Thermodynamics Research Center / ThermoML | Thermochimica Acta

ABSTRACT

The heat capacity (Cp) of crystalline and amorphous sucrose was determined using standard and quasi- isothermal temperature modulated differential scanning calorimetry. The results were combined with the published data determined by adiabatic calorimetry, and the Cp values are now reported for the wide 5 600 K range. The experimental Cp of solid sucrose at 5 300 K was used to calculate the vibrational, solid Cp based on the vibrational molecular motions. The calculated solid and liquid Cp together with the transition parameters for equilibrium conditions were used as references for detailed quantitative thermal analysis of crystalline and amorphous sucrose. Melting temperature (Tm) of the crystalline sucrose was identified in a broad 442 465 K range with a heat of fusion of 40 46 J/mol determined at heating rates 0.5 20 K/min, respectively. The equilibrium Tm and heat of fusion of crystalline sucrose were estimated at zero heating rate as To m= 424.4 K and DHo f = 32 kJ/mol, respectively. The glass transition temperature (Tg) of amorphous sucrose was at 331 K with a change in Cp of 267 J/(mol K) as it was estimated from reversing heat capacity by quasi-isothermal TMDSC on cooling. At heating rates less than 30 K/min, thermal decomposition occurred during melting, while at extreme rate of 1000 K/s, degradation was not observed. Data obtained by fast scanning calorimetry (FSC) at 1000 K/s, showed that Tm was 483 K and Tg was 364 K. Superheating effects were observed during the melting with the maximum value around 46 K at 1000 K/s.