1. UNIT-III POLYMERS

2. Spot The Polymer We rely on polymers daily!
Polymers are made up of many molecules strung together to form really long chains.

3. DEFINITION:
Macromolecules formed by the linkage of a large number of repeated units called monomers are known as Polymers.

4. Hermann Staudinger received noble prize for the discovery of polymers in 1953

5. CONTENTS Functionality and Tacticity Classification of Polymerization
Mechanism of polymerization
Plastics and compounding of plastic
Fabrication of plastics
Preparation of Thermaplastic and Thermosetting resins
Conducting polymers,LCP
Rubber-Natural rubber-vulcanization
Synthesis of Elastomers
Fibers, FRPs and their Advantages

6. Functionality
Number of bonding sites in a manomer is called Functionality
Two bonding sites- Bifunctional
Ex : Ethylene
C C
C C
C C

7. Three bonding sites - Trifunctional
C C C
C C
C C
C C

8. More than three bonding sites- Polyfunctional
C C C
C C C
C C C
C C C
C C C
C C C
C C C
C C C
C C C

9. Tacticity in polymers
Arrangement of functional groups on the carbon back
bone is known as Tacticity.
It is of three types
Alternate arrangement of functional groups
syndiotactic polymers

10. No regular arrangement of functional groups
Atactic polymers

11. Arrangement of functional groups on the same side of carbon chain
Isotactic polymers

12. Examples
This unit of a carbon atom with two hydrogen atoms followed by a carbon atom with a hydrogen atom and a methyl group repeats itself over and over again along the backbone chain. This little recurring structure is called the repeat structure or the repeat unit.

13. To make things simple, we usually only draw one unit of the repeat structure, like this:
CH2 = CH2
the repeat unit is put inside brackets, and the subscript n just stands for the number of repeat units in the polymer chain
( CH2 = CH2 )n

14. Polymers don't start out big
Polymers don't start out big. They start as little tiny molecules called
monomers.
To make a polymer, a whole mess of monomers are strung together in a line to form a long polymer chain.
For example, styrene monomers are joined together to make polystyrene:

15. Polymers basically are of two types;
Homopolymers and Co-polymers
Homopolymers- All monomers are identical
Produced by Radical polymerization
Mostly by terminal alkenes
Co-polymers- Made up of different monomers
A + B ( A-B)n-

16. Degree of polymerization
The total number of repeating units contained terminal group
The kinds of applied monomers
One kind : Homopolymer
Two kinds : Copolymer
Three kinds : Terpolymer

17. Classification of polymers based on polymerization

18. Polymerization Reactions
The chemical reaction in which high molecular mass molecules are formed from monomers is known as polymerization.
There are two basic types of polymerization, chain-reaction (or addition) and step-reaction (or condensation) polymerization.
Chain-Reaction Polymerization
One of the most common types of polymer reactions is chain-reaction (addition) polymerization.
This type of polymerization is a three step process involving two chemical entities.
The first, known simply as a monomer, can be regarded as one link in a polymer chain.
It initially exists as simple units. In nearly all cases, the monomers have at least one carbon-carbon double bond.
Ethylene is one example of a monomer used to make a common polymer.

19. The other chemical reactant is a catalyst
The other chemical reactant is a catalyst. In chain-reaction polymerization, the catalyst can be a free-radical peroxide added in relatively low concentrations.
A free-radical is a chemical component that contains a free electron that forms a covalent bond with an electron on another molecule
Ex:CH3, H. , I.
This mechanism involves three steps
Initiation ,propagation and Termination

20. Step 1: Initiation
The first step in the chain-reaction polymerization process, initiation, occurs when the free-radical catalyst reacts with a double bonded carbon monomer, beginning the polymer chain.
The double carbon bond breaks apart, the monomer bonds to the free radical, and the free electron is transferred to the outside carbon atom in this reaction.
I-I I. .
I. + CH2 = CH I- CH2 – CH
X X

21. I – CH2 – CH + CH2 = CH2 I - CH2-CH-CH2-CH X X X
Step 2: Propagation
The next step in the process, propagation, is a repetitive operation in which the physical chain of the polymer is formed.
The double bond of successive monomers is opened up when the monomer is reacted to the reactive polymer chain. The free electron is successively passed down the line of the chain to the outside carbon atom.
I – CH2 – CH + CH2 = CH I - CH2-CH-CH2-CH
X X X
Growing polymer

22. Step 3: Termination
Termination occurs by coupling or disproportionation ,
Coupling- The collision of two growing chains causes the union of the two chains at their freeradical site producing a dead polymer. This reaction produces a complete polymer chain.

23.
I-CH2-CH-CH2-CH-CH2-CH CH-CH2-CH-CH2-CH-CH2-I
X X X X X X
I-CH2-CH-CH2-CH-CH2-CH-CH-CH2-CH-CH2-CH-CH 2 -I
X X X X X X
Dead polymer
Disproportionation-Termination can also occur when two unfinished chains bond together.

24.
I-CH2-CH-{CH2-CH}-CH2-CH CH-CH2-{CH-CH2}n-CH-CH2-I
X X X X X X
I-CH2-CH-{CH2-CH}-CH2-CH-CH-CH2-{CH-CH2}n-CH-CH 2 -I
X X X X X X
Dead polymer

25. Comparison of Step-Reaction and Chain-Reaction Polymerization
Growth occurs throughout matrix by reaction between monomers, oligomers, and polymers
Monomer consumed rapidly molecular weight increases slowly
No initiator needed; same reaction
mechanism throughout
No termination step; end groups still reactive
Polymerization rate decreases steadily as
functional groups consumed
Chain reaction
Growth occurs by successive addition ofmonomer units to limited number overgrowing chains
Monomer consumed relatively slowly,
molecular weight increases rapidly
Initiation and propagation mechanisms different
Usually chain-terminating step involved
Polymerizaion rate increases initially as
initiator units generated; remains relatively constant until monomer depleted

26. Chain-Growth Polymers
Produced by chain-reaction polymerization
Initiator (radical, acid or anion) adds to a carbon–carbon double bond of an unsaturated substrate (a vinyl monomer) to yield a reactive intermediate that reacts with a second molecule of monomer and so on

27. Anionic Polymerization
Vinyl monomers with electron-withdrawing substituents (EWG) can be polymerized by anionic catalysts
Chain-carrying step is nucleophilic addition of an anion to the unsaturated monomer by a Michael reaction

28. Examples of Anionic Polymerization Products
Acrylonitrile (H2C=CHCN), methyl methacrylate [H2C=C(CH3)CO2CH3], and styrene (H2C=CHC6H5) react

29. CATIONIC POLYMERIZATION
In cationic chain polymerization the
Cation produced by the initiator attacks the ¶ electrons of the monomer carbonium ion .
Strong lewis acids likeBF3, AlCl3, etc
EX : Isobutene polymerization with AlCl3
as initiator

30. This whole process by which the AlCl3/H2O complex forms and reacts with the first monomer molecule is called initiation.

31. This process, by which monomer after monomer is added to form a polymer, is called propagation
It also generates another
carbocation, as you can see in the picture below.
This can react with another monomer, and then another, and so on.
Eventually we get a long polymer chain.

32. This process, by which monomer after monomer is added to form a polymer, is called propagation

33. This process is called termination, because no new chains are started
This process is called termination, because no new chains are started. It's the last of the three major steps in any chain growth polymerization, the first two being initiation and propagation, of course. When termination happens, the polymerization is over.

34. Ziegler–Natta Catalysts
Allow preparation of isotactic, syndiotactic, and atactic polypropylene
Prepared by treatment of an alkylaluminum with a titanium compound
(CH3CH2)3Al + TiCl4  A Ziegler–Natta catalyst

35. Isotactic Polymerization
The precise nature of the complex between the titanium and the propylene is complicated. So to make things simple we're going to just draw it like we did earlier from now on, like this:

36. the atoms rearrange themselves to form a slightly different structure, like this:

37. So when another propylene molecule comes along, the whole process starts all over, and the end result is something like this:

38. Step-reaction (condensation) polymerization is another common type of polymerization.
This polymerization method typically produces polymers of lower molecular weight than chain reactions
requires higher temperatures to occur.
Reactions are slow
Loss of atoms or groups like H2O,HCl etc takes place

39. Example 1: A carboxylic acid monomer and an amine monomer can join in an amide linkage.

40. Example 2: A carboxylic acid monomer and an alcohol monomer can join in an polyester linkage.

41. PLASTICS
Applications of plastics have increased at a much faster rate than either metals or ceramics during the last 50 years
Many parts previously made of metals are now being made of plastics

42. Plastic containers have been largely substituted for glass bottles and jars
Total volume of polymers (plastics and rubbers) now exceeds that of metals

43. 1. Thermoplastics Thermosetting resins
Chemical structure remains unchanged during heating and shaping
More important commercially, comprising more than 70% of total plastics tonnage
Thermosetting resins
Undergo a curing process during heating and shaping, causing a permanent change (cross‑linking) in molecular structure
Once cured, they cannot be remelted

44. Thermoplastic polymers Thermosetting polymers
These soften and melt on heating
These do not soften on heating but rather become hard in case prolonged heating is done these start burning.
These can be remoulded recast and reshaped.
These can not be remoulded or reshaped
These are less brittle and soluble in some organic solvents.
These are more brittle and insoluble in organic solvents.
These are formed by addition polymerization.
These are formed by condensation polymerization.
These have usually linear structures.
Ex. Polyethylene, PVC, teflon
.These have three dimensional cross linked structures.
Ex. Bakelite, urea, formaldehyde, resin. 

45. Compounding of plastics
To impart constructive engineering proprties polymer resin is mixed with various ingradients like,
Resins: Major portion of the plastic and acts
as a binder.
2) Plasticizers: Increases plasticity
and flexibility.
Ex: vegetable oils, camphor, esters

46. 5) Catalysts or Accelerators: They accelerate the process Of
3) Fillers: Give more hardness, tensile strength, opacity and decrease brittleness of the polymer
Ex: gypsum, sawdust, paperpulp,Zno etc
4) Lubricants: Gives glossy finishing to the products and makes the
moulding process easy.
EX: Oils , waxes, soaps etc
5) Catalysts or Accelerators: They accelerate the process Of
polymerization
Ex: Hydrogen peroxide, Benzoylperoxide,Cu,--
6) Stabilizers: improves thermal stability
Ex: White lead, lead chromate, red lead—
7) Colouring materials: Gives color to the plastic and Impart esthetic
beauty .
Ex: organic dye stuffs

47. Fabrication of plastics
Different methods are employed in fabricating thermoplastic and thermosetting resins.
Compression moulding
Injection moulding
Transfer moulding
Extrusion moulding
Bubble casting or blowing method
Thermoforming

48. Compression Molding
A widely used molding process for thermosetting plastics
Also used for rubber tires and polymer matrix composite parts
Molding compound available in several forms: powders or pellets, liquid
Amount of charge must be precisely controlled to obtain repeatable consistency in the molded product
Used in the manufacture of cylinders, gears handles etc

49. Compression Moulding

50. Injection Molding Machine
Diagram of an injection molding machine, reciprocating screw type

51. Injection Molding Machine
Employed for the fabrication of Thermoplastic
resins.
The plunger moves to and fro in the cylinder to send the plastics material
into the spreader in a heating chamber where the materials are
converted to viscous liquid pushed through the nozzle into the cold
mould at room temperature.
Advantages- High speed Production,loss of material is less

52. Injection Molding Glass Elastomers
Plastic pellets with copolymer elastomers.
Similar processing requirements as with injection molding of commodity and engineering plastics
Injection pressures, tonnage, pack pressure, shrinkage

54. Transfer Moulding
It involves injection moulding principle and employed
For moulding Thermosetting plastics
The softened plastic is injected into a mould by a plunger at high pressure
The mould is kept at required curing temperature
The fabricated plastic is ejected out mechanically
Advantages
very delicate articals can be moulded
Moulding cost is less
Blistering can be avoided

56. Extrusion Molding
Extrusion blow molding is used for moulding Of thermoplastic materials into articals of uniform cross section like tubes ,rods, sheets, wires, cables etc.
Thermoplastic ingradients are heated to plastic state and then pushed by means of a screw conveyor into a die having required shape.
The article gets cooled by water sprayer

58. Blow Molding
Molding process in which air pressure is used to inflate soft plastic into a mold cavity
Important for making one‑piece hollow plastic parts with thin walls, such as bottles
Because these items are used for consumer beverages in mass markets, production is typically organized for very high quantities

59. Blow Moulding Blowing is also known as Bubble casting used for moulding hollow articals like soft drink bottles,containers etc

60. Thermoforming

61. Thermoforming
Flat thermoplastic sheet or film is heated and deformed into desired shape using a mold
Heating usually accomplished by radiant electric heaters located on one or both sides of starting plastic sheet or film
Widely used in packaging of products and to fabricate large items such as bathtubs, contoured skylights, and internal door liners for refrigerators

62. Thermoforming process is useful
For fabricating three dimensional
articals , submarine nulls, disposable cups, glasses etc
It is a combination of extrusion molding with compression technique.
The thermoplastic resin is extruded in the form of a sheet and compressed between the two moulds

63. Examples of Thermoplastic resins
Polythene (PE)
Polyvinyl chloride (PVC)
Polystyrene (PS)
Polytetra fluoro ethylene ( TEFLON)

64. PREPARATION OF POLYTHENE (PE)
Polyethylene is a thermoplastic polymer consisting of long chains of the monomer ethylene (IUPAC name ethene)
The ethene molecule (known almost universally by its common name ethylene)
C2H4 is CH2=CH2,
n CH2=CH (CH2=CH2 )n
Ethylene
polythene

65. The mechanical properties of PE depend significantly on variables such as the extent and type of branching, the crystal structure and the molecular weight. With regard to sold volumes,
the most important polyethylene grades are
HDPE and LDPE
HDPE has little branching, giving it stronger intermolecular forces and tensile strength than lower-density polyethylene.
It is formed by coordination chain polymerization in the presence of Triethyl aluminium with a density of o.965gm/cc

66. LDPE is defined by a density range of 0.910 - 0.940 g/cm³.
It is not reactive at room temperatures, except by strong oxidizing agents, and some solvents cause swelling.
It can withstand temperatures of 80 °C continuously and 95 °C for a short time.
LDPE has more branching (on about 2% of the carbon atoms) than HDPE, so its intermolecular forces (instantaneous-dipole induced-dipole attraction) are weaker, its tensile strength is lower, and its resilience is higher.

67. uses of HDPE AND LDPE HDPE is resistant to many different solvents and has a wide variety of applications, including: Telecom Ducts Containers Laundry detergent bottles Milk jugs Fuel tanks for vehicles Watering cans Plastic lumber Folding tables Folding chairs
LDPE is widely used for manufacturing various containers, dispensing bottles, wash bottles, tubing, plastic bags for computer components, and various molded laboratory equipment. Its most common use is in plastic bags.

68. PREPARATION OF POLYVINYL CHLORIDE ( PVC )
Vinyl chloride on free radical polymerization
in the presence of BenzoylPeroxide at c
gives Polyvinylchloride
n CH2=CH ( CH2=CH )n
Cl Cl
PVC
Properties: 1) colorless non–inflammable chemically inert powder
with a MP 1480C.
2) Resistant to light and atm.oxygen
3) more rigid than PE
Uses : plasticized PVC is used in electrical
insulation,telephone components, conveyor belts etc
Vinyl chloride

69. Preparation of Teflon

70. Uses of Teflon
By 1941, PTFE had been patented and had its first brand name Teflon®.
By 1946, the resin product was being used to produce machine parts for military and industrial applications.
In the 1960s it began its life in the arena of nonstick cookware,pipes etc.

71. Preparation of Polystyrene (PS) VinylBenzene (styrene )on polymerization gives polystyrene

72. PROPERTIES:
It is a transperent and light weight polymer
Brittle with MP C
stable towards light and moisture.
USES:
Used in the manufacture of
radio parts,
Refrigerator parts,
battery cases etc

73. THERMOSETTING RESINS
Bakelite
Nylon-6,6
Polyester

74. Preparation of Bakelite
It is prepared by the step polymerization of Phenol with Formaldehyde in the presence of acid & alkali as a catalyst.
Addition of Hexamethylene tetramine during moulding moulding converts soluble, fusible Novalac into hard, infusible
Insoluble solid cross linked Bakelite polymer.

75. The belgian chemist Leo Hendrik Baekeland made experiments with phenol and formaldehyde ( ) and discovered, that the two compounds react with one another under release of heat to form a polymeric plastic.
Reaction

76. PROERTIES
Bakelite( Phenoplast )is a heat-resistant, thermosetting, chemically stable resin.
It doesn't soften again when heated, rather than a thermo-plastic like styrene.
They are good electrical insulators
USES :
Used in the manufacture of,
Electrical switches,plugs,heaterhandles,radio,TV cabinets
As varnishes and adhesives
As hydrogen exchanger resin in softening of water

77. PREPARATION OF Nylon-6
Polyamide from caprolactam is Nylon 6

78. Nylon6,6 – A Condensation Polymer
Nylon was first introduced to the public in 1939 at the New York World’s Fair.
Nylon is formed from the polymerization of Adipic acid and Hexamethylenediamine.
Section 14.5

79. PROPERTIES OF NYLON
Due to the presence of Hydrogen bonding Nylons are hard with high Melting points
Chemically resistant
Good electrical insulators
They do not require any lubrication
USES:
Nylon- 6,6 is used in making socks,dreses,carpets etc
Nylon- 6 , Nylon-11 are used in the preparation of gears, bearings.
Also used in making filaments for ropes,tooth brushes etc

80. Nylon – A Condensation Polymer
Nylon was first introduced to the public in 1939 at the New York World’s Fair.
Nylon is formed from the polymerization of adipic acid and hexamethylenediamine.
Section 14.5

81. Nylon-6 and Nylon-6,6

82. Preparation of Polyester
Polyethylene terephthalate (PET) is formed from the polymerization of terephthalic acid and ethylene glycol.
Section 14.5

83. Properties Highly resistant to stretching and wrinkles
Resistant to mineral acids
Easy to dye
Can be easily blended with wool and silk
Abrasion Resistant
USES
As domestic fibre and industrial fibre
In making nylon tyres
In textile industry as dacron,terylene

84. Codes for Plastics 1 – PETE – soft drink bottles
2 – LDPE – plastic bags, toys
3 – PVC – water pipes
4 – HDPE – milk jugs
5 – PP – bottle caps
6 – PS – styrofoam

85. conducting polymers Backbone of conjugated double bonds
Semiconductors (band gap > 1.5eV)
“doping” by oxidising or reducing agents → increase in conductivity of up to 11 orders of magnitude
Spectrum of electrical conductivities from insulating to semiconducting, and even metallic behaviour
polyacetylene

86. Why π-Conjugated Polymer is a Better Conductor
Larger E
Smaller E
Low energy
 bond
resonance
process
High energy 
bond-breaking
process
-bonding frame keep
the resonance  orbitals
to remain within the effective
chemical bonding distance
The escape of the vinyl
fragments make the reverse
transport process impossible 86

88. polyacetylene
The polyacetylene film forms at the gas-liquid interface when acetylene gas passes through a heptane solution of the Ziegler-Natta catalyst.
Cis polymer forms at low temperature (-78 C). Isomerization to the more stable trans form takes place on rising the temperature of the film.
Conductivity of doped cis films is two or three times greater than the trans analogues.

89. Oxidation States and Acid Base Behavior of Polyaniline (emaraldine, pernigraniline)‏
Three oxidation states: the emeraldine base (EB); the leucoemeraldine base (LEB); and the pernigraniline base (PN).

90. Liquid-crystal polymers
Liquid-crystal polymers (LCPs) are a class of aromatic polyester polymers. They are extremely unreactive and inert, and highly resistant to fire
Liquid crystallinity in polymers may occur either by dissolving a polymer in a solvent (lyotropic liquid-crystal polymers) or by heating a polymer above its glass or melting transition point (thermotropic liquid-crystal polymers).
Liquid-crystal polymers are present in melted/liquid or solid form.
In solid form the main example of lyotropic LCPs is the commercial aramid known as Kevlar.
Chemical structure of this aramid consists of linearly substituted aromatic rings linked by amide groups.
In a similar way, several series of thermotropic LCPs have been commercially produced by several companies (e.g., Vectra).

91. structure of Kevlar
structure of vectra

92. uses Lcp’s are often reffered as super polymers
Because of their various properties, LCPs are useful for electrical and mechanical parts, food containers, and any other applications requiring chemical inertness and high strength.
LCP is particularly attractive for microwave frequency electronics due to low relative dielectric constants, low dissipation factors, and commercial availability of laminates.
Packaging Microelectromechanical Systems (MEMS) is another area that LCP has recently gained more attention in.

93. Elastomers
Cross linked (networked) rubbery polymers that can be stretched easily (3-10x original size)
Rapidly recover original dimensions when applied stress is released.
Low degree of crosslinking

94. collection of latex
Latex collection from Heavia brasiliensis

95. Natural Rubber and Gutta-Percha
The upper structure is rubber, a natural elastomer
The lower structure is the nonelastic gutta-percha

98. Vulcanized rubber

99. Calendering of Rubbers
Calendering is the process for producing long runs of uniform thickness sheets of rubber either unsupported or on a fabric backing. A standard 3 or 4 roll calender with linear speed range of 2 to 10 feet/minute is typical for silicone rubber. Firm compound with good green strength and resistance to overmilling works the best for
calendering.

100. Compounding of Rubber
To improve the properties of rubber various materials are
Added to natural rubber

101. Materials Function Elastomer/raw rubber
Basic components in rubber compounding
Fillers
Used for reinforced or modified the mechanical properties and also to reduced the cost
Plasticier
To ease the processing, to modify the specific properties and also as extender’
Anti oxidant
To protect the rubber from ageing
Accelerator
To increase vulcanization process and reduced the time of vulcanization
Activator
To increased the accelerator efficiency
Vulcanization agent
Needed during vulcanization process to produced a crosslinking
Other ingredients
Used for specified purpose such as for coloring, as retarder etc

102. Elastomers or synthetic rubbers
Polymers which posses the property of elasticity is called rubber
Examples:
BUNA-S
BUTYL RUBBER
THIOKOLRUBBER

103. Preparation of BUNA-S
The material was initially marketed with the brand name Buna S.
It derives this name from:
Bu for butadiene,
Na for sodium (natrium in Latin, Natrium in German),
and S for styrene

104. PROPERTIES strong and tough polymer vulcanized by S2Cl2
excellent abrasion resistance
but sensitive to oil, wastewater
Good electrical insulator
USES
The elastomer is used widely in
pneumatic tyres
shoe heels and soles
gaskets and cable insulations

105. Preparation of BUTYL RUBBER
Butyl rubber is a synthetic rubber,
a copolymer of isobutylene with isoprene.
Polyisobutylene, also known as "PIB" or polyisobutene, (C4H8)n), is the homopolymer of isobutylene.
Butyl rubber is produced by polymerization of about 98% of isobutylene with about 2% of isoprene.
n(CH2=C-CH3) + n(CH2=C-CH=CH2)
CH CH3
CH3 CH3
-(CH2-C-CH2-C=CH-CH2)n-
CH3
Butyl Rubber

106. Preparation of Butyl rubber
Properties
Tough synthetic rubber
Highly resistant to heat abration and chemicals
Good electrical insulator
Less hard due to less no of double bonds
USES
Making
Tyres
Automobile parts
Conveyor belts
As tank linings-- etc

107. PREPARATION OF THIOKOL RUBBER

108. Properties Cannot be vulcanized Cannot form a hard rubber
Has low abrasion resistance
Resistant to mineral oils
USES
Making life rafts and jackets inflated by CO2
In making gaskets and seals for printing rolls

109. FIBRES They are of two types
Polymers which can be drawn in the form of long filaments with high tensile strength,high regidity and irreversible deformation are called FIBRES
They are of two types
Natural polymers (cotton,wool,silk)
synthetic polymers (polyester,nylon)

110. Fibre reinforced plastics ( FRP )
Plastics produced by reinforcing afibre materials like glass , graphite,alumina,carbon etc are
Fibre reinforced plastics
Glass fibre is the most extensively used reinforced composite
Common plastic resins used are polyesters,epoxy,silicone,malamine etc

111. Processing techniques of FRP’S
Matched metal die molding
Injection molding
Hand-lay-up
Continuous lamination
Centrifugal casting
sprayup

112. Applications of FRP’S High dimensional stability
Low cost of production
Good tensile strength
Low dielectric constant
Non inflammability and corrosion and chemical resistance

113. Uses of Polymers

114. THANK YOU