What Is Polyurethane-19?
Polyurethane-19 is a man-made polymer created by reacting small building blocks called diisocyanates with various polyols and a touch of hydrazine or short-chain diamines. These reactions link the molecules together into long flexible chains that behave like a clear plastic film when they dry. Although the starting materials have complex names, the finished ingredient is simply a lightweight resin that dissolves in water or alcohol and then forms a thin coating when the liquid evaporates.
Polyurethane chemistry first found fame in industrial paints and upholstery foams back in the 1940s. By the late 1980s chemists noticed that certain polyurethane films could bend and stretch without cracking, which made them perfect for hair sprays that needed strong yet touchable hold. Polyurethane-19 is one of the more recent tweaks on that idea, offering better clarity and less tackiness than earlier grades.
Manufacturing begins with a controlled step-growth reaction in large stainless-steel reactors. Temperature and pH are carefully adjusted so the chains grow to the right length, then the mixture is neutralized, filtered and dried into a fine powder or kept as an aqueous dispersion. Formulators can easily blend this dispersion into styling products without heavy solvents, which is why Polyurethane-19 shows up in aerosol and pump hair sprays, mousses, gels, styling creams and setting lotions.
Polyurethane-19’s Cosmetic Benefits/Uses
In beauty formulas Polyurethane-19 serves a single but important purpose: hair fixing. It forms an invisible film around each strand that locks a style in place, resists humidity, reduces frizz and adds a light reflective sheen while remaining flexible so hair does not feel stiff or crunchy.
Who Can Use Polyurethane-19
Because Polyurethane-19 is a film-forming resin that sits on the surface rather than soaking deeply into skin or hair, it is generally considered suitable for all skin and scalp types including oily, dry and combination. Those with very sensitive or allergy-prone skin should still pay attention to how their scalp feels since any synthetic polymer can be a trigger for a small percentage of people.
The ingredient is produced from petrochemical building blocks and contains no animal-derived substances, so it is appropriate for vegans and vegetarians.
Absorption through the skin is minimal and the material has not been linked to reproductive toxicity, which means products containing Polyurethane-19 are usually viewed as safe for pregnant or breastfeeding users. That said this is not medical advice and anyone who is expecting or nursing should pass the full ingredient list of any styling product by their physician to be certain it aligns with their personal health needs.
Polyurethane-19 does not increase sensitivity to sunlight, and it plays well with common hair-care actives like silicones, proteins and botanical extracts.
Potential Side Effects/Adverse Reactions
Reactions to topical Polyurethane-19 differ from person to person. The points below outline potential side effects, though most consumers will not encounter them when using a well-formulated product.
- Mild scalp or skin irritation – a tight, itchy or tingling feeling where the product sits
- Contact dermatitis – rare allergic rash or redness in people sensitised to isocyanate-based polymers
- Product buildup – repeated use without thorough cleansing can leave hair feeling coated or dull
- Eye irritation – stinging or watering if aerosol mist drifts into the eyes during application
- Respiratory discomfort – coughing or throat tickle from inhaling fine spray particles in poorly ventilated areas
If any of these effects occur discontinue use immediately and consult a healthcare professional if symptoms persist or worsen.
Comedogenic Rating
Rating: 1/5
Polyurethane-19 is a lightweight film former that stays on the surface and is not oily or waxy, so it rarely blocks pores. Its molecules are too large to slip into follicle openings the way heavy oils can, which keeps the risk of breakouts very low. A rating of 1 reflects that slim chance while still acknowledging the possibility of buildup if you layer it on without proper cleansing. Overall it is considered fine for acne-prone users.
Because it creates a flexible coating, thorough shampooing is important to remove any residue and keep pores clear over time.
Summary
Polyurethane-19 is used mainly for hair fixing. It forms a clear elastic film around each strand to lock styles in place, fight humidity, tame frizz and give a light glossy finish without crunch. Thanks to these perks it shows up in many modern sprays, mousses, gels and styling creams, though it is still less common than older resins like PVP so its popularity is moderate rather than blockbuster.
Safety data rate it as low toxicity, non-sensitising for most people and only mildly comedogenic. Still, everyone’s skin and scalp are different, so it is smart to patch test any new product that contains Polyurethane-19 before full use.