Polymers and their properties

report

1. POLYMERS and thEiR PROPERtiESPOLYMERS and thEiR PROPERtiES
►IntroductionIntroduction
►Basic Topics:Basic Topics:
Types of PolymersTypes of Polymers
Classification of PolymersClassification of Polymers
Characteristics of PolymersCharacteristics of Polymers
Properties of PolymersProperties of Polymers
Strength of PolymersStrength of Polymers
►Applications of PolymersApplications of Polymers

2. Introduction Introduction
►PolymersPolymers are long chain giant organic molecules are are long chain giant organic molecules are
assembled from many smaller molecules called assembled from many smaller molecules called
monomers. Polymers consist of many repeating monomers. Polymers consist of many repeating
monomer units in long chains. A polymer is analogous monomer units in long chains. A polymer is analogous
to a necklace made from many small beads to a necklace made from many small beads
(monomers). (monomers).
►Another common name for many synthetic polymers is Another common name for many synthetic polymers is
plastic which comes from the Greek word "plastikos", plastic which comes from the Greek word "plastikos",
suitable for molding or shaping. Many objects in daily suitable for molding or shaping. Many objects in daily
use from packing, wrapping, and building materials use from packing, wrapping, and building materials
include half of all polymers synthesized.include half of all polymers synthesized.

3. Basic Topics:Basic Topics:
Types of PolymersTypes of Polymers
Classification of PolymersClassification of Polymers
Characteristics of PolymersCharacteristics of Polymers
Properties of PolymersProperties of Polymers
Strength of PolymersStrength of Polymers

4. Types of PolymersTypes of Polymers
►PolythenePolythene
The first commercially produced polymer is also the simplest and most The first commercially produced polymer is also the simplest and most
common: polythene. Its systematic name is poly(ethene) meaning it is a common: polythene. Its systematic name is poly(ethene) meaning it is a
polymer made from the monomer, ethene. Ethene is a small molecule polymer made from the monomer, ethene. Ethene is a small molecule
containing two carbon atoms linked by a double bond and four hydrogen containing two carbon atoms linked by a double bond and four hydrogen
atoms, two bonded to each carbon.atoms, two bonded to each carbon.
►Free ElectronsFree Electrons
When ethene is subjected to high temperature and pressure, or reacted in the When ethene is subjected to high temperature and pressure, or reacted in the
presence of a catalyst, one of the bonds in the double bond is broken. Each of presence of a catalyst, one of the bonds in the double bond is broken. Each of
the carbon atoms then has a free electron which can form a covalent bond by the carbon atoms then has a free electron which can form a covalent bond by
pairing with another free electron. If other ethene molecules are present, the pairing with another free electron. If other ethene molecules are present, the
double bond in one of them can break, and the free electron on one of the double bond in one of them can break, and the free electron on one of the
carbons can combine with another on the original molecule. As this continues, carbons can combine with another on the original molecule. As this continues,
a long chain of carbon atoms, bonded to one another by single covalent bonds a long chain of carbon atoms, bonded to one another by single covalent bonds
forms. Each carbon atom has two hydrogen atoms bonded to it.forms. Each carbon atom has two hydrogen atoms bonded to it.

5. ►Poly(propene)Poly(propene)
Other polymers can be made in this way. Poly(propene) is very Other polymers can be made in this way. Poly(propene) is very
similar to poly(ethene). It is made from propene which has three similar to poly(ethene). It is made from propene which has three
carbon atoms, two of which are joined by a double bond. When it carbon atoms, two of which are joined by a double bond. When it
reacts to become a polymer (polymerises), the long chain is reacts to become a polymer (polymerises), the long chain is
similar to poly(ethene) except that every other carbon atom has a similar to poly(ethene) except that every other carbon atom has a
methyl (CH3-) group attached to it.methyl (CH3-) group attached to it.
►Varied UsesVaried Uses
The properties of this type of polymer depend on the regularity The properties of this type of polymer depend on the regularity
of the arrangement of the chains. If they are lined up in a regular of the arrangement of the chains. If they are lined up in a regular
way, they are strong, hard materials. If they are more irregular, or way, they are strong, hard materials. If they are more irregular, or
there are more side-chains on the molecules, they are more there are more side-chains on the molecules, they are more
flexible.flexible.

6. ►Amide LinkagesAmide Linkages
One of the most common molecules in biochemistry is a type of polymer One of the most common molecules in biochemistry is a type of polymer
called protein. These are made up from monomers known as amino acids and called protein. These are made up from monomers known as amino acids and
they are joined by an amide linkage. These linkages are made by a carboxylic they are joined by an amide linkage. These linkages are made by a carboxylic
acid group (-COOH) reacting with an amine group (-NH2) forming the acid group (-COOH) reacting with an amine group (-NH2) forming the
linkage (-NHCO-) and eliminating water. This linkage is the basis of another linkage (-NHCO-) and eliminating water. This linkage is the basis of another
type of synthetic polymers, the Nylons.type of synthetic polymers, the Nylons.
►NylonNylon
Whereas proteins use monomers with both a carboxylic acid and an amine in Whereas proteins use monomers with both a carboxylic acid and an amine in
the same molecule. Nylons are made using two types of monomer. These are the same molecule. Nylons are made using two types of monomer. These are
dicarboxylic acids and diamines. The first nylon synthesised used one dicarboxylic acids and diamines. The first nylon synthesised used one
monomer with a chain of four carbons with a carboxylic acid group on each monomer with a chain of four carbons with a carboxylic acid group on each
end and another monomer with a six carbon chain with an amine group on end and another monomer with a six carbon chain with an amine group on
each end. This produced a polymer with repeating units of six carbons joined each end. This produced a polymer with repeating units of six carbons joined
with amide linkages, but alternately reversed. This polymer is Nylon-6.6. with amide linkages, but alternately reversed. This polymer is Nylon-6.6.
Nylons are mainly used as fibres for clothing and also other hard parts in light Nylons are mainly used as fibres for clothing and also other hard parts in light
engineering. engineering.

7. ►PolyurethanePolyurethane
A further important group of polymers are polyurethanes. These A further important group of polymers are polyurethanes. These
are very similar to nylons, but are formed by reacting alcohols are very similar to nylons, but are formed by reacting alcohols
with isocyanates and have an amide linkage with an additional with isocyanates and have an amide linkage with an additional
oxygen atom in the chain. These polymers are softer and more oxygen atom in the chain. These polymers are softer and more
elastic than nylons and are used as a substitute for rubber and in elastic than nylons and are used as a substitute for rubber and in
elastic and Lycra.elastic and Lycra.
►PolyestersPolyesters
The final types of polymer we will deal with in this article are the The final types of polymer we will deal with in this article are the
polyesters. The ester linkage is a carboxylic acid group where the polyesters. The ester linkage is a carboxylic acid group where the
hydrogen has been replaced by the carbon of another organic hydrogen has been replaced by the carbon of another organic
group. Polyesters are widely used as fibres for clothes and also group. Polyesters are widely used as fibres for clothes and also
for many drinks bottles. They are also used to make thin films for for many drinks bottles. They are also used to make thin films for
applications such as video tape.applications such as video tape.

8. Classification of PolymersClassification of Polymers
►Homopolymers - consist of chains with identical Homopolymers - consist of chains with identical
bonding linkages to each monomer unit. This bonding linkages to each monomer unit. This
usually implies that the polymer is made from all usually implies that the polymer is made from all
identical monomer molecules. identical monomer molecules.
These may be represented as : -[A-A-A-A-A-A]- These may be represented as : -[A-A-A-A-A-A]-
►Copolymers - consist of chains with two or more Copolymers - consist of chains with two or more
linkages usually implying two or more different linkages usually implying two or more different
types of monomer units.types of monomer units.
These may be represented as : -[A-B-A-B-A-B]-These may be represented as : -[A-B-A-B-A-B]-

9. Polymers are further classified by the reaction Polymers are further classified by the reaction
mode of polymerization, these include: mode of polymerization, these include:
►Addition Polymers - the monomer molecules Addition Polymers - the monomer molecules
bond to each other without the loss of any other bond to each other without the loss of any other
atoms. Alkene monomers are the biggest groups atoms. Alkene monomers are the biggest groups
of polymers in this class. of polymers in this class.
►Condensation Polymers - usually two different Condensation Polymers - usually two different
monomer combine with the loss of a small monomer combine with the loss of a small
molecule, usually water. Polyesters and molecule, usually water. Polyesters and
polyamides (nylon) are in this class of polymers. polyamides (nylon) are in this class of polymers.
Polyurethane Foam in graphic. Polyurethane Foam in graphic.

10. Classification based upon the physical Classification based upon the physical
property related to heating: property related to heating:
►Thermoplastics - plastics that soften when Thermoplastics - plastics that soften when
heated and become firm again when cooled. heated and become firm again when cooled.
This is the more popular type of plastic because This is the more popular type of plastic because
the heating and cooling may be repeated. the heating and cooling may be repeated.
►Thermosets - plastics that soften when heated Thermosets - plastics that soften when heated
and can be molded, but harden permanently. and can be molded, but harden permanently.
They will decompose when reheated. An They will decompose when reheated. An
example is Bakelite, which is used in toasters, example is Bakelite, which is used in toasters,
handles for pots and pans, dishes, electrical handles for pots and pans, dishes, electrical
outlets and billiard balls. outlets and billiard balls.

11. Characteristics of PolymersCharacteristics of Polymers
►Low Density.Low Density.
►Low coefficient of friction.Low coefficient of friction.
►Good corrosion resistance.Good corrosion resistance.
►Good mould ability.Good mould ability.
►Excellent surface finish can be obtained.Excellent surface finish can be obtained.
►Can be produced with close dimensional tolerances.Can be produced with close dimensional tolerances.
►Economical.Economical.
►Poor tensile strength.Poor tensile strength.
►Low mechanical properties.Low mechanical properties.
► Poor temperature resistance.Poor temperature resistance.
► Can be produced transparent or in different colours.Can be produced transparent or in different colours.

12. Properties of PolymersProperties of Polymers
The physical properties of a polymer, such as its strengthThe physical properties of a polymer, such as its strength
and flexibility depend on:and flexibility depend on:
►Chain length - in general, the longer the chains the Chain length - in general, the longer the chains the
stronger the polymer;stronger the polymer;
►Side groups - polar side groups give stronger attraction Side groups - polar side groups give stronger attraction
between polymer chains, making the polymer stronger;between polymer chains, making the polymer stronger;
►Branching - straight, un branched chains can pack Branching - straight, un branched chains can pack
together more closely than highly branched chains, together more closely than highly branched chains,
giving polymers that are more crystalline and therefore giving polymers that are more crystalline and therefore
stronger;stronger;
►Cross-linking - if polymer chains are linked together Cross-linking - if polymer chains are linked together
extensively by covalent bonds, the polymer is harder extensively by covalent bonds, the polymer is harder
and more difficult to melt.and more difficult to melt.

13. Strength of PolymersStrength of Polymers
In general, the longer the polymer chain, the stronger the In general, the longer the polymer chain, the stronger the
polymer. There are two reasons for this:polymer. There are two reasons for this:
►longer chains are more tangledlonger chains are more tangled
►there are more intermolecular forces between the chains there are more intermolecular forces between the chains
because there are more points of contact. These forces, because there are more points of contact. These forces,
however, are quite weak for polyethene.however, are quite weak for polyethene.
►Areas in a polymer where the chains are closely packed in Areas in a polymer where the chains are closely packed in
a regular way are said to be a regular way are said to be crystallinecrystalline. The percentage . The percentage
of crystallinity in a polymer is very important in of crystallinity in a polymer is very important in
determining its properties. The more crystalline the determining its properties. The more crystalline the
polymer, the stronger and less flexible it becomes.polymer, the stronger and less flexible it becomes.

14. ►When a polymer is stretched (cold-drawn), a neck forms. In When a polymer is stretched (cold-drawn), a neck forms. In
the neck the polymer chains line up producing a more the neck the polymer chains line up producing a more
crystalline region. Cold-drawing leads to an increase in crystalline region. Cold-drawing leads to an increase in
strength.strength.
►The first polyethene which was made contained many The first polyethene which was made contained many
chains which were branched. This resulted in a relatively chains which were branched. This resulted in a relatively
disorganised structure of low strength and density. This disorganised structure of low strength and density. This
was called was called low density polyethene (ldpe)low density polyethene (ldpe)..
►In the crystalline form, the methyl groups all have the same In the crystalline form, the methyl groups all have the same
orientation along the chain. This is called the orientation along the chain. This is called the isotacticisotactic
form. In the amorphous form, the methyl groups are form. In the amorphous form, the methyl groups are
randomly orientated. This is called the randomly orientated. This is called the atacticatactic form. form.
►Polymers with a regular structure are said to be Polymers with a regular structure are said to be
stereoregularstereoregular..

15. Applications of Polymers:Applications of Polymers:
►Polymeric materials are used in and on soil to improve Polymeric materials are used in and on soil to improve
aeration, provide mulch, and promote plant growth and aeration, provide mulch, and promote plant growth and
health. health.
MedicineMedicine
►Many biomaterials, especially heart valve replacements Many biomaterials, especially heart valve replacements
and blood vessels, are made of polymers like Dacron, and blood vessels, are made of polymers like Dacron,
Teflon and polyurethane.Teflon and polyurethane.
Consumer ScienceConsumer Science
►Plastic containers of all shapes and sizes are light weight Plastic containers of all shapes and sizes are light weight
and economically less expensive than the more traditional and economically less expensive than the more traditional
containers. Clothing, floor coverings, garbage disposal containers. Clothing, floor coverings, garbage disposal
bags, and packaging are other polymer applications. bags, and packaging are other polymer applications.

16. IndustryIndustry
►Automobile parts, windshields for fighter planes, Automobile parts, windshields for fighter planes,
pipes, tanks, packing materials, insulation, wood pipes, tanks, packing materials, insulation, wood
substitutes, adhesives, matrix for composites, and substitutes, adhesives, matrix for composites, and
elastomers are all polymer applications used in the elastomers are all polymer applications used in the
industrial market. industrial market.
SportsSports
►Playground equipment, various balls, golf clubs, Playground equipment, various balls, golf clubs,
swimming pools, and protective helmets are often swimming pools, and protective helmets are often
produced from polymers. produced from polymers.