Electrospinning Of Cellulose Acetate, Property Analysis And Fabrication Of Pp/Ca/Pp Composite Filter

Cellulose acetate (CA) electrospinning was first done at varying concentrations, flow rate and voltage while the tip to collector distance (TCD) was kept constant. The morphology of the electrospun nanofibers under different conditions was then analyzed using SEM to determine the best conditions for electrospinning CA nanofibers. Efficient uniform fiber production was found to be produced at flow rate0.3ml/h at15wt.%CA concentration and0.4ml/h, at both13wt.%and15wt.%CA concentrations for all voltage range used.15wt.%CA concentrations, flow rate of0.3ml/h and voltage of25KV was then chosen for further use in the study.During the course of the study, CA solution was left for about2weeks without performing any experiment due to the breakdown of electrospinning equipment. On electrospinning the CA solution, it was found that its electrospinnability had reduced. This led to the investigation of the effect of aging CA solution on the morphology of the electrospun nanofibers. CA solutions were aged between0-30days and their SEM and FTIR images analyzed. CA solution aged for periods not exceeding5days was found to produce finer nanofibers but of relatively lower fiber distribution compared to nanofibers produced from CA solution electrospun without aging. It was also found that aging a spinning solution for10days reduced electrospinnability, hence CA solutions should not be kept for10days or over. Keeping CA solution for over20days, led to complete loss of properties, with nanofiber breakage occurring. Reduced electrospinnability was due to degradation of CA solution.CA nanofibers electrospun at15wt.%CA,0.3ml/h and25KV were characterized. It was found that the CA nanofibers had an average fiber diameter range of120-130nm and had a relatively uniform distribution. The melting and degradation temperatures were found to be256.2℃and308.4℃respectively. The Brunauer-Emett-Teller (BET) surface area was11.75m2/g. The mean pore size was0.463μm. CA nanofibers was then electrospun onto a PP nonwoven material of basis weight25g/m2, mean fiber diameter of2-4μm, mean pore size of15.640μm and filtration efficiency of50.23%, for3hours. A PP nonwoven layer was then added onto CA/PP formed to form a PP/CA/PP composite filter and characterized. Nanofibers increased the filtration efficiency of PP nonwoven to91.29%. Filtration efficiency further increased to98.26%when CA nanofiber deposition time was increased to6hours. Pressure drop increased from4.63mmH2O in PP nonwoven material to55.5mmH2O when CA deposition time was3hours. When deposition time was increased to6hours, pressure drop significantly reduced to26.7mmH2O and was attributed to slip flow that occurs to fibers of less than500nm in diameter. It was also found that electrospun CA nanofibers onto PP nonwoven had larger pores and fiber diameters than those electrospun onto aluminum foil, which reduced CA nanofiber properties and performance. CA nanofibers also lost their narrow pore distribution and fiber diameter distribution. It was concluded that CA nanofibers deposited onto nonwovens have a great potential for use in high efficiency particulate filtrations if the thickness on the nano-layer can be increased and the nonwoven charged prior to nanofiber deposition.