Polyurethane-18 is an inorganic chemical compound, a segmented block copolymer derived from urethane and synthesised from isocyanates. Significant substances used in the production method:

butanediisocyanate, polymer, hydroxypoly(oxy-1-methylpropylene)ol and 2,2-di(hydroxymethyl)propanoic acid, tris(2-hydroxyethyl)amine salts, C1-8-alkanediamines.

The name describes the structure of the molecule:

• "Polyurethane" is a term that describes a class of polymers widely used in various applications due to their versatility and desirable properties such as durability, flexibility and abrasion resistance and temperature variations.
• "-18" is a reference to the specific type or grade of polyurethane, which can be characterized by such factors as the types of isocyanates and polyols used, their relative amounts, and the presence of any additives. . This is a designation used to differentiate different molecular structures or variants of the polymer. In cosmetic chemistry, these numbers can help formulators identify specific characteristics or behaviors of a given ingredient, particularly when a chemical family has multiple derivatives or forms.

Description of raw materials used in production and their functions.

• m-tetramethylene diisocyanate. Provides isocyanate groups for the formation of polyurethane.
• Polybutylene glycol. A polyol that provides hydroxyl groups for the formation of polyurethane.
• Dimethylolpropionic Acid. Adds hydroxyl and carboxylic groups to the polymer.
• Triethylamine. Used to neutralize the pre-polymer.
• Hydrazine and short-chain diamines (C1-8 diamines). Serves to extend the polymer chain and enhance its properties.

Step-by-step summary of industrial chemical synthesis process.

• m-tetramethylene diisocyanate, polybutylene glycol, and dimethylolpropionic acid are reacted together to form a pre-polymer.
• This pre-polymer is then neutralized with triethylamine.
• The addition of hydrazine and C1-8 diamines allows for chain extension, stabilizing and completing the polyurethane formation.

What it is used for and where

Cosmetics

It is a restricted ingredient as II/201 and III/62 a Relevant Item in the Annexes of the European Cosmetics Regulation 1223/2009. Substance or ingredient reported: 

Trialkylamines, trialkanolamines and their salts.  Do not use with nitrosating systems - Minimum purity: 99% - Maximum secondary amine content: 0.5% (applies to raw materials) - Maximum nitrosamine content: 50 microgram/kg - Keep in nitrite-free containers

 Hydrazine, its derivatives and their salts

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.

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

Urethane (also called ethyl carbamate) is a by-product of fermentation 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.