09 Title of Reading Materials

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SCE3103 Exploring Materials

1.1 Natural MaterialsA natural material is any substance that is produced by natural processes. The mainsources of natural material are derived from plants, animals, or the ground. Minerals andthe metals that can be extracted are also considered as natural materials.

Some of the properties of natural materials are:

It is usually valuable It is pure and natural It can easily decompose and degrade It is derived from plants, animals, or from the ground

Figure 1.2 Natural materials(Source: http://images.google.com)

Some examples of natural materials are:

Soil Rubber

Petroleum (Fuel)

Inorganic materials (stone)

Composites (clay, porcelain)

Wood (rattan, bamboo, bark )

Metal (copper, bronze, iron, gold, silver)

Natural fibers (wool, silk, cotton, flax, hemp, jute, kapok)

There are many uses of natural materials. They are chosen to make certain objectsbecause of their properties. Wood, for example is used to make furniture, frame of

doors. It is used to make furniture because its moderate hardness, elasticity andtoughness make it possible to shape them by cutting with steel tools such as saws,chisels and planes. When nails or screws are driven into wood, they are gripped verysecurely and the wood does not usually split open. Wood is a very poor thermalconductor, so it helps to conserve energy when used in doors and window frames.Metals can be used in making structures for building. They are shiny, hard and strongmaterials. Petroleum can be used in manufacturing detergent and plastic. Natural fiberssuch as cotton, silk and wool are widely used in making clothes because they are strong,durable and have a smooth and soft texture.

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Surf the Internet (1 hour)

Access the internet to gather information on other uses of naturalmaterials. Relate their uses to their properties and discuss why thesematerials are used for making the objects.

1.2 Manufactured Materials

Manufactured materials are made by processes which result in raw materials beingtransformed into different kinds of substances through chemical processes. It isnecessary to distinguish carefully between the materials or substances of which anobject is made of. For example: stone is a natural material and a stone pebble on abeach is a natural object because it is not shaped by human activity. A cut stonebuilding-block or a roofing slate is a manufactured object although both are made ofnatural materials.

Types of manufactured materials include alloys, plastics, composite materials, industrialchemicals, soaps and detergents.

Figure 1.3 Manufactured materials(Source: http://google.images.com)

Some of the properties of manufactured materials are:

Durable Light weight

High Strength Design for flexibility Doesnt decompose and degrade easily

It is usually made from several natural materials Can be created by physical and chemical processes

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When we make something, we have to choose materials which have the right properties.Figure 1.4 compares the everyday uses of manufactured materials on the basis of theirproperties.

ManufacturedMaterials

ExamplesComposition of

Naturalmaterials

Properties

Alloys

Pewter 97% tin and 3%antimony

Does not corrode, shiny,attractive

Stainless steel 74% iron, 18%chromium, 8%nickel

Does not rust, hard, strong

Plastics

Styrene-butadienerubber

Styrene,butadiene

Can be moulded under heatand pressure, strong and light

nylon Diamine,

dicarboxylicacid

strong, cheap, extremely

durable

Compositematerials

Soda lime glassfor bottles

Sand(silicondioxide)

Easy to mould and shape,transparent, low melting point

ceramics Clay(aluminiumoxide, silicondioxide, sand,feldspar)

Good insulator of electricityand heat, inert to chemicals,hard and strong but brittle

Industrial

chemicals

Ammonia Nitrogen gasand hydrogengas

Colourless, pungent, verysoluble in water, does not burnin air

Sulphuric acid Sulphur,oxygen, water

Strong acid, non-volatile,corrosive

Soaps anddetergents

Soap Animal fats andvegetable oils

Cleaning agent in soft water

Detergent petroleum Cleaning agent in soft andhard water

Figure 1.4 Uses of manufactured materials and their properties

Thinking (2 hours)

Based on your study, construct a graphic organiser to compare andcontrast between properties of natural and manufactured materials.

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Discussion ( 2 hours)

Observe the pictures below carefully and state the natural materialsand the manufactured materials needed to make them. Suggestother possible materials that could be used and state whether theseitems are natural or manufactured materials.

References

http://en.wikipedia.org/wiki/Natural_material(natural materials)

http: // www.creamicindustry.com/CDA/Articles( uses of ceramics)

www.schoolsliason.org.uk/woodgate/materials/materials0.1.htm(natural and manufactured materials)

www.find-health-articles.com/msh-manufactured-materials(manufactured materials)

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http://en.wikipedia.org/wiki/Natural_materialhttp://www.creamicindustry.com/CDA/Articleshttp://www.schoolsliason.org.uk/woodgate/materials/materials0.1.htmhttp://www.find-health-articles.com/msh-manufactured-materialshttp://images.search.yahoo.com/search/%20http:/images.search.yahoo.com/search/images/view?back=http%3A%2F%2Fimages.search.yahoo.com%2Fsearch%2Fimages%3Fp%3Dcar%26ei%3DUTF-8%26fr%3Dyfp-t-501%26fp_ip%3DMY%26x%3Dwrt&w=700&h=445&imgurl=cgtalk.ru%2Fgallery%2Ffiles%2F2%2F2%2F8%2F5%2Fred_car_537595.jpg&rurl=http%3A%2F%2Fwww.cgtalk.ru%2Fgallery%2Fmisc.php%3Fdo%3Dprintimage%26i%3D1595&size=66.7kB&name=red_car_537595.jpg&p=car&type=jpeg&no=4&tt=13,147,645&oid=7c1709a9bdb61f82&ei=UTF-8http://images.search.yahoo.com/search/%20http:/images.search.yahoo.com/search/images/view?back=http%3A%2F%2Fimages.search.yahoo.com%2Fsearch%2Fimages%3Fp%3Dcomputer%26ei%3DUTF-8%26fr%3Dyfp-t-501%26fp_ip%3DMY%26x%3Dwrt&w=390&h=246&imgurl=www.somaliedu.com%2FSomali%2520Education%2FImages%2Fcomputer.jpg&rurl=http%3A%2F%2Fwww.somaliedu.com%2FSomali%2520Education%2FWarar%2FAgoosto_2004_Cdyaad_soomaaliyed.htm&size=8.6kB&name=computer.jpg&p=computer&type=jpeg&no=3&tt=9,131,286&oid=b63c2625be61b5ea&ei=UTF-8http://images.search.yahoo.com/search/%20http:/images.search.yahoo.com/search/images/view?back=http%3A%2F%2Fimages.search.yahoo.com%2Fsearch%2Fimages%3Fp%3Dhouse%26toggle%3D1%26cop%3Dmss%26ei%3DUTF-8%26fp_ip%3DMY%26fr%3Dyfp-t-501%26b%3D1&w=2862&h=1704&imgurl=osx.lps.org%2Fmanila%2Fdmaw%2Fhouse.jpg&rurl=http%3A%2F%2Fwww.sitebelt.com%2Fsearch%2FHouse.html&size=575.4kB&name=house.jpg&p=house&type=jpeg&no=1&tt=16,232,314&oid=98a4c833ffc37512&ei=UTF-8http://en.wikipedia.org/wiki/Natural_materialhttp://www.creamicindustry.com/CDA/Articleshttp://www.schoolsliason.org.uk/woodgate/materials/materials0.1.htmhttp://www.find-health-articles.com/msh-manufactured-materials


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TOPIC 13 NATURAL MATERIALS- RUBBER

Synopsis

There are many things around you that are made from rubber. In this topic, you will belearning about the composition of rubber, how it is processed, its properties and its usesin our daily lives.

Learning Outcomes

1. State the composition of rubber2. Explain the processing of rubber3. State the properties of rubber

4. State the uses of rubber in our daily life

Overview

Figure 13.1 Overview of contentContent

Take a rubber band and stretch it. What do you observe? Release the rubber band.What do you observe? The rubber band stretches when pulled and when the force isreleased it returns to its original length or shape. The rubber band is made from rubber,which is a type of polymer called elastomer. As an elastomer, the rubber band isdifferent from other solid materials in that it can be stretched to more than four times its

original length and when it is released it will readily return to its original length. Thisproperty is called elasticity.

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RUBBER

Composition ofrubber

Processing ofrubber

Properties ofrubber

Uses of rubber inour daily life


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13.1 Composition of rubber

Natural rubber is a addition polymerofisoprene, C5H8. The IUPAC name for isoprene is2-methylbut-1,3-diene. Rubber, for example, is very elastic and is made from isoprenemonomers.

In naturally occurring rubber, the chain extensions are on the same side of the doublebond. This form is called poly-cis-isoprene, with a molecular weight of 100,000 to1,000,000. Because rotation about the carbon-carbon double bond does nor readilyoccur, the orientation of the groups bound to the carbons is rigid. This makes rubberproducts easily oxidized by air, heat and mechanical movements like bending. Theoxidized rubber cracks and peels off easily.

Polyisoprene is also created synthetically, producing what is sometimes referred to as"synthetic natural rubber".Synthetic rubber is produced from the polymerisation of 2-chlorobuta-1,3-diene.

n CH2=CH-C=CH2 ~(CH2-CH=C-CH2) ~

Cl Cl

2-chlorobuta-1,3-diene neoprene

The product is known as neoprene. It is resistant to chemicals and used to make hosefor petrol and containers for corrosive chemicals.Another synthetic rubber is styrene-butadiene rubber (SBR), a copolymer betweenphenylethene (30%) and 1,3-butadiene (70%).

CH2=CH-CH=CH2 + CH2=CH CH2-CH=CH-CH2-CH2-CH

1,3-butadiene phenylethene styrene-butadiene rubber

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http://en.wikipedia.org/wiki/Polymerhttp://en.wikipedia.org/wiki/Isoprenehttp://en.wikipedia.org/wiki/Polymerhttp://en.wikipedia.org/wiki/Isoprene


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13.2 Processing of rubber

Rubber is a natural polymer, formed from a liquid resin or latex derived from the innerbark of the Hevea brasiliensis tree. Latex or natural rubber is made from the sap of the

wild rubber tree. The bark of the tree is 'tapped', this means cutting small V shape slitsinto the bark, so that the sticky, white sap, known as latex, drips out and is caught incollecting cups tied to the tree truck. Figure 13.2 shows the tapping of rubber trees.

Rubber trees Latex being collected from Knives used for tappinga tappedrubber tree rubber

Figure 13.2 Tapping of rubber trees(Source: http://images.google.com)

Latex consists of 35% rubber particles and 65% water. Every rubber particle containsrubber molecules which are wrapped by a layer of negatively charged proteinmembrane. It is sometimes necessary to add a few drops of ammonia solution to thecup, or to the transport tank, to prevent pre-coagulation of the latex before it reaches the

factory. It can also be left in the cup to coagulate naturally (bacteria action whichproduces acid) into cup lump for collection before the next tapping, although this willproduce a lower grade of product.

The collected latex is then brought to a collection centre and poured into a big tank. Thelatex is then filtered to remove impurities and then passed through centrifugal machinesto remove most of the water. Rubber is obtained when methanoic or ethanoic acid isadded to latex to cause coagulation of rubber molecules. The positively chargedhydrogen ions from acid will neutralise the negative charges of rubber molecules.

The coagulated latex is then rolled into sheets using rollers. The sheets are cut intosuitable size and sent to the rubber factory for processing. The rubber sheets arewashed with machines using soap and water to remove external dirt. Then, they arehanged on bamboo stems for drying for about 3-5 days depending on the thickness ofthe rubber sheets. After that, they are dried in the smoke house, maintained at atemperature of 700C, using wood from older rubber trees or coconut husks. This processis called smoking.

After smoking, the rubber sheets become more transparent, and impurities can be moreeasily seen and removed. These smoked sheets are called Ribbed Smoked Sheets orRSS. They are graded as RSS1, RSS2, RSS3, RRS4 and RSS5 depending on their

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http://en.wikipedia.org/wiki/Rubber_tappinghttp://en.wikipedia.org/wiki/Par%C3%A1_rubber_treehttp://images.google.com/imgres?imgurl=http://img.alibaba.com/photo/11254902/Banana_Knives_And_Knives_For_Rubber_Tree.jpg&imgrefurl=http://www.alibaba.com/product/cuchilleria-11254902-10836744/Banana_Knives_And_Knives_For_Rubber_Tree.html&usg=__5JJmI_8em0K-mCcRPbKTzXnvt1c=&h=400&w=500&sz=30&hl=en&start=18&tbnid=_VFkeSDWBka-uM:&tbnh=104&tbnw=130&prev=/images%3Fq%3Drubber%2Btree%26gbv%3D2%26hl%3Den%26sa%3DGhttp://images.google.com/imgres?imgurl=http://www.rbgkew.org.uk/plants/images/rubber.jpg&imgrefurl=http://www.rbgkew.org.uk/plants/rubber.html&usg=__-Z7vEupfQEpHNqSA8wsC_CIvS2A=&h=274&w=274&sz=28&hl=en&start=3&tbnid=fjnSkGzCWiebTM:&tbnh=113&tbnw=113&prev=/images%3Fq%3Drubber%2Btree%26gbv%3D2%26hl%3Den%26sa%3DGhttp://www.eds-lab.jp/images/photo_rubber01.jpghttp://en.wikipedia.org/wiki/Rubber_tappinghttp://en.wikipedia.org/wiki/Par%C3%A1_rubber_tree


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colour, purity and elasticity. The dried rubber sheets are then pressed into cubes using ahydraulic press. This form of rubber is called bulk rubber which is used to make tyresafter vulcanisation of the rubber. The processed rubber sheets are then sold to factoriesto be made into a variety of substances.

Today, Asia is the main source of natural rubber. The three largest producing countries(Indonesia, Malaysia and Thailand) together account for around 72% of all naturalrubber production.

13.3 Cross-linking in rubber

Raw natural rubber is a thermoplastic and it becomes soft and sticky on hot days andhard when it is cooled to lower temperatures. Therefore its uses are limited. It can bemade stiffer by introducing chemical bonds between the polymer chains. Forming bondsbetween chains is called cross-linking, which is shown in Figure 13.3 The greater thenumber of cross-links in a polymer, the more rigid the material.

Figure 13.3 Cross-linking in polymers

13.4 Vulcanisation of rubber

The vulcanisation of natural rubber, a process discovered by Charles Goodyear in 1839,

is an example of cross-linking. Goodyear accidentally discovered that adding sulfur torubber and then heating the mixture makes the rubber harder and reduces itssusceptibility to oxidation or other chemical attack. The sulfur changes rubber into athermosetting polymer by cross-linking the polymer chains through reactions at some ofthe double bonds. Cross-linking of about 5 percent of the double bonds creates aflexible, resilient rubber. When the rubber is stretched, the cross-links help prevent thechains from slipping, so that rubber retains its elasticity. Vulcanised rubber is stronger,harder and elastic and these properties do not change with temperature. Vulcanised

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rubber is used to make tyres and seat-belts. Figure 13.4 shows each disulphide groupconnecting two polyisoprene molecules.

Figure 13.4 Cross-linking in rubber

13.5 Properties of rubber

Rubber exhibits unique physical and chemical properties.Some of the properties ofnatural rubber are:

Flammable

Elastic and can be stretched

Reactive to chemical agents such as oil, grease and petrol

Flexible since it is a thermoplastic that softens on heating and hardens on

heating, can be melted and reshaped to be reused again and again Impermeable to water. This makes it an excellent barrier against pathogens

such as HIV virus which causes AIDS.

Sensitive to ozone cracking due to the presence of a double bond in eachand every repeat unit

Thinking (1 hour)

Can you state some of the properties of synthetic rubber? Usea graphic organiser to compare and contrast the properties ofsynthetic rubber, natural rubber and vulcanised rubber.

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13.6 Uses of rubber

The uses of rubber including natural rubber, synthetic rubber and vulcanized rubber are

varied. Natural rubber is used to make objects such as:

Erasers Water hose Rubber band Soles of shoes Surgical and medical examination gloves and condoms Spring materials for engines to cut down on vibrations

Vulcanised rubber is used to make objects such as:

Car mats

Car tyres

Radiator hoses

Window wiper blades

Seals and suspension mountings

Synthetic rubber such as neoprene is used to make objects such as:

Gaskets

Car belts

Conveyor belts

Flexible pipes or hoses for the petrol industry because it is not attacked by petrol

Insulating materials for electrical connections, especially where the environmenthas chemicals

Figure 13.5 Uses of rubber((Source: http://images.google.com)

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http://images.google.com/imgres?imgurl=http://www.lakewoodconferences.com/direct/dbimage/50045567/Full_Dipped_Rubber_Gloves.jpg&imgrefurl=http://www.lakewoodconferences.com/catalog/69/241/147334/full_dipped_rubber_gloves.html&usg=__t9OGp3YqyzLEjWsIs_gxpJQzzOw=&h=360&w=360&sz=21&hl=en&start=53&tbnid=NS11MLzlrjFTyM:&tbnh=121&tbnw=121&prev=/images%3Fq%3Drubber%26gbv%3D2%26ndsp%3D20%26hl%3Den%26sa%3DN%26start%3D40http://images.google.com/imgres?imgurl=http://www.par-group.co.uk/UserImages/Rubber_Polyurethane/Rubber%2520Bungs.jpg&imgrefurl=http://www.par-group.co.uk/rpe.aspx%3Fpage%3D150&usg=__N5H2LSE7P-T_9hmSdwTG_jQZR4A=&h=572&w=752&sz=71&hl=en&start=44&tbnid=vYMFF0WiX9Sj4M:&tbnh=107&tbnw=141&prev=/images%3Fq%3Drubber%26gbv%3D2%26ndsp%3D20%26hl%3Den%26sa%3DN%26start%3D40http://images.google.com/imgres?imgurl=http://www.germes-online.com/direct/dbimage/50315828/Metallic_Rubber_Balls.jpg&imgrefurl=http://www.germes-online.com/catalog/62/1169/118940/sell_metallic_rubber_balls.html&usg=__KiMf0tGvDw3maHYvZoo0taMhgQw=&h=360&w=360&sz=38&hl=en&start=29&tbnid=z3fMzn92eQAEzM:&tbnh=121&tbnw=121&prev=/images%3Fq%3Drubber%26gbv%3D2%26ndsp%3D20%26hl%3Den%26sa%3DN%26start%3D20http://images.google.com/imgres?imgurl=http://www.germes-online.com/direct/dbimage/50248985/Ladies__Rubber_Boots.jpg&imgrefurl=http://www.germes-online.com/catalog/69/74/260/329385/sell_farmer_s_rubber_boots.html&usg=__fyYO8uBVj4FNzE0W0ddaQa-XRMo=&h=360&w=360&sz=18&hl=en&start=5&tbnid=Uar-2jXbtYkuIM:&tbnh=121&tbnw=121&prev=/images%3Fq%3Drubber%26gbv%3D2%26hl%3Den%26sa%3DG


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Collecting Information (2 hours)

Do you know that in the late 1950s, Malaysia produced almost 40%of the worlds natural rubber. It was said that rubber built upMalaysia (Source: Countdown to 50th Merdeka!, The SUNnewspaper, Monday August 13 2007, page 12). Gather informationabout the development of the rubber industry in Malaysia.

References

Brown, T.L.; Lemay,H.E.; Bursten, B.E. (2000) Chemistry-The Central Science. EighthEdition, New Jersey:Prentice Hall.

McMurry,J.; Fay,R.C. (2001) Chemistry. Third Edition, New Jersey: Prentice Hall.

http://en.wikipedia.org/wiki/Rubber(rubber industry)

http://www.irrdb.com/IRRDB/Rubber_Industry/Other_Suppliers/ProcessingChemicals/Vulcanization.htm(vulcanisation of rubber)

TOPIC 14 NATURAL POLYMERS- SILK, COTTON AND WOOL

Synopsis

Natural polymers are used widely every day. This topic will discuss the main types ofnatural polymers, namely, cotton, wool and silk. It will explain the properties, theprocessing, and the uses of these natural polymers.

Learning Outcomes

1. State the type of natural polymers2. State the properties of natural polymers

3. Explain the processing of natural polymers

4. Explain the uses of natural polymers

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http://en.wikipedia.org/wiki/Rubberhttp://www.irrdb.com/IRRDB/Rubber_Industry/Other_Suppliers/ProcessingChemicals/Vulcanization.htmhttp://www.irrdb.com/IRRDB/Rubber_Industry/Other_Suppliers/ProcessingChemicals/Vulcanization.htmhttp://en.wikipedia.org/wiki/Rubberhttp://www.irrdb.com/IRRDB/Rubber_Industry/Other_Suppliers/ProcessingChemicals/Vulcanization.htmhttp://www.irrdb.com/IRRDB/Rubber_Industry/Other_Suppliers/ProcessingChemicals/Vulcanization.htm


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Overview

Figure 14.1 Overview of content

Content14.1 Polymer

The term polymer originated from Greek words, poly means many and mer meansparts. Polymers are long chain molecules formed by joining together many identicalrepeating sub-units called monomers. Polymers can be divided into two types:

natural polymers

synthetic polymers

Natural polymers are polymers obtained from living things such as plants and animals.

Some examples of natural polymers are shown in Figure 14.2.

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Natural polymers

Type of natural

polymers

Properties of natural

polymers Processing of natural

polymers

Uses of natural

polymers


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, Figure 14.2 Types of natural polymers

Surf the Internet (1 hour)

Access the internet to gather information to compare natural polymersand synthetic polymers.

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starch

wool

silkcotton

naturalrubber

Naturalpolymers


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14.2 Silk

Silk is a natural protein fiber obtained from cocoons made by the larvae of silkwormreared in captivity. Silk is actually made of proteins secreted in the fluid state bysilkworm caterpillar. These silkworms feed on selected food plants, namely mulberryleaves, and spin cocoons as a protective shell to perpetuate life.

Figure 14.3 Silkworm feeding on mulberry leaves(Source: http://images.google.com)

Properties of silk are:

has natural shine has smooth and soft texture resistant to mineral acids has good moisture regain poor resistance to sunlight exposure moderate elasticity and wrinkle resistance strongest of all the natural fibers but loses 20% of its strength when wet

Figure 14.4 A silk fabric(Source: http://images.google.com)

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Figure 14.4 shows some of the uses of silk

Figure 14.4 Uses of silk

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Tie

Furnishing(Bed sheets,

curtains)

Scarf

Activeclothing in

warmweather

Uses of silk


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The flowchart below explains the processing of silk:

Cocoons that have been spun by the silkworm are hand-picked and placed in oven

The heat of the oven is enough to kill the silkworm but not damage the silk in thecocoon

The cocoons are soaked in water

Multiple threads from the soaked cocoons are unraveled to form a single thread

Silk thread is further combined to form thicker strands and dyed to create desiredcolours

Figure 14.5 Process of manufacturing silk

14.3 Cotton

Cotton is a soft fiberthat grows around the seeds of cotton plant, a shrub native totropical and subtropical regions around the world, including Africa, India and America.Cotton is a thirsty crop, so it must be cultivated in areas with less rainfall. The fiber ismost often spun into yarn or thread and used to make soft breathable textile, which isthe most widely used natural fiber cloth in clothing today.

Figure 14.5 Cotton plant (Source: http://images.google.com)

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Below are the properties of cotton:

Strong

Durable

Prints well

Comfortable

Good absorbent of moisture

Low resiliency (easily wrinkled)

High resistance for alkali and organic solvent

Figure 14.6 Cotton(Source: http://images.google.com)

How cotton is processed?

Cotton fiber, once it has been processed to remove seeds (ginning),

consists of nearly pure cellulose, a natural polymer.

Each cotton fiber is made up to twenty to thirty layers of cellulose coiled in aneat series of natural springs.

When the cotton ball is opened, the fibres dry into flat, twisted, ribbon-likeshapes and shapes and become kinked together and interlocked.

This interlocked form is ideal for spinning into fine yarn.

Cotton production is very efficient, only ten percent or less of the weight islost in subsequent processing to convert the raw cotton bolls (seed coat)into pure fiber.

The cellulose is arranged in a way that gives cotton fibers a high degree ofstrength, durability, and absorbency.

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Figure 14.7 A worker carrying Figure 14.8 Cotton buds and swabsharvested cotton

(Source: http://images.google.com)

Cotton is used in the making of:

Towel

Socks

Bed sheets

T-shirts

Coffee filters

Jeans

Cotton buds and swabs

Surf the Internet (2 hours)

Access the internet to gather information on types of cotton.

14.4 Wool

Wool is a fiber derived from the specialised skin cells, called follicles, of animals in theCaprinae family, principally sheep, but the hair of certain species of othermammals suchas goats, llamas and rabbits may also be called wool. Wool has several qualities thatdistinguish it from hair or fur: it is curly, it has a different texture or handle, elastic andgrows in staples (clusters).

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http://en.wikipedia.org/wiki/Caprinaehttp://en.wikipedia.org/wiki/Domestic_sheephttp://en.wikipedia.org/wiki/Mammaliahttp://en.wikipedia.org/wiki/Cashmere_goathttp://en.wikipedia.org/wiki/Llamahttp://en.wikipedia.org/wiki/Rabbithttp://en.wikipedia.org/wiki/Crimp_(wool)http://en.wikipedia.org/wiki/Caprinaehttp://en.wikipedia.org/wiki/Domestic_sheephttp://en.wikipedia.org/wiki/Mammaliahttp://en.wikipedia.org/wiki/Cashmere_goathttp://en.wikipedia.org/wiki/Llamahttp://en.wikipedia.org/wiki/Rabbithttp://en.wikipedia.org/wiki/Crimp_(wool)


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Figure 14.9 Wool from sheep(Source: http://images.google.com)

Below are the properties of wool:

Warm materials

Tightly crimped fibers

The outer cells of the fiber repel water while the inner cells absorb moisture

High elasticity-wool possesses much greater ability to return to its natural lengthafter being stretched than any artificial fiber.

Highly absorbent-capable of retaining up to 25 percent of its weight in moisture.

ideal for dyes-wool takes on richer, deeper, purer colors than vegetable fiber

The processing of wool is listed below:

After shearing, wool contains a high level of grease which contains valuablelanolin, as well as dirt, dead skin, sweat residue, and vegetable matter.

Before the wool can be used for commercial purposes it must be scoured, orcleaned.

Scouring may be as simple as a bath in warm water, or a complicated industrialprocess using detergent and alkali.

After that, the wool is separated into five main categories:

Fleece, broken, pieces, bellies and locks.

The quality of fleece is determined by a technique known as wool classing

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http://en.wikipedia.org/wiki/Lanolinhttp://en.wikipedia.org/wiki/Detergenthttp://en.wikipedia.org/wiki/Alkalihttp://en.wikipedia.org/wiki/Lanolinhttp://en.wikipedia.org/wiki/Detergenthttp://en.wikipedia.org/wiki/Alkali


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Reference ( 3 hours)

The processing of wool involves:spinning, carding, weaving, combing, dyeing, knitting andcombing. Explain each process and the purpose of theseprocesses in manufacturing wool. You may refer to http:www.austech.unimelb.edu.au/tin/267.html

Figure 14.10 Wool Figure 14.11 Scarf made from wool(Source: http://images.google.com)

Wool is objectively measured for micron, yield, staple length, staple strength andsometimes color and comfort factor.

Wool is widely used in making of:

Clothes such as sweaters

Traditionally used to covercloth diapers

absorb odours and noise in heavy machinery and stereo speakers

Blankets, horse rugs, saddle cloths, carpeting, felt, wool insulation andupholstery

Some modern cloth diapers use felted wool fabric for covers, and there areseveral modern commercial knitting patterns for wool diaper covers

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http://en.wikipedia.org/wiki/Cloth_diapershttp://en.wikipedia.org/wiki/Carpethttp://en.wikipedia.org/wiki/Felthttp://en.wikipedia.org/wiki/Wool_insulationhttp://en.wikipedia.org/wiki/Knittinghttp://en.wikipedia.org/wiki/Cloth_diapershttp://en.wikipedia.org/wiki/Carpethttp://en.wikipedia.org/wiki/Felthttp://en.wikipedia.org/wiki/Wool_insulationhttp://en.wikipedia.org/wiki/Wool_insulationhttp://en.wikipedia.org/wiki/Knitting


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Coated paper (glossy and matt surface)

Plain paper

Newsprint

15.2 Properties of Paper

We use paper everyday. Its usefulness is due to its unique properties such as:

Basis Weight (GSM)

Brightness, Whiteness and Colour

Dimensional Stability

Folding Endurance (Double Folds)

Formation

Gloss

Machine and Cross Direction Moisture

Opacity

Porosity

Sizing / Cobb

Smoothness

Stiffness

Stretch (Elongation)

Tearing Resistance

Temperature and Humidity: Conditioning of Paper

Thickness

Wax Pick No. (Surface Strength)

Wire side and Felt side

Making Notes (2 hours)

To get a better understanding of each of the properties of paperlisted above, read the article in the following website:

http://www.biltpaper.com/atoz2.asp .Make short notes on each of the properties of paper.

15.3 Process of making paperPaper is produced by pressing together moist fibers, typically vegetable fibers composedofcellulose, which are held together by hydrogen bonds, and drying them into flexible

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http://www.biltpaper.com/atoz2.asp#1http://www.biltpaper.com/atoz2.asp#2http://www.biltpaper.com/atoz2.asp#4http://www.biltpaper.com/atoz2.asp#5http://www.biltpaper.com/atoz2.asp#6http://www.biltpaper.com/atoz2.asp#7http://www.biltpaper.com/atoz2.asp#8http://www.biltpaper.com/atoz2.asp#9http://www.biltpaper.com/atoz2.asp#10http://www.biltpaper.com/atoz2.asp#11http://www.biltpaper.com/atoz2.asp#12http://www.biltpaper.com/atoz2.asp#13http://www.biltpaper.com/atoz2.asp#14http://www.biltpaper.com/atoz2.asp#15http://www.biltpaper.com/atoz2.asp#16http://www.biltpaper.com/atoz2.asp#17http://www.biltpaper.com/atoz2.asp#18http://www.biltpaper.com/atoz2.asp#19http://www.biltpaper.com/atoz2.asp#20http://www.biltpaper.com/atoz2.asphttp://en.wikipedia.org/wiki/Fiberhttp://en.wikipedia.org/wiki/Cellulosehttp://www.biltpaper.com/atoz2.asp#1http://www.biltpaper.com/atoz2.asp#2http://www.biltpaper.com/atoz2.asp#4http://www.biltpaper.com/atoz2.asp#5http://www.biltpaper.com/atoz2.asp#6http://www.biltpaper.com/atoz2.asp#7http://www.biltpaper.com/atoz2.asp#8http://www.biltpaper.com/atoz2.asp#9http://www.biltpaper.com/atoz2.asp#10http://www.biltpaper.com/atoz2.asp#11http://www.biltpaper.com/atoz2.asp#12http://www.biltpaper.com/atoz2.asp#13http://www.biltpaper.com/atoz2.asp#14http://www.biltpaper.com/atoz2.asp#15http://www.biltpaper.com/atoz2.asp#16http://www.biltpaper.com/atoz2.asp#17http://www.biltpaper.com/atoz2.asp#18http://www.biltpaper.com/atoz2.asp#19http://www.biltpaper.com/atoz2.asp#20http://www.biltpaper.com/atoz2.asphttp://en.wikipedia.org/wiki/Fiberhttp://en.wikipedia.org/wiki/Cellulose


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sheets. While the fibers used are usually natural in origin, a wide variety of syntheticfibers, such as polypropylene and polyethylene, may be incorporated into paper as away of imparting desirable physical properties. The most common source of these kindsof fibers is wood pulp from pulpwood trees, largely softwoods and hardwoods, such asspruce and aspen respectively. Othervegetable fibermaterials including those ofcotton,hemp, linen, and rice may be used.

The steps in the process of making paper are:

Fiber processing / pulping using chemical pulping or mechanical pulping

Adding additives Drying Finishing

Fiber processing/pulping

Wood or plant cell walls are composed of fibers bound together. During pulping, thesefibers are separated from each other and carbohydrate surfaces, primarily cellulose orhemi-cellulose are exposed. Hydrogen bonding between these carbohydrate surfacesgives paper its strength. Fibers can be separated chemically, mechanically, or via acombination of the two.

Chemical pulping

The purpose of a chemical pulping process is to break down the chemical structure oflignin and render it soluble in the cooking liquor, so that it may be washed from thecellulose fibers. Because lignin holds the plant cells together, chemical pulping frees thefibers and makes pulp. The pulp must be bleached to produce white paper for printing,painting and writing. Chemical pulps tend to cost more than mechanical pulps, largelydue to the low yield, 40-50% of the original wood. Since the process preserves fiber

length, however, chemical pulps tend to make stronger paper. Another advantage ofchemical pulping is that the majority of the heat and electricity needed to run the processis produced by burning the lignin removed during pulping.

Mechanical pulping

There are two major mechanical pulps, thermomechanical pulp (TMP) and mechanicalpulp. The latter is known in the USA as groundwood pulp.In the TMP process, wood is chipped and then fed into large steam-heated refinerswhere the chips are squeezed and fiberised between two steel discs. In the groundwoodprocess, debarked logs are fed into grinders where they are pressed against rotatingstones and fiberised. Mechanical pulping does not remove the lignin, so the yield is very

high, more than 95%, but also causes paper made from this pulp to yellow and becomebrittle over time. Mechanical pulps have rather short fiber lengths and produce weakpaper. Although large amounts of electrical energy are required to produce mechanicalpulp, it costs less than chemical pulp.

Additives

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http://en.wikipedia.org/wiki/Wood_pulphttp://en.wikipedia.org/wiki/Pulpwoodhttp://en.wikipedia.org/wiki/Softwoodhttp://en.wikipedia.org/wiki/Hardwoodhttp://en.wikipedia.org/wiki/Sprucehttp://en.wikipedia.org/wiki/Aspenhttp://en.wikipedia.org/wiki/Fiber_crophttp://en.wikipedia.org/wiki/Cottonhttp://en.wikipedia.org/wiki/Hemphttp://en.wikipedia.org/wiki/Linenhttp://en.wikipedia.org/wiki/Ricehttp://en.wikipedia.org/wiki/Woodhttp://en.wikipedia.org/wiki/Carbohydratehttp://en.wikipedia.org/wiki/Ligninhttp://en.wikipedia.org/wiki/Cellulosehttp://en.wikipedia.org/wiki/Printinghttp://en.wikipedia.org/wiki/Writinghttp://en.wikipedia.org/wiki/Wood_pulphttp://en.wikipedia.org/wiki/Pulpwoodhttp://en.wikipedia.org/wiki/Softwoodhttp://en.wikipedia.org/wiki/Hardwoodhttp://en.wikipedia.org/wiki/Sprucehttp://en.wikipedia.org/wiki/Aspenhttp://en.wikipedia.org/wiki/Fiber_crophttp://en.wikipedia.org/wiki/Cottonhttp://en.wikipedia.org/wiki/Hemphttp://en.wikipedia.org/wiki/Linenhttp://en.wikipedia.org/wiki/Ricehttp://en.wikipedia.org/wiki/Woodhttp://en.wikipedia.org/wiki/Carbohydratehttp://en.wikipedia.org/wiki/Ligninhttp://en.wikipedia.org/wiki/Cellulosehttp://en.wikipedia.org/wiki/Printinghttp://en.wikipedia.org/wiki/Writing


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Besides the fibers, pulps may contain fillers such as chalk or china clay, which improvethe characteristics of the paper for printing or writing. Additives for sizing purposes maybe mixed into the pulp and/or applied to the paper web later in the manufacturingprocess. The purpose of sizing is to establish the correct level of surface absorbency tosuit the ink or paint.

Drying

After the paper web is produced, the water must be removed from it in order to create ausable product. This is accomplished through pressing and drying. The methods ofdoing so vary between the different processes used to make paper, but the conceptsremain the same. Pressing the sheet removes the water by force. Once the water isforced from the sheet, another absorbent material must be used to collect this water. Ona paper machine this is called a felt. When making paper by hand, a blotter sheet isused. Drying involves using air and or heat to remove water from the paper sheet.In the earliest days of papermaking this was done by hanging the paper sheets likelaundry. In more modern times, various forms of heated drying mechanisms are used.The most common is the steam-heated can dryer. These dryer cans heat to

temperatures above 200F (93C) and are used in long sequences of more than 40cans. The heat produced by these can easily dry the paper to less than 6% moisture.

Finishing

The paper may then undergo sizing to alter its physical properties for use in variousapplications. Paper at this point is uncoated. Coated paper has a thin layer of materialsuch as china clay applied to one or both sides in order to create a surface more suitablefor high-resolution half-tone screens. Coated or uncoated papers may have theirsurfaces polished by calendering. Coated papers are divided into matt, semi-matt or silk,and gloss.

The paper is then fed onto reels if it is to be used on web printing presses, or cut intosheets for other printing processes or other purposes. The fibers in the paper basicallyrun in the machine direction. Sheets are usually cut "long-grain", i.e. with the grainparallel to the longer dimension of the sheet. All paper produced by Fourdrinier-typemachines is wove paper, i.e. the wire mesh that transports the web leaves a pattern thathas the same density along the paper grain and across the grain. Wove paper does notexhibit "laidlines", which are small regular lines left behind on paper when it washandmade in a mould made from rows of metal wires or bamboo. Handmade papersimilarly exhibits "deckle edges", or rough and feathery borders.

15.4 Uses of paper

Paper is a versatile material with many uses. Whilst the most common is for writing andprinting upon, it is also widely used as a packaging material, in many cleaning products,and in a number of industrial and construction processes, and occasionally as a foodingredient, particularly in Asian cultures.

Paper can be produced with a wide variety of properties, depending on its intended use,such as:

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To write or print on: the piece of paper becomes a document; this may be forkeeping a record (or in the case of printing from a computer or copying fromanother paper: an additional record) and for communication.

To represent a value: paper money, bank note, cheque,voucher, ticket

For entertainment: book, magazine, newspaper, art

For packaging: corrugated box, paper bag, envelope, wrapping tissue,wallpaper

For cleaning : toilet paper, handkerchiefs, paper towels, facial tissue

For construction : paper mache, origami, quiling, paper engineering, clothing

Other uses: sandpaper, blotting paper, litmus paper, universal indicator paper,paper chromatography, electrical insulation paper, filter paper

Figure 15.4 Uses of paper(Source: http://images.google.com)

Exercise (2 hours)

Access the internet to gather information and to compare and contrast theproperties of different types of paper and their uses in daily life.

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http://images.google.com/imgres?imgurl=http://www.misr-italia.com/images/idro_sample.jpg&imgrefurl=http://www.misr-italia.com/idro.html&usg=__s0mlHX5Smy2ABch_gO0CU5iymKI=&h=300&w=300&sz=55&hl=en&start=43&tbnid=Z1mK-qy9l1_XQM:&tbnh=116&tbnw=116&prev=/images%3Fq%3Dtypes%2Bof%2Bpaper%26gbv%3D2%26ndsp%3D20%26hl%3Den%26sa%3DN%26start%3D40http://images.google.com/imgres?imgurl=http://blog.craftzine.com/tissue.jpg&imgrefurl=http://blog.craftzine.com/archive/2007/09/acidfree_tissue_paper.html&usg=__MBMAuM33pIO4cS41CR997_6yLTE=&h=400&w=400&sz=64&hl=en&start=3&tbnid=JKNOVQkWSB0q_M:&tbnh=124&tbnw=124&prev=/images%3Fq%3Dtissue%2Bpaper%26gbv%3D2%26hl%3Den%26sa%3DGhttp://images.google.com/imgres?imgurl=http://img.alibaba.com/photo/104907294/Copy_Paper.jpg&imgrefurl=http://www.alibaba.com/product/id105235084-104907294-0/Copy_Paper.html&usg=__jbuENNsWDtVZDUeRnJ-YAPTpIvE=&h=450&w=600&sz=40&hl=en&start=160&tbnid=8WHnCbsBafPFmM:&tbnh=101&tbnw=135&prev=/images%3Fq%3Dpaper%26gbv%3D2%26ndsp%3D20%26hl%3Den%26sa%3DN%26start%3D140http://images.google.com/imgres?imgurl=http://www.germes-online.com/direct/dbimage/50258655/Paper_Tea_Cups.jpg&imgrefurl=http://www.germes-online.com/catalog/54/56/1100/paper_cups_plates_food_trays.html&usg=__N1InzFbunJSKcMKhlYfKQ3aPVxY=&h=360&w=360&sz=16&hl=en&start=7&tbnid=FwgeVI_mWpndIM:&tbnh=121&tbnw=121&prev=/images%3Fq%3Dpaper%26gbv%3D2%26hl%3Den%26sa%3DG


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Thinking (10 hours)

We can reuse paper by recycling it. Make your own recycled paper. Go to the

internet for suggestions on how to make recycled paper. This websitehttp://www.recyclenow.com/why_recycling_matters/how_is_it_recycled/paper/ may be helpful. Create a useful item using the recycled paper you havemade. Organise a mini science exhibition to present the process of recyclingpaper and the products made from the recycled paper. Keep a photograph

journal of the exhibition.

At the end of the activity, answer the following questions:

What have you learnt from this activity?

Which part of the primary science curriculum teaches thistopic on paper?

Discuss how you can use this activity in your teaching andlearning.

What was the role of the teacher in this activity?

References

http://en.wikipedia.org/wiki/Paper(paper)

http://www.writersservices.com/wbs/care_history_paper.htm

(History of paper making)

http://www.writersservices.com/wbs/care_storing_books.htm(how to store books)

http://www.biltpaper.com/atoz2.asp(properties of paper)

http://www.recyclenow.com/why_recycling_matters/how_is_it_recycled/paper/(recycling of paper)

http://www.paperonweb.com/pmake.htm

(processing paper)

http://www.geocities.com/kirktayl/(how to organise a science exhibition)

http://www.paperonweb.com/density.htm (properties of paper)
http://www.recyclenow.com/why_recycling_matters/how_is_it_recycled/paper/http://www.recyclenow.com/why_recycling_matters/how_is_it_recycled/paper/http://en.wikipedia.org/wiki/Paperhttp://www.writersservices.com/wbs/care_history_paper.htmhttp://www.writersservices.com/wbs/care_storing_books.htmhttp://www.biltpaper.com/atoz2.asphttp://www.recyclenow.com/why_recycling_matters/how_is_it_recycled/paper/http://www.paperonweb.com/pmake.htmhttp://www.paperonweb.com/pmake.htmhttp://www.geocities.com/kirktayl/http://www.paperonweb.com/density.htmhttp://www.recyclenow.com/why_recycling_matters/how_is_it_recycled/paper/http://www.recyclenow.com/why_recycling_matters/how_is_it_recycled/paper/http://en.wikipedia.org/wiki/Paperhttp://www.writersservices.com/wbs/care_history_paper.htmhttp://www.writersservices.com/wbs/care_storing_books.htmhttp://www.biltpaper.com/atoz2.asphttp://www.recyclenow.com/why_recycling_matters/how_is_it_recycled/paper/http://www.paperonweb.com/pmake.htmhttp://www.geocities.com/kirktayl/http://www.paperonweb.com/density.htm

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