The previous studies suggest that hydrogen bond between chlorinated polypropylene (CPP) and polyaniline (PANI) plays a prominent role in the decision of polypropylene/CPP/PANI composites' electric property. In situ Fourier-transform infrared spectra were employed to detect and identify the relationship between the hydrogen bond and the temperature. Two kinds of hydrogen bond were carefully studied in the nitrogen–hydrogen bond (N[BOND]H) stretching, sulfur–oxygen double bond (S[DOUBLE BOND]O) stretching, and carbon–chlorine bond (C[BOND]Cl) stretching regions, using an iterative least-squares computer program to obtain the best fit of spectra. The ratio of absorptivity coefficients and the mole fraction of the “free” and two kinds of H-bonded N[BOND]H were calculated. There exists an apparent turning point in the curves of the relationship between the fraction of two kinds of H-bonded N[BOND]H and temperature. This phenomenon also exists in the S[DOUBLE BOND]O stretching region, and the turning point is at about 60°C. The mole fraction of H-bonded C[BOND]Cl decreases, and that of “free” C[BOND]Cl increases with increasing temperature. The enthalpy gap between the H-bonded N[BOND]H…O[DOUBLE BOND]S and the H-bonded N[BOND]H…Cl[DOUBLE BOND]C dissociation was also obtained as 23.2 KJ/mol. POLYM. ENG. SCI., 2012. © 2012 Society of Plastics Engineers