What Is Polyurethane-64?
Polyurethane-64 is a synthetic urethane copolymer created through a multi-step reaction that starts with isophorone diisocyanate combined with two kinds of polytetrahydrofurans, sometimes called polybutylene glycols. One of these glycols averages 14 repeating butylene glycol units while the other averages 28. After this first reaction, the partly built polymer is linked with 4,4′-methylenebis(cyclohexylamine) then any leftover isocyanate groups are capped with ethanol to complete the structure. The result is a flexible, lightweight polymer that behaves much like a breathable plastic film when spread on skin.
Polyurethanes have been used for decades in coatings, textiles and medical devices for their toughness and flexibility. Around the early 2000s formulators recognized that certain variations, including Polyurethane-64, could bring those same qualities to cosmetic products without a heavy feel or noticeable residue. Because it is water-dispersible and forms an even film at very low levels, it quickly found a place in beauty formulas that need long-lasting performance.
Today Polyurethane-64 appears in a range of topical products such as sheet masks, long-wear foundations, BB creams, anti-aging serums, hair styling gels, transfer-resistant sunscreens and colored mascaras. Anywhere a product needs a thin, flexible layer that holds actives in place or boosts durability, this polymer can be the quiet workhorse behind the scenes.
Polyurethane-64’s Cosmetic Benefits/Uses
In skin and hair care formulations Polyurethane-64 delivers one primary benefit:
Film forming: Once the product is applied the polymer dries to create a clear, flexible film that clings smoothly to the surface. This film helps lock in moisture, improves the wear time of pigments and actives, resists smudging and rubbing, and gives products a lightweight yet durable finish. Because the film is breathable it avoids the stiff or tacky feel sometimes associated with older film formers, making it comfortable for all-day wear.
Who Can Use Polyurethane-64
Because Polyurethane-64 dries to a lightweight breathable film it is generally considered suitable for most skin types including dry, normal, combination, oily and even sensitive skin. The polymer does not add oil or alcohol so it seldom triggers excess shine or stinging, yet its moisture-locking film can benefit drier complexions. People with a known allergy to polyurethanes or isocyanate derivatives should avoid it since even the small residuals in finished products could cause irritation.
The ingredient is fully synthetic with no animal or by-product inputs so it fits vegan and vegetarian lifestyles. That said compassionate shoppers should still confirm that the finished product has not been tested on animals.
No specific warnings exist for topical use by pregnant or breastfeeding women. The molecule is too large to penetrate deeply and is regarded as non-reactive on skin, yet this is not medical advice. Expectant or nursing mothers should show any product containing Polyurethane-64 to their doctor before use to be on the safe side.
Polyurethane-64 does not increase photosensitivity so you do not have to take extra sun precautions beyond normal daily SPF. It is also fragrance-free, colorless and compatible with most other cosmetic ingredients, which keeps the risk of cross-reactions low.
Potential Side Effects/Adverse Reactions
Reactions to topical Polyurethane-64 vary from person to person. The following list covers potential side effects but most users will not experience them when the ingredient is used correctly in a well-formulated product.
- Mild redness or itching in people who are sensitive to synthetic polymers
- Contact dermatitis in rare cases of polyurethane allergy
- Eye irritation if the product migrates into the eyes before it fully sets
- Temporary clogged pores for individuals who are extremely prone to congestion, especially if the product is not removed thoroughly at the end of the day
- Exacerbation of existing eczema or dermatitis when applied to already compromised skin barriers
If you notice any of these effects stop using the product and consult a healthcare professional or dermatologist.
Comedogenic Rating
Rating: 1 / 5
Polyurethane-64 is a large, inert polymer that stays on the surface of skin and is designed to create a breathable film rather than an oily seal. It contains no fatty acids or waxy residues that typically plug pores, so the likelihood of it causing comedones is very low. That said extremely clog-prone individuals could still notice congestion if the finished formula is not removed thoroughly, especially in heavy long-wear makeup.
Overall this ingredient is considered suitable for acne-prone or breakout-prone skin.
As with any film former its pore impact depends more on the total formulation and cleansing habits than on the polymer itself.
Summary
Polyurethane-64 is mainly a film former that lays down a thin flexible coating to lock in moisture, keep pigments in place and extend wear time without a stiff or greasy feel. Because it is water-dispersible it integrates easily into modern lightweight textures while still delivering durability and transfer resistance.
You will spot it most often in long wear foundations, smudge-proof mascaras, stay-put sunscreens and certain sheet masks. It is not the most famous ingredient on labels but formulators value it as a quiet workhorse that brings professional performance to mainstream products.
Safety data and decades of polyurethane use point to a low irritation profile. When used as intended it sits on the surface of skin, is non-sensitizing for most users and carries only a minimal comedogenic risk. Still, everyone’s skin is different so do a simple patch test when trying any new product that contains Polyurethane-64 to ensure it agrees with you.