Design of a measuring system of minute differential pressure by capillary and application to analysis of chemical state of polymeric materials

所设计的测量系统由两根相同尺寸的毛细管组成（直径0.5 mm，长度40 cm）；一个用于流动相另一个用于流动相和样品溶液。两个差压传感器安装在毛细管两端。设计了两个换能器输出差的放大器。用泵流动相，进样量为3ml，制备不同分子量、不同浓度的聚苯乙烯溶液，测量压差。通过压差与样品浓度的关系图，计算了聚苯乙烯样品的特性粘度。通过测量分子量分布较窄的聚苯乙烯样品的压差，得到了Mark-Houwink-Sakurada参数。利用这些参数和本征粘度计算了聚苯乙烯样品的分子量，结果与供应商的值吻合较好。对聚氯乙烯进行了类似的参数测定。聚氯乙烯的样品浓度必须是通常浓度的1/10，并且只有在这个系统中才能测量这种稀释溶液的粘度。与ubelode玻璃毛细管粘度计的性能比较表明，该系统在分析时间、样品体积和精度方面优于后者。该测量系统与SEC系统连接，测量了聚苯乙烯的平均分子量。对系统进行了微小的修改，测量结果与常用的相对方法吻合较好。该系统可作为SEC的分子敏感检测器。

The measuring system designed consisted of two capillaries of the same size (0.5 mm i.d. and 40 cm in length) ; one for the mobile phase and the other for both the mobile phase and the sample solution. Two differential pressure transducers were installed at the both ends of capillaries. Amplifier for the difference of the output of two transducer was prepared. Mobile phase was flowed with a pump and the amount of the sample solutions injected was 3 ml. Several polystiren solutions of different molecular weight and different concentrations were prepared and diffrential pressure was measured. From the plot of differential pressure and sample concentration, intrinsic viscosities of the polystirene samples were calculated. From the measurement of the differential pressure of polystirene samples of narrow molecular weight distributions, Mark-Houwink-Sakurada parameters were measured. Molecular weights of polystirene samples were calculated using these parameters and intrisic viscosities and the results were in good aggreament to the vendor values. Similary the parameters of polyvinyl chloride were measured. Sample concentrations of polyvinyl chloride had to be 1/10 to the usual ones and the viscosity measurement of such dilute solutions was possible only this system. Comparison of the performance of the system with an Ubelohde glass capillary viscometer showed that this system was superior to the latter viscometer on the points of analysis time, sample volume, and precision. This measuring system was connected to the SEC system and molecular weight averages of polystirenes were measured. The measurement was capable after minor modification in the system and the results were in good agreement with the usual relative method. The system investigated here can be used as the molecular sensitive detector for SEC.