Unit iii polymers

1. 11/11/12 1
Polymer an Insight in to the learning topicsPolymer an Insight in to the learning topics
Classification of polymers:
Thermoplastics- PE, PS, PVC, PTFE, ABS, PMMA, Synthetic Rubber

Thermosetting plastics - properties and industrial applications properties and industrial applications
of Bakelite, Melamine Resin, Epoxy Resin, of Bakelite, Melamine Resin, Epoxy Resin,
Polyurethane (PU), Polyamide (nylon Series), Polyester (PET), PC, Silicon Polyurethane (PU), Polyamide (nylon Series), Polyester (PET), PC, Silicon
PolymerPolymer
Moulding of plastics into articles:
Compression,Compression,
injection,injection,
transfer and extrusion methodstransfer and extrusion methods.
Conducting polymers: Properties and applications
Biodegradable polymers Properties and applications

2. A word polymer is a combination of two Greek words,
“Poly” means “many” and “Meros” meaning “parts or
units”.
A polymer is a large molecule of which is formed by
repeated linking of the small molecules called
“monomers”.
n(CH
2
-CH
2
) (-CH
2
-CH
2
-)
n

ethylene polyethylene

3. The number of repeating units in the chains of which
a polymer is made up is called degree of a
polymerization (n).
Polymers with high degree of polymerization are
called the “High Polymer”, and those with low degree
of polymerization are called “Oligopolymers”.
High polymers have very high molecular mass (10000
to 1000000 u) and are called macromolecules.

4. 11/11/12 4
CH2CH2
3
CH2CH2
3
Degree of Polymerization (P) = M/m;
Where, M= Mass of Polymer; m = mass of monomeric unit
PolymerisationPolymerisation
polyethylenepolyethylene
EthyleneEthylene
Degree of polymerisation (P) = 3Degree of polymerisation (P) = 3
Mass of this polymer M = (28 x 3) = 84Da

5. A macromolecule may consist of monomer of
identical or different chemical structure and
accordingly they are called Homopolymers or
copolymers (or Heteropolymers).
A A A A … Homopolymers
A A B A … Copolymers

6. 11/11/12 6
Tacticity- Plane representation of polypropylene polymerTacticity- Plane representation of polypropylene polymer
CH2CCH2CCH2CCH2
H
CH3
H
CH3
H
CH3
CCH2C
H
CH3
H
CH3
CH2CCH2CCH2CCH2
H
CH3
H
CH3
CH3
H
CCH2C
H
CH3H
CH3
CH2CCH2CCH2CCH2
H
CH3
CH3
H
CH3
H
CCH2C
H
CH3
H
CH3
1. Isotactic polymers1. Isotactic polymers
Functional groups on the Functional groups on the
same sidesame side of the main carbon of the main carbon
skeletonskeleton
2. Syndiotactic polymers2. Syndiotactic polymers
Functional groups arranged Functional groups arranged
in the in the alternate fashionalternate fashion of the of the
main carbon skeletonmain carbon skeleton
3.Atactic polymers3.Atactic polymers
Functional groups arranged Functional groups arranged
in a in a random mannerrandom manner around around
the main carbon skeletonthe main carbon skeleton

7. Polymers can be linear, branched or cross-linked.
The monomer may be arranged in the chain at
random or regularly.
(LINEAR POLYMER)
A A A A … … B B B
A A A A A A
A A A A A
A A A
(BRANCHED POLYMER)

8. A A
A A A
A A A A A A
A A A
A A A A A A
(CROSS-LINKED POLYMER)

9. 11/11/12 9
Functionality Functionality
HOCCH
2
O
NH
2
OHCH2CHCOH
O
NH2
OHCH2CHCOH
O
NH2
HOCCH2
O
NH2
Ex. SerineEx. Serine
Glycine
The The number of reactive sitesnumber of reactive sites present in a monomer is called functionality present in a monomer is called functionality
Linear chain polymer is formed if the functionality of the
monomer is only two (Bifunctional)
Ex. Glycine
1.1.
2.2.
Cross linked chain polymer is
formed if the functionality of the
monomer is more than two
(multifunctional)

10. Classification of Polymers
Classification based on Source
1. Natural polymers
E.g., Proteins, Cellulose, Starch, Rubber
2. Semi-synthetic polymers
E.g., Cellulose derivatives - Cellulose acetate
(Rayon)
3. Synthetic polymers
E.g., Buna-S, Buna-R, Nylon, Polythene, Polyester.

11. Classification based on Structure
1. Linear polymers
consist of long and straight chains. E.g., Polyvinyl chloride

2. Branched chain polymers
contain linear chains having some branches, e.g., low density polymer.


3. Cross-linked or Network polymers
formed from bi-functional and tri-functional monomers and contain
strong covalent bonds e.g. bakelite, melamine,

12. Classification based on Molecular Forces
1. Elastomers
eg. Buna-S, Buna-N, neoprene
2. Fibers
eg. Polyesters, Polyamides.
3. Thermoplastic polymers
eg. Polythene, Polystyrene, PVC.
4. Thermosetting polymers
eg. Bakelite, urea-formaldelyde resins
Order of strength :-
Thermosetting > Fibres > Thermoplastics > Elastomers

13. Classification based on mode of Polymerization
1. Addition polymers
formed by the repeated addition of monomer molecules
possessing double or triple bonds
n(CH
2
=CH
2
) -(CH
2
-CH
2
)-
Ethylene polyethylene
2. Condensation polymers
formed by repeated condensation reaction between two
different bi-functional or tri-functional monomeric units.
eg. terylene (dacron), nylon 6, 6, nylon 6.
n(H
2
N(CH
2
)
6
NH
2
) + n(HOOC(CH
2
)
4
COOH)
[-NH(CH
2
)
6
NHCO(CH
2
)
4
CO-]
n
+ nH
2
O
(Nylon 6:6)

14. Polymerization is of two types;
 Addition or chain polymerization
 Condensation polymer

15. 1. Free radical mechanism:- Alkenes or dienes and their derivatives are
polymerized in the presence of a free radical generating initiator (catalyst)
like benzoyl peroxide, acetyl peroxide, t-bu peroxide, etc.
This process involves in 3 steps –
a) Chain initiation step - addition of phenyl free radical formed by the
peroxide to the ethene double bond ,thereby forming a larger radical.
b) Chain propagation step - repetition of this sequence with new and bigger
radicals.
c) Chain terminating step - the product radical thus formed reacts
with another radical to form the polymerized product.

Some of polymers formed by this process are-
Polytetrafluroethene (Teflon), Polyacrylonitrile, Polyethylene, etc.

16. In addition polymers , the polymer is formed from the
monomer, without the loss of any material, and the
product is the exact multiple of the original
monomeric molecule.

CH2=CH2 -CH2-CH2- POLYMERIZATION (-CH2-CH2-)n
Ethylene monomer Molecular Rearrangement Polyethylene

17. Addition polymerization proceeds by the initial
formation of some reactive species such as free
radicals or ions and by the addition of the reactive
species to the other molecule, with the regeneration
of the reactive feature.

18. Chain polymerization occur in three steps:-
•Chain initiation step
•Chain propagation step
•Chain termination step

19. In chain initiation step, a free radical is first generated
as a result of physical or chemical effect, which is
responsible for the further continuation of the chain
polymerization

20. The primary free radical react with the double bond of
an unexcited monomer molecule and adds to it
forming a new radical capable of further interaction
with the initial monomers.

21. The most common termination processes are Radical
Combination and Disproportionate.
These reactions are illustrated by the following equations.

22. In condensation polymerization, the chain growth is
accompanied by the elimination of small
molecules.
The molecules are in the form of the water molecule
H
2
O ; methanol molecule CH
3
OH ,etc.

23. Step Growth polymerization:- It involves a repetitive condensation
reaction between two bi-functional monomers.
Eg. Formation of Nylon 6,6
nHOOC(CH
2
)
4
COOH + nH
2
N(CH
2
)
6
NH
2

5 5 3 K


[-N-(CH
2
)
6
-N-C(CH
2
)
4
-C-]
n

H O O
High pressure
Nylon6,6

24. Copolymerisation:- is a polymerization reaction in which a mixture
of more than one monomeric species is allowed to polymerize and
form
a copolymer. For example, a mixture of 1, 3 – butadiene and styrene
can form a copolymer.

25. Examples of Daily Use Polymers

26. Plastics
Plastics are high molecular weight organic materials
which can be moulded into any desired shape by the
application of heat and pressure in the presence of
catalyst.
Constituents of plastics:
1.Resins
2.Plasticizers
3.Fillers or Extenders
4.Lubricants
5.Stabilizers
6.Pigments
7.Anti-oxidants
8.Catalysts or Accelerators

27. Resins:
They are basic binding materials and hold the constituents
together.
They are generally linear polymers with low molecular weight
to enhance fusibility and mouldability.
It is then converted into crosslinked form during moulding in
the presence of a catalyst.
E.g. Thermoplastic resins and thermosetting resins.
Plasticizers:
They improve flow for processing by reducing the
intermolecular force of attraction
E.g. Dioctylphthalate, oleate and organic phosphates
Fillers:
They increase the tensile and compressive strength of
plastics.
They also reduce the shrinkage during setting of the plastics.
E.g. Mica, quartz, limestone, acrylics

28. Lubricants:
They makes the moulding process easier and also provide glossy
finish to the final product.
E.g. Waxes, oils and soaps
Stabilizers:
They increase the thermal stability during processing.
E.g. Stearates of lead, barium and cadmium.
Pigments:
They provide colours to the plastics
TiO
2
, ZnO – White; Cr
2
O
3
– Green, Carbon black – black, Red lead -
Red
Anti-oxidants: They protect against oxidative degradation
E.g. Phenyl p-napthyl amine, diphenyl p-phenylene diamine
Catalysts:
They are added to accelerate the polymerization of fusible resin into
cross-linked infusible form especially for thermosetting plastics.
E.g. H
2
O
2
, benzoyl peroxide

30. These are linear or slightly branched long chain
polymers, which can be softened on heating &
reversibly hardened on cooling repeatedly.
Their hardness is a temporary property & varies with
temperature.
It can be reprocessed, so sometimes also referred as
green plastics.
Definition

31. Thermoplastics possess weak intermolecular
forces(e.g. Van der Waal) & don’t have crosslinks.
Structure

32. Cellulose derivatives
- 1) Cellulose acetate
- Cellulose nitrate
Polyethenic/vinyl resins
- 2) Polyethylene
- 3) Polypropylene
- 4) Polyvinyl acetate
- 5) Polyvinyl chloride
- 6) Polystyrene
- 7) Teflon
- 8) Acrylic
- 9) Polysulfone
- 10) Polyester
Examples

33. There are mainly two types of polythene:
Low density polythene(density range of 0.910–0.940
g/cm
3
):It is obtained by the polymerisation of ethene
under high pressure of 1000-2000 atm at a
temperature of 350-570 K in the presence of traces of
oxygen or a peroxide initiator.
It is created by free radical polymerization.
Polyethylene(PE)/Polythene

34. Properties:
1.High degree of short and long chain branching.
2.intermolecular forces is less.
3.Tough but highly flexible & ductile.
4.Chemically inert.
Uses: Insulation of electricity carrying wires and
manufacture of squeeze bottles, toys and flexible
pipes.

35. High density polythene(density >= 0.941 g/cm
3
):
formed when addition polymerisation of ethene takes
place in a hydrocarbon solvent in the presence of a
catalyst such as triethylaluminium and titanium
tetrachloride (Ziegler-Natta catalyst) at a
temperature of 333-343 K and under a pressure of 6-7
atm.
Properties:
1.low degree of branching(lack of branching is ensured
by an appropriate choice of catalyst & reaction
conditions).
2.stronger intermolecular forces and tensile strength,
3.Chemically inert.

36. Uses:for manufacturing buckets, dustbins, bottles,
water pipes etc.
Environmental issue
Although polyethylene can be recycled, most of the
commercial polyethylene ends up in landfills, and in
the oceans such as the Great Pacific Garbage Patch.
Polyethylene is not considered biodegradable, except
when it is exposed to UV from sunlight. Under UV
lights tertiary carbon bonds in the chain structures
are the centres of attack. The UV rays activate such
bonds to form free radicals, which then react further
with oxygen in the atmosphere, producing carbonyl
groups in the main chain.

37. Polystyrene is actually an aromatic polymer that
is made from the monomer styrene. It is a long
hydrocarbon chain that has a phenyl group
attached to every carbon atom. Styrene is an
aromatic monomer, commercially manufactured
from petroleum. Polystyrene is a vinyl polymer,
manufactured from the styrene monomer by free
radical vinyl polymerization.
Polystyrene

38. Polystyrene is generally flexible and can come in the
form of moldable solids or viscous liquids.
The force of attraction in polystyrene is mainly due to
short range van der Waals attractions between chains.
Properties

39. The outside housing of computer, housings of
most kitchen appliances, model cars and
airoplanes, toys, molded parts in car are all made
of polystyrene.
It is also made in the form of foam that is used
for packaging and insulating.
Polystyrene is generally flexible and can come in
the form of moldable solids or viscous liquids.
Uses

40. It is a vinyl polymer constructed of repeating vinyl
groups (ethenyls) having one of their hydrogens
replaced with a chloride group.
 Obtained by heating a water emulsion of vinyl
chloride in presence of benzyl peroxide/ hydrogen
peroxide in an autoclave under high pressure.
Polyvinyl chloride

41. Properties:
1.Colurless & odourless
2.Non-inflammable & chemically inert
3.Resistant to light,O
2
, inorganic acid & alkalis.
4.Greater stiffness & rigidity than polyethylene but
brittle.

42. Uses: Third most widely produced plastic
Unplasticized PVC: Highly rigid but brittle, for
making sheets, tank lining, helmets ,mudguards etc.
Plasticized PVC(by adding plasticizers e.g.
phthalates): Making continuous sheets of varying
thickness, hoses, pipes, construction, table covers,
conveyor belts etc.

43. Polytetrafluoroethylene (TEFLON)
• It is obtained by polymerization of water-
emulsion of tetrafluoro ethylene, under pressure
and in the presence of benzoyl peroxide as a
catalyst.

44. Due to presence of high electronegative fluorine in
structure of TEFLON, strong interchain forces are
present which make it extremely tough.
High softening point (350°c).
It has high chemical resistance.
It has good mechanical and electrical
properties(high-performance substitute for
polyethylene)
Properties

45. It is used in insulating motor, transformers.
It is used in making wires.
Non-stick cookware coatings are made
from TEFLON for eg. In frying pan.
Also used for making gaskets, tank linings, pipes and
tubes for chemical industries.
Used for making non lubricating bearings.
one of the lowest coefficients of friction against any solid.
Uses

46. Is a transparent thermoplastic, often used as a light or
shatter-resistant alternative to glass. Synthetic
polymer of methyl methacrylate. Can be made by all
types of moulding processes.
Poly(methyl methacrylate)

47. Properties:
1.Strong & light weight
2.Good impact strength ,higher than both glass &
polystyrene.
3.Transmits up to 92% of light & filters UV lights.
4.coefficient of thermal expansion is relatively high.
5.Its properties can be modified to suit requirements.

48. Uses: Making aquarium glasses; automobile
headlights; spectator protection(e.g.- in ice hockey
rinks); Aircraft windows; Helmet visors; making
acrylic paints; bone cement, contact lenses etc.

49. AcrylonitrileButadieeneStyrene
•Monomers:-Acrylonitrile , Butadieene, Styrene
•Formula :-(C
8
H
8
·C
4
H
6
·C
3
H
3
N)
n
•Production :-Copolymer made by polymerizing styrene and acrylonitrile in the
presence of polybutadiene. The proportions can vary from 15 to 35% acrylonitrile,
5 to 30% butadiene and 40 to 60% styrene.
•Properties :-The styrene gives the plastic a shiny, impervious surface. The
butadiene, a rubbery substance, provides resilience even at low
temperatures.Mechanical properties vary with temperature.
•Application :-
1.Used to make light, rigid, molded products such as piping .
2.Musical Instruments such as plastic clarinet.
3.Golf club heads :- Used due to its good shock absorbance
4.Used as a colorant in tattoo inks.

51. Bakelite, a phenol-formaldehyde polymer, was the first
completely synthetic plastic, first made by Leo Baekeland
in 1907. Baekeland and an assistant started their research
in 1904 looking for a synthetic substitute for shellac.
Bakelite was commercially introduced in 1909. Bakelite
was first used to make billiard balls, but, later, was used to
make molded insulation, valve parts, knobs, buttons, knife
handles, many types of molded plastic containers for
radios and electronic instruments, and more.

52. Phenol - formaldehyde polymers are the oldest synthetic polymers. These are
obtained by the condensation reaction of phenol with formaldehyde in the
presence of either an acid or a base catalyst. The reaction starts with the initial
formation of o-and/or
p-hydroxymethylphenol derivatives, which further react with phenol to form
compounds having rings joined to each other through –CH2 groups. The initial
product could be a linear product – Novolac used in paints.
Phenolic reins set to rigid, hard, scratch resistant, infusible, water resistant, insoluble
solids, which are resistant to non-oxidizing acids, salts and many organic solvents,
but are attacked by alkalis, because of the presence of free hydroxyl group in their
structures, They posses excellent electrical insulating character.

53. Novolac on heating with formaldehyde undergoes cross linking to form an infusible
solid mass called bakelite.

54. 1.Plastic items like telephone parts,cabinets,heater handles.
2.Phonograph records
3.Electrical switches and berings used in propeller shafts in paper industry.
4.Soft bakelite used as binding glue for
laminated,wooden plants and in varnishes
5.Sulphonated bakelite are used as ion exchange resins.
6.For impregating fabrics,wood and paper.
Phonograph records
valve parts, knobs, buttons,

55. Melamine resin or melamine formaldehyde (also shortened to melamine) is a
hard, thermosetting plastic material made from melamine and
formaldehyde by polymerization at 80°C.
Melamine formaldehyde resin gives water white products,have good tensile strength,
good electrical insulation, good chemical resistance, great hardness and good
abrasion resistance.

56. The resin is formed by condensation co-polymerisation of melamine and formaldehyde.

57. It is a quite hard polymer and is used widely for making plastic crockery
under the name Melamine. The articles made from melamine polymer do
not break even dropped from considerable height. They are also used as
laminates and for making decorative items. In paper industry to improve
wet strength of paper. In fabric treatment as finishing agent.

58. Polyurethanes are made from a dialcohol and diisocyanate monomers. The isocyanate
compounds contain the functional group (O=C=N-). A rearrangement reaction leads to
the formation of the urethane linkage. Technically polyurethane is not a condensation
polymer since no molecules are lost, but the functional group does rearrange.
For example, Perlon-U (a crystalline polymer) is obtained by the reaction of 1,4-
butane diol with 1,6-hexane diisocynate

59. 1.Polyurethanes are less stable than polyamides(nylons) at elevated temperature.
2.They are characterized by excellent resistance to abrasion and solvents.
Polyuraethenes are used as coatings, films, foams,adhesives and elastomers.
Resilient polyurethene fibres (spandex) are used for foundation garments and swim
suits.They also find use as a leather substutute(corfoam). They are used to cast to
produce gaskets, and seals.

60. Silicone polymers do not have carbon as part of the backbone structure. The although
silicon is in the same group as carbon in the periodic table, it has quite different
chemistry.
Many silanes are known which are analogous to the hydrocarbons with Si-Si bonds.
These compounds are not very stable and hence not very useful.
Silicones on the other hand have an alternating -Si-O- type structure. This basic
structural unit is found in many rocks and minerals in nature including common sand.
Various organic groups such as methyl or the benzene ring may be bonded to the
silicon as shown in the graphic on the bottom.

61. Silicones are water repellent, heat stable, and very resistant to chemical
attack. They find many uses in oils, greases, and rubberlike materials.
Silicone oils are very desirable since they do not decompose at high
temperature and do not become viscous. Other silicones are used in
hydraulic fluids, electrical insulators and moisture proofing agent in fabrics.
Silicones have a number of medical applications because they are chemically
inert. A good deal of controversy has involved the the use of silicone in
polyurethane bags as breast implants. Again they were used because they
were thought to be very inert and resistant to dissolving or other reactions.
Reports have cited increased cancer risk and severe immune responses from
possible leakage of the silicone from the implants.

62. EPOXY RESIN

63. The first commercial attempts to prepare resins from
epichlorohydrin were made in 1927 in the United States.
Credit for the first synthesis of bisphenol-A-based epoxy resins
is shared by Dr. Pierre Castan of Switzerland and Dr. S.O.
Greenlee of the United States in 1936. Dr. Castan's work was
licensed by Ciba, Ltd. of Switzerland, which went on to
become one of the three major epoxy resin producers
worldwide. Ciba's epoxy business was spun off and later sold
in the late 1990s and is now the advanced materials
business unit of Huntsman Corporation of the United States.
Dr. Greenlee's work was for the firm of Devoe-Reynolds of the
United States. Devoe-Reynolds, which was active in the early
days of the epoxy resin industry, was sold to Shell Chemical
(now Hexion, formerly Resolution Polymers and others).
THE ORIGIN OF EPOXY RESINS

64. Synthesis of high molecular weight epoxy resins under
microwave irradiation
A new method of synthesis of high molecular weight epoxy resins is
presented. All reactions were performed in a multi-mode microwave
reactor “Plazmatronika” (microwave frequency - 2,45GHz, maximum
of microwave power - 300W). Shortening of the reaction time for all
processes performed in the microwave reactor, in comparison to
conventional heating, was observed.

65. Epoxy is a copolymer; that is, it is formed from two different
chemicals. These are referred to as the "resin" and the "hardener".
The resin consists of monomers or short chain polymers with an
epoxide group at either end. Most common epoxy resins are
produced from a reaction between epichlorohydrin and bisphenol-A,
though the latter may be replaced by similar chemicals. The hardener
consists of polyamine monomers, for example Triethylenetetramine
(TETA). When these compounds are mixed together, the amine
groups react with the epoxide groups to form a covalent bond. Each
NH group can react with an epoxide group, so that the resulting
polymer is heavily crosslinked, and is thus rigid and strong.
The process of polymerization is called "curing", and can be controlled
through temperature and choice of resin and hardener compounds;
the process can take minutes to hours. Some formulations benefit
from heating during the cure period, whereas others simply require
time, and ambient temperatures.
PROPERTIES

66. The applications for epoxy-based materials are extensive and include
coatings, adhesives and composite materials such as those using
carbon fiber and fiberglass reinforcements (although polyester, vinyl
ester, and other thermosetting resins are also used for glass-
reinforced plastic). The chemistry of epoxies and the range of
commercially available variations allows cure polymers to be
produced with a very broad range of properties. In general, epoxies
are known for their excellent adhesion, chemical and heat resistance,
good-to-excellent mechanical properties and very good electrical
insulating properties. Many properties of epoxies can be modified (for
example silver-filled epoxies with good electrical conductivity are
available, although epoxies are typically electrically insulating).
Variations offering high thermal insulation, or thermal conductivity
combined with high electrical resistance for electronics applications,
are available.
APPLICATION

67. Electrical systems and electronics
Aerospace applications
Wind Energy applications
Epoxy resin is used in manufacturing the rotor blades of wind turbines. The resin is
infused in the core materials (balsa wood, foam) and the reinforcing media (glass,
fabric). The process is called VARTM, i.e. Vacuum Assisted Resin Transfer Moulding.
Due to excellent properties and good finish, epoxy is the most favoured resin for
composites.

68. Paints and coatings

Adhesives
Industrial tooling and composites
Consumer and marine applications

69. Nylon is used as general name for all synthetic fiber forming polyamides,
i.e., having a protein like structure. These are the condensation polymers of
diamines and dibasic acids A number is usually suffixed with the
Nylon which refers to the number of carbon atoms present in the diamine
and the dibasic acids respectively.
Nylon-6,6 is obtained by the polymerisation of adipic acid with hexamethylene
diamine.

70. It is produced by the self condensation of caprolactum.
Beckmann Rearrangement

71. 1.They are translucent,whitish,horny,high melting polymers .
2.They posses high temperature stability and high abrasion resistance.
3.They are insoluble in common organic solvents(like methylated spirit,benzene
and Acetone), and soluble in phenol and formic acid.
4.Their mouldings and extrusions have good physical strengths(especially high
impact strength) and self lubricating properties.
1.They are light, horny, and high melting.
2.They are insoluble in common solvents.
3.They have good strength.
4.They absorb little moisture ; and are thus ’drip-dry’ in nature.
5.They are very flexible and retain original shape after use.
6.They are resistant to abrasion.
7.On blending with wool, the strength and abrasion resistance of the latter increases.

72. 1.Nylon-6,6 is primarily used for fibres, which find use in making socks, ladies hoses,
dresses, carpets,etc.
2.Nylon-6 is mainly used for moulding purposes for gears, bearings, electrical
mountings, etc. These bearings and gears work quietly without any lubrication.
3.They are also used for making filaments for ropes, bristles for tooth brushes and
films, tyre cords,etc.

73. Repeating chemical structure
unit of
Polycarbonate made from
bisphenol A
POLYCARBONATE
S

74. Structure
Polycarbonates received their name because they are
polymers containing carbonate groups (-O-(C=O)-O-). Most
polycarbonates of commercial interest are derived from
rigid monomers. A balance of useful features including
temperature resistance, impact resistance and optical
properties position polycarbonates between commodity
plastics and engineering plastics

75. •The main polycarbonate material is producted by the reaction of
bisphenol A and phosgene (COCl
2
). The first step involves treatment
of bisphenol A with sodium hydroxide, which deprotonates the
hydroxyl groups of the bisphenol A.
(HOC
6
H
4
)
2
CMe
2
+ 2 NaOH → (NaOC
6
H
4
)
2
CMe
2
+ 2 H
2
O
•The diphenoxide ((NaOC
6
H
4
)
2
CMe
2
) reacts with phosgene to give a
chloroformate, which subsequently is attacked by another phenoxide.
The net reaction from the diphenoxide is:
(NaOC
6
H
4
)
2
CMe
2
+ COCl
2
→ 1/n [OC(OC
6
H
4
)
2
CMe
2
]
n
+ 2 NaCl
 In this way, approximately one billion kilograms of
polycarbonate is produced annually
SYNTHESIS

76. Uses of polycarbonates
1)Domestic wares
2)Electrical insulator in electronic industries
3)Other uses for polycarbonate
include greenhouse enclosures, automobile
headlights, outdoor fixtures, and medical
industry applications, though the list is virtually
endless.

77. 11/11/12 77
Processing (or) moulding (or) compounding of plasticsProcessing (or) moulding (or) compounding of plastics
Compounding or mouldingCompounding or moulding is a process by which the polymer resins are is a process by which the polymer resins are
mixed with some additives like fillers, plasticizers, stabilizers etc to impart mixed with some additives like fillers, plasticizers, stabilizers etc to impart
some special properties to the moulded final product.some special properties to the moulded final product.
Ingredients of a plastic
Additives Examples Function/Importance
1. Resins
2. Plasticizers
Thermoplastic and
thermosetting resins
Dioctylphthalate (DOP)
Adipate, Oleate,
Organic Phosphate
Basic binding materials and holds the
constituents together. Major part of
the plastics. Thermosetting resins
transferred in to crosslinked plastics
during moulding in presence of a
catalyst
To improve the elasticity and to
reduce the brittleness of the plastics.
Also improves the flow of polymer
during the process

78. 11/11/12 78
Additives Examples Function/Importance
3. Fillers (or)
Extenders
4. Lubricants
5. Stabilizers
6. Pigments
7. Anti-Oxidants
8. Catalyst
Mica, quartz, Limestone,
Nylon
Waxes, Oils, soaps
Stearates of Pb, Ba and Cd
TiO2, ZnO (white), chromium
oxide (green), carbon black,
Read Lead
Phenyl, n-napthyal amine,
Diphenyl-p-
phenylenedimaine
H2O2 and Benzoyl peroxide
Increases the tensile and compressive
strength of plastics. They reduce the
shrinkage during the process of setting
To make the moulding process smooth and
give the glossy finish to the final product
To increase the thermal stability of a
polymer
To provide colours to the moilded articles
Protection against oxidation
Added only in the case of thermosetting
resins to increase the rate of polymerisation

79. 11/11/12 79
Different types of Moulding technique
The moulding is different for various polymer depends on their thermal
behaviour and nature of the resins.
1.1.Compression mouldingCompression moulding
2.2.Transfer mouldingTransfer moulding
3.3.Injection mouldingInjection moulding
4.4.Extension moulding and Extension moulding and
5.5.Blow mouldingBlow moulding
Used for moulding the Used for moulding the
thermosetting polymersthermosetting polymers
Used for moulding the Used for moulding the
thermo polymersthermo polymers
Used for moulding the Used for moulding the
bottle type articles which bottle type articles which
has narrow neckhas narrow neck

80. 11/11/12 80
PressurePressure
Pressure = 70 kg/cmPressure = 70 kg/cm
22
Molten polymer with ingredients Molten polymer with ingredients
in the cavity at 200in the cavity at 200
oo
CC
Top moulding part of the die Top moulding part of the die
(plunger)(plunger)
Bottom moulding part of the die with cavity Bottom moulding part of the die with cavity
(the shape of the cavity decides the shape (the shape of the cavity decides the shape
of the final product)of the final product)
Pressed plastic Pressed plastic
materialmaterial
Extraction pinExtraction pin
Guide pinsGuide pins
•The process of molding a material in a confined
shape by applying pressure and usually heat.
•Almost exclusively for thermoset materials
•Used to produce mainly electrical products
•A force of 2900psi is usually
required for moldings up to 1inch
(25 mm) thick.
•An added 725psi should be
provided for each 1inch (25 mm)
increase.

81. 11/11/12 81
Plunger (top molding Plunger (top molding
part)part)
Bottom molding partBottom molding part
Charger (plastic ingredients)Charger (plastic ingredients)
Molding CavityMolding Cavity
SprueSprue
Ejector pinEjector pin
HeatersHeaters
Molded Molded
plasticplastic
A process of forming articles by fusing a plastic material in a
chamber then forcing the whole mass into a hot mold to
solidify.
Used to make products such as electrical wall receptacles and
circuit breakers
This is exclusively used for thermosetting plastics. The resin ingredients mixture is preheated in a
preheating chamber. When the moulding mixture becomes plastic then it is forced through a orifice into
the hot mould by using the plunger. After setting time it is taken out. Complicated shapes can be made.

82. 11/11/12 82
*
Injection partMolding partClamping
Heater bands
Hopper
Hydraulic
screw
drive
Cavity
Barrel

83. 11/11/12 83
Pressing of molten polymer using die and plunger in Injection Molding
* Source: http://www.idsa-mp.org/proc/plastic/injection/injection_process.htm
Die
Plunger
The cavity in which the molten The cavity in which the molten
plastic will be fed and pressedplastic will be fed and pressed
The feeding or injection of
hot plastic
This method is generally used for
thermoplastics.
The moulding composition is heated in
a suitable chamber connected by a
duct leading to the mould.
The hot softened plastic is then forced
under high pressure into the relatively
cool mould cavity where it is set by
cooling and the moulded object is then
ejected.
The temperature range used is 90 to
260
o
C.

84. 11/11/12 84
It is a process in which the molten plastic material is forced through a die It is a process in which the molten plastic material is forced through a die
which produces a continuous extrudate (product) in the form of final product. which produces a continuous extrudate (product) in the form of final product.
This process is used mainly for the production of films tubes, rods, hoses.This process is used mainly for the production of films tubes, rods, hoses.
It also used for the coating cables with PVC and other plastics.It also used for the coating cables with PVC and other plastics.
Molten
polymer
Die
Extruded pipe
Heater
Raw materials
Screw
conveyer Cooling of
final product