High temperature coating techniques for amorphous fluoropolymers
A coating technique for amorphous fluoropolymer involves adding amorphous fluoropolymer resin to a solvent. The resin solvent mixture is heated to a predetermined temperature above room temperature. The amorphous fluoropolymer resin is dissolved in a heated solvent, and the liquid coating solution is applied to a substrate. The solvent is then removed from the applied liquid coating solution. The coating technique may be employed in connection with liquid core waveguides.
1. A coating technique, comprising the steps of:
selecting an amorphous fluoropolymer resin;
selecting a solvent that will dissolve the selected amorphous fluoropolymer resin;
adding the amorphous fluoropolymer resin to the solvent;
heating the resin and solvent mixture to a temperature above room temperature;
dissolving the selected amorphous fluoropolymer resin in the heated solvent to form a heated, liquid coating solution having a viscosity less than about 5,000 cP;
applying the heated, liquid coating solution to a substrate;
removing solvent from the applied liquid coating solution to form an amorphous fluoropolymer coating on the substrate; and
heating the coated substrate to a temperature above a glass transition temperature of the selected amorphous fluoropolymer resin.
2. The technique of claim 1 wherein the step of removing solvent from the applied liquid coating solution is done at a temperature about two percent to about three percent below a boiling temperature of the selected solvent.
3. The technique of claim 1 wherein heated, liquid coating solution is maintained at a working temperature that will prevent supersaturation of the solution while applying the heated, liquid coating solution to a substrate.
4. The technique of claim 1 wherein heated, liquid coating solution is maintained at a working temperature below a melting point of the selected amorphous fluoropolymer resin while applying the heated, liquid coating solution to a substrate.
5. The technique of claim 1 wherein heated, liquid coating solution is maintained at a working temperature about 15% below the difference of a boiling temperature of the selected solvent and room temperature while applying the heated, liquid coating solution to a substrate.
6. The technique of claim 1 wherein the amount of amorphous fluoropolymer resin dissolved in solvent at the temperature above room temperature is greater than the amount of amorphous fluoropolymer resin that can be dissolved in that solvent at room temperature.
7. The technique of claim 1 wherein the amorphous fluoropolymer resin is selected from TEFLON AF 1600 or TEFLON AF 2400 powdered amorphous polytetrafluoroethylene and the solvent is selected from FLUORINERT FC70 or FLUORINERT FC75 fluorinated liquid.
8. The technique of claim 1 wherein the substrate is a component of a waveguide.
9. The technique of claim 1 wherein the substrate is a glass tube of a liquid core waveguide.