Reprint of “Heat capacity and transition behavior of sucrose by standard, fast scanning and temperature-modulated calorimetry”

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 5–600K range. The experimental Cp of solid sucrose at 5–300K 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 442–465K range with a heat of fusion of 40–46J/mol determined at heating rates 0.5–20K/min, respectively. The equilibrium Tm and heat of fusion of crystalline sucrose were estimated at zero heating rate as Tom=424.4K and ΔHof=32kJ/mol, respectively. The glass transition temperature (Tg) of amorphous sucrose was at 331K with a change in Cp of 267J/(molK) as it was estimated from reversing heat capacity by quasi-isothermal TMDSC on cooling. At heating rates less than 30K/min, thermal decomposition occurred during melting, while at extreme rate of 1000K/s, degradation was not observed. Data obtained by fast scanning calorimetry (FSC) at 1000K/s, showed that Tm was 483K and Tg was 364K. Superheating effects were observed during the melting with the maximum value around 46K at 1000K/s.