Highly functional polyethylene fiber, and dyed highly functional polyethylene fiber

A polyethylene fiber, wherein

• an intrinsic viscosity [η] is higher than or equal to 0.8 dL/g, and not higher than 2.5 dL/g, as measured in a solvent of decalin at a temperature of 135° C.,
• the polyethylene fiber comprises a polyethylene consisting of an ethylene as a repeating unit,
• the polyethylene has a weight average molecular weight (Mw) ranging from 50,000 g/mol to 600,000 g/mol,
• a retention rate, at 105° C., of a storage modulus is such that a storage modulus at 105° C. is higher than or equal to 30% of a storage modulus at 30° C.,
• the polyethylene fiber comprises pores formed in a surface and an inside of the fiber,
• the pores have an average diameter ranging from 3 nm to 200 nm, and
• the polyethylene fiber has a tensile strength of higher than or equal to 12.1 cN/dtex.

A polyethylene fiber, wherein

• an intrinsic viscosity [η] is higher than or equal to 0.8 dL/g, and not higher than 2.5 dL/g, as measured in a solvent of decalin at a temperature of 135° C.,
• the polyethylene fiber comprises a polyethylene consisting of an ethylene as a repeating unit,
• the polyethylene has a weight average molecular weight (Mw) ranging from 50,000 g/mol to 600,000 g/mol,
• a storage modulus obtained at intervals of 10° C. in a range from −50° C. to 60° C. is higher than or equal to 60% of a storage modulus at 20° C., and is not higher than 130% of the storage modulus at 20° C.,
• the polyethylene fiber comprises pores formed in a surface and an inside of the fiber,
• the pores have an average diameter ranging from 3 nm to 200 nm, and
• the polyethylene fiber has a tensile strength of higher than or equal to 12.1 cN/dtex.

A polyethylene fiber, wherein

• an intrinsic viscosity [η] is higher than or equal to 0.8 dL/g, and not higher than 2.5 dL/g, as measured in a solvent of decalin at a temperature of 135° C.,
• the polyethylene fiber comprises a polyethylene consisting of an ethylene as a repeating unit,
• the polyethylene has a weight average molecular weight (Mw) ranging from 50,000 g/mol to 600,000 g/mol,
• an amount of monoclinic crystals in the fiber is higher than or equal to 0.5%, and not higher than 30%, of a total amount of monoclinic crystals, orthorhombic crystals, and amorphous components in the fiber,
• an amount of orthorhombic crystals in the fiber is higher than or equal to 40%, and not higher than 90%, of a total amount of monoclinic crystals, orthorhombic crystals, and amorphous components in the fiber,
• the polyethylene fiber comprises pores formed in a surface and an inside of the fiber,
• the pores have an average diameter ranging from 3 nm to 200 nm, and
• the polyethylene fiber has a tensile strength of higher than or equal to 12.1 cN/dtex.

A method for manufacturing a polyethylene fiber, comprising

• performing melt-spinning of a polyethylene in which the polyethylene has an intrinsic viscosity [η] higher than or equal to 0.8 dL/g, and not higher than 2.5 dL/g, as measured in a solvent of decalin at a temperature of 135° C., the polyethylene consists of an ethylene as a repeating unit, and the polyethylene has a weight average molecular weight (Mw) ranging from 50,000 g/mol to 600,000 g/mol,
• drawing the polyethylene at a temperature higher than or equal to a crystal dispersion temperature of the polyethylene,
• performing, after the drawing step, heat treatment, for a time period longer than or equal to 0.01 seconds, at a temperature higher than the crystal dispersion temperature by at least 10° C., and
• performing, after the heat treatment, taking-up at a tensile force less than or equal to 0.5 cN/dtex to form a polyethylene fiber having a maximum thermal shrinkage stress less than or equal to 0.4 cN/dtex in TMA (thermo-mechanical analysis), a thermal shrinking percentage at 100° C. less than or equal to 2.5%, and a tensile strength is higher than or equal to 12.1 cN/dtex,
• wherein the polyethylene fiber comprises pores formed in a surface and an inside of the fiber, and the pores have an average diameter ranging from 3 nm to 200 nm.