Gasket material
A gasket material comprising polytetrafluoroethylene (PTFE) and a thermoplastic polymer have a melting point lower than the melting point of PTFE. Preferred thermoplastic polymers comprise fluorinated thermoplastic polymers, and most preferred fluorinated thermoplastic polymers comprise fluorinated ethylene propylene and perfluoroalkoxy copolymer. The PTFE component preferably comprises full density PTFE, and a filler material may optionally be added. The PTFE component is present in the gasket material in an amount from approximately 50% to less than 100%, based on the total weight of the gasket material, and the thermoplastic polymer is present in an amount from greater than 0% to approximately 20%, based on the total weigh to the gasket material.
1. A method for manufacturing a gasket material comprising:
mixing polytetrafluoroethylene (PTFE) and a fluorinated thermoplastic polymer with a melting point lower than that of PTFE together with a solvent to form a combination;
charging the combination to a frame and compressing the combination to form a cake;
calendaring the cake to form a sheet;
drying the sheet by raising the temperature to remove the solvent;
heating the sheet above the melting point of both the PTFE and the fluorinated thermoplastic polymer; and
cooling the sheet in a controlled manner;
wherein the fluorinated thermoplastic polymer flows into and fills any voids in the PTFE structure resulting in a low porosity finished gasket material.
2. The method of claim 1 , wherein the steps of heating the sheet above the melting point of both the PTFE and the fluorinated thermoplastic polymer and cooling the sheet in a controlled manner further comprises performing the heating and cooling steps under an applied pressure.
3. The method of claim 2 , wherein the cooling step is performed at a pressure which is less than the pressure of the heating step.
4. The method of claim 1 , wherein the steps of heating the sheet above the melting point of both the PTFE and the fluorinated thermoplastic polymer and cooling the sheet in a controlled manner further comprises performing the heating step under an applied pressure and performing the cooling step under no applied pressure.
5. The method of claim 1 , wherein mixing polytetrafluoroethylene, the fluorinated thermoplastic polymer and the solvent further comprises mixing filler material together with the polytetrafluoroethylene, the fluorinated thermoplastic polymer and the solvent.