Kapok fiber is one of the natural cellulostic fibers which grow on the kapok plant. It has a hollow body and a sealed tail, which are desirable features of candidates for functional textiles of this nature. However, the low volume weight of kapok is (specific density 0.29g/cm3), and the short length and smooth surface of the fibers, causing poor inter-fiber cohesion, have prevented kapok from being processed by modern spinning machines.
Kapok are silky fibers that clothe the seeds of the ceiba tree of the family Bombacaseae. Kapok fibers have rich oiliness and do not have high strength and, therefore cannot be spun economically. It is conventionally used as a stuffing, especially for life preservers, bedding, and upholstery, and for insulation against sound and heat.
The Kapok fiber has a hollow structure with external radius around 8.25 (±4) _m, internal diameter around 7.25 (±4) _m, and length around 25 (±5) mm. Combined with the specific material density of 1.3 g/cm3 , large pore volume in Kapok assembly is available for NAPL sorption. Typical analyses indicate that the Kapok fibers comprise 64% cellulose, 13% lignin and 23% pentosan. Besides these constituents, they also contain wax cutin on the fiber surface which makes them water repellent notwithstanding they are preponderantly composed of cellulose.