Speciality Polymers

Engineering Chemistry

1. Rubbers also known as elastomers are linear polymers which exhibit elastic property distinctly. Natural Rubber

2. Collection of latex Processing of latex Coagulum Crepe rubber Smoked rubber Mastication Isolation & Processing of Natural Rubber

3. Collection of latex: Hevea brasiliensis (30-60 % rubber)

4. Processing of latex: Coagulum Latex is filtered to remove any dirt present in it. This latex is then coagulated by using 1% acetic acid/formic acid solution. A soft white mass is obtained called as coagulum.

5. Processing of latex Crepe rubber Coagulated rubber is drained for about 2 hrs. and then passed through creping machine to obtain pale yellow crepe rubber.

6. Smoked rubber

7. Smoked rubber Latex is coagulated long times having vertical groves where metal plates are fitted. Metal plates with groves are inserted in the tank after coagulation. The tank is kept undisturbed for about 16 hrs. The tough slabs of rubber are obtained and passed through a series of smooth rollers to get ribbon like pattern of thin rubber sheet. These thin sheets are then hanged in smoke house for 4 days at 40-50 o C. The rubber so formed called as Smoked rubber.

8. Masticated rubber Crude rubber is masticated and compounded with chemicals such as sulphur (vulcanization), accelerators & antioxidants and then converted into utility articles by suitable processing. Mastication is the process of making rubber soft & gummy by subjecting it to several mechanical working. During mastication, rubber is broken down into small particles by passing it through roller mill. Mastication causes decrease in molecular weight of rubber due to oxidative degradation.

9. Natural Rubber is a polymer of Isoprene. To understand the structure of Rubber we shall concentrate on structure of Isoprene. Isoprene is a conjugated diene containing double bonds at alternate position. Structure of Isoprene: Monomer of Natural Rubber Structure of Rubber

10. Structure of Natural Rubber

11. Polymerization of Isoprene may follow either of the two pathways; either of cis-polymerization or trans-polymerization. The rubber formed from cis-polymerization is called cis-polyisoprene or Natural Rubber. Similarly, the rubber formed from trans-polymerization is called Synthetic Rubber.

12. Structure of Rubber

13. Gutta percha

14. It becomes soft at high temperature and too brittle at low temperature. Thus, it can be used in the range of 10 to 60 o C only. It is weak & its tensile strength is 200 kg/cm 3 . It has large absorption capacity. It can be attacked by non polar solvents like vegetables and mineral oils, gasoline, benzene & carbon tetrachloride, etc It perishes, due to oxidation in air. Drawbacks of natural rubber:

15. It swells & gradually disintegrates in organic solvents. It possesses remarkable tackiness i.e. when two fresh raw rubber surfaces are pressed together, they coalesce to form a single piece. When stretched to high extent, it suffers permanent deformation. Drawbacks of natural rubber:

16. The process of compounding raw rubber with some chemicals (vulcanizing agents) like sulphur, hydrogen sulphide , benzoyl peroxide etc to improve the properties of rubber is called as vulcanization. Vulcanization of Natural Rubber

17. Comparison of Natural and Vulcanized Rubber Natural rubber Useful temp range is 10 to 60 o C Low tensile strength(200 kg/cm 2 ) High water absorption capacity High tackiness Low resistance to oxidation in air Vulcanized Rubber -40 to 100o C High tensile strength(2000 kg/cm 2 ) Low water absorption capacity Low tackiness High resistance to oxidation in air

18. Styrene - Butadiene rubber (SBR) Government Styrene rubber Ameripol Buna - S Synthetic Rubber

19. It is prepared by copolymerization of 75% butadiene & 25% styrene by weight. Cumene hydroperoxide is used as catalyst for polymerization. It is a block copolymer, prepared by emulsion polymerization. Preparation

20. Reaction

21. It possesses high abrasion resistance. It has load bearing capacity and resilience. It shows high resistance to heat. It swells in oils and solvents. It get readily oxidized by traces of ozone. It can be vulcanized by sulphur . Properties:

22. Mainly used for making motor tires because of high abrasion resistance. It is used for floor tiles, shoe soles, gaskets, electrical insulation, adhesives, carpet backing, conveyer belt etc. Applications:

23. Thermoplastic Polymers

24. Engineering thermoplastics are group of materials obtained from high polymer resins which provide one or more outstanding properties when compared with the commodity thermoplastics such as polystyrene, polyethylene, polypropylene, etc Thermoplastic Polymers

25. Advantages of Engineering Thermoplastics include, High thermal stability. Excellent chemical resistance. High tensile & impact strength. High flexibility. High mechanical strength. Light in weight. Readily mouldable into complicated shaped. High dimensional stability. Thermoplastics: Applications

26. Thermoplastic Polymers Polycarbonate (Lexan or Merlon) It can be obtained by interaction of Bisphenol-A with diphenyl carbonate.

27. Polycarbonate ( ) n

28. Preparation of polycarbonate from bisphenol-A & Diphenyl carbonate

29. Thermoplastic Polymers: Polycarbonate (PC) Physical Properties: High impact strength & tensile strength over wide range of temperature. Highly transparent plastic (higher light transmittance: 88%). It is resistance to water & many organic compounds, but soluble in number of organic solvents & alkalis. It has a good resistance (up to 140 o C), thermal stability, oxidative stability and high melting point (265 o C). It has a tendency to yellow with long term ultra violate exposure It has good thermal & oxidative stability

30. Thermoplastic Polymers: Polycarbonate (PC) Applications: Electrical and Electronic components Being good insulator, having heat resistant and flame resistant properties, it is used in various products associated with electrical & telecommunication hardware. They can be used for making electrical insulators, industrial plugs, sockets, switches, covers of cell phones, laptops, papers, etc Data Storage The production of CD, DVD’s, and Blue ray Disc by injection moulding of polycarbonate.

31. Thermoplastic Polymers: Polycarbonate (PC) Applications: Optical applications It is used for (ultra-light) Sunglasses, Swimming & SCUBA glasses, safety glasses, visors in helmets, automotive head lamp lenses as it has high optical clarity. It is also used for widescreens for motorcycles, golf carts, small planes & helicopters. It can also be used for electronic display for use In mobile and portable device for some LCD screens.

32. Thermoplastic Polymers: Polycarbonate (PC) Applications: Security components It can be laminated to make bullet-proof glass. Other applications It is used as housing for machinery / apparatus such as hair drier bodies, camera & binocular bodies. It is used as transparent food containers, cooking utensils covers, blender jars, drinking bottles, glasses, toys, etc

33. Polycarbonate

34. Biodegradable Polymers

35. Biodegradable Polymer: Definition : Biodegradation of polymer is a process carried out by biological systems (usually bacteria or fungi) where in polymer chain is cleaved via enzymatic activity.

36. Biodegradable Polymer: Factors Responsible

37. Biodegradable Polymer: Features Naturally occurring polymers are biodegradable. Synthetic addition polymers with only carbon atom main chain are not biodegradable at molecular weight above 500. If polymer chain contains atom other than carbon in backbone it may biodegrade depending on attached functional groups. Synthetic polycondensation polymers are generally biodegradable to extent depending on functional groups involved ( ester > ether > amide ).

38. Biodegradable Polymer: Features Amorphous polymers are more susceptible for biodegradation compared to crystalline polymers. Generally lower molecular weight polymers undergo biodegradation easily compared to high molecular weight polymers. Hydrophilic polymers degrade faster than hydrophobic polymers.

39. Biodegradable Polymers: Applications As Packing Material : It can be used in food packing, foam for industrial packaging, film rapping, disposable plastic packing material such as single serve cups, disposable food service items, etc. Medical Applications : Polymers like HB-HV, Polylactic acids are used in controlled drug delivery because of biocompatibility & biodegradability. Cell transplantation using biodegradable polymers scaffolds offers possibility to create completely natural new tissues & replace organ function.

40. Biodegradable Polymers: Applications Agricultural Applications : T hese polymers are used as time release coating for fertilizers & pesticides, making films for moisture & heat retention.

41. Biodegradable Polymers Polyhydroxybutarate (PHB) It is produced by the fermentation of glucose by the bacterium Alcaligenes eutrophus

42. Biodegradable Polymers Polyhydroxyvalarate (PHV) It can be produced by fermentation of glucose A. eutrophus / P. oleovorans

43. Biodegradable Polymers Polyhydroxybutarate-hydroxyvalarate (PHBV) It can be produced by A. eutophus when grown in the presence of glucose & either propanoic or valeric acid

44. Biodegradable Polymers: PHBV Physical Properties: The physical properties of biopol copolymer vary with hydroxyvalarate content of polymer. As HV content increases in the range of 0.2 %, polymer flexibility, toughness, tensile strength, resistance. Melting point reaches minimum at about 30 % mole hydroxyvalarate. It is susceptible to hydrolysis above pH 9 and below pH 3, it can be dissolved in number of chlorinated solvents like chloroform & methylene chloride.

45. Biodegradation of PHBV: PHBV shows complete biodegradation in both aerobic & anaerobic conditions. Apart from small amounts of biological material, the final product of biodegradation are C0 2 & water for aerobic condition. The final product of biodegradation are methane & some C0 2 for anaerobic condition. The rate of degradation depends on moisture, nutrients supply, temperature, pH, etc

46. Biodegradable Polymers: Applications of PHBV Medical Applications : PHBV are used for controlled drug delivery as they are biocompatible & biodegradable. Also it is non-toxic. 2. Disposable Personal Hygiene: PHBV can be used as a sole structural material or as a part of degradable composites. 3. Packaging: PHBV can be used for films, blow moulded bottles & as a coating on paper.

47. Conducting Polymers

48. Conducting Polymer: Definition : Those polymers which has ability to conduct heat better than that of metals, are called as Conducting Polymers.

49. Polymers become conducting upon doping Polymer becomes electronically charged Polymer chains generate charge carriers Concentration of dopant causes certain electrons to become unpaired Formation of polarons and bipolarons They have extended p-orbital system Conductivity

50. Conducting Polymers: Classification

51. Intrinsically conducting Polymers (ICP) Trans-polyacetylene

52. Intrinsically conducting Polymers (ICP) Polyphenylene

53. Intrinsically conducting Polymers (ICP) Polyaniline

54. Intrinsically conducting Polymers (ICP) Polypyrrole

55. Doping in polyacetylene Amount of dopant used is significantly higher Doped polyacetylene is always in tans form Neutral polyacetylene can be doped in two ways p type doping : oxidation with anions eg : ClO 4 (-) n type doping : reduction with cations eg : Na(+) - e + ClO 4 (-) + ClO 4 (-) + e + Na(+) (-) Na(+)

56. Doped Conducting Polymers P-doping N-doping

57. 3. Extrinsically Conducting Polymers : These are conducting polymers whose conductivity is achieved by adding external ingredients to them.

58. 4. Coordination Conducting Polymers : It is a charge transfer complex containing polymer, obtained by combining a metal atom with polydentate ligand . So there is a formation of coordination bond between the polymer and metal which allow the transfer of electrons easily. This there is a conduction takes place as energy gap between higher energy level and lower energy level decreases.

59. Conductivity in Conducting Polymers Conjugated polymers like polyacetylene are organic semiconductors. They have a band gap. Conducting polymers have extended delocalized bonds that creates the band structure similar to that of silicon, but with delocalized state. When charge carrier are introduced into the conduction or valence bands, the electrical conductivity increases dramatically . Doping generates charge carriers which move in electric field. +ve charges (holes) & -ve charges (electrons) move to opposite electrodes. These movement of charge is responsible for electrical conductivity.

60. Conductivity in conducting polymers In general, conductivity increases with decreasing band gap between the valence band & conduction band. Conduction band Valence band Conduction band Valence band Conduction band Valence band E g Forbidden Energy gap n-type P-type Polaron on localized band Energy band structure Energy band structure of Si Energy band structure of conducting polymer

61. Conducting Polymers: Applications In rechargeable light weight batteries, doped conducting polymers are used. In electronic devices such as transistors, photodiodes & light emitting diodes (LED). In optical display devices. In telecommunication system. In antistatic coatings for clothing. In solar cells. In drug delivery system for human body. In molecular wires & molecular switches.

62. Conducting Polymers: Limitations Conjugated polymers have few large scale applications because of high cost, problems in processing (due to their insolubility, infusibility, brittleness) & long term instability.

63. Conducting Polymers: Polyacetylene The polymer consist of a long chain carbon atoms with alternating single & double bonds between them. Each carbon posses one hydrogen atom. It can be in two forms: cis & trans (shown below) form. Trans – polyacetylene (discovered by Prof. H. Shirkawa by using Ziegler- Natta catalyst)

64. Conduction Mechanism in Polyacetylene: An electrical conductive polymer is able to conduct electricity because of the conjugated Π -bond system. The conjugated double bonds permit easy electron mobility throughout the molecule because the electrons are delocalized. When the oxidative dopants such as I 2 is added, it takes away an electron from the Π -backbone of the polyacetylene chain & creates a positive charge (hole) on one of the carbons. The other Π -electron resides on the other carbon making a radical cation known as polaron .

65. Conduction Mechanism in Polyacetylene: The lonely electron of the double bond from which electron was removed, can move easily. As a consequence the double bond moves along . A bipolaron formed on further oxidation . As the 2 electrons are removed, the chain will have 2 positive charges (holes). The chain as a whole is neutral, but the holes are mobile. When a potential is applied, they migrate from one carbon to another & accounts for conductivity .

66. Conduction Mechanism in Polyacetylene: When a Π -bond is introduced, valence band (VB)& conduction band (CB) are created. Before doping, there is sufficient energy gap between VB & CB, so the electrons remain in VB & polymer acts as an insulator . Upon doping, polaron & solitons are formed which result in the formation of new localized electronic states that fill the energy gap between VB & CB .

67. Conduction Mechanism in Polyacetylene: When sufficient solitons are formed, a new mid-gap energy band is created which overlaps the VB & CB allowing electrons to flow. The charged solitons are thus responsible for making polyacetylene a good conductor.

68. Conducting Polymers: Applications of Polyacetylene Doped polyacetylene offer a particularly high electrical conductivity therefore used as electric wiring or electrode material in light weight rechargeable batteries. Tri-iodide oxidized polyacetylene can be used as sensor to measure glucose concentration.

69. Electroluminescent Polymers

70. Electroluminescent Polymer: Definition : Electroluminescence is a phenomenon in which a material emits light in response to the passage of an electric current or strong electric field. These are the polymers which emit light in response to the passage of an electric current or strong electric field. They have potential applications in LED devices (Flat panel display for PC, TV, mobiles) and color pixels in ink jet printing.

71. Polymer Light Emitting Diode (PLED) Semiconducting polymers, with Π electron system such as PPV (Polyphenylene-vinylene) exhibit electroluminescence. To generate light with these materials, a thin film of semiconducting polymers is sandwiched between two electrodes. Indium Tin Oxide (ITO) is commonly used anode material. It is transparent electrode material which is deposited on glass / plastic substrate. Metals like Ca, Mg, Al are used for cathode .

72. Polymer Light Emitting Diode (PLED) Electrons & holes are then injected from the cathode & anode respectively into polymer. Driven by the electric field, the charge carrier move through the polymer over certain distance & recombination takes place. The recombination of these charge carriers results in luminescence.

73. Electroluminescent Polymers Polyphenylene-vinylene (PPV) Highly oriented PPV can be obtained by soluble polymeric precursor.

74. Electroluminescent Polymers: PPV Physical Properties: (Bright yellow-green fluorescence on application of electric field ) It is diamagnetic in nature & has a very low thermal conductivity (10 – 13 S/ cm). The electrical conductivity increases upon doping with iodine, ferric chloride, alkali metals or acids. However the stability of these doped materials are relatively low. Alkoxy substituted PPV shows ease of oxidation & have much higher conductivities. Large side chain substitution lowers the conductivity. It is water soluble, but its precursors can be manipulated in aq. Solution.

75. Electroluminescence Polymers: Applications of PPV It is capable of electroluminescence. Due to its stability, processibility & electrical as well as optical properties, PPV is used in organic light emitting diode (OLED). Devices based on PPV an emissive layer, emit bright yellow-green fluorescent light & derivatives of PPV are used when light of different color is required. It is also used as electron donating material in organic solar cells.

76. Liquid Crystal Polymers

77. Liquid Crystal Phase: Crystalline solids have sharp melting point. On heating, there is a sharp transition from solid crystalline phase (anisotropic) to liquid phase (isotropic). However, certain crystalline solids do not show this sharp transitions from solid to liquid on heating. Intermediate stage can be identified called as liquid crystal phase or mesomorphic phase.

78. Liquid Crystal Polymer:

79. Liquid Crystal Polymer: Definition : A polymer that under suitable conditions of temperature, pressure & concentration, exist as liquid crystal is known as liquid crystal polymer. Polymers that form liquid crystal stage contain long, rigid units or disc shaped molecular structure called as mesogens

80. Liquid Crystal Polymers: Classification

81. Liquid Crystal Polymers: Classification

82. Liquid Crystal Polymer: Classification

83. Liquid Crystal Polymer: Classification

84. Liquid Crystal Polymer: Classification 3. Cholesteric LCP

85. Liquid Crystal Polymer: When polymer exhibiting liquid crystal line properties are formed, they can be constructed with the mesogens with three forms as: Main Chain LCP Mesogens

86. Liquid Crystal Polymer: Side Chain LCP Mesogens Polymer chain

87. Liquid Crystal Polymer: Combined Chain LCP Mesogens Polymer chain

88. Liquid Crystal Polymers: Properties They have good thermal stability, high dimensional stability, easily moulded, good electrical properties at high temperature, very low coefficient of thermal expansion, high chemical & solvent resistance and high crystallinity (T g & T m are high). Liquid Crystal Polymers: Applications In electronic & electrical equipments, data storage discs, fibre optic cables, chemical appliances, encapsulation of IC engine, housing for light wave conductors, aerospace applications, as filer for composite material, military communication.

89. Liquid Crystal Polymers Kevlar (Poly paraphenylene terephthalamide ) The polymer has very high strength due to intermolecular hydrogen bond formed between carbonyl group and NH group.

90. Liquid Crystal Polymers: Kevlar Physical Properties: It has outstanding high strength to weight ratio. It is 5 times stronger than steel & 10 times stronger than aluminum on equal weight basis. It is light weight polymer with high strength. It is thermally stable (M. P. > 500 o C). It is very resistance to impact & abrasion damage. The Kevlar fibers can absorb moisture, so they are more sensitive to environment than glass or graphite composites. Although tensile strength & modulus is high, compressive properties are relatively poor.

91. Liquid Crystal Polymers: Applications of Kevlar Kevlar is often combined with carbon fibers & embedded in epoxy resins to form hybrid composite that have the ability to withstand catastrophic impact. It can also be used in light weight boat hulls, high performance race cars. It has outstanding high temperature resistance & high tensile strength, therefore can be used for fire retardant fabric & tyre cord. It can be used as cables for mooring lines, offshore drilling platforms, for parachute lines, fishing lines, mountaineering ropes & pulley ropes. It can be used in protective clothing & body armor.

92. Polymer Composites

93. Polymers Composites: Definition : Polymer composite is the material which is made up of polymer matrix & reinforcing materials being put together with a definite interface.

94. Polymers Composites: Constituents

95. Polymers Composites: Constituents

96. Polymers Composites: Classification

97. Polymers Composites: Classification a b c

98. Polymers Composites: Classification

99. Polymers Composites: Properties They have high thermal stability, high tensile strength, stiffness, chip & easily fabricable, low thermal expansion, high impact, oxidative & abrasion resistance. Polymers Composites: Applications In automobile body & parts, turbine engines, pumps, valves, etc In fabrication of roofs & floors, furniture. In manufacturing sports goods like rackets, toys, musical instruments. In marine applications – shafts, hulls, propellers, etc In components of rockets, aircraft, helicopters, etc In electronic applications – communication antenna, electronic circuit boards.

100. Polymer Composites: Fibre Reinforced Plastics

101. Fibre Reinforced Plastics (FRP): Definition : FRP is a composite material made of a polymer matrix reinforced with fibres. The characteristic properties of FRP depends upon: Nature, orientation & distribution of fibres Nature of polymer matrix Strength of interfacial bonds between fibre phase & polymer matrix phase.

102. FRP: Classification

103. FRP: Classification

104. FRP: Classification

105. FRP: Classification

106. FRP: Classification

107. FRP: Classification

108. Thank You And All the Best