Diffusion of water within an amorphous carbohydrate

被引:31
作者
Aldous, BJ [1 ]
Franks, F [1 ]
Greer, AL [1 ]
机构
[1] UNIV CAMBRIDGE, DEPT MAT SCI & MET, CAMBRIDGE CB2 3QZ, ENGLAND
关键词
D O I
10.1023/A:1018584812561
中图分类号
T [工业技术];
学科分类号
08 ;
摘要
The evaporative drying of solid amorphous Ficoll-water mixtures is studied by thermogravimetric analysis. Differential scanning calorimetry is used to determine the physical state (glass or visco-elastic rubber) from which drying is performed. Drying is observed to continue at temperatures far below the glass-transition temperature (T-g), showing that water is mobile within amorphous carbohydrate matrices. Two models for drying kinetics are tested, and it is found that the rate of water removal is limited by diffusion through the amorphous matrix and not by desorption from the surface of the material. Although the viscosity of carbohydrate-water glasses has previously been found to obey Williams-Landel-Ferry kinetics, the drying process was found to follow Arrhenius kinetics both above and below T-g. In the glass-transition region the water diffusivity is not strongly dependent on the water content, and Fickian kinetics are observed.
引用
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页码:301 / 308
页数:8
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