Porous Membrane
AssigneeBHA Altair, LLC
InventorsGopakumar Thottupurathu, David Kazemi
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Abstract
A membrane comprises a sheet of expanded polytetrafluoroethylene. The sheet includes a first extrudate made from a first PTFE fine powder resin mixed with processing lubricant at a first lube rate. A second extrudate is made from the first PTFE fine powder resin mixed with processing lubricant at the first lube rate. The first and second extrudates combined into an integrated tape structure that is stretched in first and second directions. The sheet is porous and has a gas permeability of at least 0.1 CFM according to ASTM D737. The sheet has an average Mullen Hydrostatic Burst pressure in the range of 135 psi to 175 psi according to ASTM D751.
Claims18
1-11. (canceled)
A method of making a membrane comprising the steps of:
- providing a first extrudate made from a first PTFE fine powder resin mixed with processing lubricant at a first lube rate;
- providing a second extrudate made from the first PTFE fine powder resin mixed with processing lubricant at the first lube rate;
- overlying the first and second extrudates;
- calendering the overlying first and second extrudates into an integrated tape;
- stretching the integrated tape in the machine direction;
- and
- stretching the integrated tape in the transverse direction to provide a porous sheet that has a gas permeability of at least 0.1 CFM according to ASTM D737 and an average Mullen Hydrostatic Burst pressure in the range of 135 psi to 175 psi according to ASTM D751.
A method of forming a PTFE membrane comprising the steps of:
- providing a first PTFE extrudate;
- providing a second PTFE extrudate;
- overlying the first PTFE extrudate and the second PTFE extrudate;
- calendering the overlying first PTFE extrudate and second PTFE extrudate into an integrated tape, thereby mechanically interlocking nodes and fibrils of the first PTFE extrudate to nodes and fibrils of the second PTFE extrudate;
- biaxially stretching the to integrated tape provide a microporous PTFE membrane.
Dependencies are inferred from the claim text.