Formation of Porous Poly(tetrafluoroethylene) Using a Partially Gasified Porogen

A method has been advanced to form porous poly(tetrafluoroethylene) (PTFE) using a partially gasified porogen. Sodium hydrogen carbonate (NaHCO۳) was selected as a porogen. The standard technology of porous materials production including mixing, pressing, thermal treatment, porogen leaching and drying was employed.The formation of porous PTFE structures was investigated in a wide range of NaHCO۳ concentrations. The mechanism for formation of such structures has been proposed. It is shown that the NaHCO۳ porogen affords permeable porous structures with porosities down to ۵۰% (cf. the lowest bound porosity of ۷۰% attainable with the standard NaCl porogen).The flow rate characteristics of the pressure difference as a function of the air flow rate have been measured on porous PTFE samples formed using the partially gasified NaHCO۳ porogen and the NaCl porogen. The obtained flow rate characteristics were linear, which suggests a laminar air flow in the pores. The permeability of the porous PTFE structures formed using the above porogens has been estimated.The use of the NaHCO۳ porogen has allowed a five-fold cut of the leaching time, a more than three times enhancement of the permeability of the porous structures and an increase in the hydraulic pore diameter by a factor of ۱.۸ as compared to the corresponding data obtained with the NaCl porogen.

کلیدواژه ها:

Porous polymers ، poly(tetrafluoroethylene) ، NaHCO۳ porogen ، NaCl porogen ، porous structure ، permeability