Abstract: Better mechanical properties are achieved with tubes for shell and tube heat exchangers by providing a coating on the tubes which is formed of fibers and a fluorine-containing polymer covering the fibers. The tubes are formed of fluorine-containing polymers whose use in heat exchangers is normally limited by the comparatively small compressive strength and fatigue resistance of the tubes.

Abstract: In the electrode in the form of a rectangular parallelepiped composed of impregnated graphite material for electrochemical reactors, the electrode (4,5) is provided with openings (8,9,10,11) extending perpendicular to its active electrode surfaces (6,7) at its corners. Canals (12,13) which extend parallel to the active electrode surfaces (6,7) in the direction of an adjacent opening (9,10) originates in each case from two openings (8,10) situated diagonally opposite each other. The canals (12,13) have communicating channels (14,15) to the active electrode surfaces (6,7).

Abstract: Carbon or graphite tubes which are mutually connected by an adhesive connection are less stressable than individual tubes. A sleeve formed of fibers and impregnated with a thermoplast is pulled onto the connection position. The new connection increases the stressability of connected tubes. The thermoplast limits the build up of stressing so that the reduction factor of the strength of the connection amounts only to 10 to 15%.

Abstract: Carbon or graphite tubes which are mutually connected by bonding are less highly stressable than individual tubes. A sleeve formed of fibers is drawn on to the connection location of the tubes. An intermediate section of the sleeve is firmly connected with the tubes. Foils are introduced between end sections of the sleeve and the tubes. The foils are displaceable in the direction of the tube axes. This structure increases the resistance of the connected tubes to stress. The strength reduction factor of the connection is about 10% as compared to the tubes alone.

Abstract: Method and apparatus for joining together edge surfaces of polytetrafluoroethylene material by a butt joint in which abutting surfaces of the material are placed in a chamber bounded by clamps along the abutting surfaces which press together the abutting surfaces, and heating elements in the space between the clamps to heat both sides of the material between the clamps, the boundaries of the chamber inhibiting the volume expansion of the material resulting from heating. Pressure generated in chamber may be controlled by moving a heating element. Additional pressure during cooling-down is exerted on the butt joint by moving one clamping in the direction of the butt joint. A thin foil of a fluorine-containing thermoplastic inserted between the abutting surfaces facilitates joining of the surfaces.

Abstract: Method and apparatus for joining together edge surfaces of polytetrafluoroethylene material by a butt joint in which clamps along the abutting surfaces press together the abutting surfaces, heating means spaced from and out of direct contact with a strip between the clamps heats the strip by radiation or convection, and a cooling arrangement is provided via the clamps to remove heat from the clamping zone. A thin foil of a fluorine-containing thermoplastic inserted between the abutting surfaces facilitates joining of the surfaces.