Thermochimica Acta, Vol.589, 183-196, 2014
Heat capacity and transition behavior of sucrose by standard, fast scanning and temperature-modulated calorimetry
The heat capacity (C-p) of crystalline and amorphous sucrose was determined using standard and quasiisothermal 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 c(p) 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 (T-m) 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 r degrees(m) = 424.4K and Delta H degrees(f) = 32 kJ/mol, respectively. The glass transition temperature (T-g) of amorphous sucrose was at 331 K with a change in C, 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 T-m was 483 K and T-g was 364K. Superheating effects were observed during the melting with the maximum value around 46K at 1000 K/s. (C) 2014 Elsevier B.V. All rights reserved.
Keywords:Sucrose;Heat capacity;Melting;Glass transition;Standard;Fast and temperature modulated differential scanning calorimetry