Bicomponent fiber
Also searched as: bicomponent fibre, bico, conjugate fiber, side-by-side fiber, sheath-core fiber, core-sheath fiber, islands-in-the-sea, segmented pie
A manufactured fiber extruded from two polymers, or two grades of one polymer, through the same spinneret so that both run continuously along the fiber in a defined cross-sectional arrangement.
In detail
Two polymer melts are metered separately and brought together in a spin pack designed to combine them in a set geometry. In a side-by-side arrangement, the two halves shrink differently after drawing or heating, so the fiber curls into a helical crimp, loosely comparable to the bilateral cortex of crimpy wool. In a sheath-core arrangement, a low-softening sheath can bond fibers together in nonwovens while the core carries load. In islands-in-the-sea or segmented-pie designs, one component is dissolved away or the segments are split apart to produce very fine microfibers.
The science and numbers
A review of melt-spun fibers names three main cross-sections: core-sheath, side-by-side, and multiple-core types such as segmented pie and islands-in-the-sea. The melts stay separate until the spin pack, so the filament contains unmixed components touching at an interface; the polymers need well-matched processing temperatures and viscosities and suitable adhesion. Core-sheath binder fibers pair a standard core with a low softening-point sheath that fuses in thermally bonded nonwovens. Side-by-side fibers use polymers with different shrinkage, so after heat or relaxation they curl into self-crimp. Segmented-pie fibers from poorly adhering polymers split into microfibers, and islands-in-the-sea fibers release fibrils when the sea polymer is dissolved. Functional compounds, such as conductive or antistatic additives, can be placed in one component so that the other preserves tensile strength.
A practical example
A nonwoven engineer blends sheath-core staple fibers into a batt and passes it through an oven set hot enough to soften the sheath but not the core. The sheaths fuse at fiber crossings while the cores stay solid, producing a lofty, bonded pad without any added adhesive. The example shows how two polymers in one fiber can each do a separate job.
What to distinguish
Bicomponent describes fiber construction, not a fiber blend: a blend mixes separate fibers of different types, while a bicomponent fiber combines two polymers inside each fiber. The term does not reveal which polymers are used, their proportions, or whether they can be separated for recycling. For labeling, check how the applicable fiber-naming rules treat the product rather than assuming a single generic name applies.
Origins and history
Bicomponent spinning grew from the aim of combining in one fiber properties that neither polymer offers alone. The review cited here dates the commercial launch of bicomponent fibers to the 1960s and notes that their range has grown considerably since. Today the main commercial roles are binder fibers for thermally bonded nonwovens, self-crimping fibers that give bulk without separate texturing, and precursors for microfibers.
Related terms
Sources & further reading
- Materials: Melt-spun fibers for textile applications (Hufenus et al., 2020)
- Nature: Relationship of ortho-cortex to the crimp wave in a double-crimped wool
Technical references reviewed 2026-09-22. Examples are illustrative. Industry organizations and manufacturers describe their own fields; their references are not independent product endorsements. Figures are approximate and depend on the stated test conditions.