The test of PTFE hollow fiber membrane porosity has a strong guiding significance for the evaluation of membrane performance, in general, the porosity of PTFE hollow fiber membrane is tested in the following two ways.
1. Ethanol method: the PTFE hollow fiber membrane is immersed in ethanol solution for 2h, so that the ethanol solution is completely immersed in the membrane pores, and the membrane pores are cleaned; after completing the cleaning, the membrane material is placed in a vacuum oven and dried at a temperature of 50°C for 2h, weighed after drying, and the mass of the PTFE dry membrane is recorded as m1. The PTFE hollow fiber membrane is completely moistened with anhydrous ethanol after cleaning, and is placed into deionized water for replacement, and is soaked for In the experiment, the deionized water was replaced every 4h; when the replacement was complete, the water on the inner and outer surfaces of the membrane was controlled and dried, and the membrane was weighed and recorded as m2. According to the weights of the wet and dry membranes, the porosity of the membrane could be calculated.
2. Weighing method: Due to the strong hydrophobicity of PTFE material, when testing by this method, the tiny trembling will cause the water inside the pores of PTFE hollow fiber membrane to be thrown out, resulting in a large error in the test. Therefore, most researchers use the weighing method to calculate the porosity of PTFE hollow fiber membrane. The specific operation is as follows:
Clean the PTFE hollow fiber membrane with anhydrous ethanol, put it into the oven at 50 degrees Celsius to dry completely, after drying, cut 1 meter long membrane filament weighed with a precision balance, and record the dry membrane weight of the hollow fiber membrane m. Weigh the membrane filament to intercept a section of the sample, and measure the inner and outer diameters of the membrane filament under the electron microscope, which were recorded as OD and ID, respectively. according to the following formula, the porosity of the PTFE hollow fiber membrane can be calculated.
