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1. DEFENCE ENGINEERING COLLEGE
Metallurgical And Materials Engineering
1
Present By:
Weldebrhan Hadush (Maj.)
Feb. 20, 2019

2. 2
Course cover
1. Chapter 1 …… Introduction to Polymers
2. Chapter 2 …… Classification and molecular structure of polymers
3. Chapter 3 ..…. Molecules of polymers
4. Chapter 4 …… Polymerization and copolymerization
5. Chapter 5 …… Behaviors of polymers
6. Chapter 6 ……. Strengthening, creep, and fracture of polymers
7. Chapter 7 …..... Plastic materials
8. Chapter 8 …… Elastomers
9. Chapter 9 ……. Polymer Processing
10. Chapter 10 ……Material selection for engineering design
Engineering Polymers
DUC 2018/19

3. 3
Course cover
1. Chapter 1 …… Introduction
2. Chapter 2 …… what’s a polymer?
3. Chapter 3 ..…. Characterization of the macromolecule
4. Chapter 4 …… Bulk properties, Entanglements, glass transition, crystallinity
5. Chapter 5 …… Rubber elasticity
6. Chapter 6 ……. Plasticity Vs Elasticity
7. Chapter 7 …..... Plasticity in tensile mode
8. Chapter 8 …… Semi-crystalline polymers
9. Chapter 9 ……. Ductile brittle transition
10. Chapter 10 …... Fracture of polymers
11. Chapter 11…… Visco-elastic behavior
12. Chapter 12 …... Visco-elastic Concept
13. Chapter 13…… Time temperature Equivalence
14. Chapter 14……. Polymer Processing
Engineering Polymers
DUC 2018/19

4. DEFENCE ENGINEERING COLLEGE
Metallurgical And Materials Engineering
4
Present By:
Weldebrhan Hadush (Maj.)
20 Feb., 2019

5. 5
Content
 Introduction
 Definition of Polymer
 Formation of polymers
 Characteristics of polymers
 Applications of Polymers
Introduction to Polymers
DUC 2018/19

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Introduction to Polymers
DUC 2018/19
Introduction
Classification of Materials used by human:
 Metals
 Ceramics
 Polymers

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Introduction to Polymers
DUC 2018/19
Introduction
Classification of Materials used by human:
 Metals
 Polymers
 Ceramics

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Introduction to Polymers
DUC 2018/19
Cont…
Examples of each material family

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Design problem
• Discuss materials used in bicycle frames. This is a good case study. For
our specific example here, we recommend the insightful bicycle frame
design:
Introduction to Polymers
DUC 2018/19
In the figure shows a bicycle, with forces F1 and F2
applied to the frame by the pedals. These forces
produce bending moments and torsions in the frame
tubes.

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Selection of Materials
Introduction to Polymers
DUC 2018/19

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Cont…
Use the Young’s modulus–density (E–ρ) chart of in figure above to find:
a. Polymers that are stiffer and less dense and
b. Non-Metallic materials that are both stiffer and less dense than steel.
Introduction to Polymers
DUC 2018/19

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Introduction to Polymers
1. Definition of Polymer
• Polymers are organic solids based on long chains of carbon (or, in a few,
silicon)atoms.
• Polymers are long chain giant organic molecules are assembled from
many repeating subunits called “MONOMERS”, connected by Covalent
bonds or chemical bonds. (Poly = many, mer = unit, many units)
• Polymers are giant chain-like molecules (hence, the name
macromolecules),with covalently bonded carbon atoms forming the
backbone of the chain.
• Another common name for many synthetic polymers is plastic which
comes from the Greek word "plastikos", suitable for molding or shaping.
Many objects in daily use from packing, wrapping, and building materials
include half of all polymers synthesized.
• Polymers are unique, they have thermal properties called glassy transition
temperature(Tg).
DUC 2018/19

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Introduction to Polymers
2. Formation of polymers:
Polymerization is the process of joining together many monomers, the
basic building blocks of polymers, to form the chains. For example, the
ethyl alcohol monomer has the chemical formula
• The monomer vinyl chloride has the chemical formula C2H3Cl, which,
on polymerization, becomes polyvinyl chloride (PVC). The structural
formula of polyvinyl chloride is represented by
Where n is the dgree of polymerization
DUC 2018/19

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Introduction to Polymers
3. Characteristics of polymers
► Low Density.
► Low coefficient of friction.
► Good corrosion resistance.
► Good mould ability.
► Excellent surface finish can be obtained.
► Can be produced with close dimensional tolerances.
► Economical(cheap and easy processed).
► Poor tensile strength.
► Low mechanical properties.
► poor conductors of heat and electricity. (b/c of covalent bonding)
► Can be produced transparent or in different colour
NB: Polymers are generally more resistant to chemicals than are metals, but
prolonged exposure to ultraviolet light and some solvents can cause
degradation of a polymer’s properties.
DUC 2018/19

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Introduction to Polymers
4. Applications of Polymers:
Polymeric materials are used in and on soil to improve aeration, provide
mulch, and promote plant growth and health.
Industry
►Automobile parts, windshields for fighter planes, pipes, tanks, packing
materials, insulation, wood substitutes, adhesives, matrix for
composites, and elastomers are all polymer applications used in the
industrial market.
Medicine
►Many biomaterials, especially heart valve replacements and blood
vessels, are made of polymers like Dacron, Teflon and polyurethane.
DUC 2018/19

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Introduction to Polymers
Cont…
Sports
►Playground equipment, various balls, golf clubs, swimming pools, and
protective helmets are often produced from polymers.
Consumer Science
► Plastic containers of all shapes and sizes are light weight and
economically less expensive than the more traditional containers.
Clothing, floor coverings, garbage disposal bags, and packaging are
other polymer applications.
DUC 2018/19

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“The future can not be predicted,
but it can
be made !”

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Example 1.1
Carbon black is frequently used as a particulate filler in polymers, both thermoplastic and thermoset. Describe some of the
important effects of the addition of carbon black to polymers.
Solution: Carbon black is stronger than the polymer matrix; thus, we get a stronger and harder composite. Carbon black is also
thermally more stable than the polymer matrix; therefore, its addition results in a thermally stable composite -- that is, improved
creep resistance. In addition, carbon black leads to an enhanced dimensional stability. (It has a higher modulus and lower expansion
coefficient than the polymer.)
Example 3.6
Polyethylene is a linear-chain thermoplastic; that is, relatively speaking, it is easy to crystallize by stretching or plastic deformation.
An extreme case of this is the high degree of crystallization obtained in a gel-spun polyethylene fiber. Describe a simple technique
that can be used to verify the crystallization in polyethylene.
Solution: An easy way would be to use an X-ray diffraction technique. Unstretched polyethylene will consist mostly of amorphous
regions. Such a structure will give diffuse halos. A diffuse halo indicates an irregular atomic arrangement -- that is, an amorphous
structure. A polyethylene sample that has been subjected to stretching or a gel spun polyethylene fiber will have highly crystalline
regions aligned along the draw axis. There may also be some alignment of chains in the amorphous regions. An X-ray diffraction
pattern of such a sample would show regular spots and/or regular rings. The discrete spots indicate regular spacing characteristic of
an orderly arrangement in a single crystal. Well-spaced regular rings indicate a polycrystalline region. Regular rings result from
overlapping spots due to random crystalline orientations.

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Rubber is a thermoplastic polymer with secondary bonds between the chains. Natural rubber is too
soft for many applications.
vulcanization of rubber. Sulfur reacts with the double bond in the rubber and establishes primary
bonds between the chains, effectively transforming the rubber into a thermoset.
An isomer of this molecule, trans-1,4, polyisoprene has the structure.An isomer of this molecule, trans-1,4, polyisoprene has the structure.
Polyethylene is synthesized by a chemical reaction involving a catalyst, which is a
peroxide radical, and ethylene gas. The peroxide attacks the double bond of ethylene and
transforms the latter into a radical (a molecule with an unsatisfied, chemically active,
bond).