ポリビニルアルコール濃厚溶液の定常流動における特異性 : 高分子レオロジー
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概要
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Flow curves were determined of polyvinyl alcohol solutions of some concentrations between 10% and 55%, at certain temperatures between 20℃ and 160℃, of water or dimethylsulfoxide. The experiment was performed using rotational coaxal cylinder rheometer of Green type and Koka flow tester, a capillary viscometer. Polyvinyl alcohol, which was 1700 in polymerization degree, was used for the most part of this experiment, and partially alcoholyzed polyvinyl acetate was used as well for comparison. For the experiment of Koka flow tester the solution was prepared at 150℃ for 30 min in the vessel in flow tester and kept in experimental conditions for 20 min. For the experiment of rotational rheometer it was prepared in glass ampoule at 105℃. The experiment covers a range from 10 to 10^6 sec^<-1> in shearing rate, and from 10^2 to 10^7 dynes/cm^2 in shearing stress. About the steady flow viscosity of high polymer solution it is commonly known that the apparent viscosity decreases continuously form η_0, static viscosity, to η_∞, which is an extreme value of viscosity in the higher limit of shearing rate, as the shearing rate increases from zero to the higher limit. It was found that polyvinyl alcohol solution showed a singular phenomenon in its steady flow viscosity. Its apparent viscosity decreases gradually with the increase of shearing rate when the rate is relatively low, which is similar to the case to other polymers. At fairly high shearing rate is apparent viscosity begins to increase rapidly. After the viscosity rises to some extent, it begins again to decrease gradually. This phenomenon appeares in almost all flow curves in this experiment. It takes place even if polyvinyl alcohol is dissolved into better solvents such as dimethyl sulfoxide. It takes place also in aqueous solution of partially alcoholyzed polyvinyl acetate. If polyvinyl alcohol content becomes smaller or temperature at the measurement becomes higher, such an increase of viscosity takes place at higher shearing rate. Addition of boric acid influences this phenomenon in aqueous solution of polyvinyl alcohol, and the shearing rate shifts to the lower where this phenomenon takes place. It may be supposed that this increase of viscosity is caused by some structure in polyvinyl alcohol solution built up under high shearing stress. However, it may be common among high polymer solutions, and it may occur at much higher shearing rate, and only in the case of polyvinyl alcohol solution it may appear in the region of relatively low shearing rate.
- 社団法人日本材料学会の論文
- 1961-05-15