Waterborne polyurethane coatings use water as the dispersing medium, cutting VOC emissions sharply compared with solvent-based systems. Catalysts here mainly promote three reactions: isocyanate-hydroxyl, isocyanate-water, and epoxy-amine, strengthening the cross-link network as the coating cures.
By structure, catalysts split into four groups: metal salts (such as DBTDL and stannous octoate), organotin compounds, amines (TEA, DMEA) and heterocyclic compounds (DBU, DMAP). Comparative testing showed the DBTDL system reaching a 1-hour dry time and 0.85 mol/L cross-link density, ahead of the TEA system’s 2 hours and 0.75 mol/L.
Catalyst selection needs to weigh catalytic activity, selectivity, compatibility, cost-effectiveness and environmental impact together, to match the specific coating process requirement.