The valve member according to one embodiment of the present disclosure is a resin formed product having a crosslinked ethylene-tetrafluoroethylene copolymer as a main component, and having a crosslinking density of 85.0 mol/m.sup.3 or more calculated from a storage modulus at 300° C.

Structural support (1) including a first support portion (2) delimiting at least one containment compartment (4, 4′); a second support portion (6) at least partly in front of the containment compartment (4, 4′); and a sliding element (4), housed in the containment compartment (4, 4′) and interposed between the first (2) and the second (6) support portion. The sliding element (8) substantially consists of a thermo-processable fluoro-polymer with a melt-mass flow rate—according to the ISO 1133-1:2011 standard—of less than 5.0 grams/10 minutes, for example under 3.0 grams/10 minutes.

An ethylene/tetrafluoroethylene copolymer satisfying the following formula (1), wherein peak intensities, determined by Fourier transform infrared spectroscopy, of vibrations derived from a —CF.sub.2H group, a —CF.sub.2CH.sub.2COF group, a —COF group, a —COOH group, a dimer of a —CF.sub.2COOH group and a monomer of a CF.sub.2CH.sub.2COOH group, a —COOCH.sub.3 group, a —CONH.sub.2 group, and a —CH.sub.2OH group satisfy the following formula (2):
75≤tan δ(60)/tan δ(5)×100≤225  (1)
PI.sub.A/(PI.sub.B+PI.sub.C+PI.sub.D+PI.sub.E+PI.sub.F+PI.sub.G+PI.sub.H)≥0.60  (2) wherein tan δ(60), tan δ(5), PI.sub.A, PI.sub.B, PI.sub.C, PI.sub.D, PI.sub.E, PI.sub.F, PI.sub.G and PI.sub.H are as defined in the specification. Also disclosed is a molded article obtained by molding the ethylene/tetrafluoroethylene copolymer and an electric wire including a core and a coat formed from the ethylene/tetrafluoroethylene copolymer.

A method for producing a composition containing low molecular weight polytetrafluoroethylene, the method including: (I) irradiating a composition containing high molecular weight polytetrafluoroethylene with ionizing radiation to obtain a composition containing low molecular weight polytetrafluoroethylene having a melt viscosity at 380° C. in the range of 1.0×10.sup.2 to 7.0×10.sup.5 Pa.Math.s; and (II) decomposing a low molecular weight fluorine-containing compound contained in the composition containing low molecular weight polytetrafluoroethylene obtained above.

A method for producing low molecular weight polytetrafluoroethylene which includes: (1) feeding into an airtight container in the absence of oxygen: high molecular weight polytetrafluoroethylene: and a halogenated polymer having a halogen atom other than a fluorine atom; and (2) irradiating the high molecular weight polytetrafluoroethylene to provide low molecular weight polytetrafluoroethylene having a melt viscosity at 380° C. of 1.0×10.sup.2 to 7.0×10.sup.5 Pa.Math.s.

A fluorine-containing resin particle contains 0 or more and 30 or less carboxyl groups per 10.sup.6 carbon atoms and 0 ppm or more and 3 ppm or less of a basic compound.

The disclosure provides a method for producing low molecular weight polytetrafluoroethylene containing less C6-C14 perfluorocarboxylic acids or salts thereof. The method for producing low molecular weight polytetrafluoroethylene includes: (1) irradiating high molecular weight polytetrafluoroethylene to provide low molecular weight polytetrafluoroethylene having a melt viscosity of 1.0×10.sup.2 to 7.0×10.sup.5 Pa.Math.s at 380° C.; and (2) irradiating the low molecular weight polytetrafluoroethylene to a dose that does not decompose the low molecular weight polytetrafluoroethylene.

A provided heat-resistant cushioning sheet is a heat-resistant cushioning sheet configured to be disposed between a thermocompression face of a thermocompression apparatus and a target in thermocompression treatment of the target to prevent direct contact between the target and the thermocompression face, wherein a compression strain change amount ΔS.sub.250 being a difference S.sub.250−S.sub.25 between a compression strain S.sub.25 at 25° C. and a compression strain S.sub.250 at 250° C. is −5% or more. S.sub.25 and S.sub.250 are each a compression strain S.sub.T of the heat-resistant cushioning sheet evaluated by thermomechanical analysis (TMA), S.sub.25 is evaluated at an evaluation temperature of 25° C., and S.sub.250 is evaluated at an evaluation temperature of 250° C. The compression strain S.sub.T is determined by an equation S.sub.T=(t.sub.1−t.sub.0)/t.sub.0×100(%), where to is a thickness of the heat-resistant cushioning sheet at 25° C. and t.sub.1 is a thickness of the heat-resistant cushioning sheet.

A polymer electrolyte membrane according to the present invention has a cluster diameter of 2.96 to 4.00 nm and a converted puncture strength of 300 gf/50 μm or more. The polymer electrolyte membrane according to the present invention has a low electric resistance and an excellent mechanical strength.

To provide a molded product, a metal-clad laminate and a printed wiring board, each of which contains a tetrafluoroethylene type polymer, whereby an decrease in electrical characteristics is inhibited and a hole can be easily bored with UV-YAG laser; and methods for their production. A molded product containing a tetrafluoroethylene type polymer, in which the content of components other than the tetrafluoroethylene type polymer is at most 0.9 mass %, and which has a wavelength range where the extinction coefficient becomes to be from 1.2 to 4.5 at from 200 to 380 nm; and a method for its production. A metal-clad laminate having a conductive metal layer and a layer of the molded product; and a method for its production. A printed wiring board provided with the metal-clad laminate and having through-holes in the thickness direction of the polymer layer.