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Materials

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Materials

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  1. Materials

  2. Outline • Cotton • linen • lumber • paper • Rubber • Chap 18

  3. 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.

  4. 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.

  5. Spinning • 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.

  6. 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.

  7. Cotton History • 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.

  8. Industrial Revolution • 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 • 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. • 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.

  9. Cotton Gin • 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.

  10. Cotton and Slavery • 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.

  11. Modern Cotton Production • 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.

  12. 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

  13. 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.

  14. 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.

  15. 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

  16. 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 over-harvested and got too expensive.

  17. 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.

  18. 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

  19. 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.

  20. 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.

  21. Paper Making

  22. Rubber • 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

  23. Charles Goodyear • 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

  24. Rubber Boom! • 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

  25. 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.

  26. 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.

  27. Rubber-producing Plants • 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 • Other plants also produce rubber latexes: goldenrod, milkweed, the ornamental rubber plant (Ficus), and many more. • The African rubber vineLandolphia 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. • 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.

  28. 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.

  29. Chewing Gum • 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.

  30. 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.