Material Chemistry and Engineering Applications of Polymers
1. MATRUSRI ENGINEERING COLLEGE
DEPARTMENT OF SCIENCES AND HUMANITIES
SUBJECT NAME: CHEMISTRY
FACULTY NAME: VISHNU THUMMA
MATRUSRI
ENGINEERING COLLEGE
TOPIC: MATERIAL CHEMISTRY
2. CHEMISTRY
2
COURSE OBJECTIVES:
➢Correlate the properties of materials with their internal structure and use
the for Engineering applications
➢Apply the principles of electrochemistry in storage of electrical energy in
batteries.
➢Gains knowledge in causes of corrosion and its prevention.
➢Attains knowledge about the disadvantages of hard water for domestic and
industrial purposes.
➢Also learns the techniques of softening of hard water and treatment of
water for drinking purpose.
➢Exposed to qualitative and quantitative parameters of chemical fuels.
➢Aware eco-friendly materials and processes.
MATRUSRI
ENGINEERING COLLEGE
3. CHEMISTRY
3
COURSE OUTCOMES: After completion of course students will be able to
➢Analyze and apply knowledge of electrodics in calculation of cell
potentials of batteries.
➢Identify the different types of hardness and alkalinities in water and
make use of softening methods, analyze and apply the knowledge of
corrosion for its prevention.
➢Discuss different types of polymers based on their end on use and
the need to replace the conventional polymers with polymers of
engineering applications.
➢Identify and analyze different types of chemical fuels for domestic and
automobile applications.
➢Outline the principles of green chemistry for sustainable environment
and preparation of biodiesel from renewable sources.
MATRUSRI
ENGINEERING COLLEGE
4. UNIT-III MATERIAL CHEMISTRY
4
COURSE OUTCOMES: After completion of course students will be able
to discuss different types of polymers based on their end on use
and the need to replace the conventional polymers with polymers of
engineering applications.
MATRUSRI
ENGINEERING COLLEGE
5. MODULE-1: BASIC TERMINOLOGY OF POLYMERS
The word polymer is derived from the two greek words
poly and mers
Polymers are macro molecules built-ip by linking together
of smaller molecules, called Monomers
parts or units
many
C C C C C C
H
H
H
H
H
H
H
H
H
H
H
H
Polyethylene (PE)
mer
Cl
Cl Cl
C C C C C C
H
H
H
H
H
H
H
H
H
Polyvinyl chloride (PVC)
mer
Polypropylene (PP)
CH3
C C C C C C
H
H
H
H
H
H
H
H
H
CH3 CH3
mer
e.g.
MATRUSRI
ENGINEERING COLLEGE
5
6. Examples: Polyethylene is formed by linking a large number of
ethylene molecules
n
C C
H
H H
H
C C
H
H H
H
n
Polymerisation
Ethylene polyethylene
polystyrene is formed by linking styrene molecules
H
styrene polystyrene
C C
H
H
n
Polymerisation
n
C C
H
H
H
Polymerization: The process of chemical combination of small molecules
(monomers) to form large sized molecules (polymers) is called
polymerization.
MATRUSRI
ENGINEERING COLLEGE
6
7. The number of repeating units (n) in the chain is known
as the degree of polymerization.
Polymers with high degree of polymerization are called
high polymers and these have very high molecular weights
(104 to 106).
Polymers with low degree of polymerization are called
oligomers.
e.g.,
D.P.
MATRUSRI
ENGINEERING COLLEGE
7
8. Functionality: the number of reactive sites or bonding sites
Ethylene
Vinyl chloride
1,3 butadiene
MATRUSRI
ENGINEERING COLLEGE
8
9. Some bi functional hydrocarbons
adipic acid (hexanedioic acid)
1,6-hexanediamine
Terephthalic acid
ethylene glycol
MATRUSRI
ENGINEERING COLLEGE
9
10. Nomenclature of Polymers
Homopolymer: A polymer consisting of identical monomers is
called Homopolymer.
Ex: Polyethylene, PVC, Teflon
MATRUSRI
ENGINEERING COLLEGE
10
11. Copolymer: Polymer formed by two or more monomers of
different chemical structures is called Copolymers
Styrene-butadiene rubber (Buna-S)
MATRUSRI
ENGINEERING COLLEGE
11
12. Based on the molecular structure
polymers can be classified as
➢Linear
➢Branched
➢Cross-linked
the monomeric units combine linearly with each other
In linear polymers,
secondary bonding
MATRUSRI
ENGINEERING COLLEGE
12
13. Branched polymers
Cross linked polymers
Graft copolymer: The monomers of the polymer in back bone and
branch chain differ
MATRUSRI
ENGINEERING COLLEGE
13
14. Based on the response to heat
➢Thermo plastic ➢Thermosetting
soften on heating and can be converted into any shape
and can retain its shape on cooling
thermosoftening or thermoplastics
MATRUSRI
ENGINEERING COLLEGE
14
15. under go chemical change on heating and convert
themselves into an infusible mass
thermosetting polymers
Covalent bond
MATRUSRI
ENGINEERING COLLEGE
15
16. Differences between thermoplastics and thermosetting plastics:
These are formed by additional polymerization. These are formed by condensation
Polymerization
These are long chain linear macromolecules Their set molecules have three dimensional
cross –linked network structure.
The adjacent polymer chains are held together
by either vander wal forces or by dipole-dipole
or H-bonds.
Polymer chains are held together by strong
covalent bonds.
They can be remoulded, reshaped and reused. They cannot be remoulded.
They can be reclaimed from waste. They cannot be reclaimed from waste.
Thermoplasts are soluble in organic solvents These are insoluble in almost all the solvents.
These are soft, weak and less brittle. These are hard, strong and more brittle.
Ex: PE, PVC andTeflon. Ex: Bakelite and Urea Formaldehyde resins.
MATRUSRI
ENGINEERING COLLEGE
16
17. MODULE-2: Polymerisation Reactions
There are three types of polymerization reactions.
• Addition (chain growth) polymerization
• Condensation (step growth) polymerization
• Copolymerization
MATRUSRI
ENGINEERING COLLEGE
17
18. Addition Polymerization:
It is a reaction that yields a product, which is an exact multiple of
the original monomeric molecule.
Such a monomer molecule, usually contains one or more double
bonds, which by intermolecular rearrangement, may make the
molecule bifunctional.
Must be instigated by the application of heat, light, pressure or a
catalyst for breaking down the double covalent bonds of
monomers.
C C
H
H
H
H
n
C C
H
H
H
H
n
Ethylene
(Monomer)
Polyethene
(Polymer)
Polymerization
n
Bifunctinal molecules
C C
H
H
H
H
Rearrangement
(Heat, Light,
Pressure or catalyst)
MATRUSRI
ENGINEERING COLLEGE
18
19. Condensation Polymerization:
A reaction occurring between simple polar group containing monomers with
the formation of polymer and elimination of small molecules like water, HCl,
etc.
For example, hexamethylene diamine and adipic acid condense to form a
polymer, nylon 6:6
Thus, it is an intermolecular combination, and it takes place through the
different functional group in the monomers having the affinity for each other.
MATRUSRI
ENGINEERING COLLEGE
19
20. DISTINGUISHING FEATURES OF
ADDITION AND CONDENSATION POLYMERISATION
ADDITION CONDENSATION
Monomers undergo self addition to each
other without loss of by products
Monomers undergo intermolecular
condensation with continuous elimination of
by products such as H2O, NH3, HCl, etc.,
It follows chain mechanism It follows step mechanism
Unsaturated vinyl compounds undergo
addition polymeristion
Monomers containing the functional groups (-
OH, -COOH, -NH2, ….) undergo this
polymerization
Monomers are linked together through
C – C covalent linkages
Covalent linkages are through their functional
groups
High polymers are formed fast The reaction is slow and the polymer molecular
weight increases steadily throughout the
reaction
Linear polymers are produced with or
without branching
Linear or cross linked polymers are produced
e.g., polystryrene, plexiglass, PVC, etc., e.g., nylons, terylene, PF resins, etc.,
MATRUSRI
ENGINEERING COLLEGE
20
21. Copolymerization
• It is the joint polymerization of two or more monomer species.
• High molecular-weight compounds obtained by copolymerization are
called copolymers.
• For example, butadiene and styrene copolymerize to yield Buna-S
rubber.
MATRUSRI
ENGINEERING COLLEGE
21
22. Addition polymerization can be explained on the basis of free radical
mechanism
It involves three stages
viz., (i) Initiation
(ii) Propagation
(iii) termination
D or
u.v.light
I
(Initiator)
R*
(Free radical)
Initiation
MATRUSRI
ENGINEERING COLLEGE
Module-3: Free Radical Polymerization
22
23. C C
H
X H
H
+
R*
(Free radical)
Vinyl monomer
C C *
H
H X
H
R
(new free radical)
The new free radicals attack monomer molecules further in quick
succession leading to chain propagation
Vinyl monomer
C C
H
X H
H
C* +
C
H
H X
H
R
(Free radical)
C C
H
H X
H
R C C*
H
H X
H
(new free radical)
Propagation
MATRUSRI
ENGINEERING COLLEGE
23
24. Vinyl monomer
C C
H
X H
H
+
(new free radical)
C C
H
H X
H
R C C*
H
H X
H
(another new free radical)
C*
C
H
H X
H
C C
H
H X
H
R C C
H
H X
H
at m th stage,
C C
H
X H
H
+
C
H
H
R C
X
H
C
H
H
C
X
H
m-2
C*
C
H
H X
H
C
H
H
R C
X
H
C
H
H
C
X
H
m-1
C*
C
H
H X
H
MATRUSRI
ENGINEERING COLLEGE
24
25. At some stage this chain propagation is terminated when the free radicals
combine either by coupling (combining) of the two radicals or by
disproportionation
R C
H
H
C
X
H
m-1
C*
C
H
H X
H
R
C
H
H
C
X
H
m-1
C*
X
H
C
H
H
+
R C
H
H
C
X
H
m-1
C
C
H
H X
H
R
C
H
H
C
X
H
m-1
C
H
H
C
X
H
saturated highpolymer (dead polymer)
coupling
MATRUSRI
ENGINEERING COLLEGE
25
26. R C
H
H
C
X
H
m-1
C*
C
H
H X
H
+ R
C
H
H
C
X
H
m-1
C*
X
H
C
H
H
+
R C
H
H
C
X
H
m-1
C
C
H X
H
H R
C
H
H
C
X
H
m-1
C
H
H
C
X
H
saturated oligomer
unsaturated oligomer
(dead polymer) (dead polymer)
disproportionation
MATRUSRI
ENGINEERING COLLEGE
26
27. MODULE-4: Polyvinyl Chloride (PVC)
Preparation
H
C C
Cl
H
H
n
Water emulsion
polymerization
peroxide
H
C C
Cl
H
H
n
Properties
• It is colourless, odourless, non-inflammable and chemically
inert powder.
• It is resistant to light, atmospheric oxygen, inorganic acids and
alkalis.
• It is soluble in hot chlorinated hydrocarbons such as ethyl
chloride.
• Pure resin possesses a high softening point (1480C) and a
greater stiffness and rigidity. 27
MATRUSRI
ENGINEERING COLLEGE
28. Rigid PVC (Unplasticized PVC):
It has superior chemical resistance and high rigidity, but is
brittle.
Applications:
It is used for making sheets, which are employed for
➢tank-linings, light-fittings
➢safety helmets
➢refrigerator components
➢cycle and motor cycle mudguards.
28
MATRUSRI
ENGINEERING COLLEGE
29. It is also extruded in strip and tube form for use in
place of non-ferrous metals.
29
MATRUSRI
ENGINEERING COLLEGE
30. Plasticized PVC:
It is obtained by adding plasticizers such as dibutyl phthalate,
dioctyl phthalate, tricresyl phosphate.
It used for making continuous sheets employed for Packing,
rain-coats, table-cloths, curtains.
Applications:
30
MATRUSRI
ENGINEERING COLLEGE
32. Injection moulding of articles like Toys, tool-handles,
toiled-goods, radio-components, plastic-coated cloth,
chemical containers.
32
MATRUSRI
ENGINEERING COLLEGE
33. Thermal insulating foam used in buildings, cinemas and
aircrafts.
33
MATRUSRI
ENGINEERING COLLEGE
35. MODULE-5: BAKELITE
It is a phenol formaldehyde resin.
It is prepared by condensing phenol with formaldehyde in
presence of acidic or basic catalyst.
The initial reaction results in the formation of ortho and para
hydroxyl, methyl phenol
OH
CH2OH
OH
CH2OH
OH
CH2OH
CH2OH
HOH2C
OH
HCHO + +
Phenol
Formaldehyde
o-hydroxymethyl
phenol
p-hydroxymethyl
phenol
2,4,6-trihydroxymethyl
phenol
35
MATRUSRI
ENGINEERING COLLEGE
37. During moulding, hexamethylene tetramine [(CH2)6N4] are added.
It provides formaldehyde, which converts the soluble and fusible
novolac into a hard, infusible and insoluble solid of cross-linked
structure.
37
MATRUSRI
ENGINEERING COLLEGE
38. Properties:
•Bakelite is set to rigid, hard, scratch-resistant, infusible, water-
resistant.
• Insoluble solid which is resistant to non-oxidizing acids, salts and
many organic solvents.
•It is attacked by alkalis, because of the presence of free hydroxyl
group in their structure.
•It possesses excellent electrical insulating character.
38
MATRUSRI
ENGINEERING COLLEGE
39. Applications:
•It is used for making electric insulator parts like switches, plugs,
switch-boards, heater-handles, etc.
39
MATRUSRI
ENGINEERING COLLEGE
40. •For making moulded articles like telephone parts, cabinets for
radio and television.
40
MATRUSRI
ENGINEERING COLLEGE
41. •For impregnating fabrics, wood and paper.
•As adhesives for
grinding wheels.
41
MATRUSRI
ENGINEERING COLLEGE
42. •In paints and varnishes.
•As hydrogen-exchanger resins in water softening.
•For making bearing, used in propeller shafts for paper industry
and rolling mills.
42
MATRUSRI
ENGINEERING COLLEGE
43. MODULE-6: NYLON-6,6
The aliphatic polyamides are generally known as nylons
The nylons are usually indicated by a numbering system
The nylons obtained from dibasic acids and diamines are
usually represented by two numbers
The first one indicating the number of ‘C’ atoms in the diamine
and the second that in the dicarboxylic acid
43
MATRUSRI
ENGINEERING COLLEGE
45. Properties
• It has a good tensile strength, abrasion resistance and
toughness upto 150 oC
• It offers resistance to many solvents. However, it dissolves
in formic acid, cresols and phenols
• They are translucent, wheatish, horny, high melting polymers
(160 – 264 oC)
• They possess high thermal stability
• Self lubricating properties
• They possess high degree of crystallinity
• The interchain hydrogen bonds provide superior mechanical
strength (Kevlar fibers stronger than metals)
• Its Hardness is similar to tin 45
MATRUSRI
ENGINEERING COLLEGE
46. • It is used as a plastic as well as fiber
Uses
• This is used to produce tyre cord
• It is used to make mono filaments and roaps
46
MATRUSRI
ENGINEERING COLLEGE
47. • Nylon 6,6 is used to manufacture articles like brushes and
bristles
47
MATRUSRI
ENGINEERING COLLEGE
48. • Nylon 6,6 used as sutures
• Used in making socks, ladies hoses, under-
garments, dresses, carpets etc.
48
MATRUSRI
ENGINEERING COLLEGE
49. MODULE-7: KEVLAR
• It is an aromatic polyamide in which benzene
rings linked to the amide groups.
• It is prepared by condensation between
aromatic dichloride and aromatic diamines.
49
MATRUSRI
ENGINEERING COLLEGE
50. 50
Properties:
• Kevlar is exceptionally strong, 5 times stronger than steel and 10 times
stronger than Al on a weight-for-weight bases.
• It has high heat stability and flexibility.
• The unique properties of kevlar are due to the delocalized bonding
which causes the benzene rings to be inflexible.
• The high electron-density in the chains of Kevlar also results in relatively
stronger vander waals intermolecular forces between neighboring
polymer molecules.
MATRUSRI
ENGINEERING COLLEGE
51. Applications:
• Kevlar is used extensively in the aerospace and aircraft industries.
51
MATRUSRI
ENGINEERING COLLEGE
52. Applications:
• As car parts such as tyres, brakes, clutch linings, etc.
52
MATRUSRI
ENGINEERING COLLEGE
53. • For making ropes, cables, protective clothing, bullet-
proof vests, motorcycle helmets and other high
performance materials.
53
MATRUSRI
ENGINEERING COLLEGE
54. MODULE-8: ELASTOMERS
Elastomer is defined as a long chain polymer which under
stress undergoes elongation by several times and regains its
original shape when the stress is fully released
Stretched
Returned to
randomization
54
MATRUSRI
ENGINEERING COLLEGE
55. Styrene rubber (GR-S or Buna-S or SBR)
Preparation
This is produced by copolymerization of butadiene
(about 75% by wt.) and styrene (about 25% by wt.)
H2C CH CH CH2
x
H2C CH
n
H2C CH CH CH2
n x
H2C CH
n
+
55
MATRUSRI
ENGINEERING COLLEGE
56. Properties
➢ It possess high abrasion-resistance
➢ It possess high load-bearing capacity and resilience
➢ It gets readily oxidized, especially in presence of traces of
ozone present in the atmosphere
➢ It swells in oils and solvents
➢ It can be vulcanized in the same way as natural rubber either
by sulphur or sulphur monochloride However, it requires less
sulphur, but more accelerators for vulcanization
➢ Styrene rubber resembles natural rubber in processing
characteristics as well as the quality of the finished products
56
MATRUSRI
ENGINEERING COLLEGE
57. Uses :It is used for the manufacture of
• floor tiles
• motor tyres • shoe soles
• gaskets • wire and cable insulations
57
MATRUSRI
ENGINEERING COLLEGE
58. Uses :It is used for the manufacture of
• carpet backing
• adhesives
• tank-lining
58
MATRUSRI
ENGINEERING COLLEGE
59. Butyl rubber
• It is made by copolymerization of isobutene
with small amounts of isoprene.
C
H2 C
CH3
CH3
+
C
H2 C CH CH2
CH3
m n CH2 C
CH3
CH3
CH2 C CH CH2
CH3
m
n
Isobutene
Isoprene
Polyisobutene-co-isoprene
(Butyl rubber)
59
MATRUSRI
ENGINEERING COLLEGE
60. Properties
➢It possesses outstanding low permeability to air and other
gases.
➢It has excellent resistance to heat, abrasion, ageing.
➢Chemicals such as H2SO4, HNO3, HCl and HF, polar solvents
like alcohol and acetone, but is soluble in hydrocarbon
solvents like benzene.
➢It has high resistance to ozone and good electrical insulating
properties.
➢It can be vulcanized, but it cannot be hardened much, due to
very low unsaturation. 60
MATRUSRI
ENGINEERING COLLEGE
61. Uses ➢For making cycle and automobile tubes, automobile parts,
hoses, conveyor belts for food and other materials, tank-
linings, insulation for high voltage wires and cables,etc.
61
MATRUSRI
ENGINEERING COLLEGE
62. Silicone rubber
Silicone resins contain alternate silicone – oxygen structure,
which has organic radicals attached to silicone atoms
Si
O
C
C
H
H
H
H
H
H
Si
O
C
C
H
H
H
H
H
H
O
62
MATRUSRI
ENGINEERING COLLEGE
63. Silicone rubber
Silicone resins contain alternate silicone – oxygen structure,
which has organic radicals attached to silicone atoms
Si
O
C
C
H
H
H
H
H
H
Si
O
C
C
H
H
H
H
H
H
O
63
MATRUSRI
ENGINEERING COLLEGE
64. Dimethyl silicone dichloride is bifunctional and
can yield very long chain polymer
CH3
CH3
O
Si
n
CH3
CH3
Cl Cl
Si
n
CH3
CH3
HO OH
Si
n
unstable
Hydrolysis
- HCl
H2O
polymerization
CH3
CH3
O
Si
( )
unstable
64
MATRUSRI
ENGINEERING COLLEGE
65. Vulcanized silicone rubbers are obtained by mixing high
molecular weight linear dimethyl silicone polymers with
filler
The fillers are either a finely divided silicon dioxide
or a peroxide
It may also contain the curing agents
Peroxide causes the formation of dimethyl bridge
(cross link) between methyl groups of adjacent chains
65
MATRUSRI
ENGINEERING COLLEGE
68. Properties
They possess exceptional resistance to
• prolonged exposure to sun light
• weathering
• most of the common oils
• boiling water
• dilute acids and alkalies
They remain flexible in the temp. range of 90 – 250 OC
hence, find use in making tyres of fighter aircrafts,
since they prevent damage on landing. Ordinary rubber
tyre becomes brittle and hence disintegrates
Silicone rubber at very high temp. s (as in case of fibers)
decomposes; leaving behind the non-conducting silica
(SiO2), instead of carbon tar 68
MATRUSRI
ENGINEERING COLLEGE
69. Uses
• as a sealing material in search-lights and in aircraft engines
• for manufacture of tyres for fighter aircrafts
69
MATRUSRI
ENGINEERING COLLEGE
70. • for insulating the electrical wiring in ships
• For making insulation for washing
machines and electric blankets for iron
board covers
70
MATRUSRI
ENGINEERING COLLEGE
71. • For making artificial heart valves, transfusion
tubing and padding for plastic surgery
71
MATRUSRI
ENGINEERING COLLEGE
72. • In making lubricants, paints and protective coatings for
fabric finishing and water proofing
• as adhesive in electronics industry
• For making boots for use at
very low temp., since they are
less affected by temperature
variation
e.g., Neil Armstrong used
silicone rubber boots when he
walked on the moon
72
MATRUSRI
ENGINEERING COLLEGE
73. MODULE-9: Conducting Polymers
1. Polymers which show electrical conductivity on par with
metallic conductors are known as conducting polymers.
2. Conductivities as high as 1.5 x 107 ohm-1m-1 have been
attained in these polymeric materials.
3. On volume basis, this value is equal to one-fourth of the
conductivity of copper, or is twice its conductivity on the
basis of weight.
MATRUSRI
ENGINEERING COLLEGE
75. Intrinsically Conducting Polymers
These types of polymers have a backbone made up
of extensive conjugated system, which is responsible
for conductance. They may be of two types:
1.Conjugated π – electrons conducting polymers
2. Doped conducting polymers
MATRUSRI
ENGINEERING COLLEGE
76. Conjugated π – electrons conducting polymers
Contain a conjugated π-electron system on their backbone. In presence
of electrical field, conjugated π -electrons of the polymer get excited,
thereby can be transported through the polymeric chain.
Overlapping of orbitals of conjugated π electrons over the entire
backbone results in the formation of valence bands as well as conduction
bands, which extend over the entire polymer molecule.
The presence of conjugated π -electrons in polymers increases its
conductivity.
Example: polyacetylene
MATRUSRI
ENGINEERING COLLEGE
77. Conjugated π – electrons conducting polymers
The polymer is called a ‘conjugated polymer’ because of the alternating
single and double bonds in the polymer chain.
Due to the special conjugation in their chains, it enables the electrons to
de-localize throughout the whole system and thus many atoms may
share them.
The de-localized electrons may move around the whole system and
become the charge carriers to make them conductive.
MATRUSRI
ENGINEERING COLLEGE
78. cis-polyacetylene has a lower conductivity of
1.7×10−9 Ω−1cm−1
trans-polyacetylene films have a conductivity of
4.4×10−5 Ω−1cm−1
MATRUSRI
ENGINEERING COLLEGE
80. Doped conducting polymers
➢They are obtained by exposing a polymer to a charged transfer agent in
either gas phase or in solution.
➢The conductivity of intrinsically conducting polymers can be
increased by creating either positive or negative charge on the polymer
backbone by oxidation or reduction.
Doping may be of two types:
a)P- doping b)n-doping
a)p-doping
In this process, the conducting polymer is treated with a Lewis acid like I2,
Br2, AsF5, PF6, naphthylamine etc., It involves oxidation process thereby
creating a positive charge on the polymer backbone.
MATRUSRI
ENGINEERING COLLEGE
81. (CH)x + A ---------→ (CH)X
+ A-
Polyacetylene Lewis acid p-Doped
polyacetylene
b)n-doping: It involves reduction process where the
conducting polymer is treated with a Lewis base like Li, Na,
Ca, tetrabutyl ammonium, dianionic aromatic hydrocarbons
etc.,
(CH)x + B ---------→ (CH)x
- B+
Polyacetylene Lewis base n-Doped polyacetylene
MATRUSRI
ENGINEERING COLLEGE
82. Extrinsically conducting polymers
These polymers owe their conductivity due to the presence of
externally added ingredients in them. They are of two types :
Conductivity element filled polymer:
It is a resin or polymer filled with conducting elements such as
carbon black, metallic fibres, metal oxides, etc. In this, the polymer
acts as the binder to hold the conducting elements together in the
solid entity.
Example: epoxy resin (ER) and poly vinyl chloride (PVC) are
polymers filled with metal powders such as Copper and nickel
powder ,carbon black , silica etc.,
MATRUSRI
ENGINEERING COLLEGE
84. Some of the important characteristics of extrinsically
conducting polymers are
(a)They possess good bulk conductivity.
(b)They are cheaper.
(c)They are light in weight.
(d) They are mechanically durable and strong.
(e)They are easily processable in different forms, shapes and
sizes.
Blended conducting polymer:
It is obtained by blending a conventional polymer with a
conducting polymer either by physical or chemical change. Such
polymer can be easily processed and possess better physical,
chemically and mechanical properties.
MATRUSRI
ENGINEERING COLLEGE
85. Ex: Graphene + PMMA
Used in lightening strike
protection,Electromagnetic shielding
MATRUSRI
ENGINEERING COLLEGE
93. Biodegradable polymers are the polymers that breakdown and lose
their initial integrity by bacterial decomposition process.
MODULE-10: Biodegradable Polymers
This biological decomposition process results in natural byproducts
such as gases (CO2, N2), water, biomass, and inorganic salts.
MATRUSRI
ENGINEERING COLLEGE
94. There are many natural and synthetic polymers available.
Biodegradable polymers largely consists of ester, amide and their functional
groups
These polymers are often synthesized by condensation reactions, ring
opening polymerization, and metal catalysts.
Diverse applications such as surgical sutures, wound dressings, tissue
regeneration, enzyme immobilization, controlled drug delivery and gene
delivery, tissue engineering scaffold, cryopreservation, nanotechnology,
medical implants and devices, prosthetics, augmentation, cosmetics,
sanitation products, coatings, adhesives, and many more.
MATRUSRI
ENGINEERING COLLEGE
95. Polyglycolic acid(PGA)
Polylactic acid (PLA)
Polyhydroxy butyrate (PHB)
Polyhydroxy butyrates-co-beta hydroxyl valerate( PHBV)
Polycaprolactone(pcl)
Nylon-2-nylon-6.
Polysaccharides, as starch and cellulose, represent the most
characteristic family of these.
Examples Biodegradable Polymers:
MATRUSRI
ENGINEERING COLLEGE
96. Poly(lactic acid) or polylactide (PLA) is a thermoplastic aliphatic polyester
derived from renewable resources, such as corn starch (in the United
States), tapioca roots, chips or starch (mostly in Asia), or sugarcane.
POLYLACTIC ACID (PLA)
Synthesis:
Bacterial fermentation is used to produce lactic acid from corn starch or
cane sugar.
Lactic acid cannot be polymerised to a useful product because each
reaction generates one molecule of water, presence of which degrades the
forming polymer chain.
Due to this low molecular weight polymers will be formed. Instead, two
lactic acids are dimerized to di-lactic ester.
Although dimerization generates water, it can be separated prior to
polymerisation.
MATRUSRI
ENGINEERING COLLEGE
97. PLA of high molecular weight is produced from di-lactic ester by ring opening
polymerization using stannous octate catalyst.
MATRUSRI
ENGINEERING COLLEGE
98. PLA is soluble in solvents, hot benzene, tetrahydrofuran, and
dioxane.
Polylactic acid can be processed like most thermoplastics into fibre
and film.
PLA polymers range from amorphous glassy polymer to semi-
crystalline and highly crystalline polymer with a glass transition 60–
65 °C.
The melting temperature of PLA can be increased 40-50 °C
Heat deflection temperature can be increased from approximately
60°C to up to 190 °C by physically blending the polymer with PDLA
(poly-D-lactide).
Properties of PLA:
MATRUSRI
ENGINEERING COLLEGE
99. Applications of Polylactic acid:
Poly (lactic acid) can be processed by extrusion, injection
moulding, film & sheet casting, and spinning, providing access
to a wide range of materials.
MATRUSRI
ENGINEERING COLLEGE
100. In the form of fibres and
non-woven textiles,
As upholstery,
disposable garments,
awnings,
feminine hygiene products,
and diapers.
MATRUSRI
ENGINEERING COLLEGE
101. PLA is used as medical implants in the form of anchors, screws, plates,
pins, rods, and as a mesh.
MATRUSRI
ENGINEERING COLLEGE