What Is Polyurethane-23?
Polyurethane-23 is a synthetic polymer created by combining adipic acid, 1,4-butanediol, diphenylmethane diisocyanate and trimethylolpropane. These building blocks react in carefully controlled stages to form long, flexible chains that behave like a lightweight plastic film once they dry on the skin. The material does not come from a natural plant or animal source; it is manufactured entirely in laboratories and industrial facilities that specialize in polymer chemistry.
The cosmetics industry began exploring polyurethane chemistry in the late 1970s as formulators searched for ingredients that could give products longer wear and a smoother finish. Over time, different versions were tailored to specific beauty needs, and Polyurethane-23 emerged as a reliable option when brands wanted a clear, breathable layer that stays put without feeling stiff.
Production starts with mixing the diisocyanate and polyols under anhydrous conditions. Catalysts and heat drive the reaction, creating a prepolymer. This intermediate is further reacted and then neutralized to form a stable aqueous dispersion that can be blended into creams, gels or sprays. Careful purification removes unreacted monomers so the final ingredient meets cosmetic safety standards.
You will most often find Polyurethane-23 in long-wear foundations, liquid eyeliners, waterproof mascaras, transfer-resistant lip colors, peel-off face masks and some hair styling products that need flexible hold. Its transparent finish and ability to form a thin film make it versatile across both skin and hair formulations.
Polyurethane-23’s Cosmetic Benefits/Uses
This ingredient plays a specific yet impactful role in beauty products.
As a film forming agent, Polyurethane-23 spreads into an even, continuous layer that locks other ingredients in place. This film helps makeup resist smudging, sweating or fading through the day, allows peel-off masks to come off in one piece and gives hair products humidity-defying hold while still letting skin or strands move naturally.
Who Can Use Polyurethane-23
Polyurethane-23 is generally well tolerated by most skin types including normal, dry, oily and combination skin because it forms a breathable, lightweight film rather than an occlusive layer. People with very sensitive or reactive skin may want to monitor how they feel after use since any film former can sometimes trap heat or sweat, which might trigger redness or itching in those who are easily irritated. Acne-prone users usually do fine with it, though very heavy or layered applications could contribute to congestion when combined with rich oils or waxes.
The ingredient is entirely synthetic and contains no animal derived substances so it is suitable for vegans and vegetarians.
Current safety data show no specific concerns for pregnancy or breastfeeding because Polyurethane-23 sits on the surface of the skin and is not known to penetrate in meaningful amounts. This is not medical advice and anyone who is pregnant or nursing should confirm product choices with a physician to be safe.
Polyurethane-23 does not make skin more sensitive to sunlight and has no known photosensitising properties. It is odorless, colorless and free from common allergens like gluten or nuts, which makes it a versatile option across many formulations.
Potential Side Effects/Adverse Reactions
Responses to topical Polyurethane-23 differ from person to person. The issues listed below are only potential side effects and are unlikely for the average user when the ingredient is properly formulated and used as directed.
- Contact irritation – mild redness, itching or warmth can occur in individuals with very sensitive skin
- Allergic contact dermatitis – rare allergy to residual monomers or additives may lead to rash or swelling
- Eye irritation – if mascara, eyeliner or hair spray containing Polyurethane-23 gets into the eyes it can sting or cause watering until rinsed out
- Pore clogging in acne-prone skin – heavy layering alongside comedogenic ingredients may contribute to breakouts
- Build-up on hair – repeated use in styling products can leave a dull film that needs clarifying shampoo to remove
If any discomfort, persistent redness or other adverse effect appears, stop using the product and seek advice from a healthcare professional.
Comedogenic Rating
Rating: 1/5. Polyurethane-23 forms a breathable film that sits on the surface rather than sinking into pores, so it is unlikely to block them on its own. The low rating reflects that most formulas using this polymer are water based and light. However thicker makeup or multiple layers mixed with heavy oils can trap sweat and sebum beneath the film, which may contribute to breakouts in very acne-prone skin. Overall it is generally suitable for those who are prone to acne or congestion, especially when used in lightweight products. If buildup becomes a concern, thorough cleansing at the end of the day helps keep pores clear.
Summary
Polyurethane-23 is mainly valued for its film forming ability, creating a clear flexible layer that locks pigments in place, boosts wear time and adds humidity resistance. It achieves this by spreading into a uniform lattice that dries into a lightweight plastic-like sheet, anchoring colorants while still allowing some breathability.
The ingredient enjoys steady but niche popularity, most often appearing in long wear foundations, waterproof eye products and peel-off masks rather than everyday moisturizers. Brands reach for it when durability matters, though it is not as common as silicones or acrylic copolymers.
Current data show Polyurethane-23 is low risk, non sensitizing and vegan friendly. While serious reactions are rare, skin is individual so it is wise to patch test any new product that features this polymer to confirm personal compatibility.