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Thermoplastic elastomers (TPE)

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POLYMERS - Thermoplastic elastomers (TPE)

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Thermoplastic elastomers (TPE)

  1. 1. THERMOPLASTIC ELASTOMERS (TPEs) N PRAKASAN ME METALLURGY 2
  2. 2. THERMOPLASTIC ELASTOMERS (TPE) INTRODUCTION  Elastomers:  An Elastomer is a polymeric material that has elongation greater than 100% and a significant amount of resilience.  For elastomers to experience relatively large elastic deformations, the onset of plastic deformation must be delayed.  Restricting the motions of chains past one another by cross-linking accomplishes this objective.  Cross-linking in many elastomers is carried out in a process called vulcanization (heating with Sulphur about 140oC). 2
  3. 3. THERMOPLASTIC ELASTOMERS (TPE) INTRODUCTION  Classification  Natural Rubber (Thermoset by cross-linking)  Synthetic • • • • • of Elastomers: Rubber (Thermoset by cross-linking) Polyisoprene Styrene Butadiene Rubber (SBR) Chloroprene, Polybutadiene Nitrile rubber, Butyle rubber, Silicones, Ethylene propylene diene monomer (EPDM), etc  Thermoplastic Elastomers 3
  4. 4. THERMOPLASTIC ELASTOMERS (TPE) THERMOPLASTIC ELASTOMERS:  This is a special group of polymers that do not rely on cross-linking to produce a large amount of elastic deformation.  TPEs have Rubber and thermoplastic characteristics.  They are flexible like vulcanized rubbers and are melt processible like a thermoplastic.  Many of the TPEs have block copolymer structure. Block copolymers contain rigid thermoplastic and soft thermoset polymer segments within the polymer chain  Example: copolymer of polystyrene and butadiene rubber. 4
  5. 5. THERMOPLASTIC ELASTOMERS (TPE) Copolymer of polystyrene and butadiene rubber polystyrene Rigid end block Rubber mid block polybutadiene Rigid end block 5
  6. 6. THERMOPLASTIC ELASTOMERS (TPE) Copolymer of polystyrene and butadiene rubber Rubber mid block phase Rigid end blocks 6
  7. 7. THERMOPLASTIC ELASTOMERS (TPE)  The structure of a styrene-butadiene block copolymer:  The styrene repeat units are located only at the ends of the chains. Approximately 25% of the chain is composed of styrene.  The styrene ends of several chains form sphericalshaped domains. The styrene has a high glasstransition temperature; consequently, the domains are strong and rigid and tightly hold the chains together.  The Butadiene repeat units are located between the styrene domains. The Butadiene portions have a glass-transition temperature below room temperature and therefore behave in a soft, rubbery manner. 7
  8. 8. THERMOPLASTIC ELASTOMERS (TPE) The structure of a styrene-butadiene block copolymer: Elastic deformation occurs by recoverable movement of the chains; sliding of the chains at normal temperatures is prevented by the styrene domains (Rigid). When the thermoplastic elastomer is heated, the styrene heats above the glass transition temperature, the domains are destroyed, the polymer deforms in a viscous manner and it behaves as thermoplastic, can be fabricated very easily. 8
  9. 9. THERMOPLASTIC ELASTOMERS (TPE) The structure of a styrene-butadiene block copolymer: When the polymer cools, the domains reform and the polymer reverts to its elastomeric characteristics. The thermoplastic elastomers consequently behave as ordinary thermoplastics at elevated temperatures and as elastomers at low temperatures. This behaviour also permits thermoplastic elastomers to be more easily recycled than conventional elastomers. 9
  10. 10. THERMOPLASTIC ELASTOMERS (TPE)  Advantages of TPEs compared with conventional thermoset elastomers:  No chemical cross-linking  Simpler processing and faster cycle times  Can be processed by Injection molding, Blow molding, thermoforming and extrusion.  Undercuts and complex shapes are possible with simple tooling.  Scrap and waste can be recycled. Normal cross-linked polymers cannot be recycled because they don't melt due to the cross-links tie all the polymer chains together, making it impossible for the material to flow.  Limitations:  They may have lower temperature resistance than most thermoset rubbers.  Creep resistance inferior to thermoset rubbers. 10
  11. 11. THERMOPLASTIC ELASTOMERS (TPE) Properties of TPE 11
  12. 12. THERMOPLASTIC ELASTOMERS (TPE)  Commercially available Thermoplastic elastomers and their applications:  1. Styrenic block copolymer (Polystyrene + Butadiene or polyisoprene)  Applications: • • • • • Grips on cameras, Razor handles, Medical devices Shoe soles Adhesives 12
  13. 13. THERMOPLASTIC ELASTOMERS (TPE)  Commercially available Thermoplastic elastomers and their applications:  2. Reactor thermoplastic polyolefin (Polypropylene + EPDM rubber )  Applications: • Automotive bumbers, • Cable and wire jacketing, • Hydraulic engine mount heat shield 13
  14. 14. THERMOPLASTIC ELASTOMERS (TPE)  Commercially available Thermoplastic elastomers and their applications:  3. Thermoplastic polyurethane (Polyester / polyether polyurethane + long chain diols )  Applications: • • • • • Automotive underhood applications, Seals / gaskets, Shoe soles Conveyor belts Caster / wheels. 14
  15. 15. THERMOPLASTIC ELASTOMERS (TPE)  Commercially available Thermoplastic elastomers and their applications:  4. Thermoplastic copolyester (polybutylene terepthalate + Polytetramethylene ether)  Applications: • • • • • Seals, Belting, Hoses, Combustion air swirl generator Caster / wheels. Combustion Air Swirl Generator15
  16. 16. THERMOPLASTIC ELASTOMERS (TPE)  Commercially available Thermoplastic elastomers and their applications:  5. Thermoplastic polyamide (Polyesteramide / polyetheramide + polyether polyol)  Applications: • • • • High toughness athletic equipments Cable jacketing, Seals / gaskets, Tail light housing Tail light housing 16
  17. 17. THERMOPLASTIC ELASTOMERS (TPE)  Applications of TPEs Bellows & Dust covers Corner mouldings Gear lever noise & vibration damping Trucks Auxiliary Springs 17
  18. 18. THERMOPLASTIC ELASTOMERS (TPE)  Applications Cable connection of TPEs 18
  19. 19. THERMOPLASTIC ELASTOMERS (TPE)  References :  Donald R. Askeland, Pradeep P. Fulay, Wendelin J. Wright, The Science and Engineering of Materials, Sixth Edition.  Kenneth G Budinski and Michael K Budinski, Engineering Materials - Properties and selection, Eighth edition, Prentice-Hall Inc.  William D.Callister, Fundamentals of Materials Science and Engineering, Fifth edition. 19

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