Rubber: A simple introduction - Explain that Stuff Tweet by Chris Woodford . Last updated: August 5, 2016. Think of rubber and you probably think of elastic bands, car tires, or pencil erasers. But this super-stretchy material actually finds its way into tens of thousands of different products—everything from rubber stamps and waterproof shoes to surfing wetsuits , swimming caps, and dishwasher hoses. Rubber, which has been commonly used for over 1000 years, once came entirely from natural sources; now rubber products are just as likely to be made artificially in chemical plants. That's largely because we can't produce enough natural rubber to meet all our needs. And that, in turn, is because rubber is so fantastically useful. Let's take a closer look at one of the world's most amazing materials! Photo: Half of the world's rubber is used to make vehicle tires—and at least half of them are wasted in landfills, burned in incinerators, or otherwise dumped. What is rubber? When people talk about "rubber", they don't usually specify what kind.

There are many different kinds of rubber, but they all fall into two broad types: natural rubber (latex—grown from plants) and synthetic rubber (made artificially in a chemical plant or laboratory). Commercially, the most important synthetic rubbers are styrene butadiene (SBR), polyacrylics, and polyvinyl acetate (PVA); other kinds include polyvinyl chloride (PVC), polychloroprene (better known as neoprene), and various types of polyurethane. Although natural rubber and synthetic rubbers are similar in some ways, they're made by entirely different processes and chemically quite different. Natural rubber Natural rubber is made from a runny, milky white liquid called latex that oozes from certain plants when you cut into them. (Common dandelions, for example, produce latex; if you snap off their stems, you can see the latex dripping out from them.

In theory, there's no reason why we couldn't make rubber by growing dandelions, though we'd need an awful lot of them.) Although there are something like 200 plants in the world that produce latex, over 99 percent of the world's natural rubber is made from the latex that comes from a tree species called Hevea brasiliensis, widely known as the rubber tree. This latex is about one third water and one third rubber particles held in a form known as a colloidal suspension. Natural rubber is a polymer of isoprene (also known as 2-methylbuta-1,3-diene) with the chemical formula (C5H8)n. To put it more simply, it's made of many thousands of basic C5H8 units (the monomer of isoprene) loosely joined to make long, tangled chains. These chains of molecules can be pulled apart and untangled fairly easily, but they spring straight back together if you release them—and that's what makes rubber elastic. Photo: Left: Rubber bands are a very familiar everyday use of latex rubber. Right: Guayule : one of many plants from which rubber can be made.

Photo by Peggy Greb courtesy of US Department of Agriculture/Agricultural Research Service (USDA/ARS) . Synthetic rubbers Synthetic rubbers are made in chemical plants using petrochemicals as their starting point. One of the first (and still one of the best known) is neoprene (the brand name for polychloroprene), made by reacting together acetylene and hydrochloric acid. Emulsion styrene-butadiene rubber (E-SBR), another synthetic rubber, is widely used for making vehicle tires. For the rest of this article, we'll concentrate mostly on natural rubber. How is rubber made? It takes several quite distinct steps to make a product out of natural rubber. First, you have to gather your latex from the rubber trees using a traditional process called rubber tapping. That involves making a wide, V-shaped cut in the tree's bark. As the latex drips out, it's collected in a cup. The latex from many trees is then filtered, washed, and reacted with acid to make the particles of rubber coagulate (stick together). The rubber made this way is pressed into slabs or sheets and then dried, ready for the next stages of production.

By itself, unprocessed rubber is not all that useful. It tends to be brittle when cold and smelly and sticky when it warms up. Further processes are used to turn it into a much more versatile material. The first one is known as mastication (a word we typically use to describe how animals chew food). Masticating machines "chew up" raw rubber using mechanical rollers and presses to make it softer, easier to work, and more sticky. After the rubber has been masticated, extra chemical ingredients are mixed in to improve its properties (for example, to make it more hardwearing). Next, the rubber is squashed into shape by rollers (a process called calendering) or squeezed through specially shaped holes to make hollow tubes (a process known as extrusion). Finally, the rubber is vulcanized (cooked): sulfur is added and the rubber is heated to about 140°C (280°F). Photo: In 1839, American inventor Charles Goodyear (1800–1860) developed the vulcanization (heat-treatment) process that makes rubber harder and more durable.

He'd spent many years as a struggling inventor, trying desperately to turn rubber into a useful product, when he accidentally dropped some rubber on a hot stove and watched it "cook" itself into a much more useful form: the black, vulcanized material most of us know as rubber to this day. Despite developing one of the most useful materials of all time, Goodyear never made much money from his invention and died deeply in debt. Fortunately, his name lives on in the Goodyear tire company—and his superb contribution to materials technology has never been forgotten. Photo courtesy of US Library of Congress . Where does rubber come from? As its name suggests, the rubber tree Hevea brasiliensis originally came from Brazil, from where it was introduced to such countries of the Far East as Malaysia, Indonesia, Burma, Cambodia, China, and Vietnam. During World War II, supplies of natural rubber from these nations were cut off just when there was a huge demand from the military—and that accelerated the development of synthetic rubbers, notably in Germany and the United States. Today, most natural rubber still comes from the Far East, while Russia and its former republics, France, Germany, and the United States are among the world's leading producers of synthetic rubber.

The world's largest single source of latex rubber is the Harbel Rubber Plantation near Monrovia in Liberia, established in the 1920s and 1930s by the Firestone tire company. How does vulcanization make rubber stronger? Rubber—the kind you get from a tree—starts off as white and runny latex. Even when it's set into a product, this latex-based, natural rubber is very squashy, pretty smelly, and not very useful. The kind of rubber you see in the world around you, in things like car and bicycle tires, is vulcanized: cooked with sulfur (and often other additives) to make it harder, stronger, and longer lasting. So what's the difference between raw, latex rubber and cooked, vulcanized rubber? In its natural state, the molecules in rubber are long chains that are tangled up and only weakly linked together. It's relatively easy to pull them apart—and that's why latex rubber is so stretchy and elastic. When latex is vulcanized, the added sulfur atoms help to form extra bonds between the rubber molecules, which are known as cross-links.

These work a bit like the trusses you see on a bridge, tying the molecules together and making them much harder to pull apart. Artwork: Top: Natural, latex rubber is easy to pull apart because the long polymer molecules it contains (made from carbon and hydrogen atoms) are only weakly linked together. Bottom: When natural rubber is cooked with sulfur, the sulfur atoms form extra cross-links (shown here as yellow bars) "bolting" the molecules together and making them much harder to pull apart. This process is called vulcanization and it makes the strong, durable, black rubber we see on things like car tires. What do we use rubber for? Photo: Three everyday uses of rubber. Top: A latex pencil eraser; Middle: the tough vulcanized rubber drive belt from a vacuum cleaner ; Bottom: the waterproof rubber gasket that seals a washing machine door tight. The physical and chemical properties of a material dictate what we use it for. Even if you know absolutely nothing about the real-world uses of rubber, you can probably make some very good guesses.

For example, everyone knows rubber is strong, stretchy, flexible (elastic), durable, and waterproof, so it's no surprise to find it used in things like waterproof clothes and wellington boots, sticking plasters, and adhesives . The most important use of rubber is in vehicle tires; about half of all the world's rubber ends up wrapped around the wheels of cars, bicycles , and trucks! You'll find rubber in the hard, black vulcanized outsides of tires and (where they have them) in their inner tubes and liners. The inner parts of tires are usually made from a slightly different, very flexible butyl rubber, which is highly impermeable to gases (traps them very effectively), so tires (generally) stay inflated for long periods of time. The fact that rubber can be made either soft or hard greatly increases the range of things we can use it for. Soft and stretchy latex is used in all kinds of everyday things, from pencil erasers, birthday balloons, and condoms to protective gloves, adhesives (such as sticky white PVA), and paints.

Harder rubbers are needed for tougher applications like roofing membranes, waterproof butyl liners in garden ponds, and those rigid inflatable boats (RIBs) used by scuba divers. Because rubber is strong, flexible, and a very poor conductor of heat and electricity, it's often used as a strong, thin, jacketing material for electrical cables, fiber-optic cables , and heat pipes. But the range of applications is truly vast: you'll find it in everything from artificial hearts (in the rubber diaphragms that pump blood) to the waterproof gaskets that seal the doors on washing machines! Neoprene (polychloroprene) is best known as the heat-insulating, outer covering of wetsuits —but it has far more applications than most people are aware of. Medical supports of various kind use it because, tightly fitted, it compresses and warms injured bits of your body, promoting faster healing. Since it's flexible and waterproof, it's also widely used as a building material, for example, as a roof and floor sealant, and as a spongy absorber of sound and vibration in door and window linings.

Although the world has a vast appetite for new rubber, we also produce a huge quantity of rubber waste, especially from discarded vehicle tires—and that's becoming an important raw material in its own right. According to the Rubber Manufacturers Association, the United States alone produced almost 270 million waste rubber vehicle tires in 2011, which is about a third of all the tires used worldwide. While some of these are retreaded and others are ground up to make a low-grade aggregate that can be used for the floors in things like children's playgrounds, over half of them are wasted (either burned as a fuel or buried in landfills). Rubber manufacturers have recently turned their attention to recycling tires in all kinds of new ways, making everything from mouse mats and sports bags to shoe soles and car components. Photo: Half of all rubber is used in vehicle tires, and hundreds of millions are wasted each year. I've made a very slight difference to the problem by buying this recycled rubber mouse mat, made from an old car tire. It's colored black because it's made from hard vulcanized rubber.

A brief history of rubber 1000CE: Indians living in Central and South America have learned how to made waterproof clothes and shoes using latex from rubber trees. They call rubber trees "cahuchu" (crying wood), which is why the French still call rubber caoutchouc (pronounced "cow-chew") today. 1731: During an expedition to South America, French explorer Charles Marie de La Condamine (1701–74) sends back samples of rubber to Europe, prompting intense scientific interest. 1770: The discoverer of oxygen, English scientist Joseph Priestley (1733–1804), finds he can use pieces of rubber to erase the marks made by pencil on paper. In England, erasers are still widely called "rubbers" today. 1791: Englishman Samuel Peal develops a method of waterproofing cloth with a rubber solution. 1818: Scottish medical student James Syme (1799–1870) uses rubber-coated cloth to make raincoats.

1823: Scotsman Charles Macintosh learns of Syme's discovery, refines it, and patents it, earning fame and fortune as the inventor of the rubberized, waterproof coat. Waterproof coats have been known as "Mackintoshes" (with a slight variation of spelling) ever since. 1839: American inventor Charles Goodyear (1800–1860) accidentally discovers how to vulcanize rubber after dropping a piece of the material (which has been treated with sulfur) onto a hot stove. 1876: Intrepid English explorer Sir Henry Wickham (1846–1928) smuggles thousands of seeds from the rubber tree Hevea brasiliensis out of Brazil and back to England. The English grow the seeds at Kew Gardens just outside London and export them to various Asian countries, establishing the giant plantations that now supply much of the world's rubber. 1877: US rubber manufacturer Chapman Mitchell develops the first commercial process for recycling rubber from scratch. 1882: John Boyd Dunlop (1840–1921) invents the pneumatic (air-filled) rubber tire.

The development of gasoline-powered cars with rubber tires leads to a huge increase in the need for rubber. 1883: US chemist George Oenslager (1873–1956) develops a much faster way of vulcanizing rubber using chemicals called organic (carbon-based) accelerators. 1930: A team of US chemists at the DuPont company, led by Wallace Carothers (1896–1937), develop a revolutionary synthetic rubber called polychloroprene and sold as neoprene. (Shortly afterward, the same group developed an even more revolutionary material: nylon .) Plastics On other sites The Story of Rubber : Learn about the history and development of rubber with the Polymer Science Learning Center. International Institute of Synthetic rubber Producers : Website includes some useful PDF summaries of synthetic rubbers, including polybutadiene rubber, butyl rubber, and different kinds of synthetic elastomers. Click on "Synthetic rubber" on the menu. Rubber Manufacturers Association : The US trade association for tire manufacturers has quite a lot of useful news and statistics. Articles In Thailand, Rubber Price Plunge Has Political Cost by Thomas Fuller.

The New York Times, August 29, 2013. It's easy to forget that commodities like rubber provide a living for many of the world's people. What happens to their lives as prices rise and fall? Recipe for Green Tires: Plants, Not Petroleum by Steven Ashley. The New York Times, June 18, 2010. From recycling to new kinds of synthetic rubber, this article explores the various ways of reducing the environmental impact of vehicle tires. Books For older readers Rubber Technology by Maurice Morton. Springer, 1987. Explains the basic science of rubber polymers before looking at natural and synthetic rubbers. Rubber Compounding: Principles: Materials, and Techniques, Second Edition by Fred Barlow. CRC Press, 1993. A detailed guide to manufacturing rubber compounds using a variety of additives. Natural Rubber: Biology, Cultivation and Technology by M.R. Sethuraj (Editor) and Ninan T. Mathew. Elsevier, 1992. A detailed, very comprehensive guide to rubber as a crop, including related topics such as guayule. For younger readers the rubber tree harvest the latex at the right time.

Before we see how to make the tapping, let us look back at what we learned in the course on plant stems. Let us see how the trunk of the rubber tree is made. THE TRUNK OF THE RUBBER TREE If you cut through a trunk, you see several layers. On the outside is the bark, which is about 6 millimetres thick. In the centre is the wood, Between the wood and the bark there is a layer which cannot be seen with the naked eye, because it is very thin. This is the cambium layer. The cambium makes the tree grow, by producing wood and bark. So you must not damage it if you want the tree to grow normally. If you look at rubber tree bark with a microscope, you will see several layers. One of these, the deepest, contains little channels called lactiferous vessels This layer is next to the cambium. The lactiferous vessels are little tubes that produce latex. In tapping, you cut these little tubes containing latex. But you must take care not to cut the cambium.

When a tree is 50 centimetres in circumference at a height, of 1 metre from the ground, that is, 5 years after it has been put in the plantation, you can begin to tap the tree. To start the tapping, take a metal ribbon attached to a wooden lath 1.10 metres long. This metal ribbon is at an angle of 30 degrees to the horizontal. Roll the metal ribbon round the tree. With an awl (an iron point), make a cut along the ribbon. The cut ends when you have gone right round the tree. The beginning of the cut and the end of the cut are on the same vertical line. With the awl make a vertical channel from the lower edge of the cut. The cut and the channel must be deepened. This is done with a gouge, a tool that is used by pushing it so as to remove bark. Push the gouge several times along the cut and the channel, taking away a very little bark at a time. You do this so as to cut the bark as close as possible to the cambium, but without damaging it.

As the bark is about 6 millimetres thick, the cut must be 4.5 millimetres deep. The vertical channel is 25 centimetres long. At the lower end of this channel, put a gutter. Below that, put a cup called a latex cup. Tie it to the tree. The latex flows along the cut, into the channel, and at last, through the gutter, it drops into the cup. The latex that flows when you first make the cut is not good for harvesting, so for several days you do not harvest any latex, but all the same you must come and cut the bark. go to the plantation to reopen the cut. Begin by taking away the latex that has coagulated on the cut and put it in a basket. Take away also any latex that has flowed over the bark. Then, with the gouge, take out a little piece of bark, 1.5 millimetres thick, without touching the cambium. Make the cut as far as 1.5 millimetres from the cambium. The latex flows along the cut, then down the channel, and through the gutter, it drops into the latex cup.

Then, 4 hours later, come again and collect what is in the cup. Two days afterwards, clean out the cup. One man can tap 440 trees a day. The man who does the tapping is called the tapper. If you make the cut badly, and if you touch the cambium, the bark closes up badly. It splits and turns brown. Then the tapping must be stopped. There is a product for treating this browning of the bark. The trees must be tapped very early in the morning, at daybreak, so as to harvest as much latex as possible. If you make the cuts late in the day, you harvest less latex, one third less. But you must not tap the trees every day. Each tree should be tapped on a fixed day. Thus, one tree is tapped on Monday and Thursday; another, on Tuesday and Friday; a third on Wednesday and Saturday. Each tapper can tap 440 trees. So he will have 3 groups of 440 trees, since he will tap each tree only twice a week.

He will have: Tapping Trees for Natural Rubber - How Rubber Works | HowStuffWorks Tapping Trees for Natural Rubber Bryn Campbell/ Getty Images ­The Mesoamerican peoples, such as the Mayans and the Aztecs , first tapped rubber from one of several trees found in Central and South America: Hevea braziliensis: the most common commercial rubber tree from Brazil Hevea guyanensis: originally found in French Guyana Castilla elastica: sometimes called the Mexican rubber tree or the Panama rubber tree Explorers and colonists brought samples of these trees when they headed back to Europe . Eventually, seeds from these trees were transported to rubber plantations in other tropical climates during the era of European colonialism. Up Next Currently, most natural rubber comes from Latin American-derived trees transplanted to Southeast Asia ( Thailand , Indonesia , Malaysia ), as w­ell as India , Sri Lanka and Africa . In these areas, you can find other rubber-producing trees including: Ficus elastica: found in Java and Malaysia. This species is also a common tropical houseplant.

Funtumia elastica: grows in West Africa Landolphia owariensis located in the Congo basin Of all of these trees, the best rubber-producing tree is H. braziliensis. It takes about six years for a rubber tree to grow to a point where it's economical to harvest the sap, which is called latex. Here's how you tap one: The collector makes a thin, diagonal cut to remove a sliver of bark. The milky-white latex fluid runs out of the bark, much as blood would run out of a small superficial wound on your skin. The fluid runs down the cut and is collected in a bucket. After about six hours, the fluid stops flowing. In that six-hour period, a tree can usually fill a gallon bucket. The tree can be tapped again with another fresh cut, usually the next day. The Mesoamericans would dry the collected rubber latex and make balls and other things, like shoes. They would dip their feet in the latex and allow it to dry. After several dips and dryings, they could peel a shoe from their feet. Next, they smoked their new rubber shoes to harden them.

The Mesoamericans also waterproofed fabrics by coating them with latex and allowing it to dry. This process was used to make rubber items until around the 1800s. Columbus brought back rubber balls with him upon returning from his second voyage to the New World, and in the early 1700s, rubber samples and trees were brought back to Europe. At that time, rubber was still a novelty. Rubber made in the Mesoamerican way resembled a pencil eraser. It was soft and pliable. In 1770, the chemist Joseph Priestley was the first to use rubber to erase lead marks. He coined the word "rubber" because he could remove the lead marks by rubbing the material on them. While it was useful for waterproofing fabrics and making homemade shoes, rubber had its problems. You can see these problems for yourself with a simple rubber pencil eraser. Take that eraser and place it under intense heat for several minutes. What do you see? The eraser should get very soft and sticky. Next, do the opposite -- place the eraser on ice or in a freezer for several minutes. What do you see? The eraser should get hard and brittle.

The same thing happened to early rubber. Imagine what it would be like to walk around in your rubber shoes on a hot or cold day back then. The shoes wouldn't wear well. Likewise, your rubberized clothing might stick to your chair while you were sitting, especially on a warm day. Keep reading to learn what makes rubber so intrinsically stretchy. Bounce into rubber: Natural latex from Thailand Important Announcement about Online Courses and LEARN NC . Important Message about LEARN NC LEARN NC is evaluating its role in the current online education environment as it relates directly to the mission of UNC-Chapel Hill School of Education (UNC-CH SOE). We plan to look at our ability to facilitate the transmission of the best research coming out of UNC-CH SOE and other campus partners to support classroom teachers across North Carolina. We will begin by evaluating our existing faculty and student involvement with various NC public schools to determine what might be useful to share with you. Donât worry! The lesson plans, articles, and textbooks you use and love arenât going away. They are simply being moved into the new LEARN NC Digital Archive.

While we are moving away from a focus on publishing, we know itâs important that educators have access to these kinds of resources. These resources will be preserved on our website for the foreseeable future. That said, weâre directing our resources into our newest efforts, so we wonât be adding to the archive or updating its contents. This means that as the North Carolina Standard Course of Study changes in the future, we wonât be re-aligning resources. Our full-text and tag searches should make it possible for you to find exactly what you need, regardless of standards alignment. Bounce into rubber: Natural latex from Thailand This lesson for grade nine investigates natural latex rubber sources from Thailand. Students complete research and experiments to determine which plants from Thailand are sources of latex, and explore images and audio recordings of rubber harvesting in Thailand. A lesson plan for grades 7 and 9 Science and Social Studies On a rubber tree plantation, white latex sap drips into a collection pan. (Photograph by Margery H. Freeman .

More about the photograph ) Learn more Related pages Strive to survive: Part 2 : Students will explore the concepts of survival and natural selection from scientific and historical points-of-view using inquiry-based investigations, internet research and other strategies. Marvelous metamorphosis : Most kids love insects. This integrated unit will enable students the opportunity to observe, identify, and describe the life cycle a mealworm goes through during his metamorphosis into a grain beetle. Mix and match ecology: Symbiosis : In this high-school biology lesson, students gain an understanding of the three kinds of symbiotic relationships by creating relationships between imaginary animals. Related topics Please read our disclaimer for lesson plans. Legal The text of this page is copyright ©2008. See terms of use . Images and other media may be licensed separately; see captions for more information and read the fine print . Print Pin It Rubber latex is one of the most important products to come out of the rainforest. Thailand is a major world supplier of natural rubber latex. More than 2,500 species of plants produce natural latex. Many of these plants are trees grown in tropical climates. Some of those plants come from Thailand.

In this lesson, students will conduct online and lab research and two experiments to answer these questions: What is natural rubber latex? What are its properties? What kind of plants from Thailand produce rubber? Where do they grow? What is the process for extracting rubber from plants? What other plants contain latex? Learning outcomes Students will: understand the properties of natural rubber latex, how sap is harvested, and how rubber is formed from tree sap make observations and complete research of the properties of latex rubber determine if sap gathered from plant samples is latex rubber identify plants that produce natural rubber latex identify rubber latex-producing plants that can be found in Thailand and where those plants grow within the country Teacher planning Markers or colored pencils Pre-activities Familiarize yourself with Thailand by reading sites such as the CIA World Factbook’s overview of Thailand , encyclopedias, or other reference sources. (For more suggestions, see “Websites” below.) Familiarize yourself with natural latex, which is the protective fluid contained in tissue beneath the bark of the rubber tree, Hevea brasiliensis. The tree originated in Brazil, and latex was originally gathered from wild trees in the jungles of Brazil in the 1870s.

Thailand now has extensive rubber tree plantations and harvests latex. For more information about natural latex, see “Websites.” You may also want to familiarize yourself and your students with the vocabulary listed with this lesson plan. Collect needed materials, including plant samples, before the lesson. Plant samples Plant samples used should include at least some of the following latex-producing plants. Other non-producing samples can also be included. All plants should be identified by the instructor but not the students before distribution to groups. Milkweed (Asclepiadaceae) IMPORTANT: Milkweed sap contains a toxin that is a powerful eye irritant. Have students wear safety goggles when handling milkweed and ensure that they wash their hands afterward. Sunflower (Helianthus annuus) To find suppliers of plants in your area, consult the Wildflower Center from the University of Texas at Austin . Safety precautions People with a latex allergy should not do this laboratory. Liquid latex is packaged in ammonia which acts as a preservative. Neutralization with vinegar (acetic acid) will cause the latex to solidify into rubber very quickly. The ammonia and vinegar have irritating fumes, but latex is not considered hazardous. Students should wear safety goggles or glasses at all times in the laboratory.

Milkweed sap contains a toxin that is a powerful eye irritant. Have students wear safety goggles when handling milkweed and ensure that they wash their hands afterward. Disposal: Materials can be safely disposed of in the trash. Clean-up: Latex spilled on non-porous surfaces can be allowed to dry and then peeled off. If spilled on clothing, a dry cleaner can often remove most of a latex stain. Activities Activity one: Is it rubber latex? Part 1 4 teaspoons water Paper towels Tell students that liquid latex is often mixed with water and acid to make it thicker. This process is called coagulation. Mixing latex with vinegar (acetic acid) will cause the latex to solidify into rubber very quickly. Give the students the following instructions: Add 1 tablespoon of latex into a paper cup. Measure 1 tablespoon of water and stir it into the latex with your stick. Stir the mixture. Observe closely as you add 1 tablespoon of vinegar and stir. Record any observations on your experiment log. Describe in detail any changes you notice when you add vinegar to your mixture of water and latex. Use your fingers to remove the mass from the cup and remove the stirring rod.

Carefully squeeze the mass while washing it under water in a small bucket or bowl. Form the mass into a ball. Dry it with a paper towel. Drop the mass on the floor and describe what happens. Describe the polymer on your experiment log. Part 2: Where does the rubber grow? Introduce this part of the lesson by giving students the following background information: The invention of the automobile increased the demand for rubber, and by 1914 wild rubber plants could not supply enough. Rubber plantations were established in Africa, Central and South America, and in Asian countries such as Indonesia, Thailand, Vietnam, and the Philippines. The cultivated rubber trees produce more latex than the wild trees. Today, more than 80% of the world’s natural rubber is grown in Thailand, Indonesia, and Malaysia. The Hevea Brasiliensis tree from which latex is harvested is most productive within a narrow belt extending about 700 miles on either side of the equator. About 100 trees are planted per acre. Rubber trees are planted in straight rows and dot the landscape of southern Thailand. Use a projector to show students a map of Thailand , and give each student the blank map of Thailand handout.

Have the students research the rubber tree and discover as much information as they can about where the tree grows. What kind of climate does it need to thrive? What kind of forest does it grow in? Have the students get back into groups. Drawing on the information they gathered in their research, have each group look at the following maps and infer where the rubber trees are most likely to grow in Thailand. (Tip: click on the link below each image for the largest version, and then click on the map to zoom in.) Instruct the students to color in the blank map with the locations where rubber trees would be most likely to grow. Activity three: Discovering the latex rubber process Introduce the activity by sharing the following information with the students: Rubber trees grow best in hot, moist climates. The trees grow straight, 18-20 feet high with smooth bark and dark, shiny leaves. Rubber trees produce pale yellow blossoms, which give way to seed pods, each of which contains three brown seeds about 2-3 cm long. Latex containing rubber flows through the outer wood of the trunk, just under the bark. Workers — called tappers — collect the latex by cutting a shallow groove in the bark about three feet from the ground.

At the bottom of the cut, a small spout is inserted into the tree, and a cup hangs below it to catch the drops of latex that ooze from the cut. Trees are generally tapped every day for 15 days, and then rested for 15 days. The latex is poured into tanks, and an equal amount of water is added. This liquid is strained to remove dirt. Formic acid is added to make the mixture form solid particles, which rise to the surface to form a crust of rubber. This is fed through rollers to squeeze out the water to make a solid sheet of rubber. This rubber is crude rubber, and is ready to be shipped to factories to be processed in different ways to make many different products. Tell students that they will explore the rubber-making process in pictures and in audio recordings. They will then work in their groups to create a brochure about the process of making rubber from natural latex in Thailand. Tell the groups the brochure must be full color and must “sell” the natural rubber process. Students must include the rubber images made available in this lesson, their written text, a title or logo, some text âsellingâ the latex process, and any references used.

Pre-teach any vocabulary words that the students might need to use in order to describe their pictures and sounds. Give each group access to the following images of the rubber-making process from the LEARN NC collection. (Note: the following two images are from Vietnam, but they show the same rubber-making process that is used in Thailand.) You may choose to set up a file with the digital image photos on student-accessible computers. If students don’t have access to computers, you may copy the images into a Word document and hand out printed copies: Making rubber: Separating and hanging Have the groups sketch out some rough ideas of how they want their brochure to look — including any graphics, clip art, titles, etc. Using either the printed images, scissors, glue, or the digital images and software, have the students try out different formats to fit their text. Have the students edit their text to fit their layout. If students are using software, have them transfer their rough sketches to the computer. Depending on the software you’re using, there may be templates or wizards available to provide students with even more ideas. Students can also use their maps from part two of this lesson on their brochures. Display the resulting brochures and have students discuss the rubber-making process.

Ask students in what order the process happens. Have students score each otherâs brochures using the rubric below, under “Assessment.” Assessment Assess student responses and adjust questioning and activities as needed. Grade students on completeness of work. The following rubric may be used to assess the brochure in activity three. You may have student groups assess each other’s brochures. Brochure rubric There are many citations from a variety of sources accurately listed on the brochure. There are some citations from a variety of sources accurately listed on the brochure. There are a few citations accurately listed on the brochure. Incomplete citations are listed on the brochure. Extension Any of the following options may be used to extend this lesson: Visit the Silly Putty: Synthesizing a Polymer page on the Louisiana State University Department of Chemistry website. This page in PDF format includes instructions for making Silly Putty and explains the chemistry behind it. Have the class read the article “ Natural Rubber — History and Developments in the Natural Rubber Industry .” Discuss in class how these technologies have affected the growth of the natural rubber industry. Mind map the uses of rubber.

For specific instructions, you can use the “Many Uses of Rubber” student handout, available on the “ Inventions of Necessity: Synthetic Rubber ” lesson from the Science Net Links website. Modifications and alternative assessments For students with certain learning disabilities, teachers may opt to accept verbal responses rather than written responses for the brochure text. Teachers may also want to be sure and group students of differing abilities into groups. Critical vocabulary Rubber latex The milky sap of any of several trees of the genus Hevea, especially Hevea brasiliensis, from which natural rubber is derived. Elasticity White Lotus Ltd., 2000. — Worldcat record Engel, David and Phummai, Suchart. A Field Guide to Tropical Plants of Asia . Timber Presss, 2002. Available via Google books North Carolina Essential Standards Science (2010) Biology Bio.2.1 Analyze the interdependence of living organisms within their environments. Bio.2.1.1 Analyze the flow of energy and cycling of matter (water, carbon, nitrogen and oxygen) through ecosystems relating the significance of each to maintaining the health...

Social Studies (2010) Grade 7 7.E.1 Understand the economic activities of modern societies and regions. 7.E.1.1 Explain how competition for resources affects the economic relationship among nations (e.g. colonialism, imperialism, globalization and interdependence). 7.E.1.2 Explain the... 7.G.1 Understand how geography, demographic trends, and environmental conditions shape modern societies and regions. 7.G.1.1 Explain how environmental conditions and human response to those conditions influence modern societies and regions (e.g. natural barriers,... North Carolina curriculum alignment Rubber Tree (Hevea brasiliensis) | Rainforest Alliance Mexico & Central America South America Fact First discovered by the ancient Olmec, Maya, and Aztec, the latex sap from the rubber tree was once used to make rubber balls, to waterproof clothes and even to form homemade shoes. Botany In the wild, the rubber tree will grow to heights of 100 to 130 feet, and can live up to 100 years. Its most famous feature is the milky white sap, known as latex, which flows freely from the tree when a sliver of bark is removed.

A rubber tree, also referred to as rubberwood, can be tapped for latex once it reaches approximately six years of age. In order to reproduce, the fruit of the rubberwood burst open when ripe, scattering its many seeds in an area spanning up to 100 feet from the tree. Habitat Hevea brasiliensis is a species of rubberwood that is native to rainforests in the Amazon region of South America, including Brazil, Venezuela, Ecuador, Colombia, Peru, and Bolivia. These trees are generally found in low-altitude moist forests, wetlands, riparian zones, forest gaps, and disturbed areas. It is a quick growing tree, often the first to establish itself when a gap in the canopy is produced but may be shaded out as more trees fill in the canopy opening. Today, commercially-produced rubber can also be found throughout much of Southeast Asia and Western Africa. Significance to Humans First discovered by the ancient Olmec, Maya, and Aztec, the latex sap from the rubber tree was once used to make rubber balls, to waterproof clothes, and even to form homemade shoes.

Today, the latex sap from the rubber tree is still used in the modern processing of rubber and is often a substantial source of income for indigenous populations. Did you know? Historically, cattle ranchers and rubber tappers have disagreed over the rights to clear forest land. Cutting down the forest is not only detrimental to the species that depend on that land, but also damaging to the people that earn a living by sustainably harvesting what the forest provides. Many indigenous people depend on these sources of income to provide for their families and communities. Chico Mendes, a Brazilian rubber tapper, became famous when he organized the National Council of Rubber Tappers in Brazil to help protest against the clear cutting of land for cattle grazing. Thanks to his efforts, the union gained the support of the Brazilian government and was able to set aside crucial "extractive reserves" within Brazil. These reserves allow for the sustainable harvest of goods, such as rubber or nuts, and protect against the clear cutting of trees. In 1988, Chico Mendes was murdered for his work to create extractive reserves and protect the rainforest. His efforts have been carried on by his coworkers and supporters across the world. Sources

Question: What word is used to describe how to remove rubber from trees?
Answer: Tap