旋滴法测定界面张力实验现象分析与方法探讨

Analysis of Experiment and Method of Interfacial Tension Measurement by Spinning Drop Technique

柏 洁 张玉珍 王爱芳 张 宏 祖莉华 范忠钰

BAI Jie ZHANG Yuzhen WANG Aifang ZHANG Hong ZU Lihua FAN Zhongyu

针对TX550A型旋滴法界面张力仪测定界面张力过程中出现的内相油滴回缩（界面张力值由初期迅速下降然后上升）现象，分析了该现象产生的机理，考察了油滴体积对界面张力的影响，提出了正确的操作步骤。结果表明，内相油滴体积的回缩与表面活性剂溶液的增溶作用和油水界面间存在的Marangoni对流有关。用旋滴法测定界面张力开始时，应逐渐提高仪器转速，同时缓慢地调整仪器的平衡，以防止测试管中油滴因快速左右移动而产生不正常形变。在界面张力测定过程中，内相油滴体积相对较小时，测定的界面张力值比较准确。采用大测试管（2500 μL）测定时，注入内相油滴体积控制在1～3 μL；采用小测试管（300 μL）时，注入内相油滴体积控制在0.3～1 μL。对于4种特殊形状油滴直径和长度的测量，提出了合理的测量方式。图7表1参11

The phenomena of internal phase oil droplet retraction occurred when TX550A spinning drop tensiometer was used to measure interfacial tension. The mechanism of this phenomenon that interfacial tension dropped rapidly at the early stage, then increased was analyzed, the effect of oil droplet volume on interfacial tension was investigated, and right steps were suggested. The results showed that the oil droplet retraction was associated with the solubilization effect of surfactant and Marangoni convection which existed between oil-water interface. To prevent the abnormal deformation of oil droplet which caused by horizontal movement, the rotating speed of tensiometer should be increased gradually and the tensiometer should be gently adjusted to the balance at the initial measurement stage. In the measurement process, the value of interfacial tension was more accurate when the volume of oil droplet was relatively small. The volume of internal phase oil droplet should be limited to 1—3 μL when big test tube (2500 μL) was used, while for small test tube (300 μL), the volume of that should be limited to 0.3—1 μL. The reasonable measurement method of diameter and length for four special shape oil droplets was proposed.