Hierarchical Structured Polyimide-Silica Hybrid Nano/Microfiber Filters Welded by Solvent Vapor for Air Filtration.

Electrospun polymer membranes were considered to be promising materials for fine particulate matter (PM) filtration. However, the poor mechanical properties of the electrospun membrane restricted their application for pressure-driven air filtration. Herein, strength-enhanced electrospun polyimide (PI) membranes were demonstrated via a synergistic approach. Solvent-vapor treatment was utilized to introduce extra bonding at the cross points of PI nanofiber, while SiO2 nanoparticles (SiO2 NPs) were used to reinforce the body of nanofibers. The mechanical strength and filtration performance of hybrid membranes could be regulated by adjusting the quantity of SiO2 NPs. The tensile strength of the pure PI membrane was increased by 33% via adding 1.5% SiO2 NPs, which was further promoted by 70% after solvent-vapor treatment. With a slight reduction in pressure drop (6.5%), the filtration efficiency was not greatly suppressed by welding the SiO2 NP hybrid PI nanofibers. Moreover, the welded composite filter showed high particulate (0.3-1.0 μm) filtration efficiency (up to nearly 100%) and stable pressure drop throughout the 20 tested filtration cycles.