The Structure And Properties Of Electronspun Fiber/nonwoven Composite Filters And CFD Simulation

Nylon6 solution in formic acid and PLLA solution in both acetone and trichloromethane was electrospun into nonwoven mat with the homemade electrospinning instrument. A common nonwoven fibrous filter was used as a collecting substrate in the electrospinning, so that the electrospun fiber layer and the substrate composed of a composite mat. The porous structure and properties of the composite mat were researched firstly. Then the simple filtration process was simulated with the CFD.Investigation on the technique of the electrospinning process: Solution concentration (BC), Voltage (V), tip-to-collector distance(C-SD), solution flow rate (FR), and inner diameter of spinneret (ID) of the electrospinning process were investigated. Initial optimized spinning parameters for PA6 were: BC 22wt%, V 15kv, C-SD 15cm, FR 0.06m/h and ID 0.045mm; for PLLA were: V 20, C-SD 25cm, FR 3ml/h and ID 0.85mm.Porous structure of the composite mat: PA6/nonwoven, PLLA/nonwoven and PA6/PLLA/nonwoven composite mats were prepared. Porous structure of the composite mats was obtain and analyzed by the computer, the results showed: with the increasing of the electrospinning time, the number of pores in a composite mat increased on the exponential function. The number of pores is the least in PLLA micro-fiber composite filter and the largest in PA6 nano-fiber composite filter. The average pore area in the composite filters decreased with the increasing of the electrospinning time, average pore area in both PA6 nano-fiber and PLLA micro-fiber composite filters decreased on the exponential function, while decreased on the opposite"S"in PA6/PLLA composite filters. With the increasing of the electrospinning time, HCF and the porosity decreased. The porosity of PLLA micro-fiber composite filter decreased the fastest, and PA6 nano-fiber composite filter decreased the slowest.Air permeability and filtration efficiency of the composite mat: with the increasing of the electrospinning time, the air permeability of the composite mats decreased on the exponential function. The filtration efficiency of PA6/WZ-CP-3, PLLA/WZ-CP-3 and PA6/PLLA/WZ-CP-3 was test, and the quality factor (Q) was calculated. Filtration efficiency increased with the electrospinning time increasing, with the same electrospinning time, the filtration efficiency was PA6/PLLA/WZ-CP-3 > PLLA /WZ-CP-3 > PA6/WZ-CP-3.The Q of the PA6/PLLA/WZ-CP-3 is the largest while the filtration efficiency were nearly equal, which means the filtration performance of the PA6/PLLA/WZ-CP-3 is the best.Filtration process simulation: Two-dimensional (2D) and Three-dimensional (3D) models of the nonwoven mat were built in GAMBIT, and the filtration process was simulated in Fluent. With the increasing of the fibers in the nonwoven mat, the pressure and velocity of the fluid increased. While the pure gas flow through the 2D nonwoven mat, the pressure showed lamellar distribution, the velocity changed greatly. While the gas with particles flow through the 2D nonwoven mat, low pressure center appeared, and the velocity changed greatly before and after reach the nonwoven mat. With the increasing of the fibers in the nonwoven mat, the concentration of the particles at the inlet increased, the moving condition of the particles in the nonwoven mat decreased. In the 3D simulation, the pressure and velocity changed when the fluid reach the fibers, and the concentration of particles decreased at the outlet after particles be trapped.