What Is Polyurethane-48?
Polyurethane-48 is a man-made copolymer created from several small building blocks: hexanediol, neopentyl glycol, adipic acid, isophorone diisocyanate, isophorone diamine and a sulfonated diamine that carries sodium. When these pieces are joined through a controlled reaction, they form long chains that behave like a flexible plastic yet can be dispersed in water. Polyurethanes were first invented in the 1930s for industrial coatings. By the late 1990s chemists began tailoring them for beauty formulas that needed long-lasting wear without heavy feel, leading to the inclusion of Polyurethane-48 in makeup and hair products.
The polymer is produced through step-growth polymerization. The diols and diacid link together with the diisocyanate to create urethane bonds, then the sulfonated diamine is added to make the finished polymer water friendly. Once the reaction is complete the mixture is neutralized, filtered and diluted into a ready-to-use liquid that blends smoothly with other cosmetic ingredients.
You will most often find Polyurethane-48 in products that rely on a flexible film to stay in place: long-wear foundations, liquid lipsticks, mascaras, eyeliners, brow gels, peel-off face masks, hair styling gels and certain nail polish topcoats.
Polyurethane-48’s Cosmetic Benefits/Uses
In beauty formulas Polyurethane-48 serves one key role
Film forming: The polymer lays down an even, lightweight film that locks pigments or styling agents onto the skin, hair or nails. This film boosts water and smudge resistance, keeps color from fading, adds gloss, helps masks peel off in one piece and gives hair gels flexible hold without stiffness.
Who Can Use Polyurethane-48
Because Polyurethane-48 is an inert, high-molecular-weight film former that sits on top of the skin, it is generally considered suitable for all skin types including normal, dry, oily and combination. Sensitive skin usually tolerates it as the polymer is not acidic and does not penetrate deeply, though a minority of highly reactive users could experience tightness if a product layers a very thick film. Acne-prone skin typically does fine with Polyurethane-48 because the molecule is too large to sink into pores, but cleansing thoroughly at day’s end prevents potential buildup.
The ingredient is synthetic and made from petrochemical raw materials, so it contains no animal derivatives and is typically regarded as vegan and vegetarian friendly. Always check the full formula since other components such as waxes or pigments might not meet cruelty-free or vegan standards.
No data suggests Polyurethane-48 poses a specific risk to women who are pregnant or breastfeeding; it is not known to be absorbed through intact skin and does not act as an endocrine disruptor. That said this information is not medical advice and anyone expecting or nursing should review all personal care products with a healthcare professional for individual guidance.
Polyurethane-48 does not increase photosensitivity, so products containing it do not make skin more prone to sunburn. It is also heat stable which means sun exposure will not cause it to break down into irritants. No other major usage restrictions are noted at typical cosmetic concentrations.
Potential Side Effects/Adverse Reactions
Side effects from topical Polyurethane-48 vary from person to person. The points below outline potential reactions only; when the ingredient is used correctly in a well-formulated product most people will not experience any problems.
- Allergic contact dermatitis – a small percentage of users may develop redness itching or rash if they are sensitised to any residual monomer or additive in the polymer
- Eye irritation – if mascara or liner flakes into the eyes the film can cause watering or stinging until rinsed out
- Scalp or skin buildup – in hair gels or long-wear makeup the durable film may accumulate if not removed thoroughly leading to a dull feel or flaky residue
- Transient tightness or dryness – very dry or mature skin can sometimes feel slightly tight under the flexible film until moisturizer is applied underneath or the product is removed
If any discomfort swelling or persistent irritation occurs stop using the product and seek advice from a healthcare professional.
Comedogenic Rating
Rating: 0–1/5
Polyurethane-48 is a very large, water-dispersible polymer that stays on the surface of skin rather than migrating into pores where breakouts start. It is chemically inert, does not provide an oily food source for acne bacteria and is usually removed with standard cleansing. For these reasons it is considered non-comedogenic to very low on the scale.
Suitable for acne-prone or breakout-prone skin, provided makeup or styling products containing the polymer are thoroughly washed off at the end of the day.
Heavy layering with other occlusive ingredients could trap sweat or debris under the film, so double cleansing is wise when using long-wear formulas that include Polyurethane-48.
Summary
Polyurethane-48 is mainly added to cosmetics as a lightweight film former. It forms an even flexible layer that locks pigments or styling agents in place, boosts wear time, resists water and smudging and lends a smooth glossy finish without stiffness.
The polymer shows up most in long-wear foundations, liquid lipsticks, eye products, peel-off masks and certain hair gels. It is not as famous as silicones or acrylates but formulators value it for its balance of durability and comfort, so its presence has grown steadily in modern color cosmetics.
Safety assessments rate Polyurethane-48 as low risk thanks to its high molecular weight and minimal skin penetration. Reported reactions are rare and usually mild. As with any new product, do a quick patch test first to make sure your skin responds well before applying it over larger areas.