A seal ring includes a weld and a thermoplastic material. The thermoplastic material has a weld elongation-at-break of at least 3%. The thermoplastic material can have a glass transition temperature of at least 100 C. The thermoplastic material with the weld can have a weld elongation-at-break of at least 3%. The seal ring can have a circumference of at least 0.62 meters. The seal ring can have a coefficient of friction of not greater than 0.45.

The resin composition for molding includes: a sulfur atom-containing epoxy resin; a curing agent; a release agent; an inorganic filler; and a copolymer of a C5-30 -olefin and at least one of maleic anhydride and a maleic anhydride derivative.

The present invention provides a curable composition that can smoothly follow dimensional changes in a sealing section, the dimensional change being caused by the heat during a fire, can reliably maintain a filling state of the sealing section, can prevent flames from penetrating through the sealing section, and can thus impart excellent fire resistance to a building structure. A curable composition for a sealing material according to the present invention is characterized by including 100 parts by mass of a curable resin and 10 to 150 parts by mass of a poorly water-soluble phosphorus-based compound. A cured product of the curable composition can stably maintain the closing state of the sealing section during a fire.

To provide a sealing resin composition and a seal that are capable of being used, in particular, in high temperature and high pressure gas, in particular hydrogen gas. A sealing resin composition is used in a piston ring 1 for sealing gas. When a molded body of the sealing resin composition is exposed to gas with a pressure of 82 MPa and a temperature of 200 C. for 192 hours, a dimensional change rate of the molded body relative to the molded body before the exposure is +1.0% or less, a retention rate of the tensile strength of the molded body after the exposure is 80% or more as the tensile strength of the molded body before the exposure is defined as 100%. The tensile strength of the molded body of the sealing resin composition is 100 MPa or more by a measuring method based on ASTM D638.