Synthesis, deblocking and cure reaction studies of secondary alcohol-blocked isocyanates

A series of 1,3-dichloro-2-propanol-blocked diisocyanates, based on diisocyanates including 4,4′-methylene di(phenyl isocyanate), toluene-2,4-diisocyanate, isophorone diisocyanate and 1,6-diisocyanatohexane, were prepared and characterized thoroughly by Fourier transform infrared, 1 H-NMR, 13 C-NMR spectroscopic methods and elemental analysis (CHN). The blocking reaction of 1,3-dichloro 2-propanol with aromatic diisocyanates occurs faster than with the aliphatic isocyanates. The deblocking temperature of blocked isocyanates was determined by thermogravimetric analysis, differential scanning calorimetry and the CO 2 evaluation method. Cure reactions of blocked isocyanates with hydroxyl-terminated polybutadiene were also followed to establish the structure–property relationship of the 1,3-dichloro-2-propanol-blocked isocyanates. The deblocking studies reveal that the aromatic isocyanates undergo deblocking more easily than aliphatic isocyanates. The dissolution behavior of 1,3-dichloro-2-propanol-blocked isocyanates in Terathane-2000, polypropylene glycol-2000, polycaprolactone diol-2000 and hydroxyl-terminated polybutadiene-2500 was also studied, and it was found that all adducts are soluble in these polyols.