Polyurethane-61 is an inorganic chemical compound, a segmented block copolymer derived from urethane and synthesised from isocyanates.

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.
• "-61" 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.

Significant substances used in the production method:

methylene diphenyldiisocyanate (SMDI), dimethyl aminopropylamine (DMAPA), isopropylidenediphenoxypropanol, isophthalic acid/1,6-hexanediol/adipic acid, water, triethylamine, ethylenediamine.

Description of raw materials used in production with their functions.

• Methylene Diphenyldiisocyanate (SMDI). Provides isocyanate groups for urethane bond formation.
• Dimethyl Aminopropylamine (DMAPA). A tertiary amine used to catalyze the urethane formation reaction.
• Isopropylidenediphenoxypropanol. Alcohol providing hydroxyl groups for reaction with isocyanate.
• Isophthalic Acid/1,6-Hexanediol/Adipic Acid. Blend of acids and alcohols to form polyesters and provide additional hydroxyl groups.
• Water. Used in foam formation reaction and in reaction with isocyanates to form urea bonds.
• Triethylamine. Acts as a catalyst and neutralizing agent.
• Ethylenediamine. Provides amine groups for urethane bond formation.

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

• Preparation: a blend of isopropylidenediphenoxypropanol, isophthalic acid, 1,6-hexanediol, and adipic acid.
• SMDI is added to the blend and allow for reaction.
• Upon prepolymer formation,  DMAPA and triethylamine are introduced.
• Added water to start the foam formation reaction.
• Once the desired degree of polymerization is reached, stop the reaction and cool down the polymer to obtain Polyurethane-61.

What it is used for and where

Cosmetics

Nail Conditioning agent. It is an agent that creates protection against harmful or chemical substances by strengthening the nail structure against external elements and can repair any chipping, cracking or brittle nails. It helps keep the nail's outer layer and keratin protein in good condition. It can also prevent cracking and peeling of the nail.

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. (Solvent: Water, approximately 0.0075% MI and benzisothiazolinone as preservatives, and approximately 1.3% (by weight) dimethylethanolamine as a neutralizing agent)