Rubber (Hevea Brasiliensis)

• This is a tree that produces latex, which is referred to as rubber

• It is a member of the Euphorbiaceae family

• The rubber tree is native to the Amazon region of South America

Latex

• Latex: a mixture of organic compounds produced by lacifiers, single cells which form a network of tubes

History

• Explorers in the Amazon saw that Natives dipped their feet in “sap” then held them to a fire and produced a rubber “sole”

• Later, Spanish people in the New World dipped cloaks in the sap, smoked them, and made waterproof clothing

• Up until 1880 all rubber was extracted from wild trees

  • Bark was slashed diagonally

  • Cups places at the lower end of slash

  • Cups emptied during the day

  • Latex was filtered, mixed with water, and smoked

  • Produced a ball of coagulated latex

  • Shiped to Europe in this form

• In 1823 Charles Macintosh discovered coagulated latex could be dissolved in hexane and applied to clothing to water-proof

• In 1839 Charles Goodyear developed the process of vulcanization which improves elasticity

  • Vulcanization: addition of sulfur to crosslink

• Nowadays dilute acid is used to coagulate the latex instead of smoke and sheets of rubber are produced

• In 1876 seeds of Hevea were taken to Southeast Asia

  • Plantations developed to produce rubber commercially and by WWII 90% of the world’s rubber was coming from Southeast Asia

Herring Boning Method

• The herring-bone method: cutting progressively as the V-shaped cut made to the bark of the tree can be re-opened at regular intervals

Synthetic Rubber

• Synthetic rubber was a response to the Japanese occupation of Malaya in WWII

• Modern ones are polybutadiene and polyisoprene

• Raw material for rubber comes from oil

  • with increased oil prices, research into new raw materials for rubber synthesis is underway

Styrene Butadiene

• This was the 1st synthetic rubber produced.

Natural Rubber

• Natural Rubber is still used for making radial tires

  • Safer than bias-ply tires

• Synthetic Rubber is not resilient enough so we add 30% natural rubber

• 2/3 of all rubber (synthetic or natural) goes into making tires

• Fortune Business Insights says that the global market was valued at 40.77 billion USD in 2019 and is on track to reach 51.21 billion by 2027

  • This includes both synthetic and natural rubber

• The Asia Pacific is still the leading producer of natural rubber

  • Thailand is the biggest producer

Wood and Wood Products

Fun Facts

• Bristlecone Pine: the oldest organisms that grow up to 5000 years old

• Great Sequoia (Redwood): the tallest organisms

• Aspen: Largest organisms; the largest strand of genetically identical clones (asexual reproduction)

• Wollemi Pine: the rarest organism; found at an altitude of 2000 feet in a deep shaded sandstone gorge

  • Very remote and was discovered by someone abseiling into the gorge

Wood

• secondary thickening in trees producing secondary xylem

• Heartwood is the oldest xylem and functions in support only

• Sapwood is the youngest xylem and functions in support and conduction.

• Of all the plant products wood and wood products rank second in importance to our society

  • used for construction

  • furniture

  • fuel

  • paper

• Forests are threatened

• 30% of the earth’s surface is covered by forests

  • but 30-50% of the earth’s forests have already been destroyed and deforestation is continuing

    • 32 million acres per year destroyed

• Some reforestation programs are in place but monocultures are being planted in place of old-growth forests.

• Only 2% of all forests are protected as forest reserved

• Tropical rainforests are particularly vulnerable.

  • Some are cleared for timber, used for fuel, but most are cleared for agriculture or ranching

  • “slash and burn” method

“Plant for the Planet”

• Plant for the Planet: An Environmental Program started in 2006 by the UN to plant a billion trees

• Dr. Wangari Maathai: organized women in Kenya to plant 7 billion tree seedlings in three years

  • She was the 1st African Woman to win the Nobel Peace Prize

Soft Wood

• Softwoods: usually gymnosperms, tend to grow more quickly, are cheaper and easier to work with

  • Gymnosperms only have tracheid and no vessel elements in the xylem so the wood isn’t as hard

  • It tends to be construction wood

  • Dominates 35% of Earth’s forests

Hardwood

• Hardwood: tend to be angiosperms (oak, walnut); more expensive and grows slower

  • Used for furniture

Lumber Mills

• The mill operators decide what type of cutting procedure will yield the most lumber from each long

  • Plain-sawed: the wood is cut tangential to annual rings and produces a straight grain

  • Quarter-sawed: the wood is sawed into quarters and then along the radius, produces radial cuts

  • Transversely-sawed

Other Wood Products

• Veneers: a very thin sheet of the desired wood glued to a base of less expensive lumber

• Plywood: 3 or more layers of thick veneer glued together

• Particle Boards

• Fiber Boards

Fuel

• 50% of the world’s harvested wood is used as fuel

• 1.5 billion people depend on wood or charcoal for 90% of energy needs (heating and cooking)

• Additional 1 billion people use wood for 50% of the energy need

Paper

• The US, Europe, and Japan together costume more than 75% of the world’s paper

  • The US uses more paper than any other country in the world

    • In 1999 each person in the US used 733 lbs of paper

    • 40% of all municipal garbage is paper

• Paper is almost pure cellulose

• The raw material for making paper used to be grasses, bamboo, or papyrus

• Egyptians credited with “inventing” paper

• It was in China 2000 years ago that people developed a process very much like what we do today

How Paper has been Made

• Paper is made from plant fibers (usually from wood pulp) that have been separated from one another underwater, drained, and then matted together in a thin sheet.

• Papermaking arrive in Europe (Spain) about 1000 years ago, but the primary raw material was linen, cotton, or hemp rags

  • These are plant-based fibers

  • The first drafts of the US Declaration of Independence and the US Constitution were written on paper made from hemp

• All paper was handmade and expensive until the French invented the papermaking machine in 1789

• Then there was a shortage of fabric rags to use for raw material

• 19th Century: Exploring new sources of materials for papermaking

  • Wood was used but the resulting fibers were short and still contained lignin (secondary cell wall)

• In 1851, the Chemical separation of wood fiber began

  • Different processes are used but all involve using different chemicals to dissolve the lignin

Process

• Produce pulp by stripping the bark of logs and then chipping the wood

• use conifer wood or another softwood (preferred)

• The chips can be pulped mechanically and this makes lower-quality paper like newsprint

• For chemical pulping, the wood chips are then cooked in hot acid (sulfite process) or steeped in a base (sulfate process)

  • These processes dissolve the lignin, and this provides higher quality paper that will not yellow

  • But the process generates a lot of pollution

• After digestion, the fibers are beaten to separate them

• Fibers are washed, bleached, rinsed, sized, dyed, etc, and then rolled into sheets

Reducing Environmental Impact

• To reduce the environmental impact of the paper industry, scientists are attempting to genetic-engineer aspen trees with higher cellulose and lower lignin

Recycling

• Recycling from the current 29% to 60% would save 12.5 million cubic meters of “Roundwood equivalent” per year

• Recycling Newsprint is straight-forward

  • It is shredded and dissolved with chemicals to create a slurry

  • Ink floats to the top and is removed

• Recycled paper may be of poorer quality but it can be cut with “virgin” pulp to improve quality, but improve quality, but this requires more complex monitoring of slurry composition, etc.

• Buy recycled if possible

Bamboo

• 1000 applications for the tree-like grasses

• Used for construction, draining pipes, baskets, mats, and fabrics

• 1000s of species with the greatest diversity in Asia

• 3-5-year-old plants

• In India 2/3 of all the paper is made from bamboo

• In other countries, in the future, bamboo may be a useful alternative to wood pulp to provide much of the world’s requirement for paper

Fiber

• Uses of plant fibers: Textiles (for making fabric), cordage (rope), filler (stuffing for the mattress)

• The most valuable fibers are the ones that are mostly cellulose and cotton

• Surface: on the surface of seeds, fruits, or leaves

  • cotton

• Bast: (aka soft fiber) phloem fibers in the inner bark of dicot stems

  • linen

  • Retting: a process that uses microbial action to degrade the soft tissues, leaving the rough fiber strands intact and freed

• Hard: from vascular bundles (xylem and Phloem) of leaves, these fibers contain lignin too

  • sisal

  • Usually Monocots

  • Decortication: the unwanted tissues are scraped away by hand or machine

Cotton (Gossypium hirsutum)

• Cotton comes from the Arabic word “qutn”

• Most important natural fiber

• Cultivated forms are annuals, and are grown in temperate climates, although the plant is originally a tropical shrub

• Although most cotton is naturally white there are some naturally brown-colored varieties.

  • These can produce green and brown colored fabric without needing to be dye

• There are also Bt varieties (built-in insecticide)

Old World

• Old-world cotton varieties are diploid

• Grown in India for 5,000 years, spread West to the Near East

New World

• New world varieties are tetraploid

• Native to Peru, domesticated 4,500 years ago

Surface Fibers

• Each cotton fiber is part of a single cell in the seed coat epidermis

• The fruit is a capsule (boll) with about 10 seeds

• As the seeds develop the fibers grow out of the seed coat

  • (one seed can have up to 20,000 fibers)

• Eventually, the boll splits open.

• The hairs are each projection from a single seed coat cell

• The cell wall thickens till the lumen almost disappears

• So each fiber is made of almost pure cellulose

Harvesting

• Bolls are mature 50-80 days after flowering

• Plants are sprayed with defoliants to remove the leaves

  • Defoliant: a chemical that removes the leaves from trees and plants, used in warfare.

• Today, the bolls or the seeds are picked by machine

• Next, we have to separate the seeds from the capsule wall

• Then we have to separate the fibers from the seeds

  • Very tedious and time-consuming process

The Cotton Gin

• The cotton gin was invented in 1794 by Eli Whitney.

  • Prior to this, only about 400 bales of cotton a year were harvested

  • After the gin was invented, they could harvest as much as 1800-30,000 bales

  • Ginning: the way a machine tears the fibers lose

After Ginning

• After the cotton is ginned: the fibers are bailed, combed, carded, spun (to make thread), and woven (to make fabric)

• Chemical Processes: mercerization, sizing, and sanforization

  • Mercerization: a finishing process for cotton that improves strength and luster

  • Sizing: the application of materials to the yarn or fabric that produces stiffness or firmness

The “left-overs”

• Ginning cotton produces tons of “left-over” seeds from which oil can be extracted

  • seeds can also be used to make livestock feed

• Raw oil is inedible because it contains gossypol which makes it very bitter

• In 1899, David Wesson, a chemist, developed a way to purify the seed oil and began marketing it as “Wesson Oil”

• In 1911, Proctor and Gamble, using a British technique, hydrogenated the cottonseed oil creating Crisco

• Cotton seed oil might not have become so important if cotton had not been grown for fiber

Linen

• Flax from Linum species is used to make linen

• It is a bast fiber

Flax

• Flax has been used for 10,000 years to make linen

• Oil from the seeds gives Linseed Oil which is used in paints and varnishes

• Like cotton, the fruit is a boll containing 10 brown seeds.

Hemp from Cannabis Sativa

• Hemp from Cannabis Sativa creates bast fibers like those of flax

• Historically used for making canvas (sails and wagon coverings), ropes, and twines

  • Originally used in making blue jeans

• Canada and some states including Texas have legalized the growing of Cannabis Sativa for fiber (industrial fibers)

Sisal

• Sisal: from the agave plant is an example of a hard fiber (from leaves)

• originally used to make rope and coarse garments

• Nowadays it is primarily used to create rope, string, and floormats