Name: HDI Trimer Crosslinker for Waterborne Coatings
Brand: Coatingsink
SKU: hdi-trimer-crosslinker-waterborne
Availability: InStock

Question 1

How does the NCO content of ~20% affect crosslink density and film properties?

Accepted Answer

At ~20% NCO, the HDI isocyanurate trimer provides a functionality of approximately 3.0, yielding a moderately high crosslink density when stoichiometrically matched to a hydroxy-functional waterborne polyol (typically OH:NCO molar ratio of 1:1 to 1:1.05). Higher NCO:OH ratios increase hardness and solvent resistance but reduce flexibility and can cause brittleness in thin films. For automotive clearcoats, ratios near 1:1 balance scratch resistance with stone-chip performance.

Question 2

What catalyst and dosage are recommended, and how can pot life be extended?

Accepted Answer

Dibutyltin dilaurate (DBTDL) at 0.05–0.1% on total formulation weight is standard, giving a 4–8 h pot life at 25°C. For longer working times in warm climates, switch to a bismuth-based catalyst (e.g., bismuth neodecanoate) at 0.1–0.2%, which typically doubles pot life with only a modest increase in required cure temperature. Avoid zinc-based catalysts, which can destabilize the waterborne dispersion.

Question 3

Is this crosslinker self-dispersible in water, or does it require an emulsifier?

Accepted Answer

This hydrophilic HDI trimer grade contains built-in polyethylene oxide segments that allow direct dispersion in water with vigorous agitation (≥500 rpm), eliminating the need for external emulsifiers. Self-emulsification keeps the formulation exempt from additional surfactant-related issues such as water sensitivity or foam stabilization. The dispersed particle size is typically below 200 nm, ensuring compatibility with most waterborne acrylic and polyurethane dispersions at add-in levels of 10–25% on binder solids.

NCO Content	~20.0%
Active Content	100%
Viscosity (25°C)	2000–4000 mPa·s
Isocyanate Functionality	~3.0
Pot Life (with DBTDL, 25°C)	4–8 h

HDI Trimer Crosslinker for Waterborne Coatings

Specifications

FAQ

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