The kinetic studies were proceeded via real time FT-IR and DSC, using a curing agent of 4,4'-Methylenebis(2-chloroaniline) called MOCA in the PTMG-TDI based 6.21% -NCO prepolymers. It is difficult to obtain an accurate –NCO conversion, in the initial reaction during mixing step. In this study, the –OH of polyol replaced in order to prevent from the reaction of -NCO and –OH functional groups. Every step was measured by FTIR spectrum, to verify the absorbance of the -NCO (2273cm-1) on the basis of the aromatic CH (1108cm-1). Finally, the reaction rates were calculated from the measured data, and analyzed with kinetic model.