The Fragility Of Sugar Melts

Sugar is an essential energy material in the life; it widely exists in nature and has a wide application in the field of food and medicine. We chose the small molecule carbohydrates and honey as the research objects. The application of melt fragility in the non-metallic field and its relationship with the glass forming ability had been studied. The physical nature of melt fragility and the relationship between the fragility of the supercooled liquid and melt fragility had been studied.Viscosity of small molecule carbohydrates, honey and honey-water mixtures were measured with a rotating viscometer. The thermal properties of them have been investigated by differential scanning calorimetric (DSC) and thermogravimetric analysis (TG). The melt fragility has been calculated. With the M increasing, the glass-forming ability (GFA) decreased. The results show that in a single system, melt fragility can be used to predict the glass-forming ability. At the same time, we compared the M of different systems; we found that M did not work very well.Continuous viscosity of honey-water mixture was measured in a rotating viscometer at nominal water content weight from 0% to 60% over a range of temperatures (30℃-70℃). The thermal properties of honey-water mixtures have been investigated by differential scanning calorimetric (DSC). The melt fragility during the heating process (MH) and cooling process (MC) has been calculated. The results show that viscosity and flow activation energy decrease as the water content increases; MH as a glass-forming ability (GFA) indicator is well satisfied in single honey-water system but not satisfied in the whole system. Moreover, a new parameter B, defined as B=MC/MH, has been proposed, which can distinguish two kinds of honey with different water contents.Viscosity of honey was measured by a rotating viscometer using three different crucibles which are made of highly sintered alumina (Al2O3), graphite (C), and yttrium oxide (Y2O3), as well as two rotors, C and Al2O3 The results show that both the dimension and roughness of the rotor and crucible has effect on the viscosity values. But the roughness plays a more important role in the measurement results.The melt fragility and the fragility of the supercooled liquid have been calculated. This study indicated that, for the whole sugar system, the melt fragility and the fragility of the supercooled liquid separately show negative linear relations with the glass-forming ability and can be used as indicators of this property. In an individual sugar system, the fragility of the supercooled liquid has a direct proportion to melt fragility, which depends on the different inherent characteristic temperatures.