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.

In the formula:

OD---- membrane filament outer diameter m;

ID ---- membrane filament inner diameter m;

m ---- membrane filament weight kg;

ρ ----PTFE material density kg/m³;