Physio-chemical properties of polymyxan 88A–water system

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• 作者：Boukharova ; E.N. ; Ptitchkina ; N.M.
• 关键词：Microbial exopolysaccharides ; Phase diagram ; Phase separation
• 刊名：Carbohydrate Polymers
• 出版年：2001
• 出版时间：April, 2001
• 年：2001
• 卷：44
• 期：4
• 页码：313-317
• 全文大小：134 K

文摘

The system exopolysaccharide polymyxan 88A–water was studied at several temperatures. The temperature dependence of viscosity at cooling and heating was obtained in order to estimate the phase separation temperature (T_s) and the gelation temperature (T_g). The experimental values of T_s and T_g were used to plot the phase diagram of the system under study at polymer concentrations below 1.5wt % . Viscous flow in the system was examined by the cylinder–cylinder rotation method. It has been found that: (i) at shear rates within 1–100s⁻¹ the dependence of viscosity on shear rate can be fairly expressed by the power low; (ii) the activation enthalpy of viscous flow practically does not depend on shear rate; and (iii) the activation entropy of viscous flow is negative, most likely due to an orienting action of mechanical field.