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Untitled

al44 English 39 cards

Untitled

Cards in this deck (39)

  1. 1PlasticsChange shape on application of force. Remain this shape when force is removed.
  2. 2FibresPolymeric materials forcibly drawn in one direction, changing its properties and giving greater strength in drawn direction
  3. 3ElastomersRubber-like materials. Return to original shape when force is removed.
  4. 4ThermoplasticsSoften when heated, harden when cooled. Easy to process
  5. 5ThermosetsNetwork polymers that become permanently hard once formed. Crosslinked once in mould. Cannot be reformed.
  6. 6Stress strain graph of a brittle plastic, plastic, elastomer and fibreStress strain graph of a brittle plastic, plastic, elastomer and fibre
  7. 7MnNumber average molecular weight
  8. 8MwWeight average molecular weight
  9. 9Average degree of polymerisationMn/m
  10. 10Polydispersity indexMw to Mn
  11. 11MorphologyCrystalline, semi crystalline and amorphous
  12. 12RegioisomerismHead-to-tail and head-to-head
  13. 13Geometrictrans tougher than cis
  14. 14IsotacticAll substituents on one side
  15. 15AtacticSubstituents alternate
  16. 16SyndiotacticSubstituents arranged randomly
  17. 17TgGlass transition temperature below this amorphous polymers behave like glassy solids above this they are plastic/rubbery. Pure crysaline polymers do not have one.
  18. 18Thermomechanical analyisFollows volume changes as temperature increases
  19. 19Differential scanning calorimetryFollows energy changes as temperature increased throughout transition. Shows a peak for Tm and a dip for Tc and an upwards slope that then levels for Tg
  20. 20Thermogravimetric analysisMeasures amount and rate of change in mass of a sample as a function of temperature or time in a controlled atmosphere
  21. 21SpherulitesSpherulites
  22. 22Factors affecting crystallisation1. Rate of cooling during solidification
    2. Annealing
    3. Degree of polymerisation
    4. Chain configuration
    5. Isomerism
    6. Deformation
    7. Copolymerisation
  23. 23Factors affecting TgChain flexibility, bulky pendant groups limit rotation and polar groups
  24. 24Factors affecting TmMostly the same as Tg also should consider secondary forces
  25. 25Chain entanglementLong chains become entangled and behave as if they were even longer. Critical chain length-larger for polar molecules
  26. 26LDPELow density polyethylene. From free radical polymerisation reaction of ethylene monomer.
    Contains long and short branches.
    Easily stretched in to films-plastic bags, cling film
  27. 27LLDPELinear low density polyethylene. Synthesised by copolymerisation of ethylene and longer chain olefin co-polymers. Branches all short. Heavy duty bags, flexible tubing.
  28. 28HDPEHigh density polyethylene.
    Synthesised with Zieglar-Nata catalyst reaction. Very little branching. Can be moulded-toys, chemical containers
  29. 29PolyestersStep growth reaction with carboxylic acid group and alchol group.
  30. 30PolycarbonatesBisphenol A and phosgene. Spectacle lenses, CD/DVD coating
  31. 31PolyurethanesBifunctional alcohol and isocynate. Alchol attacks carbon of isocynate followed by a proton shift. printing rollers, shoe soles; Lycra/Spandex;
  32. 32PolyethersSelf condensation reactions of glycols tend to form cyclic ethers. Nucleophilic aromatic substitutions where leaving group (X) is
    activated by strongly electron-attracting groups in Ar’. Example PEEK and polysulfone
  33. 33Step growth polymerisation conversion graphStep growth polymerisation conversion graph
  34. 34Carothers' equationDP= 1/(1-p)
    p is fraction of functional groups reacted
  35. 35Anionic polymerisationMonomer requires electron withdrawing substituents to form stable carbanion. Intiation by nucleophilic addition to monomer. Terminated by solvent, transfer, addition of impurity or not at all
  36. 36CationicRequire electron donating substituents to stabilise carbocation. Intiators are protonic acids and lewis acids. Stabilised by counter ion. Termination by dissociation (C-C+ -> C=C) or chain transfer
  37. 37Free radical polymerisationIntiators are peroxides and hydroperoxides and azo compounds. Terminated by combination, hydrogen abstraction and chain transfer.
  38. 38Living polymerIn anionic polymerisation in the absence of impurities and under the right conditions no termination step. Low polydispersity. Popular method for synthesising block polymers.
  39. 39Zieglar Natta catalystGives linear structure (HDPE).
    Isotactic addition. TM compound and organometallic complex. Formation of active site needs a catalyst and a co-catalyst. Termination by chain transfer. Double bonds undergo cis addition. Level of regularity depends on exposure of active site.

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Flashcards on Untitled, created by al44 on 16/12/2013.
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al44
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