intro to materials (fiber).pdf

7/27/2019 Intro to Materials (fIBER).pdf

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10/4/13 Intro to Materials 2

faculty.unlv.edu/landau/fibers.htm

Fibers

Plant and animal fibers have provided humans with, among other things, shelter,vessels in which to hold water and cook food, and thread for making fabrics.

Even tho most of the world has abandoned mud and waddle home constructionand baskets smeared with clay as water vessels or cooking utensils, plant fibers as

a source of weaving still remains current in use.

In prehistoric times humans probably obtained flexible plant fibers simply by

pulling off strips of bark or cutting stems and leaves onto thin, weavable ribbons.

Altho these materials can be lashed and interlaced into mats and baskets,they produce only coarse, stiff items.

Major innovation was the discovery that individual fibers could be

separated from surrounding cells and used to weave textiles.

Animal skins probably predated woven material, but plant fibers probablypredated animal fibers for woven material.

* Sandals, made of complex woven plant fibers, over 8,000 yrs old, have

been found at an archaeological site in Missouri.* By 5400 years ago, native people of Mexico were using cotton fiber.

* Linen was woven 10,000 years ago in Turkey, at least 3,000 years beforethe domestication of sheep (wool), and 5,000 years before the use of silk(silkworm).

These dates are fairly recent when you consider that the association of the genus

Homo with plants and animals dates back hundreds of thousands of years. The

recency is understandable when you consider that:Only a small number of animals (sheep, camels, vicunas, guanacos, goats,

rabbits, and the silk moth) and relatively few plants produce fibers that can betwisted or spun.Humans had to appreciate the nature of fibers, learn which plants contained

them, and learn how to extract them before spinning and weaving them.


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faculty.unlv.edu/landau/fibers.htm 2

Fibers

1. With the exception of synthetic polymers, most economically importantproducts, such as cordage, paper, textiles, are derived from plant fibers.

2. Fibers are elongate cells with tapering ends, and very thick, heavily lignifiedcell walls.

3. Fiber cells are dead at maturity and function as support tissue in plant stemsand roots.

4. The lumen, or cavity inside mature, dead fiber cells, is very small in cross

section.

5. Fibers are one of the components of sclerenchyma tissue, along withshorter, thick-walled sclereids (stone cells) which produce the hard tissue of

peach pits and the gritty texture in pears.

6. Fibers are also associated with the xylem and phloem tissue of monocot and

dicot stems and roots, but generally not the wood of gymnosperms(softwoods).

a. The primary reason why gymnosperm woods are generally softer andlighter than angiosperm woods is the presence in angiosperm wood of

dense clusters of heavily-lignified, thick-walled fiber cells.

b. The fiber cells increase the hardness and density of angiosperm wood.

Vegetable fibers Animal fibers

Composed of cellulose Composed of protein

Not subject to denaturation by high

temperatures. Cotton sheets can be

boiled when washed.

Heat cracks protein backbone of

animal fiber making it brittle.

Woolen garments ruined by hotwater.

Requires elaborate treatments to

ensure successful color adherence

Accepts dye readily

Immune to animal pests but, like

paper, attacked by fungi, mold, andtermites.

Susceptible to attack by animal

pests, such as moths and silverfish.

Less elastic than animal fibers. More elastic than vegetable fibers.

High affinity for water: moreabsorbent.

Low affinity for water: notabsorbent.


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The fundamental chemical difference, between cellulose and protein,

determines how the 2 types react to heat, various chemicals, water, and

predatory organisms.

With the exception of synthetic polymers, most economically important

products, such as paper, cordage (cords and ropes) and textiles, are derived

from plant fibers.

Properties of textile fibers

1. Fibers can be spun if they have structural properties that cause individual

strands to clasp one another when twisted.

a. Most animal hairs cannot be spun because they are too slippery tostay together when twisted around one another.

2. Elastic properties are a measure of the facility with which a fiber can regainits original shape after it has been stretched.

a. The amount a fiber has been twisted, the way in which the cells are

held together, and the number of cells per fiber contribute to itselasticity.

3. Fibers have different densities of weight relative to an equal volume of

water, which affects how fibers made from them will drape.

4. Fibers high in cellulose are considered valuable because cellulose is

extremely strong with properties of tensile strength rivaling that of

steel.

5. Fibers high in lignin are generally of poorer quality, browner in color,

with lower mechanical strength.

Kinds of fibers

1. Bast fibers comes from phloem tissues in the stems of variousdicotyledons (linen from the flax plant)

2. Hard fibers come from the leaves of a few monocotyledonous plants

century plant, Manilla hemp).

3. Surface fibers found on the covering of seeds, leaves, or fruits; cotton

cloth is made from seed hairs covering the surface of cotton seeds


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Fiber Extraction

Despite the fact that various fibers come from many different and unrelated

plants, the same basic procedures are used to separate the fibers from the massesof cells in which they are embedded. The primary processes are: retting, scotching

decorticating, and ginning.

Separating fibers from masses of other cells in which they are embedded.

1. Retting (bacterial rotting).a. Extraction process that rots away the soft plant parts and leaves fibers

intact.

b. Used mainly for bast fibers (phloem tissues of dicots) and takesadvantage of the fact that fibers have thicker cell walls than do most

other plant cells, and are therefore comparatively resistant tobreakdown by bacteria.

c. Plant material can be retted by dumping the mass into tanks of

stagnant water, or simply allowing it to remain on the ground where

it will be repeatedly covered with dew.d. During retting, tissues absorb water and swell, causing release of

soluble compounds that help provide nourishment for decomposingbacteria.

e. Retting takes a few weeks.

1. The mass of rotting material must occasionally be tested toascertain the point at which soft tissues, but not fibers, have

disintegrated.

f. There may be epidermal and thick-walled woody xylem cells that canpersist.

1. These are removed by washing and drying the material after

retting.2. They are then "broken" by means of being forced under fluted

rollers.

3. the rollers crumbles the brittle material, but not the moreflexible bast or leaf fibers.

4. Broken pieces are then removed from fibers by the process of

beating and scraping, called scutching.

5. Finally, fibers are drawn down across a set of vertical pins


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resembling a comb, called hackling.

Decorticating - entails crushing plant material and scraping nonfibrous material

from fibers. Used primarily for leaf fibers.

Ginning - unique to seed fibers. Seeds are pulled free from the fibers covering

them.Once extracted and cleaned, fibers can be further processed by bleaching or

heating, or both, in an alkali solution. Fibers are usually bleached before dying so

their natural tans and brown pigments don't effect the final color.

Seed and fruit fibers

1. Although seed and fruit fibers come from different parts of the fruit, both aid

in seed dispersal, but by different mechanisms.a. Long fibers on seed surfaces promote dispersal by wind. (e.g. tufts of

hair on top of milkweed, Asclepias spp.).

b. Fibers within fruit wall generally protect seed or provide buoyancy

for water dispersal, or both (coconut).2. Few plants have seed or fruit fibers long enough for spinning. Cotton is the

notable exception because it produces seed fibers that can be spun into thread.

a. Seed fibers from milkweed and kapok (Ceiba pentandra,

Bombacaceae) are too fine and slippery to spin. These are usedprimarily as stuffing material and kapok was formerly used for life

preserves because its lightweight and water resistant and has fibersthat trap air.

1. Kapokhairs are produced on the inner surface of the seedcapsule of the kapok tree, in tropical regions of the New

World.

2. It's an enormous rainforest tree with a massive buttressedtrunk.

3. Hairs are coated with a highly water-resistant, waxy cutin.

4. The empty lumen is larger than cotton hairs and hence thefiber is lighter in weight.

5. A kapok-filled life jacket can support 30 times its own

weight in sea water.6. Milkweed hairs were used as a substitute for kapok during

WWII.


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7. The hairs can also be twisted into dental floss.

b. Coconuts are unique because they produce the only fruits from

which fibers (coir) are extracted from the pericarp for commercial

use.

Coir

1. Bulk of mature coconut consists of thick, fibrous mesocarp that constitutes

source of a fiber called coir.a. Coir fibers are made up of bundles of cells that are longer than cotton

fibers but shorter than most bast or leaf fibers.

b. High-grade coir produced by harvesting and husking 10-month old(immature) coconuts.

1. Husks are retted for 8-10 months in brackish water.

2. When soft, husks are thoroughly washed, beaten to removepulpy remains, shaken, and washed again.

3. Clean fibers are spun into yarns primarily used for ropes andmatting.

c. That the most valuable coir fibers come from unripe coconuts

presents an economic problem because the most valuable

commodity obtained from coconuts is copra, the dried coconut

endosperm, which is eaten or used for oil.

1. Copra can be obtained only from mature fruits.2. Consequently, although mature fruits yield fibers that are

tougher than those of young coconuts, most coir is extracted

from old husks that remain after the copra has been removedfrom ripe fruits.

3. Cotton

a. Most important fiber today; most important nonfood plantcommodity.

b. Large amount of fiber produced by each plant combined with the fact

that picking, processing, and manufacturing of textiles from cottoncost less than processing other fibers.

c. Versatile fiber that produces textiles that dye well, and withstands

rigorous washing.

d. Each cotton fiber is a single long epidermal seed coat cell.

Unicellular hairs that grow out of the surface of the seed after


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fertilization.

1. Cells are so long they resemble hairs.

2. The hairs are twisted into usable thread which is tough andstrong.

3. In cultivated cotton, there is a second layer of short fuzzyhairs underneath the long fibrous hairs. These short hairs, or

linters, are removed and used in paper making whencottonseed is used as an oilseed crop.

4. Cotton thread is spun from billions of microscopic hairs

covering the surface of cotton seeds, each hair up to 50 mm

(2) long. The total length of hairs in a single cotton boll(one seed capsule) may exceed 300 miles. (How many miles

from a standard 500 lb bale?)

e. Gossypium arboreum and G. herbaceum (Old World crops).

Diploid.1. Both have short fibers, or staples, and both were eventually

replaced by New World cottons with longer fibers.2. G. hirsutum and G. barbadense are new World tetraploids.

a. Archeological excavations date to 3,400 BCE in

Yucatan, Mexico.b. G. hirsutum comprises 95% of the world's supply of

cotton.

c. G. hirsutum is relatively resistant to boll weevil.d. Cotton hairs (lint) of the tetraploid species may be up

to 50 mm (2") long.

e. Most species of cotton are tropical perennials, but in

cultivated species, humans have selected for an

annual habit and the ability to bloom and fruit in

temperate lattitudes.

1. Growing cotton as an annual is advantageous for farmersbecause it ensures a short stature, uniformity of plant size,

and synchronous fruiting.

2. On modern farms, plants are often sprayed with a defoliantwhen cotton is mature so that the foliage will not interfere

with harvesting machines that pluck mature bolls from

plants.3. Once picked, seeds with their fibers must be removed from

the fruits; fibers are then separated from the seeds.


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4. Most Americans know that Eli Whitney invented the cotton

gin, a machine that pulls cottonseeds from the fibers, in

1794, but the importance of this equipment may not bewidely appreciated.

i. In 1791, three years before Whitneys

invention, the U.S. exported 400 bales of

cotton.ii. By 1800, exports had jumped to 30, 000 bales

f. Sizing consists of the addition of a thick substance, such as starch

or a gel, on the surface to stiffen (firm) it and fill surface

irregularities. Cotton is usually sized with starch or resin.1. important for threads that will be used for

the warp (major loom threads).

2. sizing material washed out after weaving is

done.3. increase strength of thread

g. Cotton fabrics used to shrink

1. There was the tradition of buying a cotton garment 1 size toolarge in anticipation of shrinkage due to initial washing.

2. Sanforization (1970) is an ammonia process that swells

cotton fiber and prevents their shrinkage after washing.

h. Cotton fabric has a tendency to wrinkle when washed.

1. Permanent press - chemicals are used to cross-link the

cellulose polymers of cotton cloth causing the fabric to retain

shape it had when chemicals were first applied.2. This process also keeps surfaces smooth and allows pleated

or ruffled garments to retain shape after washing.

Bast fibers from the bark of stems (soft fibers)1. Thick-walled fiber cells occurring in the phloem parenchyma of stems of

various dicots.

2. Bast fibers constitute the main source of stem fibers.3. Individual bast fibers can be made up of hundreds of cells and can be over 4.6

m (15') long.


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4. Fibers usually separated from stems by retting.

Jute (Corchorus capsularis) Tiliaceae - world's foremost bast fiber1. Jute has been used since prehistoric times.

2. Probably yielded fibers for some of the sackcloth referred to in the Bible.3. Herbaceous annual, up to 5 m tall; yields fibers 1.8 - 3 m (6-10') long.

4. Fibers are relatively inelastic, and tend to disintegrate rapidly in water.5. Fibers are separated from the stems by deep-water retting.6. Their roughness, brittleness of fibers, and inability to hold dyes promote use of

jute fibers for coarse goods such as carpet backing, canvas, twine, "gunny

sacks", burlap, etc.7. Popularity of jute is primarily due to its low cost, which results from its raid

growth and the ease with which its fibers can be extracted from the stem.

Flax (Linen)Linum usitatissimum. Linaceae.1. Oldest textile fiber used by humans.

a. Archaeological digs uncovered remains of flax species in ancientsettlements occupied by Swiss Lake dwellers about 10,000 years ago

b. Egyptian mummies dated about 5,000 years ago were generallywrapped in linen cloth.

c. Carvings on Egyptian tombs document its cultivation along with

wheat, figs, and olives.

2. Etymology - the words 'line' (as in straight lines) and lingerie and the genericname, Linum, are derived from the Latin word for linen.

3. Flax is native to Europe and Eastern Asia.4. The plants from which fibers are obtained are tall, little-branched, annuals that

yield oil as well as fiber.

5. Flax fibers are smooth, long, straight, and 2-3 times stronger than cottonfibers. They are used for making buttonholes and button thread, as

well as for hoses and mailbags.

6. Flax is generally obtained by dew retting the cut stalks of mature plants.a. This takes about 3 weeks.

b. Plants are now sometimes uprooted and chemically retted (chemicalsdissolve the matrix between cells before retting begins).

c. Because of hand labor involved in traditional flax fiber extraction,

linen has always been a relatively expensive textile.

7. Linen textiles are generally soft, lustrous, and water-absorbent, and linen is

also used for towels.


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8. Linum is also the source of linseed oil, an unsaturated drying oil used in the

original linoleum and in the paint industry. Linoleum = linum (flax) + oleum

(oil).

Hemp (Cannabis sativa) Cannabaceae.1. Cannabis initially spread around the world because of its fiber, not because of

its resinous compounds (THC).2.Native to western Asia; used in Chinese Yang Shao culture around 4,000 BCE

(6,000 years ago).

a. Seeds were consumed along with millet, rice, barley, and soybeans in

ancient China.3. Dioecious, annual herbs.

4. Hemp fibers are the longest of any bast species, ranging from 1.5 - 4.5" (5-15')

in length.

a. Staminate plants produce the best and longest fibers, up to 2 meters longb. They were used to weave the cloth of which most Chinese garments were

made in ancient times.c. The yarn woven from these fibers were exceedingly fine, so much so that

people were buried in hemp garments.

5. Hemp produces dark, rough fiber and as a result is typically used for cordage,

rope, canvas (the word derives from Cannabis), covered wagons, and sailcloth

6. Etymology: Levi Strauss originally made work clothes of hemp; it was

imported from Mines, France and known as serge de nimes, later corrupted

into denim. Jeans is a derivative of the French pronunciation of the Italiancity of Genoa, a city known for its manufacture of hemp cloth.

7. Altho cultivation of hemp has been illegal in the U.S. for over a quarter

century (because of drug enforcement policies), finished hemp products maybe imported. Calvin Klein and Giorgio Armani are selling hemp clothing and

bed linens at premium prices.

8. Hemp was once extensively planted throughout the U.S. with govt support.

9. Grass root movement to legalize the production of industrial hemp. Supporters

for legalization point out the low THC content in the hemp plant.

10. Requires no irrigation or pesticide use: cotton requires considerable

amounts of both.

11. Navajo Nation now considering hemp production on their lands.

12. The Chinese harvest many tons of hemp fiber annually to produce fiber

for paper, rope, and cloth.


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13. Another hemp plant,Apocynum cannabinum, (Indian hemp), was an

important fiber plant of native North American people, and is native to certain

areas in Nevada.

Leaf Fibers (Hard fibers)

1. Most leaf fibers are obtained from rapidly growing monocots with fibers thatcan be easily and inexpensively extracted by decorticating machines.

2. The fibrous strands occur within the phloem in the vascular bundles scattered

in leaves and leaf bases.3. Within the leaves, the thick-walled fiber cells provide support.

4. Once extracted, the fibers can be spun, but they are too stiff to be made into

textiles suitable for modern clothing.5. The name 'hard' refers to its stiffness.

6. Hard fibers tend to be shorter than bast fibers.7. Leaf fibers, however, make better ropes than do bast fibers.8. Although other plants are generally used, two genera, Agave and Musa, supply

virtually all the commercially important leaf fibers.

A. Sisal

1. Sisal comes from the leaves ofAgave sisalana, native to Central America,where the Mayans and Aztecs are known to have extracted and woven sisal

fibers into rough garments.

2. In addition to fibers,A. sislana has sharp spines on the ends of its leaves thathave been used by native peoples as needles.

3. Combination of fiber and sewing utensil gave rise to the common name,

"needle and thread plant".4. Today the fibers are used for sacking, mats, and tea bags and as reinforcements

for materials such as rubber.

5. The sap tapped from this agave can also be fermented into a mildly alcoholicwine known as pulque.

6. Fiber removal

a. Outer mature leaves are cut at the base, carted to factory, and fedbetween rollers that squeeze out most of the water and turn the soft

tissues into an amorphous mush that is scraped away from the fibers.

b. Fibers are then washed and hung in the sun to dry.7. The sun-dried leaves ofYucca elata are used extensively for the main visible

white coils in baskets of native North American people, including the Papago,


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Pima, and Havasupai.

B. Abaca (Manila hemp)1. Manila hemp comes fromMusa textilis (Musaceae), a relative of the banana,

native to the Philippines.2. Fibers are extracted from the outer parts of the leaf bases that make up the

"stem" of these giant herbaceous plants.3. Most people have come into contact with products using Manila hemp in the

form of tea bags, dollar bills, "Manila" envelopes, filter-tipped cigarettes.

4. They make the finest ropes, which have held ships to docks throughout the

world. Manila hemp rope is being replaced with nylon in many parts of theworld.

intro to materials (fiber).pdf

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