Abstract: A solid polymer electrolyte composite for an electrochemical reaction apparatus that possesses satisfactory ion conduction properties and has excellent mechanical strength and heat resistance, is provided. The solid polymer electrolyte composite is characterized in that a solid polymer electrolyte is contained in the continuous pores of an expanded porous polytetrafluoroethylene sheet which has continuous pores and in which the inner surfaces defining the pores are covered with a functional material such as a metal oxide. An electrochemical reaction apparatus containing an electrolyte, wherein said electrochemical reaction apparatus is characterized in that the aforementioned solid polymer electrolyte composite is used as this electrolyte is also provided.

Abstract: The present invention is directed to a sealing element which comprises at least a spirally rolled, film-like material made of expanded polytetrafluoroethylene (ePTFE), the sealing element over its cord cross-section having a density gradient which increases, starting from the outer side of the sealing element, in the direction towards the center of its cross-section. Furthermore, the present invention provides a sealing element which has a second annular formation which is connected to the first annular formation by means of a flexible-tube-like intermediate region made of the same film-like material. The two annular formations may also be arranged at a predetermined distance from one another.