Polyurethane-6 is an inorganic chemical compound, an urethane and Dimethicone by-product. Significant substances used: isophthalic acid, adipic acid, hexylene glycol, neopentyl glycol, dimethylolpropanoic acid, isophorone diisocyanate and bis-ethylaminoisobutyl-dimethicone.
Description of raw materials used in production and their functions.
- Isophthalic acid. Acts as a crosslinking agent and provides strength to the polymer.
- Adipic acid. Contributes to the flexibility and plasticity of the polymer.
- Hexylene glycol. Used as a chain extender component and flexibilizer.
- Neopentyl glycol. Another chain extender component used to improve the thermal properties of the polymer.
- Dimethylolpropanoic acid. Serves as a bonding agent and crosslinker.
- Isophorone diisocyanate (IPDI). Acts as crosslinking agents and provides the necessary reactivity for polymer formation.
- Bis-ethylaminoisobutyl-dimethicone. Modifies the surface properties of the polymer and acts as a flexibilizer.
Step-by-step summary of industrial chemical synthesis process.
- A mixture of the acids (isophthalic, adipic, and dimethylolpropanoic) is prepared and subsequently reacted with hexylene glycol and neopentyl glycol.
- Once the prepolymer mix is obtained, IPDI is introduced and the reaction proceeds.
- The bis-ethylaminoisobutyl-dimethicone is then added at the last stage to ensure the desired end properties of Polyurethane-6.
What it is used for and where
Cosmetics
Binder agent. Ingredient that is used in cosmetic, food and pharmaceutical products as an anti-caking agent with the function of making the product in which it is incorporated silky, compact and homogenous. The binder, either natural such as mucilage, gums and starches or chemical, may be in the form of a powder or liquid.
Film-forming agent. It produces a continuous ultra-thin film with an optimal balance of cohesion, adhesion and stickiness on the skin or hair to counteract or limit damage from external phenomena such as chemicals, UV rays and pollution.
Hair fixative. This ingredient has the ability to create, with its protective film, stiffness and hold in the hair, and also has the ability to form, with its hydrophilic and elastic properties, bonds between the hair fibres, to keep the hair in a particular shape for a certain time.
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.
