Waterborne Polyisocyanate Hardener for 2K PU Coatings: HDI-Based, Non-Yellowing, Low-VOC Crosslinker
As VOC limits tighten worldwide through 2026, waterborne polyisocyanate hardener has shifted from optional to a tender requirement for industrial 2K PU coatings. The Dongsen WD hardener (model WD-8780 / WD-8980) is an HDI-based, anionic, water-dispersible polyisocyanate — delivering solvent-borne performance without the solvent: high gloss, full body, excellent chemical resistance, and a non-yellowing aliphatic backbone.
Technical Specifications
| Property | Value |
|---|---|
| NCO content | 15.0 ± 1 % |
| Free HDI monomer | ≤ 0.3 % |
| Solid content | 80.0 ± 2.0 % |
| Viscosity (25 °C) | 300 ± 200 mPa·s |
| Backbone | HDI (aliphatic, non-yellowing) |
| Modification | Anionic, water-dispersible |
Typical values; production COA governs each shipment.
Key Properties & Applications
The aliphatic HDI backbone does not yellow under UV, suiting both interior and exterior use — unlike aromatic TDI hardeners restricted to indoor application. Free HDI monomer ≤ 0.3 % supports worker safety and non-EU import compliance (US, Canada, Australia, Mexico, Southeast Asia, Middle East). The anionic modification self-emulsifies under hand-stir conditions, ideal for field-mixed 2K systems.
Primary applications: waterborne 2K industrial maintenance coatings; concrete floor coatings for parking structures, warehouses, and logistics centers; rail transit and rolling-stock livery; and as a crosslinker in waterborne polyurethane adhesives.
Formulation Note
Waterborne systems need a higher NCO:OH ratio than solvent-borne — typically 1.5:1 to 2.0:1 — because some isocyanate is consumed reacting with water. Pot life is shorter than solvent-borne equivalents; confirm working time at your application temperature before scale-up.
FAQ
Does waterborne polyisocyanate yellow over time?
No. The Dongsen WD hardener is HDI-based — an aliphatic backbone that does not yellow under UV, making it suitable for color-critical and exterior applications.
What NCO:OH ratio for a waterborne 2K PU system?
Typically 1.5:1 to 2.0:1, higher than solvent-borne, because some isocyanate reacts with water. Confirm by lab trial with your polyol dispersion.
Is the free monomer level low enough for US import?
Yes — free HDI ≤ 0.3 %, satisfying worker-safety and import requirements for the US, Canada, Australia, Mexico, Southeast Asia, and the Middle East.
Can it be used for exterior and rail coatings?
Yes. The non-yellowing aliphatic HDI backbone is weather-stable, suitable for exterior industrial, floor, and rail transit coatings.
Contact Us Now
Sample requests (1–5 kg) ship within 7 working days. Dongsen Chemicals — ISO 9001 / ISO 14001 dual-certified.
marketing@dongsenchem.com | +86 18813800209
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