Fibre obtained from the large, tropical silk cotton, or kapok, tree ( Ceiba pentandra , family Bombacaceae), which bears hundreds of seedpods filled with fibrous seeds.
The tree is grown chiefly in Asia and Indonesia. Sometimes called silk cotton or Java cotton, this moisture-resistant, quick-drying, resilient, buoyant fibre has been used in life preservers and other water-safety equipment. Kapok is also used to stuff pillows, mattresses, and upholstery, as insulation, and as a cotton substitute in surgery. However, it is highly flammable, and the fibres are too brittle for spinning. Its importance has decreased with the development of foam rubber, plastics, and man-made fibres.