Dielectric substrate comprising unsintered polytetrafluoroethylene and methods of making the same

1. A dielectric substrate comprising:

an unsintered polytetrafluoroethylene; and

a high dielectric constant filler, wherein the dielectric constant of the high dielectric constant filler is greater than or equal to 35;

wherein the dielectric substrate is subjected to a dry calendering step after a step of removing a lubricant from the dielectric substrate to thereby provide the dielectric substrate with a specific gravity of greater than or equal to 90% of a calculated theoretical density of the dielectric substrate, wherein the theoretical specific gravity is calculated based on a measured specific gravity of the high dielectric constant filler, the specific gravity of the unsintered polytetrafluoroethylene, and the relative weight fractions of the unsintered polytetrafluoroethylene and the high dielectric constant filler; and

wherein the dielectric substrate has a dielectric constant of greater than or equal to 11.5 as determined at a frequency of 10 GHz.

2. The dielectric substrate of claim 1 , wherein the unsintered polytetrafluoroethylene comprises a polytetrafluoroethylene homopolymer.

3. The dielectric substrate of claim 1 , wherein the unsintered polytetrafluoroethylene comprises a trace modified polytetrafluoroethylene homopolymer, wherein the trace modified polytetrafluoroethylene homopolymer comprises less than 1 wt % of a repeat unit derived from a co-monomer other than tetrafluoroethylene based on the total weight of the trace modified polytetrafluoroethylene homopolymer.

4. The dielectric substrate of claim 1 , wherein the unsintered polytetrafluoroethylene polymer is made by emulsion polymerization.

5. The dielectric substrate of claim 1 , wherein the high dielectric constant filler has a dielectric constant of greater than or equal to 100.

6. The dielectric substrate of claim 1 , wherein the high dielectric constant filler comprises titanium dioxide.

7. The dielectric substrate of claim 1 , wherein the high dielectric constant filler comprises titanium dioxide, calcium titanate, strontium titanate, barium titanate, or a combination comprising at least one of the foregoing.

8. The dielectric substrate of claim 1 , wherein the dielectric substrate comprises 50 to 85 wt % of the high dielectric constant filler based on the total weight of the dielectric substrate.

9. The dielectric substrate of claim 1 , wherein the dielectric substrate comprises 15 to 50 wt %, of the unsintered polytetrafluoroethylene based on the total weight of the dielectric substrate.

10. The dielectric substrate of claim 1 , wherein the dielectric substrate consists essentially of the unsintered polytetrafluoroethylene and the high dielectric constant filler.

11. The dielectric substrate of claim 1 , wherein the specific gravity is at least 95% of the theoretical specific gravity of the dielectric substrate.

12. The dielectric substrate of claim 1 , wherein the dielectric constant of the dielectric substrate is greater than or equal to 12.

13. An article comprising the dielectric substrates of claim 1 .

14. The article of claim 13 , wherein the article is a mobile phone, a tablet, or a laptop.

15. The article of claim 13 , wherein the article is an antenna.