Polyurethane-28 is an inorganic chemical compound, an urethane and Dimethicone by-product, polymer formed by the reaction of bis-hydroxyethoxypropyl dimethicone with isophorone diisocyanate and sorbitan isostearate.
Description of raw materials used in production and their functions.
- Bis-Hydroxyethoxypropyl Dimethicone. A modified form of silicone with hydroxyl functional groups. Acts as an emollient and skin conditioner, giving a smooth and velvety feel to the product.
- Isophorone Diisocyanate. A reactive compound used in forming polymers and resins. It acts as a crosslinking agent that helps to bind molecules together.
- Sorbitan Isostearate. A non-ionic surfactant and emulsifying agent. It assists in stabilizing emulsions and improving the distribution of components in the product.
Step-by-step summary of industrial chemical synthesis process.
- The Bis-Hydroxyethoxypropyl Dimethicone is reacted with Isophorone Diisocyanate (IPDI) in the presence of a catalyst and at a controlled temperature.
- After the pre-polymer formation, Sorbitan Isostearate is introduced to further extend the reaction and form the desired polymer, i.e., POLYURETHANE-28.
- The resulting product is then purified, filtered, and ready for use in various cosmetic applications.
What it is used for and where
Cosmetics
Surfactant - Cleansing agent. Cosmetic products used to cleanse the skin utilise the surface-active action that produces a lowering of the surface tension of the stratum corneum, facilitating the removal of dirt and impurities.
Surfactant - Emulsifying agent. Emulsions are thermodynamically unstable and are used to soothe or soften the skin and emulsify, so they need a specific, stabilising ingredient. This ingredient forms a film, lowers the surface tension and makes two immiscible liquids miscible. A very important factor affecting the stability of the emulsion is the amount of the emulsifying agent. Emulsifiers have the property of reducing the oil/water or water/oil interfacial tension, improving the stability of the emulsion and also directly influencing the stability, sensory properties and surface tension of sunscreens by modulating the filmometric performance.
It appears as a white powder or colorless liquid.
Safety
Dimethicone ((polydimethylsiloxane) is a chemical compound, a high molecular weight polymer derived from silicone, a chemically inert mixture of linear methylated siloxane polymers. The term 'dimeth' denotes two methyl groups bonded to the silicone molecule that provide the formation of dimethicone. It possesses a pronounced viscoelasticity characteristic and is hydrophobic, thus adding shine and slipperiness when applied to hair or skin. It forms a kind of barrier that prevents exogenous substances from entering the stratum corneum and at the same time prevents water loss. It is also UV-resistant, non-greasy and cost-effective. At low concentrations it is considered by the US FDA (Food and Drug Administration) to be a skin protector with a good degree of safety.
It is therefore considered safe when formulated to be non-irritating in cosmetic products as, given its high molecular weight, it is poorly absorbed by the skin or scalp.
Urethane (also called ethyl carbamate) is a fermentation by-product and is considered a genotoxic agent.
Polyurethanes are rather complex, inert and biostable materials that are also used in biomedical applications. They are typically synthesised by the reaction of a glycol or polyol with polyisocyanate or diisocyanate. It is known that exposure to isocyanates can cause asthma, contact allergies, conjunctival and skin irritation. However, a study by the Cosmetic Ingredient Review Expert Panel in 2017 found that the rates of harmful residues are not significant for human health. ((Polyurethane-28, -42, and -69 are reported to contain no detectable residual isophorone diisocyanate)
