POLYMERS
Group Members
Seda KOCA
Bengi AYDİLEK
Didem Büşra KABAKÇI
Gözde ERGİN
11.11.2009
Hacettepe University
The Outline
 Reactions of polymers
Addition Polymerization
Step Growth Polymerization
 Kinetic Of Polymerization
 Polymerization Processes
Bulk Polymerization
Solvent Polymerization
Suspention Polymerization
Emulsion Polymerization
Special Processes
The Outline
 Chemical and Physical Structures of Polymers
 Polymer’s molecular structures
Confriguration and conformation of polymers
Chain structures of polymers
 Physical Structures of Polymers
Polymer crystallinity
Crystallinity and amorphousness of polymers
Outline
 Types of Polymers and Polymer Processing
 Members of Polymers
Definition of Thermosets & Thermoplastics
Common products and their properties
 Forming Techniques of Polymers
Extrusion of polymers
Injection Molding
Blow Molding
Thermoforming
Compression Molding
Casting
The Outline
 Recycling of Polymers
Definiton of Recycling
Why is recycling important?
Benefits
Recycling of polymers
Addition Polymerization (Chain Growth)
Step Growth Polymerization (Condensation)
Differences between step-growth polymerization and
chain-growth polymerization
Step-growth polymerization
Chain-growth polymerization
Growth throughout matrix
Growth by addition of monomer only at
one end of chain
Rapid loss of monomer early in the
reaction
Some monomer remains even at long
reaction times
Same mechanism throughout
Different mechanisms operate at
different stages of reaction (i.e.
Initiation, propagation and
termination)
Average molecular weight increases
slowly at low conversion and high
extents of reaction are required to
obtain high chain length
Molar mass of backbone chain increases
rapidly at early stage and remains
approximately the same throughout the
polymerization
Ends remain active (no termination)
Chains not active after termination
No initiator necessary
Initiator required
Step of Radical Chain Polymerization
 Initiation
 Propagation
 Termination
INITIATION
PROPAGATION
TERMINATION
Dead Polymer
i.) Coupling or Combination;
ii.) Disproportionation
CHAIN TRANSFER REACTIONS
Transfer to monomer reaction
Transfer to initiator reaction
Transfer to solvent reaction
IONIC CHAIN POLYMERIZATION
 Using catalyst, not initiator
 Highest reaction rate
 Termination step is just disproportionation
 Environment must be pure
 Reaction occurs in the cold
Anionic Polymerization=Living Polymerization
If the starting reagents are pure and the
polimerization reactor is purged of all oxygen and
traces of water, polimerization can proceed until
all monomer is consumed.
CONDENSATION POLYMERIZATION
 Using catalyst
 Minumum two functional groups required
 Usually linear
 Molecular weight increases slowly at low conversion
 High extents of reaction are required to obtain high
chain length
KINETICS OF POLYMERIZATION
 Reaction rate of ionic polimerization more than
radicalic polimerization
 So kinetics of ionic polimerization are not calculated
 But kinetics of radicalic polimerization can be
analysed
Kinetic of Radicalic Polymerization
Initiation;
Propagation;
Termination;
Kinetic of Radicalic Polymerization
 Ro = overall rate of
polimerization
 Rp = rate of chain
propagation
 Ri = rate of initiation
step
 Rt = rate of termination
step
Kinetic of Condensation
Polymerization
 Equivalent reactivity
of functional groups.
 It may be first, second
or third order by
depending upon.
Kinetic of Condensation
Polymerization
 Assumption = a stoichiometry balance of monomer concentration
POLYMERIZATION PROCESSES
 Bulk Polymerization
 Solvent Polymerization
 Suspention Polymerization
 Emulsion Polymerization
 Special Processes
 Electrochemical Polymerization
 Radiation Polymerization
 Grow-discharge (Plasma)
Bulk Polymerization
 The simplest technique
 It gives the highest-purity polymer
 Ingredients : monomer,
monomer-soluble initiator,
perhaps a chain transfer agent
Advantages
Disadvantages
High yield per reactor volume
Difficult of removing the lost
traces of monomer
Easy polymer recovery
Dissipating heat produced during
the polimerization
Final product form
Solution Polymerization
 Heat can be removed by conducting the polymerization in an organic solvent or
water
 Initiator or monomer must be soluble in solvent
 Solvents have acceptable chain-transfer characteristics
 Solvents have suitable melting or boiling points for the conditions of
polymerization
 Ingredients : monomer
initiator
solvent
Advantages
Disadvantages
Temperature control is easy
Small yield per reactor volume
Easy removed
Solvent recovery
Suspention Polymerization
 Coalescense of sticky droplets is prevented by PVA
 Near the end of polymerization, the particles harder and they can be
removed by filtration, then washing
 Ingredients : water-insoluble monomer,
water-insoluble initiator,
sometimes chain transfer agent
suspention medium (water-usually)
Advantages (according to bulk
polymerization)
Disadvantages
Forming process not using
Polymer purity is low
Stirring is easy
Reactor capital costs are higher
than for solution polymerization
Separation process is easy
Emulsion Polymerization
 Particles are formed monosize with emulsion polymerization
 Polymerization is initiated when the water-soluble radical enters
a monomer-containing micelles.
 Ingredients : water-insoluble monomer,
water-soluble initiator,
chain transfer agent,
dispersing medium (water),
fatty acid,
surfactant such as sodium salt of a long chain
Molecular structure of polymers




Typical structures are :
linear (end-to-end, flexible, like PVC, nylon)
branched
cross-linked (due to radiation, vulcanization)
network (similar to highly cross-linked structures,termosetting
polymers)
Figure1. Schematic representation of (a) linear, (b and c) branched, and (d and e) cross-linked polymers.
The branch points and junction points are indicated by heavy dots (Plastic Technology Handbook-Manas Chanda Salil K. Roy)
Chemical Structure of Polymers
Molecular configuration of polymers
Side groups atoms or molecules with free bonds, called free-radicals, like H, O,
methyl affects polymer properties.

Stereoregularity describes the configuration of polymer chains :
 Isotactic is an arrangement where all substituents are on the same side of the
polymer chain.
 Syndiotactic polymer chain is composed of alternating groups
 Atactic the radical groups are positioned at random
Figure 2: Isotactic Syndiotactic and Atactic combinations of a stereoisomers of polymer chain
(http://www.microscopy-uk.org.uk/mag/imgsep07/atactic.png)
Molecular configuration of polymers
FIGURE.3. Diagrams of (a) isotactic, (b) syndiotactic, and (c) atactic configuration in a vinyl polymer.
The corresponding Fischer projections are shown on the right.
(Plastic Technolgoy Handbook)
Table 1. Properties of Polypropylene Stereoisomers
(Plastic Technology Handbook)
Molecular configuration of polymers
Geometrical isomerism:
 The two types of polymer configurations are cis and trans. These structures
can not be changed by physical means (e.g. rotation).
 The cis configuration  substituent groups are on the same side of a carboncarbon double bond.
 Trans  the substituents on opposite sides of the double bond.
Figure4.cis trans configurations of polyisoprene
( http://openlearn.open.ac.uk/file.php/2937/T838_1_019i.jpg )
Conformations of a Polymer Molecule

Conformation The two atoms have other atoms or groups attached
to them configurations which vary in torsional angle are known as
conformations (torsional angle:The rotation about a single bond which
joins two atoms )

Polymer molecule can take on many conformations.

Different conformation different potential energies of the
moleculeSome conformations: Anti (Trans), Eclipsed (Cis), and Gauche (+
or -)
Other Chain Structures
 Copolymers polymers that incorporate more than one kind of
monomer into their chain (nylon)
 Three important types of copolymers:
 Random copolymer contains a random arrangement of the multiple
monomers.
 Block copolymer contains blocks of monomers of the same type
 Graft copolymer contains a main chain polymer consisting of one type
of monomer with branches made up of other monomers.

Figure 5 :Block Copolymer Graft Copolymer Random Copolymer
http://plc.cwru.edu/tutorial/enhanced/FILES/Polymers/struct/struct.htm
Physical Characteristics of Polymers
 The melting or softening temperature ↑ molecular weight ↑
 The molecular shape of the polymer has influence on the elastic
properties. ↑ coils the ↑ elasticity of the polymer
 The structure of the molecular chains has an effect on the strength
and thermal stability. ↑ crosslink and network structure within the
molecule ↑ the strength and thermal stability.
Polymer Crystallinity
 Crystallinity is indication of amount of crystalline region in polymer
with respect to amorphous content
 X-ray scattering and electron microscopy have shown that the
crystallites are made up of lamellae which,in turn, are built-up of
folded polymer chains

Figure.6 Schematic representation of (a) fold plane showing regular chain folding, (b) ideal stacking oflamellar
crystals, (c) interlamellar amorphous model, and (d) fringed micelle model of randomly distributed crystallites

(Plastic Technology Handbook)
Polymer crystallinity
 Crystallinity occurs when linear polymer chains are structurally
oriented in a uniform three dimensional matrix. Three factors that
influence the degree of crystallinity are:
 i) Chain length
ii) Chain branching
iii) Interchain bonding
Figure 7: Crystalline chain
http://plc.cwru.edu/tutorial/enhanced/FILES/Polymers/orient/Orient.htm
Polymer cristallinity
Crystallinity influences:
Hardness,modulus tensile, stiffness, crease, melting point of polymers.
 Most crystalline polymers are not entirely crystalline. The chains, or
parts of chains, that aren't in the crystals have no order to the
arrangement of their chains
 Crystallinity makes a polymers strong, but also lowers their impact
resistance
 Crystalline polymers are denser than amorphous polymers, so the
degree of crystallinity can be obtained from the measurement of
density  Wc=Φcρc/ ρ
ρ  density of entire sample
ρc  density of the crystalline fraction.
Φc volume fraction
Wc mass fraction
Determinants of Polymer Crystallinity
 The degree of crystallinity of a polymer depends on the rate of cooling
during solidification as well as on the chain configuration.
 In most polymers, the combination of crystalline and amorphous
structures forms a material with advantageous properties of strength
and stiffness.
Figure 8: Mixed amorphous crystalline macromolecular polymer structure
(http://web.utk.edu/~mse/Textiles/Polymer%20Crystallinity.htm)
Polymer cristallinity
 Polymer molecules are very large so it might seem that they could not
pack together regularly and form a crystal. Regular polymers may form
lamellar crystals with parallel chains that are perpendicular to the face
of the crystals.
 A crystalline polymer consists of the crystalline portion and the
amorphous portion. The crystalline portion is in the lamellae, and the
amorphous portion is outside the lamellae .
Figure 9. Arrangement of crystalline and amorphous portions
http://pslc.ws/mactest/crystal.htm#structure
Cristillanity and amorphousness
 An amorphous solid is formed when the chains have little orientation
throughout the bulk polymer. The glass transition temperature is the point
at which the polymer hardens into an amorphous solid.
 In between the crystalline lamellae,regions with no order to the
arrangement of the polymer chains  amorphous regions
 Polyethylene can be crystalline or amorphous. Linear polyethylene is nearly
100% crystalline. But the branched polyethylene is highly amorphous.
Figure 10.Linear and Branched Polyethylene
(http://pslc.ws/macrog/kidsmac/images/pe03.gif )
Examples...
 Highly crystalline polymers:
Polypropylene, Nylon, Syndiotactic polystyrene..
 Highly amorphous polymers:
Polycarbonate, polyisoprene, polybutadiene
 Polymer structure and intermolecular forces has a major role of a
polymer’s crystallinity.
Classification of Polymers
…with regard to their thermal processing behavior ;
 Thermoplastic Polymers (Thermoplastics)
soften when heated and harden when cooled
 Thermosetting Polymers (Thermosets)
once having formed won’t soften upon heating
Thermoplastics
 have linear or branched structure
chains are flexible and can slide past each other
 have strong covalent bonds and weak intermolecular van
der Waals bonds
 elastic and flexible above glass transition temperature
 can be heat softened, remolded into different forms
 reversible physical changes without a change in the
chemical structure
Thermosets
 chains chemically linked by covalent bonds
 hardening involves a chemical reaction which
connects the linear molecules together to form a
single macromolecule.
Thermosets
 once polymerization is complete, cannot be softened, melted
or molded non-destructively.
 have higher thermal, chemical and creep resistance than
thermoplastics
 Thermosets suitable materials for
Composites
Coatings
Adhesive applications
Common thermoplastics
Commodity Polymers
POLYETHYLENES
POLYPROPYLENE
POLYSTYRENE
POLYVINYLCHLORIDE-PVC
POLYMETHYLMETHACRYLATE-PMMA
Engineering Polymers(have a thermal resistance 100-150°C)
POLYCARBONATE
NYLON(POLYAMIDE)
POLYETHYLEN TEREPHATALATE-PET
High Performance Polymers (have a thermal resistance >150°C)
POLYTETRAFLUOROETHYLENE-teflon
POLYARYLETHERKETONES-PEEK
POLYETHYLENE
 prepared directly from the polymerization of ethylene (C2H4).
 two main types are; low-density (LDPE) and high-density
polyethylene (HDPE)
 Advantages
cheap
good chemical resistance
high impact strength
 Limitations
low heat resistance (upper temperature limit is 60°)
degrade under UV irradiation.
high gas permeability, particularly CO2
 Applications
extensively for piping and packaging
chemically resistant fittings, garbage bags
containers, cable covering
POLYPROPLYLENE
 improved mechanical properties compared to polyethylene;
has a low density (900–915 kg/m3), harder, and has a higher
strength
Good chemical and fatigue resistance
 Disadvantages
Oxidative degradation, high thermal expansion, high creep
poor UV resistance
 Applications
medical components, films for packaging (e.g. cigarette
packets)reusable containers, laboratory equipment
POLYSTYRENE
 a light amorphous thermoplastic
 Advantages
low cost, easy to mould, rigid, transparent
no taste, odor, or toxicity, good electrical insulation
 Disadvantages
sensitive to UV irradiation (e.g. sunlight exposure)
chemical resistance is poor, brittle
 Applications
CD-DVD cases, electronic housings, food packaging, foam
drink cups and egg boxes
POLYVINYLCHLORIDE-PVC
 was the first thermoplastic used in industrial applications
 very resistant to strong mineral acid and bases, good electrical
insulators, flame-retardant
 Two grades of the PVC material are available:
rigid PVC is used in the construction industry for piping
cold water and chemicals
flexible PVC is used in wire and cable coating, paints, signs
Common thermosets
 EPOXIES
 UNSATURATED POLYESTERS
 PHENOL FORMALDEHYDE (PHENOLIC)
 POLYURETHANES
EPOXIES
 Advantage
mechanically strong, highly adhesive
good chemical and heat resistance
electrical insulators
 Disadvantage
expensive
 Applications
as industrial adhesives, coatings or as matrices in advanced
reinforced plastics and also as encapsulation media
UNSATURATED POLYSTERS
 Advantage
hard, high strength
cheap compared to Epoxy
good electrical insulator
high heat resistance
 Disadvantage
poor solvent resistance compared to other thermosets
 Applications
molding or casting materials for a variety of electrical
applications, matrix for composites such as fiberglass
boats, fences, helmets, auto body components
PHENOLICS
 most commonly used thermosets
 high hardness, excellent thermal stability; low
tendency to creep
 Applications
wiring devices, bottle caps, automotive parts, plugs
and switches, as adhesives coatings and molded
components for electrical applications
POLYURETHANES
 depending on the degree of cross-linking they behave as
thermosets or thermoplastics
 low cost, high impact strength, high adhesion properties
 be processed into coatings, adhesives, binders, fibers and
foams
Methods of polymer fabrication

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Extrusion of polymers
Injection Molding
Blow Molding
Thermoforming
Compression Molding
Casting
Extrusion of polymers
 method used mainly for thermoplastics
 is a continuous process as long as raw pellets are supplied
 is a process of manufacturing mostly long products of constant
cross-section;
i.e.. rods, sheets, pipes, films, wire insulation coating
… extrusion
 pelletized material is successively compacted, melted and
formed into a continuous charge of viscous fluid
 temperature of the material is controlled by thermocouples
 forcing soften polymer through a die with an opening
 the product going out of the die is cooled by blown air or in
water bath
extruder
Injection Molding
 most widely used technique for thermoplastics
 highly productive method, profitable in mass production of
large number of identical parts
 polymer in form of pellets is fed into machine and is pushed
forward into a heating chamber then the molten plastic is
forced through a nozzle into the enclosed mold cavity
 pressure is maintained until solidification and then the mold
opens and the part is removed
Blow Molding
 is a process in which a heated hollow thermoplastic tube
(parison) is inflated into a closed mold
 disposable containers, recyclable bottles, automotive fuel
tanks, tubs are produced
 involves manufacture of parison by extrusion, injection or
stretching
 parison in a semi molten state is placed in a two piece mold
having the desired shape
 parison is inflated by air blown, taking a shape conforming that
of the mold cavity
 parison is then cut on the top, mold cools down, its halves
open, and the final part is removed
Thermoforming
 is a process of shaping flat thermoplastic sheet
 softening the sheet by heat, followed by forming it in the mold
cavity
 Thermosets can not be formed by the thermoforming because
of their cross linked structure
 widely used in the food packaging industry; manufacturing of
Thermoforming methods
three thermoforming methods, differing in the forming stage:
1. Vacuum Thermoforming; shaping a preheated thermoplastic
sheet by means of vacuum produced in the mold cavity
2. Pressure Thermoforming;... by means of air pressure.
3. Mechanical Thermoforming;... by direct mechanical force
Thermoforming by vacuum and mechanical force
Compression Molding
used mostly for molding thermoset resins
 pre-weighed amount of a polymer mixed with additives is
placed into the lower half of the mold
 polymer is preheated prior to placement into heated mold
cavity ,half of the mold moves down, pressing on the polymer
charge and forcing it to fill the mold cavity
 suitable for molding large flat or moderately curved parts; side
panels for automotive, electric housings etc.
Casting
 both thermosets and thermoplastics may be cast.
 molten polymer is poured into a mold and allowed to solidify
 for thermoplastics solidification occurs upon cooling
while thermoset’s hardening is a consequence of
polymerization reaction
REFERENCES
 François Carderelli, Materials Handbook: A Concise Desktop






Reference,2nded.,Springer
Donald Hudgin, Plastics Technology Handbook, 4th ed., Taylor & Francis
Group
J. A.Brydson, Plastics Materials, 7thed., Heinemann
William D. Callister ,Materials Science and Engineering,7th ed., Wiley
http://www.substech.com
http://www.azom.com
http://en.wikipedia.org
Recycling:
A Sector of Solid
Waste Management
http://environment.utk.edu/policy.html
What is Recycling?
Recycling refers to the process of collecting used materials
which is usually considered as ‘waste’ and reprocessing
them. Recycling varies from ‘re-use’ in the sense that while
re-use just means using old products repeatedly, recycling
means using the core elements of an old product as raw
material to manufacture new goods.
Why Recycling is Important?
 Recycling Saves Energy
 Recycling Saves Environmental Conditions and Reduces
Pollution
 Recycling Saves Natural Resources
 Economic Benefits
 Recycling Saves Space for Waste Disposal
Benefits
• Conserves Resources
• Prevents emissions of greenhouse gasses &
water pollutants
• Supplies valuable raw materials to industry
• Saves tax-payer dollars
• Creates jobs
• Stimulates development of greener technologies
• Reduces the need for new landfills and
incinerators
Recycling of polymers
Recycling of Polymers
Chemical recycling
Mechanical recycling
Chemolysis
Glycolysis
Methanolysis
Hydrolysis
Energy recycling
Thermolysis
Pyrolysis
Hydrogenation
Why do we use mechanical, chemical and
energy recycling?
 Hence mechanical recycling is realy best suited to clean plastic
waste,such as packaging material.
•Chemical recycling of waste plastics is important issue.
We have applied reaction in water or organic solvent in
sub- or supercritical condition to convert polymers into its monomers.
Condensed polymers such as polyethylene terephthalate or
nylon 6 were depolymerized to its monomers by hydrolysis of
alcoholysis in supercritical water or alcohol.
Conclusive Facts
1 t = 20,000 plastic bottles
 25,000 t of bottles recycled in the UK in 2003 saved approximately
25 million kWh of energy
 25 recycled PET bottles can be used to make an adult’s fleece jacket
 Recycling a single plastic bottle can conserve enough energy to light
a 60 W lightbulb for up to 6 h
SOME PHOTOS
We have done it!!!
Ref: http://www.container-recycling.org/ assets/ppt/1PlasticDebrisConference9.ppt
Look at the changes you could
make with recycling...
http://environment.utk.edu/policy.html
REFERENCES
 http://www.buzzle.com/articles/why-is-recycling-important.html
 http://www.chevroncars.com/learn/wondrous-world/recycling-process
 www.container-recycling.org/ assets/ppt/1PlasticDebrisConference9.ppt
 François Carderelli, Materials Handbook: A Concise Desktop
Reference,2nded.,Springer
 Donald Hudgin, Plastics Technology Handbook, 4th ed., Taylor & Francis
Group
REFERENCES
 J. A.Brydson, Plastics Materials, 7thed., Heinemann
 William D. Callister ,Materials Science and Engineering,7th ed., Wiley
 http://www.substech.com
 http://www.azom.com
 http://en.wikipedia.org
REFERANCES
 Plastic Technology Handbook, 4th Edition, Authors: Manas Chanda,Salil K.
Roy
 http://pslc.ws/mactest/crystal.htm#structure
 http://plc.cwru.edu/tutorial/enhanced/FILES/Polymers/struct/struct.htm