Polymers and Plastics - SWPS

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From Prentice Hall Science Explorer Chemical Interactions and Chemical Building Blocks©2006

Polymers and Plastics Table of Contents

Section 1 Chemical Bonding, Carbon Style Page 1. The Carbon Atom and Its Bonds Page 1

Forms of Pure Carbon Page 2

Section 2 Carbon Compounds Page 5 Oganic Compounds Page 5

Hydrocarbons Page 6

Straight Chains and Branches Page 7

Double and Triple Bonds Page 8

Saturated amd Imsaturated Hydrocarbons Page 9

Substitute Hydrocarbons Page 9

Polymers (Introduction) Page 11

Section 3 Polymers and Composites Page 13 Carbon’s Strings. Rings, and Other Things Page 13

Carbon Compounds Form Polymers Page 13

Natural Polymers Page 14

Synthetic Polymers Page 15

Composites Page 16

Too Many Polymers? Page 19

Appendix 1: Plastics Timeline Page 21

Appendix 2: Plastic Recyling Codes Page 22

Appendix 3: Some Common Synthetic Polymers Page 23

Appendix 4: 2000 U.S. Plastics Production

Appendix 5: Glossary

POLYMERS AND PLASTICS


From Prentice Hall Science Explorer Chemical Interactions and Chemical Building Blocks©2006 - 1 -

Section 1 Chemical Bonding, Carbon Style

GUIDE FOR READING

Why can carbon form a huge variety of different compounds?

What are the different forms of pure carbon?

Open your mouth and say "ash." Uh-oh, you have a small cavity. Do you know

what happens next? Your tooth needs a filling. But first the dentist's drill clears away the

decayed part of your tooth.

Why is a dentist's drill hard enough and sharp enough to cut through teeth? The

answer has to do with the element carbon. The tip of the drill is made of diamond - a

form of carbon and the hardest substance on Earth. Because it has a diamond tip, a

dentist's drill stays sharp and useful. To understand why diamond is such a hard

substance, you need to take a close look at the carbon atom and the bonds it forms.

Figure 1 The tip of a dentist's drill is

made of diamond, a form of carbon.

The Carbon Atom and Its Bonds Recall that the atomic number of carbon is 6. This means that the nucleus of a

carbon atom contains 6 protons. Surrounding the nucleus are 6 electrons. Of these

electrons, four are valence electrons - the electrons available for bonding.

Figure 2 A. Only four of the six

electrons in a carbon atom are valence

electrons. B. Electron dot structures

show just the valence electrons.

Highlighted is a shared pair of

electrons between two carbon atoms.

C. Spherical models represent two

carbon atoms bonded together.

Interpreting Diagrams How many

valence electrons are involved in one

bond?




As you have learned, a chemical bond is the force that holds two atoms together.

You can think of the two atoms as hooked together. A chemical bond between two atoms

is made up of the atoms' valence electrons. Two atoms gain, lose, or share valence

electrons in the way that makes the atoms most stable. The transfer or sharing of valence

electrons creates chemical bonds.

Atoms of all elements (except the noble gases) form chemical bonds. But few

elements have the ability of carbon to bond with both itself and other elements in so

many different ways.

Carbon atoms form more bonds than most other atoms. With four valence

electrons, each carbon atom is able to form four bonds. In comparison, hydrogen, oxygen,

and nitrogen can form only one, two, or three bonds. With four bonds to each carbon

atom, it is possible to form substances with many carbon atoms, even thousands of them.

As you can see in Figure 3, it is possible to arrange the same number of carbon

atoms in different ways. Carbon atoms can form straight chains, branched chains, and

rings. Sometimes even networks of two or more rings of carbon atoms are joined

together.

Figure 3 These carbon chains and

rings form the backbones for

molecules. In these molecules,

atoms of other elements are bonded

to the carbons.

Checkpoint How many bonds can a carbon atom form?

Forms of Pure Carbon Because of the ways that carbon forms bonds, the pure element can exist in

different forms. Diamond, graphite, and fullerene are three forms of the element carbon.

Diamond The hardest mineral-diamond-forms deep within Earth. At very high

temperatures and pressures, carbon atoms form diamond crystals. Each carbon atom is

bonded strongly to four other carbon atoms. The result is a solid that is extremely hard

and unreactive. The melting point of diamond is over 3,500°C. That's as hot as the

surface temperatures of some stars.

Diamonds are prized for their brilliance and clarity when cut as gems. They can

have color if there are traces of other elements in the crystals. Industrial chemists are able

to make diamonds artificially, but these diamonds are not beautiful enough to use as

gems. Like many natural diamonds, artificial ones are used in industry. Diamonds work

well in cutting tools, such as drills.




Figure 4 The carbon atoms in a diamond are arranged in a crystal structure. Each atom

is bonded to 4 other atoms. The diamonds in this photo have not yet been cut and

polished by a jeweler.

Graphite Every time you write with a pencil, you leave a layer of carbon on the

paper. The "lead" in a lead pencil is actually graphite, another form of the element

carbon. In graphite, each carbon atom is bonded tightly to three other carbon atoms in flat

layers. However, the bonds between atoms in different layers are very weak, so the layers

slide past one another easily.

Run your fingers over pencil marks, and you can feel how slippery graphite is. If

you did the Discover activity, you have observed this property. Because it is so slippery,

graphite makes an excellent lubricant in machines. Graphite reduces friction between the

moving parts. In your home, you might use a graphite spray to help a key work better in a

sticky lock.

Figure 5 The carbon atoms in graphite are arranged in layers. The weak bonds between

the layers are not shown.

Applying Concepts How can you explain the slipperiness of graphite?

http://images.google.com/hosted/life/f?q=uncut+diamond&prev=/images?q=uncut+diamond&imgsz=xxlarge&gbv=2&hl=en&safe=active&sa=G&imgurl=1859ba425ff677c9




Figure 6 The arrangement of

the carbon atoms in fullerenes

resembles the structure of a

geodesic dome or the pattern

on a soccer ball.

Fullerenes In 1985, scientists at Rice University in Texas made a third form of the

element carbon, a form that no one had identified before. The new form of carbon

consists of carbon atoms arranged in repeating patterns like the one shown in Figure 6.

This unique form of carbon is called a fullerene (FUL ur een) in honor of the architect

Buckminster Fuller. Fuller designed dome-shaped buildings, called geodesic domes,

which some fullerenes resemble. Because of its shape, one of these fullerenes, called

buckminsterfullerene, has been given the nickname "buckyballs."

Chemists are looking for ways to use fullerenes. Because fullerenes enclose a

ball-shaped open area, they may be able to carry other substances inside them. For

example, fullerenes may be used someday to carry medicines through the body.

Section 1 Review

1. What bonding properties of carbon allow it to form so many different compounds?

2. List three different forms of pure carbon.

3. What happens to valence electrons when a chemical bond forms between atoms?

4. Thinking Critically Comparing and Contrasting How do the differences in carbon

bonds explain why graphite and diamonds have different properties?




Section 2 Carbon Compounds

GUIDE FOR READING

*What properties do many organic compounds have in common?

*What kinds of carbon chains are found in hydrocarbons?

*What are some examples of substituted hydrocarbons?

Imagine that you are heading out for a day of shopping. Your first purchase is a

red cotton shirt. Then you go to the drugstore, where you buy a bottle of shampoo and a

pad of writing paper. Your next stop is a hardware store to buy propane, a fuel used in

camping stoves and lanterns. Your final stop is the grocery store, where you buy cereal,

meat, and vegetables.

What do all of these purchases have in common? They all are made of carbon

compounds. Carbon atoms act as the backbone or skeleton for the molecules of these

compounds. Carbon compounds include gases (such as propane), liquids (such as olive

oil), and solids (such as wax and cotton). Mixtures of carbon compounds are found in

foods, paper, and shampoo. In fact, more than 90 percent of all known compounds

contain carbon.

Organic Compounds Carbon compounds are so numerous that they are given a specific name. With

some exceptions, a compound that contains carbon is called an organic compound. The

word organic means "of living things". Scientists once thought that organic compounds

could be produced only by living organisms. Organic compounds are indeed part of the

solid matter of every living thing on Earth. Products made from living things, such as

paper made from the wood of trees, are also organic com-pounds. However, organic

compounds can be produced artificially. For example, plastics, fuels, cleaning solutions,

and many other such products are organic compounds. The raw materials for most

synthetic organic compounds come from petroleum, or crude oil.

Figure 7 Did you know that

when you buy a shirt you are

buying carbon compounds?




Figure 8 All living things contain organic compounds. Organic compounds include the

oils used to fry foods, the plastic wrap and foam tray in which these apples are packaged,

and even the apples themselves.

Inferring What does the dog have in common with the cooking oil, apples, plastic

wrap, and tray?

Many organic compounds have similar properties - for example, low melting

points and low boiling points. As a result, many organic compounds are liquids or gases

at room temperature. Organic liquids generally have strong odors. They also do not

conduct electricity. Many organic compounds do not dissolve well in water. You may

have seen vegetable oil, which is a mixture of organic compounds, form a separate layer

in a bottle of salad dressing.

Hydrocarbons Scientists classify organic compounds into different categories. The simplest

organic compounds are the hydrocarbons. A hydrocarbon (hy droh KAHR bun) is a

compound that contains only the elements carbon and hydrogen. The carbon chains in a

hydrocarbon may be straight, branched, or ring-shaped.

You might already recognize several common hydrocarbons. Methane, the main

gas in natural gas, is used to heat homes. Propane is used in portable stoves and gas grills

and to provide heat for hot-air balloons. Butane is the fuel in most lighters. Gasoline is a

mixture of several different hydrocarbons. And paraffin wax is a hydrocarbon that is used

to make candles.

Properties of Hydrocarbons All hydrocarbons are flammable, which means that

they burn easily. When hydrocarbons burn, they release a great deal of energy. This is

why they are used as fuels to power stoves and heaters, as well as cars, buses, and

airplanes.

Like most other organic compounds, hydrocarbons mix poorly with water. Have

you ever been at a gas station during a rainstorm? If so, you may have noticed a thin

rainbow-colored film of gasoline or oil floating on a puddle.




Formulas of Hydrocarbons Hydrocarbon compounds differ in the number of

carbon and hydrogen atoms in each molecule. You can show how many atoms there are

of the elements that make up each molecule of a compound by writing a formula. A

molecular formula includes the chemical symbols of the elements in each molecule of a

compound, as well as the number of atoms of each element.

The simplest hydrocarbon is methane. Its molecular formula is CH4. The number

4 indicates the number of hydrogen atoms (H). Notice that the 4 is a subscript. Subscripts

are written lower and smaller than the letter symbols of the elements. Notice that the

symbol for carbon (C) in the formula is written without a subscript. This means that there

is one carbon atom in the molecule.

A hydrocarbon with two carbon atoms is ethane. The formula for ethane is C2H6.

The subscripts in this formula show that an ethane molecule is made of two carbon atoms

and six hydrogen atoms. A hydrocarbon with three carbon atoms is propane (C3H8). How

many hydrogen atoms does the subscript indicate? If you answered eight, you are right.

Checkpoint: What is a hydrocarbon?

Figure 9 The natural gas burning at

the top of this oil well is composed of

hydrocarbons.

Straight Chains and Branches If a hydrocarbon has two or more carbon atoms, the atoms can form a single line,

or a straight chain. In hydrocarbons with four or more carbon atoms, it is possible to have

branched arrangements of the carbon atoms as well as the straight chain.

Structural Formula To show how atoms are arranged in the molecules of a compound,

chemists use a structural formula. A structural formula shows the kind, number, and

arrangement of atoms in a molecule. Figure 10 shows the structural formulas for

molecules of methane, ethane, and propane. Each dash (-) represents a bond (two shared

electrons). In methane, each carbon atom is bonded to four hydrogen atoms. In ethane

and propane, each carbon atom is bonded to at least one carbon atom as well as to

hydrogen atoms. As you look at structural formulas, notice that every carbon atom forms




four bonds. Every hydrogen atom forms one bond. There are never any dangling bonds -

no dangling dashes.

Figure 10 Each carbon atom in these

structural formulas is surrounded by

four dashes corresponding to four

bonds.

Each molecule of the propane

used as the fuel in this camping lantern

(right) has 3 carbon atoms.

Isomers Consider the molecular formula of butane - C4H10. This formula does not

indicate how the atoms are arranged in the molecule. In fact, there are two different ways

to arrange the carbon atoms in C4H10. These two arrangements are shown in Figure 11.

Compounds that have the same molecular formula but different structures are called

isomers (EYE soh murk). Each isomer is a different substance with its own characteristic

properties.

Notice in Figure 11 that a molecule of one isomer, butane, is a straight chain. A

molecule of the other isomer, isobutane, is a branched chain. Both molecules have four

carbon atoms and 10 hydrogen atoms, but the atoms are arranged

differently in the two molecules. And these two compounds have

different properties. For example, butane and isobutane have very

different melting points and boiling points.

Checkpoint: How do structural and molecular formulas differ?

Figure 11 C4H10 has two isomers, butane and isobutane.

Interpreting Diagrams Which isomer is a branched chain?

Double Bonds and Triple Bonds So far in this section, structural formulas have shown only single bonds between

any two carbon atoms. One bond; one dash. However, two carbon atoms can form a

single bond, a double bond, or a triple bond. A carbon atom can also form a single or

double bond with an oxygen atom. Structural formulas represent a double bond with a

double dash (C=C). You might think of the two atoms as doubly hooked together. A




triple bond is indicated by a triple dash (C C). Bonds beyond triple bonds are not found

in nature.

Saturated and Unsaturated Hydrocarbons

Hydrocarbons can be classified according to the types of bonds between the

carbon atoms. If a hydrocarbon has only single bonds, it has the maximum number of

hydrogen atoms possible on its carbon chain. These hydrocarbons are called saturated

hydrocarbons. You can think of each carbon as being "saturated," or filled up, with

hydrogens. Hydrocarbons with double or triple bonds have fewer hydrogen atoms for

each carbon atom than a saturated hydrocarbon does. They are called unsaturated

hydrocarbons.

Notice that the names of methane, ethane, propane, and butane end with the suffix

-ane. Any hydrocarbon with a name that ends in -ane is a saturated hydrocarbon. If the

name of a hydrocarbon ends in -ene or -yne, it is unsaturated.

The simplest unsaturated hydrocarbon with one double bond is ethene (C2H4).

Many fruits, such as bananas, produce ethene gas. Ethene gas helps the fruit to ripen.

The simplest hydrocarbon with one triple bond is ethyne (C2H2), which is commonly

known as acetylene. Acetylene torches are used in welding.

ACTIVITY

Which of the following hydrocarbons contain single, double, or triple

bonds? (Hint: Remember that carbon forms four bonds and hydrogen forms

one bond.) C2H6 C2H4

C2H2 C3H8

C3H6 C3H4

C4H10

Figure 12 Unsaturated hydrocarbons have double and triple bonds. Ethene gas causes

fruits such as bananas to ripen.

Substituted Hydrocarbons

Hydrocarbons contain only carbon and hydrogen. But carbon can form stable

bonds with several other elements, including oxygen, nitrogen, sulfur, and members of

the halogen family. If just one atom of another element is substituted for a hydrogen atom

in a hydrocarbon, a different compound is created. Such compounds are called substituted

hydrocarbons. In a substituted hydrocarbon, atoms of other elements replace one or more

hydrogen atoms in a hydrocarbon. Substituted hydrocarbons include halogen-containing

compounds, alcohols, and organic acids.




Compounds Containing Halogens In some substituted hydrocarbons, one or more

halogen atoms replace hydrogen atoms. Recall that the halogen family includes fluorine,

chlorine, bromine, and iodine.

One compound, Freon (CCl2F2), was widely used as a cooling liquid in

refrigerators and air conditioners. When Freon was found to damage the environment, its

use was banned. Safer compounds have taken Freon's place. Two compounds containing

halogens are still used in dry - cleaning solutions - trichloro-ethane (C2H3Cl3) and

perchloroethylene (C2H2Cl2).

Alcohols The group -OH can also substitute for hydrogen atoms in a hydrocarbon.

Each -OH, made of an oxygen atom and a hydrogen atom, is called a hydroxyl group

(hy DRAHKS il). An alcohol is a substituted hydrocarbon that contains one or more

hydroxyl groups.

Most alcohols dissolve well in water. They also have higher boiling points than

hydrocarbons of similar size. This is why the hydrocarbon methane (CH4) is a gas at

room temperature, while the alcohol methanol (CH3OH) is a liquid. Methanol is used to

make plastics and synthetic fibers. It is also used in solutions that remove ice from

airplanes. Methanol is very

poisonous.

Figure 13 Methanol is used for de-

icing an airplane in a snowstorm.

Classifying What makes methanol

a substituted hydrocarbon?

When a hydroxyl group is substituted for one hydrogen atom in ethane, the resulting

alcohol is ethanol (C2H50H). Ethanol is produced naturally by the action of yeast or

bacteria on the sugar stored in corn, wheat, and barley. Ethanol is a good solvent for

many organic compounds that do not dissolve in water. It is also added to gasoline to

make a fuel for car engines called "gasohol." Ethanol is used in medicines and found in

alcoholic beverages.

The ethanol used for industrial purposes is unsafe to drink. Poisonous compounds

such as methanol have been added. The resulting poisonous mixture is called denatured

alcohol.




Figure 14 Formic acid is the simplest organic

acid. It is the acid produced by ands and is

responsible for the pain caused by an ant bite.

Organic Acids Bite into a lemon, orange, or grapefruit. These fruits taste a little

tart or sour, don't they? The sour taste of many fruits comes from citric acid, an organic

acid. An organic acid is a substituted hydrocarbon that contains one or more carboxyl

groups. A carboxyl group (kahr BAHKS il) is written as -COOH.

You can find organic acids in many foods. Acetic acid (CH3COOH) is the main

ingredient of vinegar. Malic acid is found in apples. Butyric acid makes butter smell

rancid when it goes bad. Stinging nettle plants make formic acid (HCOOH), a compound

that causes the stinging feeling. The pain from ant bites also comes from formic acid.

Esters If an alcohol and an organic acid are chemically

combined, the resulting compound is called an ester. Many

esters have pleasant, fruity smells. If you have eaten

wintergreen candy, then you are familiar with the smell of

an ester. Esters are also responsible for the smells of

pineapples, bananas, strawberries, and apples. Other esters

are ingredients in medications, including aspirin and the

local anesthetic used by dentists.

Checkpoint: What atoms are in a carboxyl group?

Figure 15 Esters are responsible for the pleasant

aroma and flavor of this strawberry shake.

Polymers Organic compounds, such as alcohols, esters, and others, can be linked together to

build huge molecules with thousands or even millions of atoms. A very large molecule

made of a chain of many smaller molecules bonded together is called a polymer (PAHL

ih mur). The smaller molecules-the links that make up the chain-are called monomers

(MAHN hi mur) The prefix poly- means "many," and the prefix mono- means "one."

Some polymers are made naturally by living things. For example, sheep make wool,

cotton plants make cotton, and silk-worms make silk. Other polymers, called synthetic




polymers, are manufactured, or synthesized, in factories. If you are wearing clothing

made from polyester or nylon, you are wearing a synthetic polymer right now! And any

plastic item you use is most certainly made of synthetic polymers.

Figure 16 Chains of monomers that make up polymer

molecules are somewhat like these chains of plastic beads.

Natural polymers include the wool being sheared from

this sheep.

Comparing and Contrasting How do polymer molecules

differ from monomer molecules?

Section 2 Review 1. List properties common to many organic compounds.

2. Describe the different kinds of carbon chains that are found in hydrocarbons.

3. What is a substituted hydrocarbon? List four examples of substituted hydrocarbons.

4. Thinking Critically Problem Solving You are given two solid materials, one that is

organic and one that is not organic. Describe three tests you could perform to help you

decide which is which.




Section 3 Polymers and Composites

GUIDE FOR READING

How does a polymer form?

Why are composite materials often more useful than single polymers?

D id you ever step into tar on a hot summer

day? Tar is a thick, smelly, black goo that sticks to

your shoes. Tar, from crude oil or coal, can be made

into rope, insulating fabric for clothes, and safety gear.

Manufacturers use tar to make countless products

ranging from sports equipment and automobile parts to

plastic house wares and toys.

Look around the room. How many things can

you see that are made of plastic? What materials do

you think people used to make these items before

plastic was invented? Many things that were once

made of metal, glass, paper, or wood have been

replaced by plastic materials.

Figure 1 The clothing, boots, goggles, and helmet

worn by this climber are all made of polymers. So is

the rope that protects her from falling off this frozen

waterfall in Colorado.

Carbon's Strings, Rings, and Other Things Plastics and the cells in your body have something in common. They are made of

carbon compounds. Carbon compounds contain atoms of carbon bonded to each other

and to other kinds of atoms. Carbon is present in more than two million known

compounds, and more are being discovered or invented every day.

Carbon's unique ability to form so many compounds comes from two properties.

Carbon atoms can form four covalent bonds. They can also bond to each other in chains

and ring-shaped groups. These structures form the "backbones" to which other atoms

attach.

Hydrogen is the most common element found with carbon in its compounds.

Other elements include oxygen, nitrogen, phosphorus, sulfur, and the halogens, especially

chlorine.

Carbon Compounds Form Polymers Molecules of some carbon compounds can hook together, forming larger

molecules. A polymer (PAHL uh mur) is a large, complex molecule built from smaller

molecules joined together. The smaller molecules from which polymers are built are

called monomers (MAHN uh murz). Polymers form when chemical bonds link large




numbers of monomers in a repeating pattern. A polymer may consist of hundreds or even

thousands of monomers.

Many polymers consist of a single kind of monomer that repeats over and over

again. You could think of these monomers as linked like the identical cars of a long

passenger train. In other cases, two or three monomers may join

in an alternating pattern. Sometimes links between monomer

chains occur, forming large webs or netlike molecules. The

chemical properties of a polymer depend on the monomers from

which it is made.

Checkpoint: What are the patterns in which monomers come

together to form polymers?

Figure 2 Carbon atoms can form straight chains, branched

chains, and rings. In these drawings, lines represent covalent

bonds that can form between atoms.

Interpreting Diagrams How many covalent bonds does each

carbon atom form?

Figure 3 Like chains of paper clips

made of the same or different pieces,

polymers can be built from one kind or

several kinds of monomers.

Natural Polymers Polymers have been around as long as life on Earth. Plants, animals, and other

living things produce many natural materials made of large polymer molecules.

Plant Polymers Look closely at a piece of coarse paper, such as a paper towel. You

can see that it is made of long strings, or fibers. These fibers are bundles of cellulose.

Cellulose (SEL yoo lohs) is a flexible but strong natural polymer that gives shape to plant

cells. Cellulose is made in plants when sugar molecules (made earlier from carbon

dioxide and water) are joined into long strands. The cellulose then forms cell structures.




Figure 4 Both animals and plants make polymers. A. The leaves and stems of these

desert plants are made of cellulose and other polymers. B. A cotton plant is a source of

polymers that people make into thread and cloth. C. These silk fabrics were made from

the threads of silkworm cocoons.

Comparing and Contrasting What do the polymers shown in these photos have in

common?

Animal Polymers Gently touch a spider web and feel how it stretches without

breaking. It is made from chemicals in the spider's body. These chemicals mix and react

to form a silken polymer that is one of the strongest materials known. Spiders spin webs,

egg cases, and traps for prey from these fibers. You can wear polymers made by animals.

Silk is made from the fibers of silkworm cocoons. Wool is made from sheep's fur. These

polymers can be woven into thread and cloth.

Your own body makes polymers. Tap your fingernail on a tabletop. Your

fingernails and the muscles that just moved your finger are made of proteins. Proteins are

polymers. Within your body, proteins are assembled from combinations of smaller

molecules (monomers), called amino acids. The properties of a protein depend on which

amino acids are used and in what order. One combination builds the protein that forms

your fingernails. Another combination forms the protein that carries oxygen in your

blood. Yet another forms the hair that grows on your head.

Checkpoint What are two examples of natural polymers from plants and animals?

Synthetic Polymers Many polymers you use every day are synthesized from simpler materials. Recall

that a synthesis reaction occurs when elements or simple compounds combine to form

complex compounds. The starting materials for polymers come from coal or oil. Plastics,

which are synthetic polymers that can be molded or shaped, are the most common

products. But there are many others. Carpets, clothing, glue, and even chewing gum can

be made of synthetic polymers.




Figure 5 lists just a few of the hundreds of polymers people use. Although the

names seem like tongue-twisters, see how many you recognize. You may be able to

identify some polymers by their initials printed on the bottoms of plastic bottles.

Compare the uses of polymers listed in Figure 5 with their characteristics. Notice

that many products require materials that are flexible, yet strong. Others must be hard or

lightweight. When chemical engineers design a new product, they have to think about

how it will be used. Then they synthesize a polymer with properties to match.

Synthetic polymers are often used in place of natural materials that are too

expensive or wear out too quickly. Polyester and nylon fabrics, for example, are used

instead of wool, silk, and cotton to make clothes. Laminated countertops and vinyl floors

replace wood in many kitchens. Other synthetic polymers have uses for which there is no

suitable natural material. Compact discs, computer parts, artificial heart valves, and even

your bicycle tires couldn't exist without synthetic polymers.

Figure 5 You can find many applications of synthetic polymers in your own home (see

Appendixes 2 and 3.

Composites Every substance has its advantages and disadvantages. What would happen if you

could take the best properties of two substances and put them together? Composites

combine two or more substances as a new material with different properties. By

combining the useful properties of two or more substances in a composite, chemists can

make a new material that works better than either one alone. Many composite materials

include one or more polymers.

A Natural Composite The idea of putting two different materials together to get

the advantages of both comes from the natural world. Many synthetic composites are

designed to imitate a common natural composite-wood. Wood is made of long fibers of

cellulose, held together by another plant polymer called lignin. Cellulose fibers are

flexible and can't support much weight. At the same time, lignin is brittle and would

crack under the weight of the tree branches. But the combination of the two polymers

makes a strong tree trunk




The Development of Polymers The first synthetic polymers were made by changing natural

polymers in some way. Later, crude oil and coal became the

starting materials. Now new polymers are designed in

laboratories every year. See Appendix 1 for a more complete

timeline.

1839 Synthetic Rubber

Charles Goodyear invented a process that turned natural rubber

into a hard, stretchable polymer It did not get sticky and soft

when heated or become brittle when cold, a natural rubber does

Bicycle tires were an early use.

1869 Celluloid

Made using cellulose, celluloid became a substitute

for ivory in billiard balls and combs and brushes. It

was later used to make movie film. Because

celluloid is very flammable, other materials have

replaced it for almost all purposes, except table-

tennis balls.

1909 Bakelite

Bakelite was the first commercial polymer made from

compounds in coal tar. Bakelite doesn't get soft when heated,

and it doesn't conduct electricity. These properties made it

useful for handles for pots and pans, telephones, and for

parts in electrical outlets.

1934 Nylon

A giant breakthrough came with a synthetic fiber

that imitates silk. Nylon replaced expensive silk in

women's stockings and fabric for parachutes and

clothing. It can also be molded to make objects like

buttons, gears, and zippers.

1952 Fiberglass Composite




Fiberglass is mixed with polymers to form a material with the strength of glass fibers and

the moldability of plastic. Fiberglass composite is useful for

boat and airplane parts because it is much lighter than metal,

and it doesn't rust.

1971 Kevlar

Kevlar is five times as strong as the same weight of steel.

This polymer is tough enough to substitute for steel ropes

and cables in offshore oil-drilling rigs, but light enough to

use as parts for spacecraft. Kevlar is also used in protective

clothing for firefighters and police officers.

1989 LEP

Light-emitting polymers (LEP) are plastics that give off light

when exposed to low voltage electricity. Research on LEPs

points toward their use as flexible and more easy to- read

viewing screens in computers, digital camera monitors,

watch-size phones, and televisions.

Figure 6 Fiberglass makes a snowboard (left) both

lightweight and strong. The composites in a fishing rod

(right) make it so flexible that it will not break when

pulling in a large fish.

Synthetic Composites The idea of combining the properties of two substances to

make a more useful one has led to many new products. Fiberglass composites are one

example. Strands of glass fiber are woven together and strengthened with a liquid plastic

that sets like glue. The combination makes a strong, hard solid that may be molded

around a form to give it shape. These composites are lightweight, but strong enough to be




used as a boat hull or car body. Fiberglass also resists corrosion. It will not rust as metal

does.

Other composites made from strong polymers combined with lightweight ones

have many uses. Bicycles, automobiles, and airplanes built from such composites are

much lighter than the same vehicles built from steel or aluminum. Some composites are

used to make fishing rods, tennis racquets, and other sports equipment that need to be

flexible but strong.

Too Many Polymers? It is difficult to look around without seeing something made of synthetic

polymers. They have replaced many natural materials for several reasons. First, polymers

are inexpensive to make. Second, they are strong. Finally, they last a long time.

But synthetic polymers have caused some problems, too. Many of the disadvantages of

using plastics come from the same properties that make them so useful. It is often cheaper

to throw away plastic materials and make new ones than it is to reuse them. As a result,

they increase the volume of trash. Most plastics don't react very easily with other

chemical compounds. This means they don't break down into simpler materials in the

environment. In contrast, natural polymers do. Some plastics are expected to last

thousands of years. How do you get rid of something that lasts that long?

Is there a way to solve these problems? One solution is to use waste plastics as

raw material for making new plastic products. You know this idea as recycling.

Recycling has led to industries that create new products from discarded plastics. Bottles,

fabrics for clothing, and parts for new cars are just some of the many items that can come

from waste plastics. A pile of empty soda bottles can even be turned into synthetic wood.

Look around your neighborhood, and you may see park benches or "wooden" fences

made from recycled plastics. Through recycling, the disposal problem is solved and new,

useful items are created.

Figure 7 These rulers are just one product made from recycled plastic bottles.

Drawing Conclusions What would have happened to these bottles if they weren't

recycled?




Section 3 Review

1. How are monomers related to polymers?

2. What advantage does a composite have over the individual materials from which it is

made?

3. Why is it possible for carbon to form so many different kinds of compounds?

4. Make a list of polymers you can find in your home. Classify them as natural or

synthetic.

5. Thinking Critically Making Judgments Think of something plastic that you have

used today. Is there some other material that would be better than plastic for this use?




Appendix 1: Plastics Timeline

1862 Alexander Parker uses cellulose to make Parkesine but it is very expensive to

produce.

1865 End of the Civil War in the United States.

1866 Cellulose is used to make celluloid, which becomes a huge commercial success.

1891 Rayon is made from cellulose and used in clothing.

1907 Leo Baekeland creates Bakelite, a plastic that does not melt, burn, or dissolve in

acid.

1908 Cellophane, made from cellulose, becomes the first flexible, waterproof wrap.

1918 End of World War I.

1926 Polyvinyl chloride is developed from hydrocarbons.

1933 Polyethylene and Saran Wrap are produced in the same year.

1938 Teflon is discovered and is later developed for use as a non-stick coating in

cookware.

1939 Nylon is invented, and it replaces animal hair in toothbrushes.

1941 The creation of polyester eventually results in the manufacture of easy-care fabrics.

1943 Silly Putty is invented during the war and later sold as a toy.

1945 End of World War II.

1957 Both polypropylene and Velcro (made from nylon) are developed.

1965 The production of a polyamide known as Kevlar results in plastics with incredible

strength.

1971 The creation of hydrogels and hydroxyacrylates result in new products, such as

contact lenses.

1977 The first plastic that conducts electricity is developed.

1981 An increase in recycled plastic results in new applications. Recycled polyester

becomes Polar Fleece, a material used in outdoor gear.

1989 Technology to make extremely thin strands of different plastics results in

microfibers.

1990s Researchers create completely biodegradable plastics made from plants.

2001 Plastic superconductors are invented.




Appendix 2: Plastic Recycling Codes




Appendix 3: Some Common Synthetic Polymers

Type of Plastic Commercial

Names

Some Uses

Acrylic Acrylic, Orion sweaters, carpets

Cellulose acetate Tenite,

Chromspun,

Celera

toys, plastic forks, curtains double

knit fabrics

Nylon Cantrece, Antron clothing, carpet

Polyacrylic acid acrylic paint cars, homes, art

Polyacrylonitrile Orlon, Acrilan clothing, fabrics

Polybutadiene rubber, Buna S automobile tires

Polycarbonate Lexan, Merlon football helmets

Polyethylene Alathon shopping bags, electrical insulation

Polyethylene terephthalate

(polyester)

Mylar, Dacron,

Avisco,Jetspun,

Zantrel

soft drink bottles, photo-graphic film,

audiotapes, clothing, fabrics

Polymethacrylate Lucite, Plexiglass aircraft windshields

Polypropylene Herculon,Vectra luggage, fabrics

Polystyrene Styrofoam foam cups, videocassettes

Polytetrafluoroethylene Teflon stain-proof coating on upholstery,

non-stick coating on cooking utensils

Polyurethane foam rubber sofa cushions

Polyvinyl acetate Vinylite chewing gum, adhesives

Polyvinyl chloride Naugahyde,

Koroseal

raincoats, drain pipes, phonograph

records

Polyvinylidene chloride Saran Wrap food wrapping

Silicone RTV 615, Silastic water-repellant coatings, lubricants

Spandex Lycra, Spandelle elastic waistbands, tights, ski pants

Viscose rayon cellophane transparent tape




Appendix 4: 2000 U.S. Plastics Production




Appendix 5: Glossary

acid A substance that tastes sour, reacts with metals and carbonates, and turns blue litmus

red. Releases an H+ ion when in solution.

alcohol A substituted hydrocarbon that contains one or more hydroxyl groups.

amino acid One of 20 kinds of organic compounds that are the monomers of proteins

base A substance that tastes bitter, feels slippery, and turns red litmus blue. Releases on

OH- ion in solution.

boiling point The temperature at which a substance changes from a liquid to a gas.

boiling The process that occurs when vaporization takes place inside a liquid as well as

on the surface.

bonding. The electrostatic attraction between atoms to form a stable unit, such as a

molecule.

BTU. Abbreviation for British Thermal Unit; unit of heat in the English system. Defined

as the amount of heat required to raise the temperature of one pound of water one degree

Fahrenheit. It is equivalent to 252 calories, 1055 joules, or 0.293 watt-hours.

buoyancy. Ability of an object to float in water. The less the density is compared to

water the more buoyant it will be.

calorie. The amount of heat required to raise the temperature of one gram of water one

degree Celsius. Food Calories (spelled with a capital C) are equal to 1000 calories, or one

kilocalorie.

carbohydrate An energy-rich organic compound made of the elements carbon,

hydrogen, and oxygen.

carboxyl group A -COOH group, found in organic acids. .

cellulose A flexible but strong natural polymer that gives shape to plant cells.

chemical bond The force that holds atoms together.

chemical change A change in which one or more substances combine or break apart to

form new substances.

chemical energy A form of energy that comes from chemical bonds.

chemical equation A short, easy way to show chemical reactions, using symbols instead

of words.

chemical formula A combination of symbols that represent the elements in a compound.

chemical reaction A process in which substances undergo chemical changes, forming

new substances with different properties.

chemical symbol A one- or two-letter representation of an element.

coefficient A number in front of a chemical formula in an equation that indicates how

many molecules or atoms of each reactant and product are involved in a reaction. In

3H2O the 3 is the coefficient, meaning there are 3 molecules of water.

combustion A rapid reaction between oxygen and fuel that results in fire.

complex carbohydrate A long chain, or polymer, of simple carbohydrates.

composite A combination of two or more substances that creates a new material.

compound A substance made of two or more elements chemically combined.

concentration The amount of one material in a certain volume of another material.




condensation The change of state from a gas to a liquid.

covalent bond A chemical bond formed when two atoms share electrons.

cross-linking. A process in which chemical links are set up between polymer chains.

crude oil. A fossil fuel; also known as petroleum; typically refers to oil taken directly out

of the ground (prior to processing).

density. The measurement of how much mass of a substance is contained in a given

volume; the mass per unit volume, specifically grams per milliliter. Density equals mass

divided by volume (d=m/v).

diamond A form of the element carbon; it is the hardest mineral crystal on Earth.

DNA DeoxyriboNucleic Acid.

double bond A chemical bond formed when atoms share two pairs of electrons.

elasticity. Ability of a material to stretch and then return to its original shape.

electron A tiny, negatively charged particle that move around the nucleus of an atom.

electron dot diagram A representation of the number of valence electrons in an atom,

using dots placed around the symbol of an element.

element A substance that cannot be broken down into any other substances by chemical

or physical means.

energy. A quantity possessed by an object or a system, which gives it the capability to do

work, or change the condition of matter. Energy can be measured in many units,

including kilocalories, joules or BTUs.

ester An organic compound made by chemically combining an alcohol and an organic

acid.

evaporation The process that occurs when vaporization takes place only on the surface

of a liquid.

feedstock. The raw or starting materials for industrial processes.

fiber. A slender and greatly elongated natural or synthetic filament capable of being spun

into yarn. Examples include wool, cotton, asbestos, and rayon.

flammable. Easily ignited. Syn: inflammable.

fluid Any substance that can flow.

fuel A material that releases energy when it burns.

fullerene A form of the element carbon that consists of carbon atoms arranged in a

repeating pattern.

gas A state of matter with no definite shape or volume.

glucose A sugar found in the body; the monomer of many complex carbohydrates.

graphite A form of the element carbon in which carbon atoms form flat layers.

halogen family The elements in Group 17 (7A) of the periodic table.

hydrocarbons. Molecules composed mostly of hydrogen and carbon atoms.

hydrogen ion A positively charged ion (H+) formed of a hydrogen atom that has lost its

electron.




hydroxide ion A negatively charged ion made of oxygen and hydrogen, OH-. found in

alcohols.

indicator A compound that changes color in the presence of an acid or a base.

International System of Units (SI) The system of units used by scientists to measure the

properties of matter.

ion An atom or group of atoms that has become electrically charged.

ionic compound A compound made of ironically bonded atoms or molecules.

ionic bond The attraction between oppositely charged ions.

isomer One of a number of compounds that have the same molecular formula but

different structures.

isotope An atom with the same number of protons and different number of neutrons from

other atoms of the same element.

Joule. International System of Units (SI) unit of energy; defined as the amount of energy

exerted by a force of one Newton over one meter. One joule (J) equals 0.239 calories.

Kilocalorie. International System of Units (SI) unit of heat; defined as the amount of heat

needed to raise the temperature of one kilogram of water by one degree Celsius. One

kilocalorie (kcal) equals 4,184 joules.

kilogram. International System of Units (SI) unit of mass. One kg (1000 grams) is

equivalent to 2.2 pounds.

liquid A state of matter that has no definite shape but has a definite volume.

mass A measure of how much matter is in an object.

mass number The sum of the protons and neutrons in the nucleus of an atom.

matter Anything that has mass and occupies space.

melting point The temperature at which a substance changes from a solid to a liquid.

melting The change in state from a solid to a liquid.

mixture Two or more substances that are mixed together but not chemically combined.

model. Any representation of a system, or its compo-nents, to help one study and

understand how it works.

molecular compound A compound consisting of molecules of covalently bonded atoms.

molecular formula A combination of chemical symbols that represent the elements in

each molecule of a compound.

molecule. A combination of two or more atoms.Smallest unit of matter that retains its

physical and chemical properties. A molecule may be a single atom or a group of atoms

bonded together. Examples include Ne, H2, H2O.

monomer One molecule that makes up the links in a polymer chain. Small, carbon-based

molecules from which polymers are built. Literally means "one part."

natural polymer. Polymers found in the environment. Examples include cellulose, DNA,

and starch.

neutralization A reaction of an acid with a base, yielding a solution that is not as acidic

or basic as the starting solutions were.




neutron A small particle in the nucleus of the atom, with no electrical charge.

noble gas An element in Group 18 of the periodic table.

nonpolar The description of a covalent bond in which electrons are shared equally, or of

a molecule containing nonpolar bonds, or polar bonds that cancel out.

nucleic acid A very large organic compound made up of carbon, oxygen, hydrogen,

nitrogen, and phosphorus; examples are DNA and RNA.

nucleotide An organic compound that is one of the monomers of nucleic acids.

nucleus The central core of an atom containing protons and usually neutrons.

organic acid A substituted hydrocarbon with one or more of the -COOH group of atoms.

organic compounds Most compounds that contain carbon.

period A horizontal row of elements in the periodic table.

periodic table A chart of the elements showing the repeating pattern of their properties.

petroleum. A fossil fuel; also known as crude oil; typically refers to oil during and after

industrial processing.

pH scale A measure of the concentration of hydrogen ions in a solution.

physical change A change in a substance that does not change its identity; for example, a

change of state.

physical property. An intrinsic property of a material, such as density, melting point, or

hardness.

plasma A state of matter in which atoms are stripped of their electrons and the nuclei

packed closely together.

plastic A synthetic polymer that can be molded or shaped. (adjective) Capable of being

molded. (noun) Any of numerous processed polymers of high molecular weight.

plasticizer. A material added to a plastic to increase its flexibility and workability.

polar The description of a covalent bond in which electrons are shared unequally, or of a

molecule containing polar bonds that do not cancel out.

polyatomic ion An ion that is made of more than one atom.

polymer. A very large molecule made of many repeating small molecular units bonded

together; lit-erally means "many parts."

polymerization. The act of chemically bonding many identical or related basic units

(monomers) together to form a polymer.

precipitate A solid that forms from a solution during a chemical reaction.

product A substance formed as a result of a chemical reaction.

protein An organic compound that is a polymer of amino acids.

pure substance A substance made of only one kind of matter and having definite

properties.

PVA. Abbreviation for polyvinyl alcohol, a liquid polymer.

PVC. Abbreviation for polyvinyl chloride, a solid plastic polymer used to make objects

such as pipes.

reactant A substance that enters into a chemical reaction.

reactivity The ease and speed with which an element or compound combines with other

elements and compounds.




replacement reaction A reaction in which one element replaces another in a compound;

or when two elements in different compounds trade places.

RNA RiboNucleic Acid.

salt An ionic compound that can form from the neutralization of an acid with a base.

saturated hydrocarbons A hydrocarbon in which all the bonds between carbon atoms

are single bonds.

saturated solution A mixture that has so much solute in it that no more will dissolve.

semiconductor An element that can conduct electricity under some conditions.

solid A state of matter that has a definite volume and a definite shape.

solubility A measure of how well a solute can dissolve in a solvent at a given

temperature.

solute The part of a solution present in a lesser amount and that is dissolved by the

solvent.

solution A very well-mixed mixture.

solvent The part of a solution present in the largest amount and that dissolves other

substances.

structural formula A description of a molecule that shows the kind, number, and

arrangement of atoms. Method of expressing chemical bonds among atoms in a molecule

using lines to represent bonds between shared pairs of electrons.

subscript A number in a formula written lower and smaller than the symbol to indicate

the number of atoms of an element in a molecule. In 3H2O the 2 is the subscript, meaning

there are 2 atoms of hydrogen in a molecule of water.

substituted hydrocarbon A hydrocarbon in which one or more hydrogen atoms have

been replaced by atoms of other elements.

suspension A mixture in which particles can be seen and easily separated by settling or

filtration.

symbol A one- or two-letter set of characters that is used to identify elements.

synthesis A chemical reaction in which two or more simple substances combine to form

a new, more complex substance.

synthetic. Produced by chemical reactions in a laboratory rather than through natural

processes, manufactured.

temperature A measure of the average energy of motion of the particles of a substance.

thermal energy The total energy of a substance's particles due to their movement or

vibration.

thermoplastic. Any of the plastics that can be continually and repeatedly formed and

reshaped with the application of heat and pressure.

thermosetting. Applied to plastics that cannot be reshaped once formed. Thermosetting

polymers are often a result of cross-linked bonds.

trade-off. A balancing of factors, all of which are not attainable at the same time; getting

one thing at the cost of another. The trade-off is the aspect that is given up and can only

be evaluated in the context of what it was exchanged for.

unsaturated hydrocarbon A hydrocarbon in which one or more of the bonds between

carbon atoms is double or triple.




unsaturated solution A mixture in which more solute can be dissolved.

valence electrons The electrons that are farthest away from the nucleus of an atom and

are involved in chemical reactions.

vaporization The change of state from a liquid to a gas.

viscosity The resistance of a liquid to flowing.

volume The amount of space that matter occupies.

waste stream. General term used to denote the discarded material output of an area,

location, or facility.

weight A measure of the force of gravity on an object.

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Polymers and Plastics - SWPS