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What are the different types of Isocyanates?

Isocyanates are chemical compounds known for their ability to form strong bonds and are used widely in the production of polyurethanes, especially in coatings and adhesives.  There are two main types of isocyanates, consisting of aliphatic and aromatic compounds.

In this blog, we’ll explore the difference between the two and highlight which products are safe to use.

The difference between Aliphatic and Aromatic Compounds

The greatest difference between aromatic and aliphatic compounds is their toxicity. Aromatic isocyanates which include Toluene and Xylene, contain harmful compounds that are toxic, compared to safe to use aliphatic compounds.

In addition to this, the following notable differences can be used to distinguish aliphatic compounds from aromatic compounds:

 Molecule size

Aliphatics have a larger particle size (molecular weight) than aromatics. The larger particle size is designed to drop to the floor within seconds, rather than remaining airborne, to minimise workplace exposure, especially when spraying.

Unlike aromatic’s smaller particle size, aliphatic’s larger particle sizes cannot be absorbed through the skin’s dermal and hypo-dermal layers, or inhaled deeply into the respiratory system.


Aliphatic isocyanates have a low degree of acute toxicity and a lower environmental impact than aromatic alternatives.

Aliphatic compounds have very low solubility in water and a high adsorption to organic matter, meaning they bond with organic matter, but will not absorb to the same extent as aromatic compounds which distribute widely and build up in the environment.

Health implications

When it comes to using aromatic compounds, there are severe health and safety concerns due to its toxicity. Aromatics can be easily absorbed into the human body and if used in the long term can have a higher chance of building up in your system, even the smell is toxic.

Aromatics such as tolylidene diisocyanate have long been considered a carcinogenic by ‘The International Agency for Research on Cancer’, with links to long term respiratory problems and depending on the levels of exposure, other acute or chronic symptoms.

Exposure to other aromatic compounds, such as toluene can cause irritation to the eyes and nose, nerve damage, inflammation of the skin, and in worst cases, liver and kidney damage. Xylene has similar side effects and serious exposure can be fatal.

Hesse PU: A safe solution

Hesse products adhere to German regulations, which are typically stricter than UK regulations, making Hesse PU a safe sustainable solution.

The Hesse PU range is formaldehyde free and safe to use, it uses N-Butyl Acetate, which unlike toxic toluene and xylene, is used as a fruit flavouring in some sweets, baked goods and ice-cream!

Hesse uses synthesised aliphatic compounds, which uses a manufacturing process to increase the molecular weight and size, for an even safer, user-friendly product.

The Hesse PU range offers a wide range of products, from base coats and primers to multi coat, clear and pigmented lacquers. With special effects, such as concrete effect, rust effect, metallic effect, old country stains and many more.

Check out our full Hesse PU range here.

For a safe solution that meets your project’s requirements. Contact us on 023 9223 3310 or email