Adipic Acid/Neopentyl Glycol/Trimellitic Anhydride Copolymer

This is a high–molecular weight polyester copolymer used as a film former/binder (e.g., in long-wear color cosmetics) at low to moderate percentages and is not intended to act as a biologically active ingredient. In clinical experience and patch-testing patterns, such inert polymers have low irritancy because they have minimal skin penetration, though any residual reactive monomers/impurities can rarely trigger irritation in highly reactive or compromised skin. Given its generally low reactivity in finished formulations but nonzero risk in very sensitive patients, it fits a very gentle score. Safety Notes: This film-forming polyester copolymer is used in consumer skincare primarily as a texture/feel modifier and water-resistant film former, where it commonly appears at very low levels (~0.05–0.5%) in lotions/serums and in makeup-adjacent skincare (e.g., primers, blurring moisturizers). Higher-strength OTC products that rely on a substantive, durable film (long-wear, transfer-resistant, water-resistant face products and high-hold peel-off or “grip” style formulations) can push polymer solids into the mid-to-high single digits, with observed maxima around ~10–12% when it is a primary structuring/film component. Leave-on products dominate its use; rinse-off products typically sit at the low end because high levels can increase residue/tack and are not cost-effective.