TDI-TMP Adduct Curing Agent 75% EA Solution

TDI-TMP adduct offers approximately 3× higher reactivity than HDI-based isocyanates (trimer or biuret) due to the aromatic ring activating the isocyanate groups, resulting in pot lives of 4–8 hours vs. 8–24 hours for HDI systems at 25°C. This makes TDI adducts preferred where fast throughput and high-volume production is critical (automotive OEM spray lines, wood furniture factories). However, TDI cured films yellow on UV exposure (aromatic amine chromophores form) making them unsuitable for exterior topcoats. HDI trimers are chosen where non-yellowing exterior durability is the primary requirement. Typical use level is 1 part TDI-TMP to 4–6 parts hydroxyl-functional resin at OH:NCO = 1:1–1.05.