What are diisocyanates

There are many types of diisocyanates, of which the main ones are the following: aromatic diisocyanates such as methylene diphenyl diisocyanate (MDI), toluene diisocyanate (TDI) and aliphatic isocyanates, hexamethylene diisocyanate (HDI), methylene dicyclohexyl diisocyanate or hydrogenated MDI (HMDI) and isophorone diisocyanate (IPDI). Isocyanates are the building blocks of polyurethane.


Polyurethane derives from the chemical reaction (polymerisation) between diisocyanates and polyols.

Polyurethanes are versatile, modern and safe compounds. They are used in a wide range of applications to help create a variety of consumer and industrial products that play a crucial role in making our lives more convenient, comfortable and sustainable.

Whether in rigid or flexible form, as binders or coating materials, polyurethane has many uses and applications. Thanks to its versatility and unique properties, the list of manufactured products continues to grow with new, innovative applications introduced to the market all the time.

Polyurethane is a product for the future. It plays a central role in our evolving needs, allowing us to do things that would have seemed impossible in the past.

In order to meet quality standards and technical specifications of products, pigments and additives may be added to polyurethane to ensure the exact formulation of products, be it foam, adhesives, elastomers or sealants and coatings. The range of possible applications is endless. As the molecule is adapted to provide different properties, polyurethane foam can display different levels of rigidity or flexibility.

For example, a comfortable sofa requires the use of carbon dioxide as a blowing agent for the production of soft foam. In rigid foams, a gas such as pentane is “trapped” in the foam’s closed cells, optimising its insulation capacity.

In addition, the durability, corrosion resistance and weather resistance of polyurethanes makes them suitable for coating all kinds of surfaces. Polyurethane can also be used to safely bind together vastly different materials, such as wood, rubber, cardboard or glass.

For example, polyurethane adhesives enable the reuse of vehicle tyres in playgrounds, sports tracks or surfaces for sports stadiums after they are collected and shredded. Polyurethane coatings can furthermore protect substrates against corrosion and weathering, significantly increasing their durability and saving resources.

Further applications of diisocyanates include highly durable compact materials like thermoplastic polyurethane (TPU) and elastomers. Such materials are widely used for a variety of different applications including (car) wheels, ski boots and the production-use of artificial leather.

Diisocyanates under REACH

The Annex of Directive 76/769/EEC sets out the diisocyanates restricted under REACH. Information about these substances is available on the website of the European Chemicals Agency (ECHA) and in the Safety Data Sheets (SDSs) of products.

Diisocyanates, as a group, include the substances listed in the table below. The table has been prepared by ECHA to facilitate the searching of restricted substances in the Annex XVII of the REACH Regulation.

The list is not exhaustive and is continually updated.

ECHA website about the restrictions on diisocyanates:

Find below a non-exhaustive list of substances restricted under REACH.