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Polymers final

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Polymers final

  1. 1. Polymers
  2. 2. Introduction to Polymers Poly = many, mer = unit, many units Polymer science is relatively a new branch of science . It deals with chemistry physics and mechanical properties of macromolecule .
  3. 3. A polymer is a large molecule which is formed by repeated linking of the small molecules called “monomers”. polymer is organic substance made up of many repeating units or building blocks of molecules called ‘monomers’ OR
  4. 4. POLYMER • Combine, many monomers to create a polymer. • Polymer is often used as a synonym for ‘plastic’. • All plastic are polymers. Poly mers are made up of many Mono mer ↓ ↓ ↓ ↓ Many Units One Unit
  5. 5. Monomer molecules joined in units of long polymer.
  6. 6. It consist of large no. of repeating units known as monomers The no. of repeating units in a chain of polymer is known as degree of polymerization
  7. 7. POLYMER a family of natural and synthetic materials made of repetition of high weight molecules in a form of flexible chain NATURAL POLYMER • Collagen • Gelatin • Silk • Wool • Natural rubber • DNA SYNTHETIC POLYMER • Polyethylene terephthalate (PET) • High Density Polyethylene (HDPE) • Polyvinyl Chloride (PVC) • Low Density Polyethylene (LPDE) • Polypropylene (PP) • Polystyrene (PS)
  8. 8. MONOMERS • The smallest unit of polymer which gets polymerised under certain conditions to form polymer, called monomers. • EXAMPLE: • In the above example Ethene is monomer and Polyethene is polymer C C H H H H n ethene high pressure/trace O2 catalyst C C H H H H n poly(ethene)
  9. 9. POLYMERISATION The process of formation of polymers from respective monomers is called polymerisation. EXAMPLE : C C H H H H n ethene high pressure/trace O2 catalyst C C H H H H n poly(ethene)
  10. 10. Examples Of Polymers • Polypropylene (PP) - Carpet, upholstery • Polyethylene low density (LDPE) - Grocery bags • Polyethylene high density (HDPE) - Detergent bottles, toys • Poly(vinyl chloride) (PVC) - Piping, decking • Polystyrene (PS) - Toys, foam • Polytetrafluoroethylene (PTFE, Teflon) - non-stick pans, electrical insulation • Poly(methyl methacrylate) (PMMA, Lucite, Plexiglas) - Face shields, skylights • Poly(vinyl acetate) (PVAc) - Paints, adhesives • Polychloroprene (cis + trans) (Neoprene) - Wetsuits
  11. 11. Characteristics of Polymers • Low Density. • Low coefficient of friction. • Good corrosion resistance. • Good mould ability. • Excellent surface finish can be obtained. • Can be produced with close dimensional tolerances. • Economical. • Poor tensile strength. • Low mechanical properties. • Poor temperature resistance. • Can be produced transparent or in different colours.
  12. 12. Properties of Polymers The physical properties of a polymer, such as its strength and flexibility depend on: • 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; • Branching - straight, un branched chains can pack together more closely than highly branched chains, giving polymers that are more crystalline and therefore stronger; • Cross-linking - if polymer chains are linked together extensively by covalent bonds, the polymer is harder and more difficult to melt.
  13. 13. Properties of Polymers • Reflective • Impact resistant • Tough • Brittle • Translucent • Malleable • Soft • Elastic • Inelastic • Insulative
  14. 14. Classification of Polymer is based on Source of availability Structure Mode of Polymerization Molecular force Type of monomers
  15. 15. Classification based on Source Natural polymers Semi-synthesis polymers Synthesis polymers
  16. 16. Natural polymers • The definition of a natural polymer is a polymer that results from only raw materials that are found in nature (plants and animals). • Example:- • Starch : It is a polymer of α-D-Glucose • Cellulose : It is a polymer of β-D-Glucose • Proteins : It is a polymer of α-Amino acid • Nucleic acid : It is a polymer of Nucleotide • Natural Rubber : It is a polymer of Isoprene
  17. 17. Semi-synthesis polymers • Chemically treated polymers of natural origin are quite common and of great practical importance. • Cellulose, for example, is used in two different ways: • it is dissolved using some special solvent and precipitated again in a different physical shape, e.g. • viscose silk (Rayon) • Cellulose acetate used as semi-permeable membrane in RO,s Chemically treated polymers, that are of natural origin termed as semi synthesis.
  18. 18. Synthesis polymers (Man – Made) • Synthetic polymers are derived from petroleum oil, and made by scientists and engineers in laboratories and industries. • Examples of synthetic polymers include nylon, • polyethylene, • polyester, • Teflon, • PVC, etc.
  19. 19. Based on structure Linear polymers Branched chain polymers Cross linked chain polymer
  20. 20. Linear polymers • Monomeric units are linked together to form long and linear chains. • They are well packed. • Due to this they have following properties: • High densities • High tensile strenght • High melting point • E.g • High Density Polyethylene (HDPE) • PVC, Nylon, etc.
  21. 21. Branched chain polymers • Polymers with branches at irregular intervals along the polymer chain are called branched polymers • difficult for the polymer molecules to pack in a regular array • Less density. • Amount and type of branching also affects physical properties such as viscosity and elasticity (low) • Branches often prevent chains from getting close enough together for intermolecular forces to work effectively (low tensile strength) • E.g. Low density polyethylene(LDPE)
  22. 22. Cross linked chain polymers • These are also called three-dimensional network polymer. • Contain strong covalent bonds • Contain short side chains (cross links) • Connect different polymer chains into a “network” • Adding cross-links between polymer chains makes the polymer hard, rigid and brittle. • Example : - Bakelite, Melamine- formaldehyde resins etc. Cross links between chains
  23. 23. Based on mode of polymerization addition condensation
  24. 24. Addition Polymers • Formed by the direct addition of monomer molecules possessing double or triple bonds, without the elimination of by product molecules • These polymers have same empirical formula as their monomers. • Example :- Polyethene, PVC, Polystyrene, PAN, Teflon, Natural rubber, Neoprene, polybutadiene, BuNa-S, BuNa-N, etc. C C H H H H n ethene high pressure/trace O2 catalyst C C H H H H n poly(ethene)
  25. 25. Condensation polymers • Formed by condensation reaction between two different bi-functional monomeric units with the elimination of simple molecules like water etc. Example :- Terylene (dacron), Nylon-6,6; Nylon-6, Nylon-2,6; Glyptal etc.
  26. 26. Based on molecular force Elasromers Fibre Thermoplastic Thermosetting plastic
  27. 27. Elastomers • These are rubber – like polymers with elastic properties. In these elastomeric polymers, the polymer chains are held together by the weakest intermolecular forces. These weak binding forces permit the polymer to be stretched. • A few ‘crosslinks’ are introduced in between the chains, which help the polymer to retract to its original position after the force is released as in vulcanised rubber. The examples are BuNa-S, BuNa-N, Neoprene, etc.
  28. 28. Fibres • Fibres are the thread forming polymers which possess high tensile strength and high modulus. These characteristics can be attributed to the strong intermolecular forces like hydrogen bonding between polymeric chains. • These strong forces also lead to close packing of chains and thus impart crystalline nature. The examples are polyamides (Nylon 6, 6), polyesters (Terylene), PAN (ORLON) etc.
  29. 29. Thermoplastic polymers • 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. • Example:- Polyvinyl chloride, Polyethene, Polystyrene, Teflon
  30. 30. Thermosetting polymers • These polymers are cross linked or heavily branched molecules, which on heating undergo extensive cross linking in moulds and again become infusible. • These cannot be reused and remoulded. • Some common examples are bakelite, urea-formaldelyde resins, melamine- formaldehyde resins, etc.
  31. 31. Based on type of monomers Homo polymers Co-polymers
  32. 32. HOMOPOLYMERS • Consist of chains with identical bonding linkages to each monomer unit. This usually implies that the polymer is made from all identical monomer molecules. • These may be represented as : -[A-A-A-A-A-A]- • Example : Polyethene, PVC, Polystyrene, Teflon, Polyacrylonitrile, Polybutadiene, Nylon-6, Natural rubber, Neoprene
  33. 33. CO-POLYMERS • Consist of chains with two or more linkages usually implying two or more different types of monomer units. • These may be represented as : -[A-B-A-B-A-B]- • Example : Nylon-6,6; Nylon-2,6; Terelene; Glyptal; PHBV; Bakelite; Melamine etc.
  34. 34. Applications of Polymers: AGRICULTURE Polymeric materials are used in and on soil to improve aeration, provide mulch, and promote plant growth and health.
  35. 35. Medicine • Many biomaterials; • heart valve replacements • blood vessels, are made of polymers like Dacron, Teflon and polyurethane.
  36. 36. Consumer Science • Plastic containers of all shapes and sizes are light weight and economically less expensive than the more traditional containers. • Clothing • floor coverings • garbage disposal bags • packaging are other polymer applications.
  37. 37. Industry • Automobile parts • windshields for fighter planes • Pipes • Tanks • packing materials • insulation, wood substitutes • elastomers are all polymer applications used in the industrial market.
  38. 38. Sports • Playground equipment • various balls • golf clubs • swimming pools • protective helmets are often produced from polymers.
  39. 39. Strength of Polymers In general, the longer the polymer chain, the stronger the polymer. There are two reasons for this: • longer chains are more tangled • there are more intermolecular forces between the chains because there are more points of contact. These forces, however, are quite weak for polyethene. • Areas in a polymer where the chains are closely packed in a regular way are said to be crystalline. The percentage of crystallinity in a polymer is very important in determining its properties. The more crystalline the polymer, the stronger and less flexible it becomes.
  40. 40. • When a polymer is stretched (cold-drawn), a neck forms. In the neck the polymer chains line up producing a more crystalline region. Cold-drawing leads to an increase in strength. • The first polyethene which was made contained many chains which were branched. This resulted in a relatively disorganised structure of low strength and density. This was called low density polyethene (LDPE). • In the crystalline form, the methyl groups all have the same orientation along the chain. This is called the isotactic form. In the amorphous form, the methyl groups are randomly orientated. This is called the atactic form. • Polymers with a regular structure are said to be stereoregular.
  41. 41. THANKS