What Is Pei-45/Tmp/Xylene Diisocyanate Crosspolymer?
Pei-45/Tmp/Xylene Diisocyanate Crosspolymer is a synthetic polymer created by reacting xylene diisocyanate with polyethylenimine (PEI-45) and trimethylolpropane (TMP). The result is a large, mesh-like molecule that forms a flexible yet durable film when it dries on the skin or hair. This ingredient has no natural source; it is made entirely in the lab to deliver consistent quality and performance.
The use of film formers in cosmetics gained momentum in the 1970s when formulators began looking for better ways to lock active ingredients in place and improve product wear. Over time chemists refined crosslinked polymers like this one to give lighter feel, better breathability, and higher resistance to water and sweat, making them popular in modern beauty products.
Manufacturing starts with carefully controlled reactions of the monomers in solvent at moderate temperatures. The growing polymer chains are then crosslinked to create a three-dimensional network. After purification and removal of residual monomers, the finished polymer is dried into a fine powder or kept as a viscous solution ready for use in cosmetic factories.
You will most often find Pei-45/Tmp/Xylene Diisocyanate Crosspolymer in long-wear foundations, smudge-proof mascaras, liquid eyeliners, setting sprays, peel-off face masks, transfer-resistant lip colors and certain hair gels or styling creams where it helps the product stay put under humidity and friction.
Pei-45/Tmp/Xylene Diisocyanate Crosspolymer’s Cosmetic Benefits/Uses
This ingredient is valued by formulators because of its key function below
Film forming – once applied and allowed to dry it creates a thin, invisible layer that holds pigments or active ingredients in place, improves water and rub resistance, adds gloss or a soft-focus finish, reduces flaking in mascaras and helps hair or skin feel smoother without a heavy residue
Who Can Use Pei-45/Tmp/Xylene Diisocyanate Crosspolymer
This polymer suits most skin types including oily, combination, normal and dry because it sits on the surface rather than sinking deeply into the skin. Those with very sensitive or allergy-prone skin should still keep an eye out for any redness or itching since any film former can occasionally trap heat or sweat and lead to discomfort.
The ingredient is made entirely from lab-synthesized chemicals with no animal by-products, so it is considered suitable for both vegans and vegetarians.
Current data shows no specific risks for women who are pregnant or breastfeeding when the polymer is used in rinse-off or leave-on cosmetics. That said, this is not medical advice. Anyone who is expecting or nursing should run new products by a doctor just to be safe.
Pei-45/Tmp/Xylene Diisocyanate Crosspolymer does not make skin more sensitive to sunlight and there are no known interactions with common active ingredients like retinol or vitamin C.
Potential Side Effects/Adverse Reactions
Side effects from topical use can vary from person to person. The points below outline possible reactions yet they are unlikely to be the average user experience when the ingredient is formulated and used correctly.
- Mild skin irritation such as redness or itching
- Contact dermatitis in individuals allergic to isocyanates or amines
- Eye stinging or watering if the product gets into the eyes
- Build-up on hair shafts leading to dullness or stiffness if not washed out properly
- Minor clogged pores in people already prone to heavy comedone formation
If any negative reaction occurs stop using the product and consult a healthcare professional.
Comedogenic Rating
Rating: 1/5
This polymer sits on the surface and forms a breathable film that is lightweight, so it rarely blocks pores. It is not oily or waxy, ingredients that typically trigger breakouts, yet any film former can trap existing sebum and debris if layered too heavily which is why the score is not zero.
Suitable for acne-prone skin in most cases.
No published data suggest that the molecule feeds acne-related bacteria or increases sebum production, so its low rating is widely accepted among formulators.
Summary
Pei-45/Tmp/Xylene Diisocyanate Crosspolymer is mainly a film former that locks pigments and actives in place, boosts water and rub resistance, and gives products longer wear while feeling light on skin or hair. It achieves this by drying into a flexible mesh that adheres well yet allows some movement.
The ingredient is not as famous as big names like dimethicone or acrylates but it appears in a growing number of long-wear foundations, eye products and styling gels where durable hold is needed.
Current research shows it is generally safe with a very low rate of irritation or pore clogging, though anyone with highly sensitive skin should watch for any discomfort. As with any new cosmetic, patch testing a small area first is a smart precaution.