How does the porosity of the ePTFE membrane affect its filtration efficiency?

1. Improvement of filtration efficiency:
Studies have shown that ePTFE coated filter materials can effectively intercept PM2.5-PM10 fine dust, and the filtration efficiency can reach more than 99.999%. The ePTFE membrane with higher porosity has more micropores, which can capture more particles, thereby improving the filtration efficiency.
2. Relationship between pore size and porosity:
Porosity is a function of the distance between nodes. As the distance between nodes increases, the porosity increases, which may affect the filtration efficiency because the change in porosity affects the size and distribution of pore size.
3. Air permeability and filtration efficiency:
The high air permeability and high interception efficiency of the ePTFE membrane enable the vacuum cleaner to not only effectively intercept wind dust particles, but also keep the vacuum cleaner at a low energy consumption. This means that the high porosity ePTFE membrane can reduce the resistance to air flow while maintaining high filtration efficiency.
4. The influence of pore size:
Generally speaking, the smaller the pore size, the higher the filtration accuracy of the membrane. In ePTFE microporous membrane technology, pore size refers to the size of the holes on the surface of the ePTFE microporous membrane, and the number of holes per unit area is usually used as a characterization of the pore size. The size of the pore size directly affects the filtration efficiency, and a smaller pore size can intercept smaller particles.
5. Effect of heat treatment on porosity:
Heat treatment can affect the pore size, pore size distribution, porosity and surface morphology of the ePTFE microporous membrane, resulting in a decrease in porosity, which may affect the filtration efficiency. The maximum pore size, average pore size and porosity of the membrane after heat treatment are all reduced, and the retention rate of nanoparticles suspended in organic solvents is close to 100%.
6. Effect of filter cake layer structure:
Experimental studies have also shown that the ePTFE film composite filter material follows the surface filtration mechanism. The microstructure of the filter membrane does not change during filtration, and its filtration resistance is mainly concentrated on the filter cake layer formed on the surface of the filter material. The inlet dust concentration has little effect on the filter cake layer structure. The membrane's pore size, porosity, thickness and other structural parameters have little effect on the filter cake layer structure. However, the dust particle size has a significant effect on the filter cake layer structure and its filtration pressure drop.