What Is Hdi/Pei-45/Smdi Crosspolymer?
Hdi/Pei-45/Smdi Crosspolymer is a synthetic ingredient created by linking together three building blocks: PEI-45, saturated methylenediphenyldiisocyanate (SMDI) and hexamethylene diisocyanate (HDI). When these components react they form a three-dimensional network that behaves like a light porous powder. Because the material is lab-made it is not sourced from plants or animals, which gives formulators consistency and helps avoid common allergens tied to natural sources.
The technology behind crosslinked polymers began gaining attention in the 1990s as cosmetic chemists looked for new ways to improve texture and oil control in makeup. Over time refinements in polymer chemistry produced versions that were more efficient at soaking up excess sebum without leaving skin feeling dry. Hdi/Pei-45/Smdi Crosspolymer is one of those newer generations and it made its way into commercial products in the early 2010s.
Manufacturing involves carefully combining PEI-45 with SMDI and HDI under controlled heat and pH. The reaction creates long chains that lock together, then the resulting solid is milled into an ultrafine powder. Strict purification steps remove unreacted monomers so the finished ingredient meets cosmetic safety standards.
You are most likely to find this polymer in primers, liquid foundations, pressed powders, mattifying moisturizers, facial masks and long-wear sunscreen formulas. It can also show up in hair styling products where oil control and flexible hold are desired.
Hdi/Pei-45/Smdi Crosspolymer’s Cosmetic Benefits/Uses
This ingredient serves multiple roles inside a formula, making it a versatile tool for product developers.
- Absorbent – The crosslinked structure acts like a sponge that pulls in excess oil and moisture. In skin care and makeup this helps reduce shine, blur the look of pores and extend wear time. In hair products it can cut down on greasiness at the roots.
- Plasticiser – It softens rigid film formers or pigments so a product spreads smoothly and feels flexible on skin. This improves comfort, prevents cracking in long-wear makeup and can enhance the evenness of color payoff.
Who Can Use Hdi/Pei-45/Smdi Crosspolymer
This ingredient suits most skin types. Oily and combination complexions benefit the most because the polymer soaks up excess sebum and reduces shine. Normal skin can also enjoy the silky feel it gives. Those with very dry or dehydrated skin may notice a slight tightness if the formula is heavy on oil-absorbing powders, so pairing it with a richer moisturizer helps balance things out. The powder is generally nonreactive and fragrance-free, making it a low-risk choice for sensitive users.
Because Hdi/Pei-45/Smdi Crosspolymer is fully synthetic and contains no animal by-products it aligns with vegan and vegetarian preferences.
The molecule is large and stays on the surface of the skin, so it is not expected to enter the bloodstream. Current safety assessments show no reproductive or developmental concerns, yet anyone who is pregnant or breastfeeding should still run products past their healthcare provider for personalized advice as this is not medical guidance.
The ingredient does not make skin more prone to sunburn and it plays well with sunscreen filters, so no extra photosensitivity worries apply. It is also chemically stable, meaning it does not interfere with common actives like vitamin C or retinoids.
Potential Side Effects/Adverse Reactions
Responses to topical Hdi/Pei-45/Smdi Crosspolymer differ among individuals. The effects listed below are only potential outcomes and are unlikely for most people when the ingredient is used correctly in a finished product.
- Mild dryness or tightness in areas with very little natural oil
- Transient redness or irritation in highly sensitive skin
- Temporary clogged pores if heavy, occlusive formulas trap oil and debris beneath the absorbent powder
- Rare allergic contact dermatitis for those with a specific sensitivity to polyurea/polyurethane materials
- Respiratory irritation if loose powder is inhaled before it is pressed or mixed into a liquid base
If any unwanted reaction occurs discontinue use and seek advice from a qualified medical professional.
Comedogenic Rating
Rating: 1 out of 5
Hdi/Pei-45/Smdi Crosspolymer is an inert, oil-free powder that sits on the surface of the skin and actually helps soak up excess sebum. Because it does not melt into pores or form an occlusive film the risk of pore blockage is very low, hence the near-non-comedogenic score of 1. Those who are prone to acne or breakouts can generally use products containing this polymer without added concern.
The full formula still matters; rich oils, heavy waxes or inadequate cleansing can override the low comedogenicity of the polymer itself.
Summary
Hdi/Pei-45/Smdi Crosspolymer acts mainly as an absorbent and a plasticiser. Its sponge-like network pulls in excess oil to control shine while its softening effect helps pigments and film formers glide smoothly for flexible, long-wear performance. You will spot it most often in mattifying primers, foundations, pressed powders, oil-control moisturizers and occasionally in hair styling products.
The ingredient is moderately popular in modern makeup because it improves texture without adding greasiness, though it has not reached the household-name status of silica or talc. Formulators appreciate its consistent quality and vegan origin.
Current safety data shows it to be low risk for irritation, sensitisation or systemic absorption. As with any new product it is wise to patch test first to make sure your skin agrees with the complete formula.