What Is Polyurethane-90?
Polyurethane-90 is a synthetic polymer formally known as Bis-HEMA Poly(Hexamethylene/Methylpentylene Carbonate)/Neopentyl Glycol/IPDI Copolymer. In simple terms it is a network of repeating building blocks created from hexamethylene diisocyanate, isophorone diisocyanate, neopentyl glycol and carbonate-based monomers. Chemists combine these small molecules through a controlled reaction called step-growth polymerization, producing a flexible yet durable resin that dissolves in cosmetic solvents.
The polymer traces its roots to classic polyurethane research of the mid 20th century, where materials scientists searched for lightweight waterproof coatings. As beauty companies looked for ways to improve the feel and longevity of color cosmetics in the 1990s and early 2000s, they adapted this resin technology. Polyurethane-90 gained favor because it forms clear breathable films that help makeup stay put without feeling heavy.
Today you will most often find Polyurethane-90 in nail lacquers, liquid eyeliners, tubing mascaras, long wear foundations, transfer-resistant lip colors, certain sunscreens and flexible hair-styling products. It can also appear in specialty skincare masks or primers where a smooth uniform layer is needed.
Polyurethane-90’s Cosmetic Benefits/Uses
Formulators rely on Polyurethane-90 mainly for one key role within a product.
Binding: The polymer acts like a microscopic glue that holds pigment, shimmer and other ingredients together so they cling evenly to skin, hair or nails. This binding action improves color payoff, boosts water and sweat resistance and helps products resist flaking or smudging throughout the day.
Who Can Use Polyurethane-90
Polyurethane-90 is generally compatible with all skin types including dry, oily, combination and sensitive skin because it sits on the surface and does not penetrate deeply. Those with very reactive or eczema-prone skin should still keep an eye on how their skin feels since any film-forming polymer can occasionally trap heat or sweat and aggravate existing irritation.
The ingredient is synthetic and contains no animal-derived components so it suits both vegans and vegetarians.
No research suggests that Polyurethane-90 poses specific risks during pregnancy or while breastfeeding. That said this is not medical advice and anyone who is pregnant or nursing should consult a doctor before introducing new cosmetic products, just to be safe.
Polyurethane-90 does not increase photosensitivity. Users do not need to take extra sun precautions beyond normal daily SPF use.
Potential Side Effects/Adverse Reactions
Reactions to topical Polyurethane-90 vary from person to person. The following bullet points outline potential side effects that are considered rare when the ingredient is formulated correctly in a finished product.
- Contact irritation – mild redness or itching, typically in those with very sensitive skin
- Allergic dermatitis – uncommon localized rash due to a true allergy to the polymer or trace monomer residues
- Occlusive breakout – occasional clogged pores or heat bumps if heavy layers are applied on oily skin in hot humid conditions
- Eye watering or stinging – possible when the ingredient is present in eye makeup and comes into direct contact with the eye surface
If any of these reactions occur users should discontinue use and seek medical advice if symptoms persist or worsen.
Comedogenic Rating
Rating: 1/5 – Polyurethane-90 forms a breathable film on top of skin rather than sinking into pores and it does not contain heavy oils or waxes that typically cause blockages. Because it is almost entirely inert once dried the risk of it trapping sebum is low, though thick layered applications in hot climates could still create a warm micro-environment that encourages clogged pores in very oily skin.
In most cases Polyurethane-90 is considered suitable for acne-prone users. Anyone who notices congestion after using a product with a high concentration of the polymer may prefer lighter application or switching to an oil-free formula.
Worth noting: finished products often pair Polyurethane-90 with silicones or film formers that have different comedogenic profiles so judge the whole formula rather than this single ingredient.
Summary
Polyurethane-90 is mainly valued as a binder that locks pigments and actives into a flexible film, improving color payoff, water resistance and long wear. Its ability to grab onto surfaces without feeling heavy makes it a popular go-to in long-lasting makeup, nail lacquers and certain hair or skin primers though it is still a niche pick compared with older acrylic or silicone resins.
Current safety data shows it is low risk for irritation or sensitization when properly formulated, earning it approval from global cosmetic regulators. As with any new product it is wise to patch test first so you can spot rare sensitivities before applying more broadly.