Cellulose nanofiber/polyimide composites for highly-efficient air filters

Cellulose nanofiber (CNF) nanopapers from garlic skin prepared by vacuum filtration were soaked in various concentrations of polyimide (PI) solution (0–15% w/v). The samples were dried in a vacuum oven and pressed in a hot pressing machine at 120 °C for 1 h to obtain CNF/PI composite nanopapers. Even though the composites showed lower Young’s modulus and tensile strength, their toughness and elongation were much higher than those of the CNF nanopapers. Moreover, the impregnation of nanopapers in PI solution caused the formation of smaller pores and limited the pore size distribution but increased the BET-specific surface area of the samples, which led to a superior filtration capacity and a high quality factor (QF). The composites prepared by impregnation with 5% wt PI showed the most promising composite to be developed as air filters, as these composites had flexibility and showed superior filtration (99%) efficiency and higher QF than the commercial filters. Graphical abstract