HDI
HDI
Hexamethylene Diisocyanate (HDI), also known as 1,6-diisocyanatohexane, is a versatile aliphatic diisocyanate with the molecular formula C8H12N2O2. HDI appears as a colorless to yellowish liquid with a pungent odor and is classified as toxic. While it is insoluble in water, it dissolves readily in a range of organic solvents.
Production
HDI is primarily synthesized through the phosgenation of hexamethylenediamine. Though it represents a small fraction of global diisocyanate production, HDI, alongside Isophorone diisocyanate (IPDI), plays a crucial role in specialized applications. HDI is notable for its ability to oligomerize, producing forms like trimers and biurets, which, despite their higher viscosity, exhibit reduced volatility and toxicity, making them more manageable in certain industrial processes.
Applications
The primary use of HDI lies in the production of polyurethane resins (PUR), particularly in coatings that are resistant to UV light, chemicals, and mechanical stress. These coatings are highly sought after in industries requiring durable finishes, such as aerospace, automotive, and marine sectors, where HDI-based polyurethanes are used in exterior paints to withstand harsh environmental conditions.