Electrospinning of PTFE
An improved process for forming a PTFE mat is described. The process includes providing a dispersion with PTFE, a fiberizing polymer and a solvent wherein said dispersion has a viscosity of at least 50,000 cP. An apparatus is provided which comprises a charge source and a target a distance from the charge source. A voltage source is provided which creates a first charge at the charge source and an opposing charge at the target. The dispersion is electrostatically charged by contact with the charge source. The electrostatically charged dispersion is collected on the target to form a mat precursor which is heated to remove the solvent and the fiberizing polymer thereby forming the PTFE mat.
1. A method of preparing a spinning dispersion, comprising: adding a fiberizing polymer to a polytetrafluoroethylene (PTFE) aqueous dispersion to form a PTFE/Polymer dispersion, wherein the PTFE/Polymer dispersion comprises at least 1% by weight of the fiberizing polymer in relation to weight of the PTFE/Polymer dispersion to no more than 10% by weight of the fiberizing polymer in relation to weight of the PTFE/Polymer dispersion, and wherein the PTFE/Polymer dispersion has a viscosity of at least 50,000 cP.
2. The method of claim 1 , wherein the PTFE/Polymer dispersion comprises 50-80 wt % PTFE solids.
3. The method of claim 2 , wherein the PTFE/Polymer dispersion comprises 59-61 wt % PTFE solids.
4. The method of claim 1 , wherein the PTFE/Polymer dispersion comprises a weight ratio of fiberizing polymer to PTFE/Polymer dispersion of at least 3.0 to no more than 5.5.
5. The method of claim 1 , wherein the fiberizing polymer comprises polyethylene oxide (PEO), the PTFE/Polymer dispersion comprises a PTFE/PEO dispersion, and wherein the ratio of PEO to PTFE corresponds to a ratio in the range of 0.03 to 0.06 grams of PEO per ml of 60 wt % PTFE dispersion.
6. The method of claim 5 , wherein the ratio of PEO to PTFE corresponds to a ratio of between 0.032 and 0.052 grams of PEO per ml of 60 wt % PTFE dispersion.
7. The method of claim 6 , wherein the ratio of PEO to PTFE corresponds to a ratio of about 0.048 grams of PEO per ml of 60 wt % PTFE dispersion.
8. The method of claim 5 , further comprising mixing the PTFE/PEO dispersion in a jar roller turning at a constant rate.
9. The method of claim 8 , wherein mixing the PTFE/PEO dispersion comprises mixing in a jar roller turning at a constant rate for at least 24 hours.
10. The method of claim 5 , further comprising filtering PTFE/PEO dispersion to remove clumps.
11. The method of claim 5 , further comprising allowing the PTFE/PEO dispersion to homogenize.
12. The method of claim 1 , wherein a molecular weight of the fiberizing polymer is 200,000 to 4,000,000 Mw.
13. The method of claim 1 , wherein the spinning dispersion is spun to create one or more fibers, the one or more fibers having a diameter of about 0.8 microns.
14. The method of claim 1 , wherein PTFE particles dispersed in the spinning dispersion have a particle size of no more than 0.8 microns.
15. The method of claim 1 , wherein PTFE particles dispersed in the spinning dispersion have a particle size of at least 0.1 microns.
16. The method of claim 1 , wherein PTFE particles dispersed in the spinning dispersion have a particle size in a range of 0.2 microns to 0.6 microns.