1. POLYMERS
& Advanced Materials

2. Polymers
You may think of polymers as being a relatively modern invention however naturally occurring polymers have been used for thousands of years
– wood, rubber, cotton, wool, leather, silk,.. etc.
Artificial polymers are, indeed, relatively recent and mostly date from after WW-II
in many cases, the artificial material is both better and cheaper than the natural alternative

4. A polymer is a large molecule made by linking together repeating units of small molecules called monomers

5. General Characteristics of Polymers
Low Density.
Low coefficient of friction.
Good corrosion resistance.
Good mould ability.
Excellent surface finish can be obtained.
Can be produced transparent or in different colors.
Chain length - in general, the longer the chains the stronger the polymer.
Side groups - polar side groups give stronger attraction between polymer chains, making the polymer stronger.
Cross-linking - if polymer chains are linked together extensively by covalent bonds, the polymer is harder and more difficult to melt.
Medicine; Sports; Industry

7. Polymers
A macromolecule is a very large molecule consisting of repeating units called monomers. These structural units are bound together
by covalent bonds.
A collection of macromolecules is called a polymer. For example, polyethylene

8. Polymerization of ethylene to form polyethylene
Polymers are prepared by polymerizing a monomer. The reaction is called polymerization
Polymerization of ethylene to form polyethylene

9. Some Important Terms
Degree of polymerization: The number of repeating units present in a polymer is called degree of polymerization.
“n” is called degree of polymerization. When n is large, the polymers are called high polymers. For low values of n, less than 10, the polymers are called oligomers.
Tacticity: relative stereochemistry/ orientation of atoms or groups

12. Classification of polymers
Natural and Synthetic Polymers: (Based on occurrence)
Natural polymers: wood, cellulose,, jute, cotton, wool etc.
Synthetic polymers: PE, PVC, epoxy resin etc.

13. (based on thermal behavior)
2. Thermoplastic and thermosetting polymers
(based on thermal behavior)
Thermoplastic polymers: The polymers that soften on heating and which can be converted into any shape on cooling are called thermoplastics. The process of heating, reshaping, and retaining the shape on cooling can be repeated several times without affecting their properties much. Ex: PE, Polycarbonate (PC), Polytetrafluoro ethylene (PTEE) etc.
Thermosetting polymers: Polymers that undergo chemical changes and cross-linking on heating and become permanently hard, rigid and infusible on cooling, are called thermosetting polymers. They do not soften on reheating; instead they undergo degradation. Ex: phenol-formaldehyde (bakelite), urea-formaldehyde etc.

14. 3. a) Addition polymers (Based on type of polymerization)
The polymers formed by self-addition of several monomers to each other without elimination of byproducts are called addition polymers. Ex: PVC, PE etc.
Monomers add successively to a growing polymer chain
Polyethylene and polystyrene are addition polymers.
Only olefinic or vinyl compounds can undergo addition polymerization.
No elimination of byproducts.
Double bond provides required bonding sites.
The elemental composition of the polymer is the same as that of monomer.
The addition of monomers takes place rapidly.
Polymerization is brought about by initiators like free radicals.

15. Addition Polymerization Example
In this type of polymerization C=C bonds of monomers react to form larger monomers until the unit is a larger polymer chain as seen here.
Table on the next slide shows ethylene monomer based polymers

16. Examples of addition polymers.

17. Polymers Derived from Modified Ethylene Monomers (e. g
Polymers Derived from Modified Ethylene Monomers (e.g. of addition polymerization )

18. Contd...

19. 3. b) Condensation Polymer (Based on type of polymerization)
The polymers formed by intermolecular condensation reaction by the functional groups of monomers with continuous elimination of small molecules such as ammonia, water etc. Ex: nylon-6,6; polyester etc.
Polymer chain grows when monomers combine and split out water or other small molecule.
Nylon 6,6 and polyurethane are condensation polymers.
The monomers having two or more reactive functional groups can undergo condensation polymerization.
There is continuous elimination of byproducts.
Polymerization proceeds through intermolecular condensation.
Polymerization is catalyzed by acids or alkali.
The polymer chain built up is slow and stepwise.
The elemental composition of the polymer is different from that of the monomers.

20. Condensation Polymer Example

21. Linear, branched and cross-linked polymers (Based on chemical structure)

22. 5. Organic and Inorganic polymer

23. Organic and Inorganic Polymers
A polymer whose backbone chain is essentially made up of carbon atoms is termed as an organic polymer. The atoms attached to side valencies are oxygen, nitrogen, hydrogen etc. Majority of synthetic polymers are organic polymers, for example PE, PVC.
On the other hand, the polymers that do not contain a carbon atom in their backbone chain are called inorganic polymers.

24. Atactic, isotactic and syndiotactic polymers
6. Atactic, isotactic and syndiotactic polymers (Based on stereochemistry)
Side Group is random
Side Groups are on same side
Side Groups are on alternating fashion
Atactic, isotactic and syndiotactic polymers

25. Elastomers, Fibers, Resins and Plastics
(7. On the basis of ultimate structure and end use)
Elastomer: The polymers which undergo very long elongation when pulled apart, and return to their original length on release are called elastomers. Example Natural rubber, Buna-S, etc.
Fibers: These are long, thin and thread like polymers, whose length is at least 100 times their diameter. They do not undergo stretching and deformation like elastomers. Example jute, wood, silk
Resins: These are low molecular weight polymers used as adhesives. They can be in the form of liquids or powder.. Example Urea-formaldehyde, epoxy resin.
Plastics: These are polymers, which can be molded into desired shapes by the application of heat and pressure. Example PVC, PC, Teflon.

26. Homopolymers and copolymers
Homopolymers: If same type of monomers
e.g., PE, PVC etc.
Homopolymers: If two or different type of monomers
e.g., Styrene-Acrylonitrile (SAN), Styrene-butadiene (SBR), Acyronitrile-butadiene-styrene (ABS) copolymers

27. Homo Polymerization
Example
In this type of polymerization C=C bonds of monomers react to form larger monomers until the unit is a larger polymer chain as seen here.
Table on the next slide shows ethylene monomer based polymers

29. Copolymerization
The polymerization of two or more different monomers resulting in the formation of a polymer containing both monomers linked in one chain is called copolymerization. It is considered as a type of addition polymerization. The polymers so formed are called copolymers.
A copolymer is a polymer that has two types of monomer units in its chain.
Block copolymer: When repeating units of each kind appear in blocks, it is called a block copolymer.
Random copolymer: If the various repeating units occur randomly along the chain structure, the polymer is called a random copolymer.
Graft copolymers: They are formed when chains of one kind are attached to the backbone of a different polymer.

30. Methods of Polymerization
Addition Polymerization
Condensation Polymerization
Chain-growth polymers, also known as addition polymers, are made by chain reactions

32. Step-growth polymers, also called condensation polymers, are made by combining two molecules by removing a small molecule

35. Structure–Property Relationship of Polymers
Strength: Tensile strength increase with molecular mass up to a certain point and then become constant. Commercially a polymer should have high tensile strength. Melt viscosity shows gradual increase with increase in molecular mass.
Crystallinity: Degree of crystallinity of polymer depends on its structure. Linear polymer will have high crystallinity. Eg HDPE is more crystalline than LDPE. LDPE is more crystalline than Polystyrene. Isotactic, syndiotactic highly crystalline. Nylon 66 high degree of crystallinity. Polymers having polar groups can formed hydrogen bond with neigbouring chain.
Elasticity: It is mainly because of uncoiling and recoiling of molecular chains on application of force. Can be avoided by :
introducing cross linking
avoiding bulky side groups
more non-polar groups in chain

36. Plastic deformation: Thermoplastic material/ polymer on application of heat and pressure, initially become soft, flexible and undergo deformation. On further heating above their melting point they melt and flow. Thermoplastic exhibit plastic deformation (linear chains , weak vanderwaals force). While thermosetting plastic doesn’t because of cross linking.
Chemical Resistivity: It depends on the structure of polymer and nature of attacking reagent. When the chemicals attack on polymer, it first softens, swells and loses its strength, and then dissolves. It also depends on several factors such as polar and non polar groups, molar mass, degree of crystallinity, cross linking etc.
Non-elastic Nature of Fibers: The chain mobility is reduced by very close packing of the polymer chain backbone without cross linking. Polar groups and aromatic rings in the backbone chain impart high strength to the polymer fiber.
Glass transition temperature (Tg) is the temperature below which a polymer is hard, brittle and above which it is soft and flexible.

37. Glass transition temperature (Tg)
It is the temperature below which a polymer is hard, brittle and above which it is soft and flexible. Denoted by Tg. Hard brittle state is known as glassy state and soft flexible state is called the rubbery state.
Factors affecting Tg:
1. Flexibility: Presence of rigid groups (aromatic, bulky) in the carbon chain backbone hinders freedom of rotation. This restriction in the chain mobility increases the Tg value.
2. Effect of side group: Poly(-methyl styrene) has higher Tg (170°C) while polystyrene has lower (100°C) due to presence of extra methyl group which hinders free rotation.
3. Intermolecular forces: Presence of large number of polar groups in the molecular chain lead to strong intermolecular cohesive forces which restricts the segmental/molecular mobility. This leads to increase in Tg value.

38. 4. Branching and Cross linking: A small amount of branching will reduce the value of Tg, because the free volume increases with branching and thus decreases the Tg. High density of branching brings the chain closer and thus reduces the mobility, thereby increasing Tg.
5. Presence of Plasticizers: Addition of plasticizers reduces the Tg value. Eg diisooctyl phthalate which is added to PVC reduces its Tg from 80 c to below room temperature.
6. Stereo-regularity: Tg increases with stereo-regularity. Thus Tg of isotactic polymer is greater than syndiotactic which in turn has greater tg than atactic polymer.
7. Molecular Weight: Tg of all polymers increases with molecular weight up to 20,000 and beyond this, the effect is negligible.

39. Significance of Tg Tg value is a measure of flexibility.
Its value gives and idea of thermal expansion, heat capacity, refractive index, electrical and mechanical properties of a polymer.
Its value decides whether a polymer at room temperature will behave like rubber or plastic.
It helps in choosing the right temperature for fabrication.

40. Structure-property relationship
The Structure of the polymers depends upon:
Size and shape of the polymer chain .
Chemical nature of the monomers.
The Structure of the polymers further effects the physical and mechanical properties of polymers.
Strength
Crystallinity
Elasticity
Non-elastic Nature of Fibers
Plastic deformation
Chemical Resistivity

41. Strength
The tensile strength of a material quantifies how much stress the material will endure before suffering permanent deformation.
For example, a rubber band with a higher tensile strength will hold a greater weight before snapping
A candle and Polyethylene (PE) have basically the same molecular structure. The chain length of the candle is just much shorter than that of the PE. If you bend a bar of PE in half – it will bend, if you bend a candle in half, it will fracture.

42. For a polymer to be commercially useful , It should have low melt viscosity, high tensile strength and impact strength

43. The higher the crystallinity, the harder, stiffer.
Amorphous and crystalline regions in a polymer. The crystalline region (crystallite) has an orderly arrangement of molecules.
The higher the crystallinity, the harder, stiffer.

44. Linear polymers have higher crystallinity, because the atoms along the chain Permit closer approach, branched polymer will have low crystallinity.
Polymers containing polar groups can form H-bonding, so have higher crystallinity.

45. Advanced polymeric materials (plastic)

46. Classification: Thermoplastic and Thermosetting
Plastics
Classification: Thermoplastic and Thermosetting

48. Classification of plastic

49. Plastic Molding Techniques
Involves conversion of the solid polymer into desirable shape and size.
During molding the plastic material is heated to the appropriate temperature for it flow and material is shaped and then cooled to preserve the desired shape.

50. plastic molding techniques
(only first 3 in syllabus)
Injection molding (for thermoplastics)
Extrusion molding (for thermoplastics)
Compression molding (for thermosetting)
Blow molding
Injection blow molding
Thermoforming
Transfer molding
Injection-Compression molding

51. 1. Injection molding
Known quantity of polymer may in the form of granules , pellet or powder is fed to the hopper.
Passed to a hot chamber where the polymer material soften flows under the pressure applied by means of electrically operated plunger.
As the plunger moves in the forward direction ,the soften material passes into mold through a nozzle , solidifies upon cooling ,takes the shape of mold.

52. Injection molding
Injection molding with (a) plunger, (b) reciprocating rotating screw, (c) a typical part
made from an injection molding machine cavity, showing a number of parts made
from one shot, note also mold features such as sprues, runners and gates.

58. Materials such as polystyrene, nylon, polypropylene and polythene can be used in a process called injection moulding. These are thermoplastics - this means when they are heated and then pressured in a mould they can be formed into different shapes.  The DVD Storage unit seen opposite has been made in one piece using this process An animation of an injection moulding machine is shown below. The product being produced is the DVD / CD storage unit seen opposite.

59. Advantages of Injection molding
speed production
Low costs in mass production
very low loss of material
flexibility to make parts with complex shapes
high precision

60. Makings Bottles caps Mugs Dustbins Automotives dashboards Chairs
Applications
Makings
Bottles caps
Mugs
Dustbins
Automotives dashboards
Chairs

61. Injection moulding is used to create many things such as wire spools, packaging, bottle caps, automotive parts and components, Gameboys, pocket combs, some musical instruments (and parts of them), one-piece chairs and small tables, storage containers, mechanical parts (including gears), and most other plastic products available today.
Injection moulding is the most common modern method of manufacturing parts; it is ideal for producing high volumes of the same object

62. 2. Extrusion Molding
Production of thermoplastic material into finished articles such as sheets, films and rod.
Done by using machine Extruders.
Raw materials in the form if thermoplastic pellets, granules, or powder, placed between the screw and extruder barrel.(feed zone)
The barrel is equipped with a screw . As screw rotates , the pellets are dragged forward and compressed (transition or compaction zone)
Heaters around the extruder’s barrels heats the pellets and liquefies them. (molten plastic) (metering zone).
Screw has 3-sections
Feed section
Melt or transition section
Pumping section.

63. Extruders

65. LDPE granules are heated and made into a molten state
LDPE granules are heated and made into a molten state. The liquid is extruded through a nozzle in the form of a tube called a 'Parison'.  The two halves of the mould close on the 'Parison' and shut tight.  Compressed air is blown into the Parison forcing the LDPE to the sides of the mould, where it cools. The moulds open, releasing the product.

66. Complex shapes with constant cross-section Solid rods, channels, tubing, pipe, window frames, architectural components can be extruded due to continuous supply and flow. Plastic coated electrical wire, cable, and strips are also extruded Pellets :extruded product is a small-diameter rod which is chopped into small pellets

67. The screw depth is constant in both the feed and metering zones and varies in transition zone to begin generating pressure and to force the pellets to begin to melt.
Length of each zone in screws design varies according to type of plastic being processed. Example LDPE- melt gradually ,the overall length of the screw is roughly divided into three zone.
Nylon- have sharp melting point ,screw designed such that transition zone only consist of one turn of the screw flight.
PVC- prone to thermal degradation and melt very gradually may be processed with screw whose entire length is composed of a compression zone.

68. Low initial setup Fast setup Low production cost
Advantages
Low initial setup
Fast setup
Low production cost

69. Application Manufacturing of Tubes Rods Plumbing pipes Electric cable
Door insulation seals
Optical fibers

70. 3. Compression Molding Thermosetting are molded by this method.
Known quantity of polymer (resin) which may in any form (powder or pellet) is placed in the lower portion of mold cavity.
It is heated electrically or by passing steam to soften the material.
The mold cavity gets filled with fluidized plastic.
The melt is compressed by the upper mold.
compression mass gets cured and hardened and is open after cooling and the article removed.

71. Compression Molding
Types of compression molding, a process similar to forging; (a) positive, (b) semi positive, (c) flash (d) Die design for making compression-molded part with undercuts.

73. Advantages and Applications
Low cost
Very low loss of materials
God surface finish
Fast setup time
Electrical parts
Cooker Handles
Electronic devices
Appliance housing and large container.

75. Some Important Commercial Thermoplastics
Polythylene (PE): LDPE and HDPE
Polypropylene

76. Polystyrene
Polyvinylchloride

78. Polyvinyl Acetate
Polytetrafluoroethylene/Teflon

79. Polymethyl Methacrylate/Plexiglass

80. Resol resin Some Important Commercial Thermosetting Resins
Phenol–Formaldehyde Resins
Novolac resin
Resol resin
Engineering Chemistry
Copyright  2012 Wiley India Pvt. Ltd. All rights reserved.

81. Both resol and novolac on curing with wood flour filler give highly cross-linked product called Bakelite. (Cross linking Novolac polymer)
Engineering Chemistry
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82. Making golf balls.

83. Elastomers (Rubber) Natural rubber is prepared from latex of Hevea rubber trees or gutta-percha and balata. It is a linear polymer of isoprene and is called poly-isoprene.

86. Vulcanization is the cross-linking of polymer chains with sulfur atoms by applying heat.
Vulcanization increases the abrasion resistance and the useful temperature range of rubber.
Engineering Chemistry
Copyright  2012 Wiley India Pvt. Ltd. All rights reserved.

88. A Segment of Vulcanized Rubber
Engineering Chemistry
Copyright  2012 Wiley India Pvt. Ltd. All rights reserved.

89. The double bonds in isoprene polymer allows for cis-trans isomers.
Cis-trans isomers are molecules that differ only in the spatial orientation of their atoms
Natural rubber is cis-polyisoprene.
Gutta-percha is trans-polyisoprene
Engineering Chemistry
Copyright  2012 Wiley India Pvt. Ltd. All rights reserved.

90. Engineering Chemistry
Copyright  2012 Wiley India Pvt. Ltd. All rights reserved.

92. Some Important Synthetic Rubbers
Butyl rubber (GR-I rubber)
Polychloroprene (Neoprene or GR-M rubber)
Styrene-Butadiene rubber (SBR) (Buna-S or GR-S rubber)
Nitrile rubber (NBR) (Buna-N or GR-A rubber)
Polysulphide rubber
Silicone rubber
Engineering Chemistry
Copyright  2012 Wiley India Pvt. Ltd. All rights reserved.

93. Application: Making sports gear, fishing lines, sports equipments Making brushes and combs.

95. Advanced materials

96. Adhesives
Adhesive is a polymeric material used to bind together two or more similar/dissimilar surfaces, so that the resulting material can be used as a single piece. Ex Fevicol.
The surfaces may be metals , glasses, plastics, papers etc.
-Process of binding two surface is known as bonding.
-surfaces joined are called Adherents.
Classification:
Composition of principal components:
Natural ( gum, glue, starch, natural rubber) –low bond strength
Synthetic( PF, UF, Epoxy resins, etc.)-Superior Strength
Classification based on Mechanism of adhesion
Solvent responsive adhesives:
- Flow of the adhesives during application and adherence during bonding is caused by volatile liquid carrier. These adhesives are used in the form of solution ,pastes, gels and dispersions. Ex. Vegetable gums, starch, natural rubber.
Engineering Chemistry
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97. b) Heat sealing adhesives: These adhesives solid at room temperature ,but they become sticky and undergoes fusion by the application heat and then they applied on the bonding surfaces. These adhesives are tougher , flexible, resistance to moisture ,solvent and chemicals. Ex. Waxes, cellulose , esters, polyvinyl alcohol, resins etc. C) Pressure sensitive adhesives: Used as adhesives tapes, - should be capable of providing instanteous adhesion when applied with light pressure. -they should be capable of being removed from the surface with a very pull if not required. Ex- butyl rubber , neoprene , acrylic polymers , alkyl resins etc.

98. Application 1. epoxy resins used to join glass, metals, wood.
2. Used in Industrial flooring , skid resistance, highways surfacing, patching materials.
3. used as laminating materials in electrical equipments.
4. Molds made from epoxy resins are used in the production of aircraft and automobiles components.
5. Used as matrix in fiber reinforced plastics.

99. What is a composite Material?
A broad definition of composite is: Composites is a material formed by combining two or more chemically distinct materials (insoluble in each other and retain their individual identities). Composites has improved properties over it’s individual materials, it could be natural or synthetic.
Wood is a good example of a natural composite, combination of cellulose fiber and lignin. The cellulose fiber provides strength and the lignin is the "glue" that bonds and stabilizes the fiber.
A common example of a synthetic composite is concrete. It consists of a binder (cement) and a reinforcement (gravel). Adding another reinforcement (rebar) transforms concrete into a three-phase composite
Ken Youssefi
Mechanical Engineering Dept.

100. gravel
rebar

101. Composites
Modern technology require such as aircraft application –low density, high strength, good corrosion resistance, good abrasion and impact resistance .
Not possible by single use of any metal, alloys, ceramic.
Search of particle leads to composite.
Two different materials combine to form a material suitable for structure application as refer as composites.
A composite is a combined material formed by the assembly of two or more components, such as fillers or reinforcing agents and a compatible matrix binder in order to obtain specific characteristic properties.
Made up of two phases- matrix (continuous part or binder of composite materials and dispersed phase constructed by reinforcing particulates and fillers.
Classification:
On the basis of Matrix constituent: OMCs, MMCs, CMCs
On the basis of Reinforcement form: Fiber reinforced composites, laminar composites, particulate composites
Engineering Chemistry
Copyright  2012 Wiley India Pvt. Ltd. All rights reserved.

102. On the basis of Matrix constituent
Metal Matrix Composites (MMCs) ‑
Ceramic Matrix Composites (CMCs) ‑ especially in high temperature applications
The least common composite matrix
Organic (can be Polymer or carbon) Matrix Composites (OMCs) ‑ thermosetting resins are widely used in OMCs and PMCs
©2002 John Wiley & Sons, Inc. M P Groover, “Fundamentals of Modern Manufacturing 2/e”

103. Functions of the Matrix Material
Provides the bulk form of the part or product made of the composite material
Holds the imbedded phase in place, usually enclosing and often concealing it
When a load is applied, the matrix shares the load with the secondary phase, in some cases deforming so that the stress is essentially born by the reinforcing agent
©2002 John Wiley & Sons, Inc. M P Groover, “Fundamentals of Modern Manufacturing 2/e”

104. On the basis of Reinforcement form
Fiber reinforced composites,
laminar composites,
particulate composites
Function is to reinforce (To strengthen by adding extra support or material) the primary phase
Imbedded phase is most commonly one of the following shapes:
Fibers
Particles
Flakes
©2002 John Wiley & Sons, Inc. M P Groover, “Fundamentals of Modern Manufacturing 2/e”

105. (a) fiber
(b) particle
(c) flake
Figure 9.1 ‑ Possible physical shapes of imbedded phases in composite materials: (a) fiber, (b) particle, and (c) flake
©2002 John Wiley & Sons, Inc. M P Groover, “Fundamentals of Modern Manufacturing 2/e”

106. Components of composite materials
Reinforcement: fibers
Glass Carbon Organic Boron Ceramic Metallic
Matrix materials
Polymers Metals Ceramics
Interface
Bonding surface
Ken Youssefi
Mechanical Engineering Dept.

107. 1. Fiber Reinforced Composite

108. Continuous vs. Discontinuous Fibers
Continuous fibers - very long; in theory, they offer a continuous path by which a load can be carried by the composite part
Discontinuous fibers (chopped sections of continuous fibers)
©2002 John Wiley & Sons, Inc. M P Groover, “Fundamentals of Modern Manufacturing 2/e”

109. Fiber in composite materials:
(a) continuous fibers; (b) continuous fibers; and (c) random, discontinuous fibers
©2002 John Wiley & Sons, Inc. M P Groover, “Fundamentals of Modern Manufacturing 2/e”

110. 3. particulate Composite
2. Laminar Composite
Two or more layers bonded together in an integral piece
3. particulate Composite
Particles may be flakes,
powder, and wood particles
©2002 John Wiley & Sons, Inc. M P Groover, “Fundamentals of Modern Manufacturing 2/e”

111. Fiber‑Reinforced Polymers (FRPs)
A PMC consisting of a polymer matrix imbedded with high‑strength fibers
Polymer matrix materials:
Usually a thermosetting (TS) plastic such as unsaturated polyester or epoxy
Can also be thermoplastic (TP), such as nylons (polyamides), polycarbonate, polystyrene, and polyvinylchloride
Fiber reinforcement is widely used in rubber products such as tires and conveyor belts

112. -Components of a composite do not dissolve or merge completely into each other but act together while retaining their individual properties.
Matrix constituent: OMCs (Organic matrix composites), MMCs (metal matrix composites), CMCs( ceramics matrix composites)
Term organic matrix composites include –polymer matrix composites and carbon matrix composites.(Carbon-carbon composites)
-Second classification – refer to reinforcement form,

113. Laminar Composites
-Long with sandwich structure belong to the class of structural composites.
Composed of thin layers held together by matrix.
Sheets or panels of constituting materials are stacked and glued together with different orientation that yield material with high isotropic strength.
Materials used in fabrication- include sheets, papers, glass fibers are embedded in plastic matrix.

115. Fiber reinforced plastics (FRP)
Composed of fibers and polymer matrix.
Fibres are the reinforcement and main source of strength .
-polymer matrix glues up all the fiber together in shape and transfer stress between reinforcing fibers.
Fillers or modifier are added to smoothen the manufacturing process ,impart special properties .
Common fiber reinforcing agents include –Aluminum and its oxide, aluminum silica , abestos, beryllium carbide, carbon graphite , glass molybdenum, polyesters, quartz etc.
Polymer matrix include thermoplasticmaterials like acetals, acryronitrile, butadiene, styrene, nylon,PE,PP etc.
Thermoset resin matrix include polyesters(widely used), vinyl,epoxy( higher adhesion) ,phenolic resins.
Polyester widely used because of low cost.

116. Uses of FRP - Light weight- used in making aircraft, cars
High strength(graphite epoxy) –used in making bridges
Resistance to corrosion- fiber glass used in making cars and boats.
Elastic in nature – used in car leaf springs.
High strength and insulation – used in making armors.
Fiber glass Used in thermal and sound absorption.
Non conductive nature , ladders made with fiberglass (power line)

117. Conductive polymers or, more precisely, intrinsically conducting polymers (ICPs) are organic polymers that conduct electricity. Such compounds may have metallic conductivity or can be semiconductors

118. Conducting polymers Before 1960 organic polymers used as insulators.
In 1960 Chemist Shirakawa ,Plastic research lab. BASF, Germany, accidentally added a catalyst 1000 times more than the required during polymerization of acetylene ,which result in conducting polyacetylene.
Organic polymers having electrical conductance of the order of conductors are called conducting polymers.
Classification:
Extrinsically conducting polymers (conductivity due to mixing conducting fillers like metal fibers, metaloxide, carbon black with insulating materials)
Also called as Conductive element filled polymers.
Insulation material formed the continuous phase and the added filler form the conducting networks.
Minimum concentration of conducting filler has to be added so that polymers start conducting.
Conductance is not due to matrix is due to fillers.

119. Intrinsically conducting polymers (for example, poly (p- phenylene), polyacetylene, polyaniline)
-Conductivity is due to organic polymers themselves.
They conduct electricity when doped with Oxidizing ,reducing agents or protonic acids

120. Conducting polymers with conjugated pi- electrons
-due to high delocalized Pi- electron systems organic polymer has conductance in the range of conductor are called as inherently or intrinsically conducting polymers or synthetic metals.
EX-
1. Poly (p- phenylene)
2. polyaniline
3. polyacetylene
These conjugated polymers in their pure state are insulators or semiconductor. (pi- electron are localized)
These electron are delocalize on doping and conduct electricity..
Dopant are oxidizing (p-doping) , reducing( n-doping), protonic acid (H-doping)
Redox doping of organic conductor s is similar to doping of silicon semiconductor.

121. e.g., conducting polymer

122. Discuss in terms of VB and CB
When Pi- bond is formed VB( Valence band) and CB (conduction band) are created.
Before doping sufficient gap between in VB and CB. Electron remains in VB.
Upon doping Polaron and solitons are formed which results in formation of new localized electronic states that fills the energy gap between VB and CB.
Sufficient solitons are formed , a new mid gap band formed which overlaps the CB and VB allowing the electron to follow.

127. Liquid Crystals
Liquid crystals (LCs) are matter in a state that has properties between those of conventional liquid and those of solid crystal. For instance, an LC may flow like a liquid, but its molecules may be oriented in a crystal-like way.
Nematic liquid crystal
The nematic liquid crystal phase is characterized by molecules that have no positional order but tend to point in the same direction. In the following diagram, notice that the molecules point vertically but are arranged with no particular order
Nematic liquid crystal

128. Smectic phases Smectic phases
The smectic phases, which are found at lower temperatures than the nematic, form well-defined layers that can slide over one another in a manner similar to that of soap. In the smectic state, the molecules not only maintain the general orientational order of nematics, but also tend to align themselves in layers or planes.
Smectic phases
In the nematic phase the molecules of a liquid crystal are rod shaped and pack next to each other. In the smectic phase basically the molecules are placed in layers that can slide past each other.

129. Directional order: Yes
Positional order: No
Directional order: Yes
Positional order: Yes

130. Liquid crystals
.Liquid crystals are substances that exhibit a phase of matter that has properties between those of a conventional liquid, and those of a solid crystal. For instance, a liquid crystal (LC) may flow like a liquid, but have the molecules in the liquid arranged and/or oriented in a crystal-like way.
Molecules posses charterstics order in orientation in order like solid but randomness in their position like liquid phase.
- Most of LC compound exhibits polymorphism. (more than one phase is observed in crystalline state) .Subphases of LC materials is called Mesophases. All this formed due to different ordering in the sample.

131. Compound shows liquid crystal Properties
1 methyoxybenzilidenebutylanaline (MBBA)
2. p-Azoxyanisole
3. p-Azoxyphenetole
4. Phentyl-p-cyanobiphenyl (PCB)

132. Classification of liquid crystal
Thermotropic liquid crystals :Thermotropic phases are those that occur in a certain temperature range. If the temperature is raised too high, thermal motion will destroy the delicate cooperative ordering of the LC phase, pushing the material into a conventional isotropic liquid phase. too low a temperature, most LC materials will form a conventional (though anisotropic) crystal. Many thermotropic LCs exhibit a variety of phases as temperature is changed. For instance, a particular mesogen may exhibit various smectic and nematic (and finally isotropic) phases as temperature is increased.
Lyotropic liquid crystals :A lyotropic liquid crystal consists of two or
more components that exhibit liquid-crystalline properties in
certain concentration ranges. In the lyotropic phases, solvent
molecules fill the space around the compounds to provide fluidity to
the system. In contrast to thermotropic liquid crystals, these lyotropics
have another degree of freedom of concentration that enables them to
induce a variety of different phases.

133. Types of Mesophases
Nematic Liquid crystal: One of the most common LC phases is the nematic , where the molecules have no positional order, but they do have long-range orientational order. the molecules flow and their centre of mass positions are randomly distributed as in a liquid, but they all point in the same direction (within each domain).
Liquid crystals are a phase of matter whose order is intermediate between that of a liquid and that of a crystal. The molecules are typically rod-shaped organic moieties about 25 angstroms (2.5 nanometers) in length and their ordering is a function of temperature.
The nematic phase, for example, is characterized by the orientational order of the constituent molecules. The molecular orientation (and hence the material's optical properties) can be controlled with applied electric fields. Nematics are (still) the most commonly used phase in liquid crystal displays (LCDs), with many such devices using the twisted nematic geometry.

134. These nematic crystal are thread like when seen from polarized light
These nematic crystal are thread like when seen from polarized light. (Nematos- Greek word means thread).
These LCs flow like liquid and hence no positional order but on the average arranged parallel.
Uniform Alignment with respect to their long axis.
The average direction along which the molecules orient themselves are (n).
Easily aligned in external magnetic or magnetic field.
Used in LCDs.

135. Nematic phase of a chiral substance is called Cholestric because it observed like cholestrol derivatives.
Only Chiral molecules and optically active molecule can give rise to such phase.
Intramolecular forces between chiral molecules favor alignment at a small angle to the adjacent group of molecules. Direction in each layer is twisted with respect to the layers above and below it.
Such that the director takes a helical pathway as travel through LCs.

136. -Cholestric mesophases is charterized by an important property called pitch , which is defined as the distance it takes for director to rotate on full turn in the heliex .
Chiral Nematic crystal has ability to reflect light whose wavelength is equal to pitch length.
Pitch length depends upon temperature . (temperature increases pitch length shorter) because greater thermal energy increases the angle at which the director changes. , thus tightening the pitch.

137. Sematic liquid crystals
The word "smectic" is derived from the Greek word for soap. This seemingly ambiguous origin is explained by the fact that the thick, slippery substance often found at the bottom of a soap dish is actually a type of smectic liquid crystal.
Molecules in this phase show a degree of translational order not present in the nematic. In the smectic state, the molecules maintain the general orientational order of nematics, but also tend to align themselves in layers or planes. Motion is restricted to within these planes, and separate planes are observed to flow past each other. The increased order means that the smectic state is more "solid-like" than the nematic.
Sematic A and C are arises – when the molecules are oriented along the layers normalor.

138. Photo of the smectic A phase (using polarizing microscope)
Picture of the smectic A phase
Photo of the smectic C phase (using polarizing microscope)
Picture of the smectic C phase

139. Applications of liquid crystals
1. LCs used to detect Tumor, since tumor cell are at higher temperature than normal cell, these indicated by color change.
2. Used in electronic industry , a break in circuit increases the temperature , which is detected by change in color of LCs.
3. Used in thermostrips and disposable thermometers to read body temperature.
4. Used in Optical imaging and recording .
5. Used to detect radiation and pollution in atmosphere.
6. LCD screen used in watches ,calculator, laptops, television, sigh board.
7. used in non-destructive testing of materials under stress.
8. low molecular mass LCs used in erasable optical disks and light modulator for color electronic imaging.

140. The End
Extra slides....

141. Processing of Latex (for rubber formation)
Bark is the outer most skin of the tree.

143. Recovering the Rubber
The preferred method of recovering rubber from latex involves coagulation - adding an acid such as formic acid (HCOOH); coagulation takes about 12 hours
coagulation of rubber latex

144. The coagulum, now soft solid slabs, is then squeezed through a series of rolls which drive out most of the water and reduce thickness to about 3 mm (1/8 in)

145. The sheets are then dried in smokehouses
The sheets are then dried in smokehouses. Several days are normally required to complete the drying process