Polymers

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INTRODUCTION TO POLYMERS AND ITS TYPES & ADDITION POLYMERISATION

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Polymers

  1. 1. POLYMERS •POLYMERS •INTRODUCTION & CLASSIFICATION OF Introduction to Polymers POLYMERS •ADDITION & CONDENSATION – POLYMERIZATION •FREE RADICAL REACTION MECHANISM BY, MOHAMMED MAAZ1
  2. 2. WHAT ARE POLYMERS, MONOMERS AND POLYMERIZATIONS?Polymers are macromolecules built up by the linking Introduction to Polymers together of large numbers of much smaller molecules.Polymerization : The process of linking the repeating units (monomers) is termed as polymerization 2
  3. 3. WHAT ARE POLYMERS, MONOMERS AND POLYMERIZATIONS?The small molecules which combine with each other to Introduction to Polymers form polymer molecules are termed monomers. 3
  4. 4. Introduction to Polymers 4
  5. 5. HOW BIG ARE POLYMERS? Ethylene Polyethylene Introduction to Polymers Let CH2-CH2 ≈ 1 inchConsider only a 200 - mer, Mw ≈ 5600 This ends up with a chain of approximately 1/4 inch (6.4 mm) in diameter and 1/2 mile (805 m) long. 5
  6. 6. CLASSIFICATION OF POLYMERSDEPENDING ON THEIR STRUCTURELinear polymers Introduction to Polymers 6
  7. 7. CLASSIFICATION OF POLYMERS DEPENDING ON THEIR STRUCTURE Branched polymers Introduction to Polymers What is the effect of branching on polymer Crystallinity properties?Is it branched polymer?!!! 7
  8. 8. Introduction to Polymers LINEAR POLYMER Branched polymer8
  9. 9. CLASSIFICATION OF POLYMERS DEPENDING ON THEIR STRUCTURE Cross-linked polymersCrosslinked polymers do not dissolve but can be swelledby liquids. Introduction to PolymersLight cross-linking improves elasticity properties Using appropriate monomers Chemical reactions⇒ polymer is used as rubberHigh degree of crosslinking gives high rigidity andthermal stability (high melting point). Polymer molecules are connected together at pointsBOTHthan their ends other CROSSLINKED POLYMERS CANNOT BE RECYLED OR REPOROCESSED 9
  10. 10. TYPES OF POLYMERS &POLYMERIZATIONS Classification of Polymers Polymerization Polymer Structure Mechanism Condensation Addition Step- Chain- Polymers Polymers Polymerization Polymerization Introduction to Polymers 10
  11. 11. TYPE OF POLYMERIZATION Monomers undergo polymerizaton by two types. They are: Introduction to Polymers• Addition or chAin polymerizAtion• condensAtion or step polymerizAtion 11
  12. 12. THE ADDITION-CONDENSATIONSYSTEMWhat are addition polymers? Introduction to PolymersAddition polymers are those formed from monomers without the loss of a small molecule. Y Y 12
  13. 13. Polymer Structure The addition-condensation systemCondensation polymers (New definition) Introduction to Polymers Polymers whose repeating units are joined together by functional units such as ester (-OCO-), amide (-NHCO-), urethane (-OCONH-), sulfide (- SO2-) and other linkages. -R-Z-R-Z-R-Z-R-Z-R-Z- R is aliphatic or aromatic grouping and Z is functional unit. 13
  14. 14. Polymer StructureThe addition-condensation system Introduction to PolymersThe major addition polymers are those formed by polymerization of monomers containing carbon-carbon double bond; such monomers are called vinyl monomers or substituted ethylenes. 14
  15. 15. ADDITION POLMERIZATION Self addition of several bifunctional monomers to each ohter takes place by chain reaction without the elimination of any simple molecules. Introduction to Polymers  GENERAL REACTION: n [CH2=CH]  [-CH2-CH-]n | | Y Y Where Y=H,Ethylene,CH3,Propylene,Cl, Vinyl 15 Chloride, C6H5, Sterene, CN , Acrylonitrile
  16. 16.  Addition polymerization is initiated by small qty of substance called Introduction to Polymers Initiators. E.g.-Zeigler-Natta catalyst, potassium persulphate , dibenzoyl sulphat e. 16
  17. 17. CONDENSATIONPOLYMERIZATION• Self addition of several bifunctional monomer to each other takes place accompanying elimination of simple molecues like H2O,NH3 & HCL Introduction to Polymers• General reaction: n[HOOC-X-COOH] + n[HO-Y-OH]HO-[….OC-X-COO-Y-O]n-H + (2n-1)H20 17
  18. 18. E.g.. Terylene is obtained by condensing terpthalic Introduction to Polymers acid [HOOC-C6H4-COOH] with ethylene glycol [HO-C2H4-OH] Nylon is made by the condensation of adipic acid [HOOC-(CH2)4-COOH] with hexamethylene diamine [NH2-(CH2)6-NH2] 18
  19. 19. MECHANISM OF ADDITION POLYMERIZATION{FREE RADICLE REACTION MECHANISM} Free Radical Mechanism of chain reaction involves 3 stages namely Introduction to PolymersII. InitiationIII.PropagationIV.Termination SCHEMATIC REPRESENTATION[ R* - Free radical M* - Unsaturated Monomer] 19
  20. 20. • Generation of free radical : I  2R E.g. I  CH2=CH2• Initiation : R + M  RM1 Introduction to Polymers• Propagation : RM1 + M  RM2 RM2 + M  RM3 RM( x – 1 ) + M  RM x RM( y – 1 ) + M  RM y• Termination : RM x + RM y  RM x + y (COUPLING) RM x + RM y  RM x + RM y (DISPROPORTIONATION) 20
  21. 21. MECHANISM OF ADDITIONPOLYMERIZATION OF POLY-ETHYLENE Synthesis of poly-ethylene -(CH2-CH2)- n fromEthylene, CH2=CH2 using di-benzoyl peroxide Introduction to Polymers (C6H5COO)2 as the indicator n CH2=CH2  -(CH2-CH2)- n (C6H5COO)2 Generation of free radical(C6H5COO)2 2C6H5COO 2CO2 + 2C6H5 or (R)InitiationR + CH2=CH2 R-CH2-CH2In General : R-(CH2-CH2)X-CH2-CH2 21 R-(CH2-CH2)Y-CH2-CH2
  22. 22. Termination By coupling (by the combination of two radicals)R-(CH2-CH2)X-CH2-CH2 + CH2-CH2-(CH2-CH2)Y-R Introduction to PolymersR-(CH2-CH2)X-CH2-CH2-CH2-CH2-(CH2-CH2)Y-RBy disproportionationR-(CH2-CH2)X-CH2-CH2 + R-(CH2-CH2)Y-CH2-CH2R(CH2CH2)X-CH2-CH3 + R(CH2CH2)Y-CH=CH2 22

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