Viscosity and Dynamic Rheological Properties of Job's-tears as a Function of Moisture Content

수분함량에 따른 율무가루의 점도변화 및 동적물성 특성에 관한 연구

Changes in viscosity and dynamic theological properties of Job's-tears were measured by Bohlin dynamic tester as a function of moisture, and measurement was performed within a linear viscoelastic range. The result of the shear stress vs shear rate of Job's-tears at different moisture contents $(50{\sim}75%)$ was applied to mathematical models and Herschel-Bulkley model showed the highest correlation coefficient. Lower moisture content (55%) produced higher yield stress and consistency index, but lower flow behavior index, whereas higher moisture content showed reverse effects. Job's-tears with $50{\sim}70%$ moisture contents showed a higher storage modulus (G') than loss modulus (G') at all frequencies, showing a higher concentrated polymer characteristics. However, higher moisture content (>75%) showed crossover point between G' and G', and frequency dependency. As the moisture content was increased, the amount of viscoelastic properties such as G', G', complex viscosity decreased during heating, and initial temperature and miximum value of viscoelastic properties shifted to higher temperatures, representing the moisture-dependence of Job's-tears upon theological properties.