The blocking reaction of polyisocyanates with active hydrogen containing subs tances and the deblocking of the reaction products have been investigated by IR and TGA. The results showed that the initial deblocking temperature of the blocked polyisocyanates were mainly determined by active hydrogen substances. The deblocking temperature of toluene diisocyanate blocked with methylethylketoxime was 110 ℃ and this temperature could be more or less reduced by using organic tin catalyst at deblocking reaction.
