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个相同大小(0.5 mm直径)的毛细管组成。和40厘米长)；一个用于流动相，另一个用于流动相和样品溶液。在毛细管两端安装了两个差压传感器。研制了两台变送器输出差值放大电路。以泵为流动相，进样量为3ml，配制了几种不同相对分子质量、不同浓度的聚苯乙烯溶液，并测量了差压。根据差压和样品浓度曲线图，计算了聚苯乙烯样品的特性粘数。通过测量窄相对分子质量分布的聚苯乙烯样品的压差，得到了Mark-Houwink-Sakurada参数。使用这些参数和固有粘度计算了聚苯乙烯样品的相对分子质量，结果与供应商的值吻合良好。同样，测量了聚氯乙烯的各项参数。聚氯乙烯的样品浓度必须是通常浓度的1/10，只有这个系统才能测量这种稀溶液的粘度。与Ubelohde玻璃毛细管粘度计的性能比较表明，该系统在分析时间、进样量、精密度等方面均优于后者。将该测量系统与SEC系统相连，测量了聚苯乙烯的平均分子质量。对系统稍加修改后即可进行测量，测量结果与通常的相关方法吻合较好。该体系可作为SEC的分子灵敏检测器。

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.