Ingredient dictionary

Adipic Acid/Neopentyl Glycol/Trimellitic Anhydride Copolymer

A polyester resin built from three small building blocks. It forms a thin, flexible film that helps hold color, shape and shine on nails and lashes. It is on the label of 15 products in our library. Checked against our library November 6, 2026.

The catch: none for most people; check the full product list if your skin reacts easily.

What Adipic Acid/Neopentyl Glycol/Trimellitic Anhydride Copolymer does

Forms a flexible, thin film
Helps color and shine stay put
Helps the layer grip lashes and nails

Adipic acid, neopentyl glycol and trimellitic anhydride are linked together in a reaction to form a polyester, which is a long chain of repeating units. Because it is made from more than one starting ingredient, chemists call it a copolymer. The mix of building blocks gives the resin a balance of flexibility and firmness.

In mascara, a film like this helps the formula coat lashes evenly and stay put through the day. In nail treatments, it adds shine and helps the layer grip the nail surface. As it dries, it feels smooth and firm rather than tacky, a feel that suits both of these product types.

Good for

Suits anyone who wants mascara or nail products that stay put and keep a smooth, glossy finish.

Be careful if

Nothing in particular for most skin types.

Frequently asked questions

Is Adipic Acid/Neopentyl Glycol/Trimellitic Anhydride Copolymer safe to use?

It is a polymer, a very large molecule that sits on the surface rather than soaking in. It is generally well tolerated. If your skin or eyes are sensitive, patch test a new product first and stop if you notice redness or stinging.

What does it do in mascara?

In mascara it acts as a film former. As it dries, it forms a thin layer that helps coat lashes evenly, add definition and help resist smudging. Film formers are a common part of lash and nail formulas.