In many jurisdictions, uncured resin is classified as a hazardous waste. Small amounts can often be cured fully (with hardener or UV light) before disposal. Check your local disposal regulations.

Rags soaked in polyester resin or solvents can undergo spontaneous combustion. Hang them flat to dry in a well ventilated area, never ball them up and put them in a trash can. For related reading, see our article on whether epoxy specifically is flammable.