Challenging toxic tin catalysts in polyurethane coatings through serendipity

Traditional polyurethane (PU) catalysts, especially dibutyl tin dilaurate, face scrutiny over toxicity concerns, leading to interest in safer alternatives. In an unexpected turn of events, research into a commercially available antibacterial agent revealed that it drastically reduced the pot life of PU coatings. Experiments show that when PU coatings were formulated with the antibacterial agent as catalyst, drying time and solvent resistance were improved as compared to traditional tin and zirconium catalysts. Further analysis showed that this was the result of copper compounds and it could be shown that a similar catalytic effect was achieved through Cu(II)-sulfate and Cu(II)-acetate. Such copper salts are not yet commonly known as replacements for tin catalysts. Possible mechanisms such as heterogenous catalysis or in-situ formation of the active compound were discussed.