fibres0_cdmm2005.ppt

Numerical model Main assumptions The electric field created by the generator is considered static and is approximated using a sphere-plate capacitor configuration The fibre is a perfect insulator with a constant electric charge density distributed over its surface The melt is viscoelastic and has constant elastic modulus, viscosity and surface tension Numerical model 3. Discretized equations Mass conservation: Stress balance Momentum balance Numerical model 4. Boundary conditions The last particle introduced at the tips keeps a constant velocity until the distance to the tip exceeds the initial bead length l0: A small perturbation is added to the position of each new particle introduced near the tip: Particles that reach the collector are considered neutralized and are removed from the fibre. l0 – initial bead length [input] Q – volume flow rate [input] e – distance to the main axis [input] j – random phase Numerical model 5. Parametric simulations Reference case: a = 0.07 N/m F = 5000 V ? = 10 Pa.s G = 105 Pa r = 1000 kg/m3 a0 = 150 μm H = 20 cm l0 = 1 μm q = 200 C/m3 Q = 3.6 cm3/h Case a F m G 1 2 3 4 5 6 3 x2 x5 /3 x2 /2 Numerical model Reference case: a = 0.07 N/m F = 5000 V ? = 10 Pa.s G = 105 Pa r = 1000 kg/m3 a0 = 150 μm H = 20 cm l0 = 1 μm q = 200 C/m3 Q = 3.6 cm3/h Numerical model Reference case Numerical model Triple surface tension Numerical model 1/3 surface tension Numerical model ? Voltage Numerical model 5 times higher viscosity Numerical model Double elastic modulus Numerical model Half elastic modulus Numerical model Reference case: a = 0.07 N/m F = 5000 V ? = 10 Pa.s G = 105 Pa r = 1000 kg/m3 a0 = 150 μm H = 20 cm l0 = 1 μm q = 200 C/m3 Q = 3.6 cm3/h a = 0.21N/m F = 2500V a = 0.023N/m ? = 2 Pa.s G = 5.104 Pa G = 2.105 Pa Conclusions Electrostatic elongation of polymer threads allows to produce relatively easily fibres in nano range diameters Collection of nano-woven of bio-active polymers, e.g.. chitin may have