부산대학교 도서관

Small deformation measurements have been used to characterize the rheological behaviour of two understudied natural polymers obtained from the leaves and calyxes of Sesamum radiatum and Bombax buonopozense respectively, by extraction with water, and then precipitation with absolute ethanol. Measurements performed on 1%w/v aqueous dispersion of each polymer at ambient conditions include viscosity, yield stress, oscillatory stress sweep, oscillatory frequency sweep, creep and recovery, and then temperature ramp. The measurements were done on the same samples on the first day and fourth day after storage at ambient temperature. The polymers exhibited shear- thinning with the viscosity of bombax gum remaining basically same on the 1st and 4th day while sesamum gum had a significant drop in viscosity by the 4th day. Bombax gum (yield value - 5.499 Pa at shear 0.114 s−1) had more internal strength than sesamum gum (yield value - 0.338 Pa at shear 0.032 s−1). In addition, bombax gum exhibited more elasticity and extended visco-elastic region than sesamum gum. The present study suggests that bombax gum can be used for matrices and hydrogels with improved physicomechanical strength and sustained drug release while sesamum gum may require modification to achieve similar properties. [ABSTRACT FROM AUTHOR]