Active fibre

A knitted or woven fabric for use as clothing, comprising:

• first yarns extending in a first direction;
• and
• second yarns extending in a second direction, the first yams and the second yarns being knitted or woven together such that small gaps are defined between the first yarns and the second yarns;
• and
• wherein each one of the first yarns and/or each one of the second yarns includes a plurality of shape-memory active fibers;
• wherein each one of the shape-memory active fibers includes a sheath formed of a first extruded material, and a core formed of a second extruded material, the core being coextruded with the sheath, the core being located inside the sheath, the core being eccentric and off-center relative to the sheath, and the first extruded material being different from the second extruded material, and wherein the first extruded material and the second extruded material respond differently to an external stimulus;
• wherein each one of the shape-memory active fibers has (1) first helical configuration in an unactivated state and (2) a second helical configuration, with a decreased radius and pitch relative to the first helical configuration, in an activated state, and wherein, in the first helical configuration, the shape-memory active fibers are long relative to the second helical configuration, and, in the second helical configuration, the shape-memory active fibers are short relative to the first helical configuration, and wherein each one of the, shape-memory active fibers changes from the first helical configuration to the second helical configuration, with the decreased radius and pitch, in response to increased humidity;
• wherein each one of the shape-memory active fibers changes from the second helical configuration to the first helical configuration in response to reduced humidity, and wherein each one of the shape-memory active fibers of the first yarns and/or each one of the second yarns moves reversibly between the active state and the unactivated state in proportion to humidity as the external stimulus, such that the small gaps between the first yarns and the second yarns increase in size in response to an increase in humidity and decrease in size in response to a decrease in humidity, and such that air flow resistance and air permeability of the knitted or woven fabric decreases and increases, respectively, in response to increased humidity, and increases and decreases, respectively, in response to decreased humidity;
• and
• wherein the first extruded material is from 70% to 80% by volume Nylon 6, and the second extruded material is from 20% to 30% by volume polypropylene.