What Is Polyurethane-35?
Polyurethane-35 is a synthetic copolymer created from a blend of adipic acid, dicyclohexylmethane diisocyanate, ethylenediamine, hexanediol, neopentyl glycol and sodium N-(2-aminoethyl)-3-aminoethanesulfonate. Chemically, these building blocks link together to form a flexible yet durable chain that behaves like a fine plastic film when spread on skin or hair. The material was first explored in the late 20th century by industrial chemists looking for lightweight water-resistant coatings. Its smooth feel and strong adhesive qualities quickly caught the attention of cosmetic formulators who needed reliable film formers that would not flake or crack. Production begins with controlled reactions between the diisocyanate and polyol components under heat, followed by chain extension with ethylenediamine and sulfonate monomers to improve water dispersibility. Once fully reacted, the polymer is neutralized and milled into an aqueous dispersion that can be easily mixed into creams, gels or sprays.
Today Polyurethane-35 is most often found in long-wear makeup such as foundations, mascaras and eyeliners, waterproof sunscreens, hair styling products like gels or mousses and transfer-resistant skin tints or BB creams. Its ability to create an invisible, flexible film helps these products stay put through sweat, humidity and daily movement.
Polyurethane-35’s Cosmetic Benefits/Uses
In personal care formulas Polyurethane-35 serves one primary purpose that delivers several practical advantages.
Binding: The polymer acts as a film former that binds pigments, UV filters and other active particles to skin or hair. This binding action improves wear time, boosts water and smudge resistance and reduces product transfer onto clothing or masks. The resulting finish feels lightweight yet secure, allowing makeup or styling products to remain intact for hours without frequent touch-ups.
Who Can Use Polyurethane-35
Polyurethane-35 is generally well tolerated by all major skin types including oily, dry, combination and normal because it forms a lightweight breathable film that does not trap excessive oil or moisture. Very sensitive or eczema-prone skin may occasionally feel tight or experience mild irritation if multiple film formers are layered, so those users should introduce it slowly and monitor comfort levels.
The polymer is produced from synthetic petrochemical building blocks with no animal-derived inputs which makes it suitable for both vegans and vegetarians. Cruelty policies vary by brand so individuals who avoid animal testing should still confirm the finished product’s stance.
Current research shows that the large molecular size of Polyurethane-35 limits skin penetration which means systemic absorption is extremely unlikely. There is no evidence of harm for pregnant or breastfeeding women when the ingredient is used topically in cosmetics, but this is not medical advice and anyone who is expecting or nursing should review their routine with a healthcare professional to stay on the safe side.
Polyurethane-35 does not cause photosensitivity and can safely be worn during daytime exposure. It is also compatible with most skincare actives and removes easily with standard cleansers or oil-based makeup removers.
Potential Side Effects/Adverse Reactions
Reactions to topical Polyurethane-35 differ from person to person. The points below outline possible side effects though they are uncommon when the ingredient is properly formulated and used as directed.
- Contact irritation: A small number of users may notice redness or itching caused by individual sensitivity to the polymer or residual monomers
- Allergic dermatitis: Rare allergic responses can appear as rash hives or swelling especially in those with isocyanate allergies
- Temporary clogged pores: Heavy layered applications could trap debris on very oily skin leading to minor breakouts
- Eye or mucous membrane stinging: If mascaras or sprays containing Polyurethane-35 migrate into the eyes they can produce transient burning or watering
- Inhalation discomfort: Aerosol hair products may irritate the respiratory tract if inhaled directly during application
- Build-up on hair strands: Repeated use in styling products without proper cleansing might leave a dull film that makes hair feel stiff
If any of these effects occur stop using the product and consult a medical professional for guidance.
Comedogenic Rating
Rating: 1/5
Polyurethane-35 forms a thin breathable film that lets sweat and sebum escape instead of blocking pores like heavier waxes or oils can. It is water dispersible and rinses off easily with regular cleansers which limits build-up. Because of this it earns a low comedogenic score of 1 meaning it is very unlikely to trigger clogged pores for most users.
People who are prone to acne or breakouts can generally use products with Polyurethane-35 without major concern.
As with any film former overusing several long-wear products at once could create surface residue so thorough cleansing at the end of the day is still important.
Summary
Polyurethane-35 is a synthetic film former that binds pigments UV filters and styling agents to skin or hair creating flexible long-lasting wear. Its large polymer chains sit on the surface where they lock ingredients in place boost water and smudge resistance and help products look fresh for hours.
The ingredient shows up most often in long-wear makeup waterproof sunscreens and styling gels. It is not as common as older fixatives like acrylates but its light feel and strong hold are making it steadily more popular with modern formulators.
Safety data and everyday experience point to a low risk of irritation or clogging for the average user. Still everyone’s skin is unique so it is wise to patch test any new product containing Polyurethane-35 and watch for signs of discomfort before adding it to your regular routine.