Chemically, cotton is the purest vegetable fiber, containing >90% cellulose with little or
no lignin. The other fibers contain 40–75% cellulose, depending on processing.
Boiled and bleached fiax and degummed ramie may contain >95% cellulose.
Kenaf and jute contain higher contents of lignin, which contributes to their stiff-
ness. Although the cellulose contents are fairly uniform, the
other components, eg, hemicelluloses, pectins, extractives, and lignin vary widely
without obvious pattern. These differences may characterize specific fibers.
Except for the seed-hair fibers, the vegetable
fibers of bast or leaf origins are multicelled and are used as strands.
In contrast to the bast fibers, leaf fibers are not readily
broken down into their ultimate cells. The ultimate cells are composites of micro-
fibrils, which, in turn, are comprised of groups of parallel cellulose chains.
Bast and leaf fibers are stronger (higher tensile strength and modulus
of elasticity) but lower in elongation (extensibility) than cotton. Vegetable fibers
are stiffer but less tough than synthetic fibers. Kapok and coir are relatively
low in strength; kapok is known for its buoyancy.