Unit iii polymers


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Unit iii polymers

  1. 1. Polymer an Insight in to the learning topicsClassification of polymers: Thermoplastics- PE, PS, PVC, PTFE, ABS, PMMA, Synthetic Rubber Thermosetting plastics - properties and industrial applications of Bakelite, Melamine Resin, Epoxy Resin, Polyurethane (PU), Polyamide (nylon Series), Polyester (PET), PC, Silicon Polymer Moulding of plastics into articles: Compression, injection, transfer and extrusion methods. methods Conducting polymers: Properties and applications Biodegradable polymers Properties and applications 11/11/12 1
  2. 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(CH2-CH2) (-CH2-CH2-)n ethylene polyethylene
  3. 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. 4. Degree of Polymerization (P) = M/m; Where, M= Mass of Polymer; m = mass of monomeric unit Polymerisation 3 CH2 CH2 CH2 CH2 3 Ethylene polyethyleneDegree of polymerisation (P) = 3 Mass of this polymer M = (28 x 3) = 84Da11/11/12 4
  5. 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. 6. Tacticity- Plane representation of polypropylene polymer 1. Isotactic polymers H H H H H CH2 C CH2 C CH2 C CH2 C CH2 C Functional groups on the CH3 CH3 CH3 CH3 CH3 same side of the main carbon skeleton 2. Syndiotactic polymers H CH3 H CH3 H Functional groups arranged CH2 C CH2 C CH2 C CH2 C CH2 C in the alternate fashion of the main carbon skeleton CH3 H CH3 H CH3 3.Atactic polymers H CH3 CH3 H H Functional groups arranged CH2 C CH2 C CH2 C CH2 C CH2 C in a random manner around the main carbon skeleton CH3 H H CH3 CH311/11/12 6
  7. 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)
  9. 9. Functionality The number of reactive sites present in a monomer is called functionality1. O Linear chain polymer is formed if the functionality of the HO C CH2 NH2 monomer is only two (Bifunctional)2. Ex. Glycine O O HO C CH2 NH2 OH CH2 CH C OH NH2 Ex. Serine O OH CH2 CH C OH Cross linked chain polymer is formed if the functionality of the NH2 monomer is more than two (multifunctional) 11/11/12 Glycine 9
  10. 10. Classification of PolymersClassification based on Source1. Natural polymers E.g., Proteins, Cellulose, Starch, Rubber2. Semi-synthetic polymers E.g., Cellulose derivatives - Cellulose acetate (Rayon)3. Synthetic polymers E.g., Buna-S, Buna-R, Nylon, Polythene, Polyester.
  11. 11. Classification based on Structure1. Linear polymers consist of long and straight chains. E.g., Polyvinyl chloride2. 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. 12. Classification based on Molecular Forces 1. Elastomers eg. Buna-S, Buna-N, neoprene2. Fibers eg. Polyesters, Polyamides.3. Thermoplastic polymers eg. Polythene, Polystyrene, PVC.4. Thermosetting polymers eg. Bakelite, urea-formaldelyde resinsOrder of strength :-Thermosetting > Fibres > Thermoplastics > Elastomers
  13. 13. Classification based on mode of Polymerization1. Addition polymers formed by the repeated addition of monomer molecules possessing double or triple bonds n(CH2=CH2) -(CH2 -CH2 )- Ethylene polyethylene2. 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(H2N(CH2)6 NH2) + n(HOOC(CH2)4COOH) [-NH(CH2)6NHCO(CH2)4CO-]n + nH2O (Nylon 6:6)
  14. 14. Polymerization is of two types; Addition or chain polymerization Condensation polymer
  15. 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. 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. 17. Addition polymerization proceeds by the initialformation of some reactive species such as freeradicals or ions and by the addition of the reactivespecies to the other molecule, with the regenerationof the reactive feature.
  18. 18. Chain polymerization occur in three steps:-•Chain initiation step•Chain propagation step•Chain termination step
  19. 19. In chain initiation step, a free radical is first generatedas a result of physical or chemical effect, which isresponsible for the further continuation of the chainpolymerization
  20. 20. The primary free radical react with the double bond ofan unexcited monomer molecule and adds to itforming a new radical capable of further interactionwith the initial monomers.
  21. 21. The most common termination processes are RadicalCombination and Disproportionate.These reactions are illustrated by the following equations.
  22. 22. In condensation polymerization, the chain growth isaccompanied by the elimination of smallmolecules.The molecules are in the form of the water moleculeH2O ; methanol molecule CH3OH ,etc.
  23. 23. Step Growth polymerization:- It involves a repetitive condensationreaction between two bi-functional monomers.Eg. Formation of Nylon 6,6nHOOC(CH2)4COOH + nH2N(CH2)6 NH2 553K High pressure [-N-(CH2) 6-N-C(CH2)4-C-]n H O O Nylon6,6
  24. 24. Copolymerisation:- is a polymerization reaction in which a mixtureof more than one monomeric species is allowed to polymerize andforma copolymer. For example, a mixture of 1, 3 – butadiene and styrenecan form a copolymer.
  25. 25. Examples of Daily Use Polymers
  26. 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. Resins2. Plasticizers3. Fillers or Extenders4. Lubricants5. Stabilizers6. Pigments7. Anti-oxidants8. Catalysts or Accelerators
  27. 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 phosphatesFillers: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. 28. Lubricants: They makes the moulding process easier and also provide glossy finish to the final product. E.g. Waxes, oils and soapsStabilizers: They increase the thermal stability during processing. E.g. Stearates of lead, barium and cadmium.Pigments: They provide colours to the plastics TiO2, ZnO – White; Cr2O3 – Green, Carbon black – black, Red lead - Red Anti-oxidants: They protect against oxidative degradation E.g. Phenyl p-napthyl amine, diphenyl p-phenylene diamineCatalysts: They are added to accelerate the polymerization of fusible resin into cross-linked infusible form especially for thermosetting plastics. E.g. H2O2, benzoyl peroxide
  29. 29. Definition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.
  30. 30. Structure Thermoplastics possess weak intermolecular forces(e.g. Van der Waal) & don’t have crosslinks.
  31. 31. Examples 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
  32. 32. Polyethylene(PE)/Polythene  There are mainly two types of polythene:  Low density polythene(density range of 0.910–0.940 g/cm3):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.
  33. 33.  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.
  34. 34.  High density polythene(density >= 0.941 g/cm3): 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.
  35. 35.  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.
  36. 36. Polystyrene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.
  37. 37. Properties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.
  38. 38. Uses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.
  39. 39. Polyvinyl chloride of repeating vinylIt is a vinyl polymer constructed 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.
  40. 40.  Properties:1. Colurless & odourless2. Non-inflammable & chemically inert3. Resistant to light,O2, inorganic acid & alkalis.4.Greater stiffness & rigidity than polyethylene but brittle.
  41. 41. 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.
  42. 42. 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.
  43. 43. Properties of high electronegative fluorine inDue to presence 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)
  44. 44. Uses 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.
  45. 45. Poly(methyl methacrylate)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.
  46. 46.  Properties:1. Strong & light weight2. 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.
  47. 47. 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.
  48. 48. AcrylonitrileButadieeneStyrene•Monomers:-Acrylonitrile , Butadieene, Styrene•Formula :-(C8H8·C4H6·C3H3N)n•Production :-Copolymer made by polymerizing styrene and acrylonitrile in thepresence 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. Thebutadiene, a rubbery substance, provides resilience even at lowtemperatures.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 absorbance4.Used as a colorant in tattoo inks.
  49. 49. Bakelite, a phenol-formaldehyde polymer, was the firstcompletely synthetic plastic, first made by Leo Baekelandin 1907. Baekeland and an assistant started their researchin 1904 looking for a synthetic substitute for shellac.Bakelite was commercially introduced in 1909. Bakelitewas first used to make billiard balls, but, later, was used tomake molded insulation, valve parts, knobs, buttons, knifehandles, many types of molded plastic containers forradios and electronic instruments, and more.
  50. 50. Phenolic reins set to rigid, hard, scratch resistant, infusible, water resistant, insolublesolids, 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 theirstructures, They posses excellent electrical insulating character.Phenol - formaldehyde polymers are the oldest synthetic polymers. These areobtained by the condensation reaction of phenol with formaldehyde in thepresence of either an acid or a base catalyst. The reaction starts with the initialformation of o-and/orp-hydroxymethylphenol derivatives, which further react with phenol to formcompounds having rings joined to each other through –CH2 groups. The initialproduct could be a linear product – Novolac used in paints.
  51. 51. Novolac on heating with formaldehyde undergoes cross linking to form an infusiblesolid mass called bakelite.
  52. 52. 1.Plastic items like telephone parts,cabinets,heater handles.2.Phonograph records3.Electrical switches and berings used in propeller shafts in paper industry.4.Soft bakelite used as binding glue for laminated,wooden plants and in varnishes5.Sulphonated bakelite are used as ion exchange resins.6.For impregating fabrics,wood and paper. valve parts, knobs, buttons, Phonograph records
  53. 53. Melamine resin or melamine formaldehyde  (also shortened to melamine) is ahard, thermosetting plastic material made from melamine andformaldehyde 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.
  54. 54. The resin is formed by condensation co-polymerisation of melamine and formaldehyde.
  55. 55. It is a quite hard polymer and is used widely for making plastic crockeryunder the name Melamine. The articles made from melamine polymer donot break even dropped from considerable height. They are also used aslaminates and for making decorative items. In paper industry to improvewet strength of paper. In fabric treatment as finishing agent.
  56. 56. Polyurethanes are made from a dialcohol and diisocyanate monomers. The isocyanatecompounds contain the functional group (O=C=N-). A rearrangement reaction leads tothe formation of the urethane linkage. Technically polyurethane is not a condensationpolymer 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
  57. 57. 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.
  58. 58. Silicone polymers do not have carbon as part of the backbone structure. The althoughsilicon is in the same group as carbon in the periodic table, it has quite differentchemistry.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 basicstructural 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 thesilicon as shown in the graphic on the bottom.
  59. 59. Silicones are water repellent, heat stable, and very resistant to chemicalattack. They find many uses in oils, greases, and rubberlike materials.Silicone oils are very desirable since they do not decompose at hightemperature and do not become viscous. Other silicones are used inhydraulic fluids, electrical insulators and moisture proofing agent in fabrics.Silicones have a number of medical applications because they are chemicallyinert. A good deal of controversy has involved the the use of silicone inpolyurethane bags as breast implants. Again they were used because theywere thought to be very inert and resistant to dissolving or other reactions.Reports have cited increased cancer risk and severe immune responses frompossible leakage of the silicone from the implants.
  60. 60. EPOXY RESIN
  61. 61. THE ORIGIN OF EPOXY RESINSThe first commercial attempts to prepare resins fromepichlorohydrin were made in 1927 in the United States.Credit for the first synthesis of bisphenol-A-based epoxy resinsis shared by Dr. Pierre Castan of Switzerland and Dr. S.O.Greenlee of the United States in 1936. Dr. Castans work waslicensed by Ciba, Ltd. of Switzerland, which went on tobecome one of the three major epoxy resin producersworldwide. Cibas epoxy business was spun off and later soldin the late 1990s and is now the advanced materialsbusiness unit of Huntsman Corporation of the United States.Dr. Greenlees work was for the firm of Devoe-Reynolds of theUnited States. Devoe-Reynolds, which was active in the earlydays of the epoxy resin industry, was sold to Shell Chemical(now Hexion, formerly Resolution Polymers and others).
  62. 62. A new method of synthesis of high molecular weight epoxy resins ispresented. All reactions were performed in a multi-mode microwavereactor “Plazmatronika” (microwave frequency - 2,45GHz, maximumof microwave power - 300W). Shortening of the reaction time for allprocesses performed in the microwave reactor, in comparison toconventional heating, was observed.Synthesis of high molecular weight epoxy resins undermicrowave irradiation
  63. 63. PROPERTIESEpoxy is a copolymer; that is, it is formed from two differentchemicals. These are referred to as the "resin" and the "hardener".The resin consists of monomers or short chain polymers with anepoxide group at either end. Most common epoxy resins areproduced from a reaction between epichlorohydrin and bisphenol-A,though the latter may be replaced by similar chemicals. The hardenerconsists of polyamine monomers, for example Triethylenetetramine(TETA). When these compounds are mixed together, the aminegroups react with the epoxide groups to form a covalent bond. EachNH group can react with an epoxide group, so that the resultingpolymer is heavily crosslinked, and is thus rigid and strong.The process of polymerization is called "curing", and can be controlledthrough temperature and choice of resin and hardener compounds;the process can take minutes to hours. Some formulations benefitfrom heating during the cure period, whereas others simply requiretime, and ambient temperatures.
  64. 64. APPLICATIONThe applications for epoxy-based materials are extensive and includecoatings, adhesives and composite materials such as those usingcarbon fiber and fiberglass reinforcements (although polyester, vinylester, and other thermosetting resins are also used for glass-reinforced plastic). The chemistry of epoxies and the range ofcommercially available variations allows cure polymers to beproduced with a very broad range of properties. In general, epoxiesare known for their excellent adhesion, chemical and heat resistance,good-to-excellent mechanical properties and very good electricalinsulating properties. Many properties of epoxies can be modified (forexample silver-filled epoxies with good electrical conductivity areavailable, although epoxies are typically electrically insulating).Variations offering high thermal insulation, or thermal conductivitycombined with high electrical resistance for electronics applications,
  65. 65. 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.erospace applicationsectrical systems and electronics
  66. 66. Paints and coatings Adhesivesdustrial tooling and compositesonsumer and marine applications
  67. 67. Nylon is used as general name for all synthetic fiber forming polyamides,i.e., having a protein like structure. These are the condensation polymers ofdiamines and dibasic acids A number is usually suffixed with theNylon which refers to the number of carbon atoms present in the diamineand the dibasic acids respectively.Nylon-6,6 is obtained by the polymerisation of adipic acid with hexamethylenediamine.
  68. 68. It is produced by the self condensation of caprolactum. Beckmann Rearrangement
  69. 69. 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,benzeneand 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.
  70. 70. 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, electricalmountings, etc. These bearings and gears work quietly without any lubrication.3.They are also used for making filaments for ropes, bristles for tooth brushes andfilms, tyre cords,etc.
  71. 71. POLYCARBONATE SRepeating chemical structureunit ofPolycarbonate made frombisphenol A
  72. 72. StructurePolycarbonates received their name because they arepolymers containing carbonate groups (-O-(C=O)-O-). Mostpolycarbonates of commercial interest are derived fromrigid monomers. A balance of useful features includingtemperature resistance, impact resistance and opticalproperties position polycarbonates between commodityplastics and engineering plastics
  73. 73. SYNTHESIS•The main polycarbonate material is producted by the reaction ofbisphenol A and phosgene (COCl2). The first step involves treatmentof bisphenol A with sodium hydroxide, which deprotonates thehydroxyl groups of the bisphenol A. (HOC6H4)2CMe2 + 2 NaOH → (NaOC6H4)2CMe2 + 2 H2O•The diphenoxide ((NaOC6H4)2CMe2) reacts with phosgene to give achloroformate, which subsequently is attacked by another phenoxide.The net reaction from the diphenoxide is: (NaOC6H4)2CMe2 + COCl2 → 1/n [OC(OC6H4)2CMe2]n + 2 NaCl In this way, approximately one billion kilograms ofpolycarbonate is produced annually
  74. 74. Uses of polycarbonates 1) Domestic wares2) Electrical insulator in electronic industries3)Other uses for polycarbonate include greenhouse enclosures, automobile headlights, outdoor fixtures, and medical industry applications, though the list is virtually endless.
  75. 75. Processing (or) moulding (or) compounding of plasticsCompounding or moulding is a process by which the polymer resins aremixed with some additives like fillers, plasticizers, stabilizers etc to impartsome special properties to the moulded final product. Ingredients of a plasticAdditives Examples Function/Importance1. Resins Thermoplastic and Basic binding materials and holds the thermosetting resins constituents together. Major part of the plastics. Thermosetting resins transferred in to crosslinked plastics during moulding in presence of a catalyst2. Plasticizers Dioctylphthalate (DOP) To improve the elasticity and to Adipate, Oleate, reduce the brittleness of the plastics. Organic Phosphate Also improves the flow of polymer during the process 11/11/12 77
  76. 76. Additives Examples Function/Importance 3. Fillers (or) Mica, quartz, Limestone, Increases the tensile and compressive Extenders Nylon strength of plastics. They reduce the shrinkage during the process of setting 4. Lubricants Waxes, Oils, soaps To make the moulding process smooth and give the glossy finish to the final product To increase the thermal stability of a 5. Stabilizers Stearates of Pb, Ba and Cd polymer 6. Pigments TiO2, ZnO (white), chromium oxide (green), carbon black, To provide colours to the moilded articles Read Lead Phenyl, n-napthyal amine, Protection against oxidation 7. Anti-Oxidants Diphenyl-p- phenylenedimaine 8. Catalyst H2O2 and Benzoyl peroxide Added only in the case of thermosetting resins to increase the rate of polymerisation11/11/12 78
  77. 77. Different types of Moulding techniqueThe moulding is different for various polymer depends on their thermalbehaviour and nature of the resins. 1. Compression moulding Used for moulding the 2. Transfer moulding thermosetting polymers 3. Injection moulding Used for moulding the thermo polymers 4. Extension moulding and Used for moulding the 5. Blow moulding bottle type articles which has narrow neck 11/11/12 79
  78. 78. Pressure • The process of molding a material in a confinedPressure = 70 kg/cm 2 shape by applying pressure and usually heat. • Almost exclusively for thermoset materials • Used to produce mainly electrical products Top moulding part of the die (plunger) •A force of 2900psi is usually required for moldings up to 1inch (25 mm) thick. Guide pins •An added 725psi should be provided for each 1inch (25 mm) increase. Molten polymer with ingredients in the cavity at 200oC Bottom moulding part of the die with cavity (the shape of the cavity decides the shape of the final product) Extraction pin Pressed plastic material 11/11/12 80
  79. 79. This is exclusively used for thermosetting plastics. The resin ingredients mixture is preheated in apreheating chamber. When the moulding mixture becomes plastic then it is forced through a orifice intothe hot mould by using the plunger. After setting time it is taken out. Complicated shapes can be made. Heaters Plunger (top molding part) Charger (plastic ingredients) Sprue Molding Cavity Bottom molding part Ejector pinA process of forming articles by fusing a plastic material in achamber then forcing the whole mass into a hot mold tosolidify.Used to make products such as electrical wall receptacles andcircuit breakers Molded plastic 11/11/12 81
  80. 80. Clamping Molding part Injection part * Cavity Hopper Hydraulic screw Barrel drive Heater bands11/11/12 82
  81. 81. Pressing of molten polymer using die and plunger in Injection Molding The feeding or injection of hot plastic This method is generally used for thermoplastics. Die 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 The cavity in which the molten cool mould cavity where it is set by plastic will be fed and pressed Plunger cooling and the moulded object is then ejected. The temperature range used is 90 to 260oC.*11/11/12 http://www.idsa-mp.org/proc/plastic/injection/injection_process.htm Source: 83
  82. 82. 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. 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. Raw materials Molten polymer Die Extruded pipe Screw Heater conveyer Cooling of final product11/11/12 84