Plant fibers have been used throughout human history, initially as strips of bark, stems or leaves to make mats, baskets, etc.

Wild cotton used for spinning and twining is traceable to Peru 12,000 ybp. Flax has been used for 8000 years, so plant fibers were apparently used in weaving before animal fibers.

Use of fibers (plant and animal) is fairly recent probably because very few plants or animals produce fibers that can be twined or spun.

Plant fibers are composed of cellulose - long chain of glucose molecules, animal fibers are protein.

Properties of cellulose
Withstand high temperature
Does not incorporate colors easily
Resistant to animal pests but susceptible to fungi and termites
Less elastic than animal fibers and have higher affinity for water.

Most synthetic fibers are produced from petroleum

Plant fibers that are short brittle, or slippery cannot be twined, woven, plaited or spun but these can be used for paper, fiberboard, cellophane and rayon.

Fibers must stand up to twisting in spinning process, which holds the fibers together mechanically. Types:
1. Seed and fruit fibers
2. Bast (soft) fibers - phloem tissues of dicots
3. Hard (leaf) fibers - leaves of monocots

Fiber characteristics
1. Look and feel
2. Strength
3. Elasticity
4. Density
5. Resistance to heat, chemicals, sun, etc.

Fiber extraction

Retting - produces bast fibers; plant stems are placed in water or wet area and allowed to rot. The thick-walled xylem also remains and must be removed by scutching, which does not break bast fibers. Fibers are hackled (separated and aligned) by drawing them across a comb.

Ginning - seed fibers, fibers are removed from seed.

Milkweed - Asclepias

Kapok - Ceiba pentandra
The fibers of both of these are fine and slippery, used as stuffing material.

Cotton - Gossypium - most important nonfood plant. Cotton is easily processed mechanically. Fibers dye well and withstand vigorous washing. Natural history of cotton is complicated. Spcies were independently domesticated in New and Old World. Cotton fabrics 5000 years old have been found in Pakistan. Fibers are called staples, New World cottons have larger staples and are the ones most commonly grown.
Gossypium hirsutum - tetraploid, upland cotton, 95% of world production.

Gossypium barbadense - tetraploid, Egyptian cotton, other important cultivar, produces fine quality threads.

Cottons are perennials but are grown as annuals, tremendous amount of pesticides are used in cotton culture, plants are defoliated chemically and machine harvested. Eli Whitney's invention of cotton gin led to explosion of cultivation of cotton in U.S. and increased need for slaves to work fields.

Cotton processing

1. Ginning - removal of seeds and debris
2. Carding - fibers are combed parallel to produce a web
3. Sliver - made by twisting web into a large rope
4. Drawing - more alignment
5. Spinning
6. Cleaning - boiled in caustic soda and bleached.
7. Mercerization - stretched and placed in cold caustic soda, increases luster, dye upstake and durability.
8. Sizing - stiffening agent before weaving.
9. Sanforization - use of ammonia process that swells fibers and prevents shrinking.
10. Permanent press - chemicals used to crosslink polymers.

Coir - Cocos nucifera - coconut fiber. Fibers come from thick fibrous mesocarp. Best coir comes from immature coconuts, which are retted, washed and beaten. This conflicts with harvesting of coconuts for food or oil, so most coir comes from mature fruits. Fibers are used as mattress stuffing, bristles in brooms and brushes.

Produced by retting and pounding

Jute - Corchorus sapsularis - second only to cotton, native of Mediterranean, fibers are rough, brittle, and don't take dyes easily, used in sacks, twine, carpet backing. Easily grown and processed.

Flax - Linum usitatissimum - linen, area of origin unknown, fibers are smooth, straight and 2 to 3 times as strong as cotton so exceptionally durable. Flax industry never became mechanized since mechanically processed flax is not as good as that produced by hand, so linen is expensive.

Hemp - Cannabis sativa - used for at least 6000 years. Fibers are stiffer than flax, used in cordage, rope, canvas and sailcloth. Made original set of Levis from hemp, jeans are currently made of cotton.

Ramie - Boehmeria nivea - China grass - problems with growing and processing but makes longest and silkiest of all plant fibers. Mechanization may result in it becoming an important fiber.

Use of monocot leaf fibers is a fairly recent development, make better ropes than bast.

Sisal - Agave sisatana - Needle and thread plant
Henequen - Agave fourcroydes - both from Central America; Mayans and Aztecs made them into rough garments. Processed by squeezing leaves and scraping away fibers, grow well in arid regions.

Abaca - Musa textilis - banana relative, used in tea bags, dollar bills, manila envelopes, cigarette filters.

Chemistry of bonding of dyes to fibers is complex, involves direct bonding, H-bonds, hydrophobic interactions.

Mordants - increase binding of dye to fabric by forming a chemical bridge from dye to fiber, can also affect color.

Natural dyes
Indigo - Indigofera tinctoria - blue (Fabaceae)
Saffron - Crocus sativus - from red stigmas
Confederate gray - Juglans cinerea (butternuts)
Woad Blue - Isatis tinctoria (Brassicaceae)
Bloodroot - Sanguinaria canadensis (Papaveraceae)

There is currently very little commerical use of natural dyes - used mostly as food dyes and histological stains. Synthetic dyes from coal tar (aniline) produce a wide array of colors and are more colorfast

Tanning makes animal skins resistant to water, heat and microrganisms. Two types:
1. Hydrolizable - easily breaks down into alcohols and water.
2. Condensed - polymers of cyclic compounds, more resistant than hydrolizable.

Animal skins (leather) are composed of collagen, some regions of which are easily attacked by microrganisms. Tanning impregnates and protect these regions. Biological function of tannins may be as feeding deterrents, also have anti-microbial activity.

Vegetable tannins in U.S. are imported. Major sources are:
1. Quebracho - Schinopsis lorentzii
2. Wattle - Acacia (Fabaceae)
Both of these are from the heartwood of the plants.

Synthetic tannins are also available.

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