Synthesis and characterization of diethylene glycol monobutyl ether—Blocked diisocyanate crosslinkers

Typically blocked isocyanate systems are used to obtain the performance of two component polyurethane (PU) system in a one-component mixture. In this study four types of isocyanates namely, hexamethylene diisocyanate (HDI), diphenylmethane diisocyanate (MDI), isophorone diisocyanate (IPDI) and toluene diisocyanate (TDI) were blocked with diethylene glycol monobutyl ether (DEGMBE). Elimination of the isocyanate groups and the formation of urethane bonds were studied by FTIR spectroscopy and titration methods. Thermal dissociation of blocked diisocyanates was analyzed by DSC and TGA techniques.Deblocking temperature obtained by DSC and TGA techniques was compared. Based on DSC data, it was found that deblocking of blocked MDI and TDI starts at lower temperatures compared to that of the aliphatic one (HDI). Reactivity of the blocked IPDI is between blocked MDI and blocked TDI.In general, TGA results show the same trend as DSC except for IPDI which shows the lowest deblocking temperature. Deblocking temperature values obtained by TGA technique were lower than DSC values.