Name: HDI Biuret Crosslinker (Aliphatic, Low NCO)
Brand: Coatingsink
SKU: hdi-biuret-crosslinker-desmodur-n100
Availability: InStock

Question 1

What is the difference between an HDI biuret and an HDI trimer (isocyanurate) crosslinker?

Accepted Answer

HDI biurets are formed by reacting HDI with water and have a branched urea structure with typically ~3 NCO groups per molecule. HDI trimers (isocyanurates) form a cyclic ring structure with higher thermal stability and hardness. Biurets generally give slightly better flexibility and adhesion, while trimers provide superior chemical resistance and heat resistance. Biurets are preferred for maintenance topcoats; trimers are the standard for automotive OEM clear coats.

Question 2

Why are aliphatic isocyanates like HDI chosen for UV-stable finishes?

Accepted Answer

Aromatic isocyanates (TDI, MDI) contain chromophoric rings that absorb UV radiation and oxidize to yellow quinone-imide structures, causing rapid yellowing. Aliphatic isocyanates such as HDI do not have aromatic chromophores, so the resulting PU coatings retain gloss and color on exterior exposure for significantly longer — typically 5–10 years outdoors versus months for aromatic PU.

NCO Content	22.0–23.5%
Solvent-Free	yes (100% active)
Functionality	~3.0
Color (Gardner)	≤1
Viscosity (25°C, 100%)	2500–5000 mPa·s

HDI Biuret Crosslinker (Aliphatic, Low NCO)

Specifications

FAQ

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