Name: HDI Biuret Crosslinker N-75 Type
Brand: Coatingsink
SKU: hdi-biuret-crosslinker-n75
Availability: InStock

Question 1

What is the recommended stoichiometric ratio when using this HDI biuret crosslinker with an OH-acrylic resin?

Accepted Answer

Calculate the isocyanate index (NCO/OH ratio) targeting 1.0–1.1 for balanced cure. Use the formula: parts crosslinker = (OH value of polyol × polyol weight) / (NCO content × 42 × 1000). An index of 1.05 is typical for automotive topcoats requiring optimum hardness and flexibility.

Question 2

How does this biuret-type crosslinker compare to HDI isocyanurate (trimer) types?

Accepted Answer

HDI biuret crosslinkers offer higher flexibility and impact resistance versus trimer types due to the biuret linkage geometry. Trimer types generally provide slightly better hardness and chemical resistance. Biuret grades are preferred for wood coatings and flexible substrates; trimer grades suit rigid industrial or automotive OEM applications.

Question 3

What pot life can be expected in a typical 2K PU formulation?

Accepted Answer

Pot life with a standard OH-acrylic (OH value 100 mg KOH/g) at 25°C is typically 4–8 hours without catalyst. Addition of DBTL or bismuth catalyst at 0.05–0.1% (on total binder) accelerates cure but reduces pot life to 1–3 hours. Elevated temperature (60–80°C) forced-dry cycles are fully compatible.

Solids Content	75% in ethyl acetate
Density (25°C)	1.06 g/ml
Viscosity (25°C)	2000–3000 mPa·s
Average Functionality	≈3.5
NCO Content (solution)	16.5 ± 0.5%

HDI Biuret Crosslinker N-75 Type

Specifications

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