Abstract: There is disclosed a far infra-red radiant composite fiber composed of a core polymer containing 10 to 70 percent by weight of a far infra-red radiant grained material covered with a sheath polymer containing 1 to 10 percent by weight of a far infra-red radiant grained material. The above far infra-red radiant grained material in core polymer and the above far infra-red radiant grained material in sheath polymer have a far infra-red emissivity of 65% or over on an average in the spectral range from 4.5 .mu.m to 30 .mu.m at 30.degree. C. Such fiber can be woven or knitted into fabrics to wear or otherwise used to exert a warming effect on human body and thereby facilitate blood circulation, resulting in favorable effects in medical care and therapy as well as in health enhancement. Because of the sheathed fiber construction with a sheath polymer containing a low content of grained material, the fiber can be produced and treated as smooth as the ordinary sheathed composite fiber.

Abstract: There is disclosed a process for manufacturing far infra-red radiant fibrous structures from sheathed composite fiber that contains a far infra-red radiant grained material in core polymer.