Customization of hierarchical air filter media by tailoring the structural parameters of needle punched nonwoven

An attempt has been made to investigate the filtration behaviour of filter media with gradient structure created through layers of needle punched nonwoven. Batts of different fibre orientation influenced by carding parameters were prepared. Carding parameters i.e. feeder, cylinder and doffer speed were optimized by using response surface methodology to achieve the batts of different fibre orientation. Three batts with a wide range of fibre orientation were selected to create the gradient structures by placing them in a different position in the layered structure. The physical, mechanical and functional properties of nonwoven were evaluated. The different order of fibre orientation of batts was also analysed with the help of SEM images. The fabric with inverse gradient structure having batts in increasing order of fibre orientation in the layered structure provided very high (close to the highest) filter efficiency and very low (close to lowest) pressure drop instead of having higher (close to highest) mean flow pore size.