【摘要】 对聚苯乙烯 (PS)/甲苯稀及极稀溶液的粘度用常规的乌氏粘度法进行了测定。发现高分子在毛细管壁上无稳固吸附。在极稀浓度区,粘数 (sp/c) 值波动较大,在时间测量精度不变的条件下,粘数测量误差与浓度成反比,以致sp/c~c曲线的线性及重现性变差,并推导出了粘数测量误差与浓度及时间测量误差间的关系式。在此基础上,讨论了确定浓度测量下限的原则及计算公式,认为常规的乌氏粘度测定方法对极稀溶液的应用值得商榷。更多还原

【Abstract】 In this paper, PS (polystyrene)-toluene solution is selected as an example to touch the problem of viscosity anomaly of polymer solution in extremely dilute concentration region using the traditional method of Ubbelohde viscosity measurement. It is founded that there is not stable adsorption on the inner wall of the capillary for the polymer investigated. It is also founded that, the range of the reduced viscosity Δ(sp/c) has an obvious trend of increase along with the decrease of the concentration under Δt <0.2s (Δt is the range of the flow time measuring); furthermore, through deducing strictly, the relationship among the measurement error E of the reduced viscosity, solution concentration c and Δt is abstracted quantitatively, and in this equation, in given sample and experimental conditions, E is in proportion to Δt and in inverse proportion to c, and thus E will increase prominently with the reduction of the concentration, so there may be a lowest concentration limit cL corresponding to a certain experimental precision; thirdly, an approximate formula of cL is suggested also, according to that formula, it can be inferred that cL is permitted to go down in pace with both the improvement of the precision for timekeeping and the decrease of measurement error E required. Finally, these theoretical analyses are well supported by the following experimental results: although the repeatability of the flow times for three repeated experiments under each concentration is fairly good (Δt <0.2s), the sp/c~c curves are still not coincident, and along with the decrease of the concentration, the fluctuation of the reduced viscosity grows so great that the linearity of the curves becomes too bad to obey the regularity of the data, consequently, it is little significant for further work under c<cL. Therefore, the conclusion is that it needs to seriously consider the appreciation for Ubbelohde viscosity measurement in the extremely dilute polymer solution under classic conditions.更多还原