Why expanded PTFE and PTFE are more suitable for sealing?

E-PTFE is a porous, low-density and high-toughness material, which is made by expanding PTFE resin through certain production and processing technology. The so-called "puffing" is a processing method that makes raw materials suddenly decompress and expand under the condition of heating and pressure. American chemical researcher Wilbert Gore used the word "puffing" in his patent 1972. In his description of "puffing", the specific gravity of the material decreases after processing, and such microstructure is described as "fibrous".