What Is Phthalic Anhydride/Benzoic Acid/Trimethylolpropane Copolymer?
Phthalic Anhydride/Benzoic Acid/Trimethylolpropane Copolymer is a synthetic resin made by reacting three building blocks: phthalic anhydride, benzoic acid and trimethylolpropane, a trifunctional alcohol. When these ingredients are heated together they join to form long, flexible chains that behave like a clear plastic film once they dry on the skin or hair. The material belongs to the family of aromatic polyester resins and is sometimes shortened on labels to “PABT copolymer.”
This copolymer has roots in industrial coatings, where similar resins were prized for their strong yet lightweight films. As cosmetic chemists looked for ways to give makeup and hair products better staying power, they borrowed the idea in the late 1990s and adapted the resin for personal care use. Today it is produced in specialized reactors that carefully control temperature, pressure and pH to avoid unwanted by-products. Once the reaction is complete the thick resin is cooled, crushed into flakes or beads and purified before being added to cosmetic formulas.
You can spot Phthalic Anhydride/Benzoic Acid/Trimethylolpropane Copolymer in a wide range of products that need a flexible, long-lasting film. It shows up in nail enamels, liquid lipsticks, mascara, brow gels, long-wear foundations, setting sprays, transfer-resistant sunscreens and some peel-off face masks.
Phthalic Anhydride/Benzoic Acid/Trimethylolpropane Copolymer’s Cosmetic Benefits/Uses
The main job of this ingredient is to act as a film former. Once the product is applied the copolymer dries into an invisible layer that helps pigments, actives or moisturizing oils stay put. This film resists water, sweat and rubbing so makeup lasts longer, nail polish chips less and sunscreens keep their protection even during a swim.
Who Can Use Phthalic Anhydride/Benzoic Acid/Trimethylolpropane Copolymer
This film forming resin is generally considered suitable for all skin types. It creates a breathable lightweight layer that does not significantly clog pores so both dry and oily skin usually tolerate it well. Extremely sensitive or allergy-prone skin may want to watch for any resin-related irritation but such reactions are rare.
The material is fully synthetic and contains no animal-derived substances so it is acceptable for vegans and vegetarians. It is also not routinely tested on animals when sourced from suppliers that follow modern cosmetic regulations, though individual brand policies can differ.
No studies link this copolymer to hormonal disruption or systemic absorption, which means it is not singled out as an ingredient of concern for pregnancy or breastfeeding. This is not medical advice and anyone who is pregnant or nursing should still run every product past a doctor to be safe.
The copolymer does not absorb UV light or make skin more sensitive to sunlight, so it is not classed as a photosensitiser. It can even help sunscreens stay in place, adding a minor layer of water resistance.
Potential Side Effects/Adverse Reactions
Responses to topical Phthalic Anhydride/Benzoic Acid/Trimethylolpropane Copolymer vary from person to person. The issues listed below are only potential effects and are unlikely for the average user when the ingredient is used correctly in a finished product.
- Mild skin irritation or redness in individuals allergic to resin-based ingredients
- Eye stinging or watering if the raw material or a product containing it gets into the eyes before it sets
- Temporary pore congestion for those highly prone to acne if very thick layers are applied repeatedly
- Dry feeling on nails or skin if the film is removed aggressively without moisturising afterwards
- Respiratory irritation from inhaling airborne powder during manufacturing or decanting of loose pigments, not typical for end users
If any adverse effect occurs stop using the product and seek advice from a healthcare professional or dermatologist.
Comedogenic Rating
Rating: 1/5 — The copolymer forms a thin breathable film that sits on top of the skin rather than sinking into pores. It does not contain heavy oils or waxes known for clogging and its large molecular size limits penetration. A rating of 1 reflects the very low but not zero chance of congestion in users who layer thick makeup repeatedly without proper cleansing.
This ingredient is generally suitable for acne-prone skin, provided normal cleansing habits are followed.
Because it helps pigments and sunscreens adhere, the copolymer is often used alongside more occlusive materials. Breakout-prone users should consider the whole formula, not just this single ingredient.
Summary
Phthalic Anhydride/Benzoic Acid/Trimethylolpropane Copolymer is mainly a film former that locks makeup, nail color and sunscreen in place by drying into a clear flexible layer that resists water and friction. Its popularity is moderate: common in long-wear products and nail polish but absent from many basic lotions and cleansers.
Current data show it is safe for topical use with low irritation and negligible comedogenicity. Still, skin can be unpredictable so it is wise to patch test any new product that contains this resin.