Transcript Materials - NIU Department of Biological Sciences

Materials
Outline
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Cotton
linen
lumber
paper
Rubber
• Chap 18
Fibers
• Fibers are used to make rope, cloth, paper, etc.
• Animal fibers: wool or silk, for example, are made
of protein, while plant fibers are made of cellulose.
They are attacked by very different pests: insects
and other animals like protein, but fungi and
bacteria go for cellulose.
• Fibers come from bundles of vascular tissue or
cells supporting the vascular tissues.
• Fiber cells have cell walls thickened with extra
layers of cellulose, mixed with varying amounts of
lignin and gums, pectin, and other polysaccharides
that act as a glue to hold the cellulose together.
• The most valuable fibers are pure cellulose.
Cellulose had a very high tensile strength: it is hard
to break by pulling it apart.
Types of Fiber
• Surface fibers: found on seed or leaf coverings. Ex: cotton.
• Bast, or soft fibers, are clusters of phloem cells, from the inner bark
(dicots). Ex. linen and hemp.
• Leaf, or hard fibers, are vascular bundles (xylem and phloem) from
leaves, usually monocots. Ex. sisal. Hard fibers have more lignin than
soft fibers, and they are often used for rope, mats, and other coarse
fiber products.
Spinning
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Most plant fibers are quite short, so they need to be
spun together to make long threads. Spinning involves
stretching a group of fibers and twisting them together.
The fibers are elastic, and when the tension is released
they stick together.
The raw fibers must first be cleaned to remove any
remaining plant debris, then carded, to align and
straighten the fibers. Carding is essentially the same
as combing your hair: pulling the fibers through wire
teeth.
The hand spindle, invented in prehistoric times, is the
simplest method: a group of carded fibers are attached
to the spindle, which is then given a spinning motion
and dropped, twisting the fibers together. The twisted
yarn is then wound around the spindle. This technique
was invented in prehistoric times.
The spinning wheel allowed continuous high speed
rotation around a spindle. Spinning wheels were
invented independently in several different cultures.
Cotton
• Cotton is the most important plant fiber. Cotton
fibers are almost pure cellulose.
• Cotton is produced by several plants from the genus
Gossypium. Most of today’s cotton is derived from
from Gossypium hirsutum, which was domesticated
in Mexico 8000 years ago. Cotton from another
Gossypium species was independently domesticated
in the Old World at least 7000 years ago, in the
Indus River valley (India).
– New World cotton is a tetraploid and produces longer fibers
than Old World (diploid) cotton.
• The cotton plant is a shrubby perennial, but it
doesn’t survive harsh winters, so it is mostly grown
as an annual.
• The fruit is the cotton boll, which contains about 10
seeds, each covered with long hairs that help with
wind dispersal.
Cotton History
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Cotton was widely used from ancient times in India,
Egypt, and China.
Cotton cloth first entered Europe with Alexander the
Great’s conquests, where he got as far as western India
(which he thought was pretty close to the edge of the
world). However, the Greeks and Romans preferred
linen.
Cotton was spread by Arab merchants, reaching Spain in
the 800’s.
Little was known about how cotton was produced: In
1350 Sir John Mandeville wrote a book about his travels
in exotic places, most of which he made up. He said,
“There grew there [India] a wonderful tree which bore
tiny lambs on the endes of its branches. These branches
were so pliable that they bent down to allow the lambs to
feed when they are hungrie” This was called the
Vegetable Lamb of Tartary.
Columbus found cotton growing in America in 1492, and
cotton was planted in the earliest colonies.
Industrial Revolution
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Beginning in the late 1700’s in England, major changes in manufacturing
increased average income 10-fold while supporting an large population
increase.
The steam engine was invented (or improved to being a practical device) in
1775 by James Watt: portable power not based on animal or human muscle.
– Originally used to pump water out of mines
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This led to having larger machines. The first manufacturing to benefit was
textile industry. Spinning jenny, power loom, etc.
– Before this time textile manufacture was a cottage industry: people spun and wove
cloth at home, mostly from wool. Cotton and linen were luxury goods.
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Machines that carded the fibers, spun it, and wove it were all invented over a
25 year period in the late 1700's, allowing the manufacture of cloth at high
speed in factories.
Originally the textile mills used Indian cotton, but domesticated American
cotton was superior (longer fibers) and cheaper to ship to England. Indian
cotton became popular again during the American Civil War, due to a
blockade.
Cotton Gin
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Cotton is long hairs attached to the seed
coat: it is necessary to remove the
seeds.
This was done by hand, which is very
slow.
Eli Whitney invented a machine that
was much more efficient in 1793
The raw cotton is fed onto a rotating
drum that has saw teeth that pull the
fibers apart. The teeth pass through a
metal comb that doesn’t allow the seeds
to pass through.
– The fibers, called lint cotton, are then
processed further.
– The seeds are pressed for oil, and the
dry seed meal is used as animal feed.
Cotton and Slavery
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Until the invention of the cotton gin in 1793, production was
very low. In 1791, the US exported 400 bales of cotton, but
in 1800, 30,000 bales were exported.
– Also important inventions at this time: steam powered
spinning and weaving machines in textile mills in
England. Cotton fabric suddenly got much cheaper than
linen or wool.
– After this, growing cotton became more profitable than
tobacco.
Harvesting cotton was long done by hand, and before the
Civil War, it was done by slaves. In 1850, more than half of
the 3.2 million slaves in the southern US worked in the
cotton fields.
– In the off season, corn was grown.
– Very hard work under very bad conditions.
– Slavery was hereditary: a slave’s children were also
slaves.
Modern Cotton Production
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Cotton needs a long growing season, but it is tolerant
of drought and mild salinity. This makes it an
excellent crop for irrigation in the southern Great
Plains, especially parts of Texas. Also, it is still
grown extensively in the Southeast: Georgia,
Alabama, Mississippi, South Carolina, North
Carolina, and Tennessee.
In the 1940’s, chemical defoliants were developed
that killed the leaves before harvest. This allowed
mechanical devices to pick the bolls without
damaging the fibers. Up to this time (and continuing
in some poorer countries) all cotton was picked by
hand.
Cotton Pests
• Insect pests are a problem, notoriously the
boll weevil, but many others as well. This
means lots of pesticide use.
– The boll weevil has largely been eradicated,
due to regional cooperation and an
understanding of how they overwinter:
treatment with pesticide in the late fall is
very effective. Also, the male pheromone
was isolated and used to bait traps.
• Other insects are still a problem.
Genetically modified cotton containing the
Bt gene has helped reduce pesticide use.
However, many insect pests are immune to
Bt.
• A small amount of organic cotton farming
occurs.
Boll weevil monument
in Enterprise, Alabama
Linen
• Linen is made from the stem fibers (bast) of the
flax plant, Linum usitatissimum.
• Native to Europe and east Asia, but today there are
no wild flax populations except escapes from
fields.
• Linen is certainly one of the oldest plant fibers in
use, with cloth samples found in 10,000 year old
lake dwellings from Switzerland.
– Possibly even 36,000 years ago: some dyed fibers
have been found.
• Linen was used to wrap ancient Egyptian
mummies.
• In the Bible, garments made of wool/linen mixtures
are forbidden (Deuteronomy 22:11 and Leviticus
19:19). Not really explained, and subject to much
speculation among religious writers since ancient
times.
More Linen
• Linen fibers have 2-3 times the strength of cotton fibers, and they are
much longer: up to 150 cm (5 feet). They also are very absorbent:
linen became a synonym for underwear, and the word “lingerie”
comes from linen.
– So are line, lining, linament, linoleum, and linseed oil.
• Linseed oil also comes from flax, but a different strain from the fiber
plant. It is produced by pressing the seeds. It is a drying oil, used to
preserve wood.
• Linen is now very expensive relative to other fabrics, because
production involves much hand labor.
• Linen production was big cottage industry in Ireland and Holland
between 1600 and 1900. This was especially important during the
American Civil War (1861-65), when the cotton supply to Europe was
disrupted.
Extracting Fiber
• Linen fibers need to be extracted from the
surrounding plant tissue. The primary process is
retting: allowing the soft material in the plant stems
to rot away, leaving the more resistant fibers intact.
– Retting is done by letting the plants sit in stagnant
water for several weeks or months. It can also be
done chemically.
• Retting doesn’t remove all contaminating material.
Once the retted fibers are dried, they are broken:
repeatedly bent to break up any woody parts. Then
they are scutched (or decorticated): beaten or
scraped to remove the broken debris.
• After this they are hackled (combed) to remove
short fibers, leaving only the long ones. Then,
spun into yarn and thread.
• http://www.youtube.com/watch?v=96KFc3Dj8Oo
&feature=related
Paper
• The earliest writing was done on
clay tablets, which were then baked
to make the writing permanent.
• Papyrus was made from stems of a
reed that were sliced open, pressed
flat, then glued in layers at right
angles to each other. It couldn’t be
folded, but worked well for scrolls.
– Papyrus grows in the swamps in
southern Sudan, far up the Nile
River.
• Parchment is made from sheep skin
that is scraped and smoothed It is
reusable: you can erase what was
written on it by re-scraping. It was
originally a replacement for
papyrus: the reed was overharvested and got too expensive.
Paper History
• Paper was invented in China about 105 AD, when Ts’ai
Lun, an official in the Imperial court of the Han dynasty,
created it from the inner bark of the mulberry tree (a bast
fiber). He had been inspired by paper-making wasps.
– Also used hemp, bamboo, rags, silk
• Papermaking was a state secret, but it slowly spread to
Korea and Japan.
• Paper was introduced to the Arab world after they
defeated the Chinese in a battle near Samarkand in
western China, in 751 AD. The Chinese had a major
paper mill there, to take advantage of flax (source of
linen) that grew there. The Muslims refined the art of
papermaking into a bulk industrial process.
• Europeans started using paper following its introduction
into Spain by the Arabs, around 1000 AD.
• Independently invented in the New World by the Mayans
and Aztecs.
Papermaking
• The basic process is to convert plant material
into a suspension of short fibers (pulp) in
water, then pass it through a screen and press
it flat. The fibers end up in random
orientations that interlock.
• After drying, paper is often pressed between
rollers to give a harder surface. This is called
calendering (a calendar shows the days of the
week).
• The surface can also be sized with starch or
gelatin (an animal product) to produce a
harder, less absorbent surface. Ink then dries
on the surface rather than being absorbed into
the paper. Sizing coats the hydrophilic
cellulose fibers with a hydrophobic layer.
– Unsized paper: newsprint, paper towels
– Sized paper: printer paper
Fibers for Paper
• The cellulose fibers are glued together by lignin and
other substances. This needs to be broken down to
extract the fibers.
• Before wood pulp got started, paper was made from
bast fibers: the cells that strengthen the phloem in the
inner bark of trees. These fibers are very tough, and
they can be separated from the phloem cells and other
plant material by beating them and treating them with
alkali.
– Originally the beating was done by hand, but Muslims
invented the use of water or animal powered
triphammers.
• Cotton and linen rags are an excellent source of fiber,
since most of the lignin has already been removed. Old
clothes mostly ended up as paper before about 1850.
Wood Pulp
• The demand for paper eventually led to a shortage of rags and a search for a
substitute. The use of wood pulp for paper dates from about 1850.
• Proved to be much cheaper than using other fibers. Also, the pencil, the
fountain pen, and the steam-driven printing press were developed around this
time, leading to an explosion of printed and written material.
• Wood is xylem cells, whose cell walls are cellulose fibers held together with
lignin.
• The earliest wood pulp mills separated the fibers from each other
mechanically, by grinding the wood against a grindstone.
– In modern times, this is done with hardened steel plates, in the presence of steam
and pressure.
• Chemical pulping works by dissolving away the lignin in sulfate or sulfite
compounds at high temperature. After digestion, the pressure is suddenly
released, and the fibers rapidly expand and separate.
• After washing out the dissolved lignin, the pulp is bleached.
– Unbleached pulp is used to make brown paper bags, cardboard, and kraft paper.
Paper Making
Rubber
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The rubber tree, Hevea brasiliensis, is a New World
species. Before Columbus, the natives tapped the
tree by making incisions in the trunk. The sap
(latex) that came out was collected, and then
smoked over a fire to coagulate it. It was then used
to make rubber balls and waterproof shoes.
Brought back to Europe, it could be dissolved in
solvents like naphtha, and used to make various
things.
– The macintosh raincoat was invented with this
form of rubber: two sheets of cloth glued
together with rubber dissolved in naphtha.
– The pencil eraser was also invented about this
time. The word "rubber" comes from this: you
rub out your mistakes.
However, rubber was sticky when warm and brittle
when cold, and smelled bad all the time: not
practical for most purposes.
Aztec god Xiuhtecuhtli with
offering of rubber balls
Charles Goodyear
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Rubber became a practical material with the invention of
vulcanization by Charles Goodyear.
Charles Goodyear spent many years working on improving
rubber. He was a visionary who felt that he had been
called by God to do this. He suffered many reverses,
including debtor's prison and broken health due to
chemical fumes, before he succeeded.
In 1839, he discovered that heating the rubber latex with
sulfur produced a stable product: it was waterproof,
elastic, and relatively insensitive to temperature. He then
invented and promoted a great many of what are now
common rubber items: doormats, baby bottle nipples,
elastic cords, inflatable boats, pulley belts, etc.
– His process was stolen and patented by someone else in
England and France. Goodyear was too poor to hire lawyers
to successfully challenge this, and he died in poverty.
– Pneumatic tires invented in 1845. Became very popular on
bicycles and eventually, automobiles
Rubber Boom!
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The rubber tree grows wild in the Amazon jungle in
Brazil. This area was very isolated until Goodyear’s
vulcanization process made rubber the new wonder
material.
Major rubber boom 1879-1912 produced great wealth in
Manaus Brazil and other jungle cities. Cities had
electricity, running water, sewers, and a fancy opera
house.
– Manaus even became the world’s center of diamond
sales for a brief time.
Ended when rubber trees were smuggled out of the
country to Malaysia, Sri Lanka, and tropical Africa.
Planted in orchards; the Brazilian trees were wild. Also,
natural diseases were left behind, specifically the leaf
blight fungus.
– When Henry Ford tired to establish rubber plantations in
South America, they were wiped out by the fungus, which
quickly spread between the trees.
Opera house in Manaus
Rubber Chemistry
• Rubber starts out as isoprene, a compound with 5 carbons.
Isoprene molecules get attached together into long
polymers that are elastic.
– Acts as a wound sealant for rubber trees, and it may also
gum up the mouths of animals trying to eat the plant.
• Vulcanization crosslinks the isoprene polymers with
bridges made of sulfur atoms.
– Rubber starts out of tangled mix of many molecules, which gets
cross-linked into one big molecule” much harder to pull apart.
– Various chemical additives catalyze (accelerate) the process,
which is very slow. Goodyear used lead oxide as an
accelerant, but other materials are used today.
• The rubber molecules are twisted and curled up in their
relaxed state. When stretched, the molecules straighten out
temporarily.
Rubber Production
• Rubber latex is produced in the inner bark, and is
tapped by cutting the bark, but not the cambium
layer.
• Trees are tapped every third day, in a diagonal cut
extending halfway around the tree.
• The collected latex is cleaned and then coagulated
into sheets or blocks for export.
• At the factory, the raw rubber is dissolved with
solvents, mixed with sulfur and vulcanization
accelerants, and injected into a mold.
– Often, powdered carbon is added to color it black.
• Today, most rubber is grown in Southeast Asia:
Indonesia, Malaysia, and Thailand.
• Commercial rubber trees are grown from cuttings
of high-yielding varieties.
Rubber-producing Plants
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The Brazilian rubber tree (Hevea) , which is native to the
Amazon rain forest, is the primary source for natural (para)
rubber. However, most rubber is produced in tropical Asia:
Malaysia, Indonesia, and Thailand.
– 42% of today's rubber is natural. The rest is synthetic, derived
from petroleum
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Other plants also produce rubber latexes: goldenrod, milkweed,
the ornamental rubber plant (Ficus), and many more.
The African rubber vine Landolphia grows in the Congo.
Under the Belgians, African slaves were used to harvest the
latex under terrible conditions.
– Read The Heart of Darkness by Joseph Conrad.
– Overharvesting led to the end of African production by 1914.
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Guayule, a desert shrub native to the American Southwest,
produces latex very similar to Hevea. It has been bred to
produce about as much raw rubber as Hevea, and it grows in an
area not used much for crops. It may become an increasingly
important source of rubber.
Synthetic Rubber
• Natural rubber has always been in short supply.
• Organic chemists devised many forms of synthetic rubber,
especially in the first half of the 1900’s, when supplies of
natural rubber were cut off due to war.
• Neoprene and Buna rubbers were developed in the US and
in Germany 1930’s.
• During World War 2, Japan conquered the rubber
producing parts of Asia in 1942. This cut the US off from
nearly all the natural rubber supply. Led to major increase
in synthetic rubber production.
• Silicone rubber incorporates some silicon atoms in place of
carbon atoms. It is much more heat stable and water
repellant than other rubbers.
Chewing Gum
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The base of chewing gum is chicle, the sap of the
Manikara zapota tree. It is native of South America, and
has been chewed there since ancient times.
Its use in the United States is the result of a visit by
Mexican politician and general Antonio Lopez de Santa
Anna, to New York in 1866.
– Santa Anna was a colorful figure who served 11
separate times as president of Mexico.
– He is best known as the general who led the Mexican
troops in the Battle of the Alamo, where Davy
Crockett, Jim Bowie, and William Travis died in
1836. This was part of the Texas Revolution where
American settlers in what was then a Mexican state
rebelled against the authorities in Mexico City, and
set up the Republic of Texas.
– Although Santa Anna won at the Alamo, his troops
were defeated, and he was captured, at the Battle of
San Jacinto.
Chewing Gum
• Santa Anna was in New York trying to
raise money for another comeback.
Unfortunately, unscrupulous friends stole
all his money.
• However, he met Thomas Adams, who
served as his aide. Adams wanted to
extract rubber from chicle, so Santa Anna
arranged the shipment of two tons of
chicle from Mexico. Extracting rubber
didn’t work, but Adams turned it into
chewing gum.
– Up to that time, sweetened paraffin was
chewed: it’s not very chewy.
– Adams added sugar and molded it into
little tablets, which he named Chiclets.
• These days, chewing gum is made from
petrochemicals instead.