Chlorendic anhydride

Chlorendic anhydride (CAS 115-27-5), also known as HET anhydride, is a halogenated cyclic anhydride used as a reactive flame retardant and curing agent in polymer systems. Unlike additive flame retardants, it chemically incorporates into the polymer backbone, delivering durable fire resistance without migration or leaching during the product lifecycle.

In epoxy resin formulations for electrical laminates and printed circuit boards, it functions as a hardener that simultaneously imparts flame retardancy, reducing the need for separate additive packages. Unsaturated polyester resins for construction panels, ducting, and marine components use this material to meet fire performance standards required in building and transportation applications.

Aerospace and defense composite manufacturers specify it where structural parts must satisfy stringent self-extinguishing or low flame-spread requirements for critical safety components. It is also used in alkyd resin synthesis where halogen-based fire resistance must be built into the resin rather than applied as a coating, ensuring long-term material stability.

The product is supplied as an off-white to pale yellow crystalline powder or solid. Technical grade is the standard commercial form, with purity typically specified at 98% or higher. Packaging is available in fiber drums or multi-wall bags suited for bulk industrial procurement. Proper storage in a cool, dry environment is recommended to maintain chemical integrity.