HEAT-CAPACITY AND THERMAL-DECOMPOSITION OF DICYANDIAMIDE

A thermochemical study of dicyandiamide (DCD) has been performed using adiabatic calorimetry, differential scanning calorimetry (DSC) and th ermogravimetric analysis (TG). The low-temperature heat capacity of DC D was determined with an automated adiabatic calorimeter in the range 80-370 K. A phase transition was found between 265 and 275 K, and the peak temperature, enthalpy and entropy of transition were determined t o be 269.49 K, 2.98 kJ mol(-1) and 11.07 JK(-1) mol(-1), respectively. The high-temperature heat capacity of DCD was measured with a differe ntial scanning calorimeter in the range 330-500 K. The DSC curve showe d that DCD melts at 487.56 K and the enthalpy and entropy of melting w ere evaluated as 22.96 and 47.68 JK(-1) mol(-1), respectively. The TG analysis of DCD was carried out in the range 300-850 K, from which it was found that decomposition starts at 521.20 K and ends at 659.62 K i n three steps. (C) 1997 Elsevier Science B.V.