What Is Polyurethane-34?
Polyurethane-34 is a synthetic polymer created through a series of carefully controlled chemical reactions. It starts with a copolymer made from hexanediol, neopentyl glycol and adipic acid. This base is then linked with hexamethylene diisocyanate to form a strong polyurethane backbone, which is finally modified with N-(2-aminoethyl)-3-aminoethanesulfonic acid and ethylenediamine to give the material extra stability and water compatibility. Because the raw materials come from standard petrochemical feedstocks, supplies are consistent and quality can be tightly regulated.
The use of polyurethane chemistry in cosmetics dates back to the late 20th century when formulators were looking for film formers that offered flexibility without cracking. Polyurethane-34 emerged as a reliable option in the early 2000s once manufacturers refined the production process for large scale personal care use. Its popularity grew as consumers demanded longer-lasting makeup and lightweight textures.
Production begins by heating and reacting the alcohol components with adipic acid to produce an ester-rich prepolymer. Hexamethylene diisocyanate is then added under nitrogen to prevent moisture interference. After the main polymer forms, the mixture is cooled and treated with the two amine-containing molecules, which cap the reactive ends and improve water dispersibility. The finished polymer is filtered, tested and shipped as a concentrated dispersion or fine powder.
In everyday products you will most often find Polyurethane-34 in long-wear foundations, mascaras, liquid eyeliners, hair styling creams, peel-off masks and transfer-resistant lip colors. Its film-forming ability helps these formulas stay put yet remain comfortable on skin and hair.
Polyurethane-34’s Cosmetic Benefits/Uses
Polyurethane-34 serves a single yet important role in cosmetic formulations.
Binding: As a binder it creates a thin uniform film that holds pigments, powders and other ingredients together. This improves color payoff in makeup, boosts wear time and reduces flaking or smudging. In hair products the same film helps tame flyaways and maintain style while still allowing natural movement.
Who Can Use Polyurethane-34
Polyurethane-34 is generally well tolerated by all skin types, including dry, oily, combination and sensitive skin, because it sits on the surface and forms a flexible film rather than penetrating deeply. Those with very reactive or allergy-prone skin should still watch for irritation since any film former can occasionally trap sweat or sebum.
The ingredient is entirely synthetic and contains no animal-derived materials, making it suitable for both vegans and vegetarians.
Current safety data show no specific risks for pregnant or breastfeeding women when the polymer is used topically in finished cosmetics, yet this is not medical advice. Anyone who is pregnant or nursing should review all personal care products with a qualified healthcare professional to be extra cautious.
Polyurethane-34 does not absorb UV light or make skin more sensitive to the sun, so it has no known phototoxic or photoallergic concerns.
Because it forms a water-resistant film, long-term or very heavy use without proper cleansing could lead to product buildup on skin or hair. Gentle removal at the end of the day is recommended.
Potential Side Effects/Adverse Reactions
Side effects from topical Polyurethane-34 differ from person to person. The points below outline potential issues users could encounter, but most people will not experience them when the ingredient is used at normal cosmetic levels.
- Mild skin irritation
- Contact allergy marked by redness, itching or small bumps
- Eye stinging if the product accidentally gets into the eyes
- Temporary clogged pores in individuals highly prone to acne
- Dry or dull hair if residue is not fully washed out in styling products
If you notice any of these reactions stop using the product and consult a healthcare professional if symptoms persist or worsen.
Comedogenic Rating
Rating: 1/5
Polyurethane-34 earns a low score because it is a large, film-forming polymer that stays on the skin’s surface rather than sinking into pores. It is not oily or waxy and does not provide a food source for acne-causing bacteria, so the risk of clogged pores is minimal for most users. Those with extremely acne-prone skin may still notice the occasional blocked pore if heavy layers are left on overnight, but this is uncommon and usually linked to insufficient cleansing rather than the ingredient itself.
Suitable for acne-prone skin: Yes, in most cases.
Because it repels water, thorough cleansing at day’s end can help prevent any residue-related congestion in very breakout-prone individuals.
Summary
Polyurethane-34 is primarily a binder that creates a flexible, long-lasting film to lock pigments, powders and styling actives in place. This film boosts color payoff in makeup, reduces smudging, keeps hairstyles neat and helps peel-off masks form an even layer. Its popularity sits in the middle of the pack: widely used in long-wear cosmetics and some hair products, yet not as mainstream as classic silicones or acrylates.
Current data show Polyurethane-34 to be safe for topical use with a very low irritation and allergy profile. As with any new cosmetic ingredient it’s smart to perform a quick patch test when trying a fresh product just to be on the safe side.