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Polyamide crystallization structures

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Crystal structures of polyamide

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Polyamide crystallization structures

  1. 1. About crystallization of polyamide Ted Brink
  2. 2. Page  2 Contents • H-bonds in polyamide • Thermal properties • Crystallization • Influence of moisture • Crystal structures • Conclusions
  3. 3. Page  3 Hydrogen bonds and interaction with water water
  4. 4. Page  4 Consequences of H-bonds in polyamide H-bonds influence: • stiffness • flexibility • crystallinity • glass transition point • gas permeability
  5. 5. Page  5 Thermal properties of PA6 1 0 50 100 150 200 250 300 1 2 3 processing range crystal growth melting point glass transition temperature temperature[°C]
  6. 6. Page  6 Crystallization of polyamide • fast cooling prevents crystallization • low cooling rate results in large crystals • presence of nucleant results in small crystalls • moisture uptake results in decrease of Tg - when Tg below ambient conditions → crystallization
  7. 7. Page  7 Influence crystallinity on the density of PA6 1.23 1.084 1 1.1 1.2 1.3 crystalline amorphous density [kg/m3]
  8. 8. Page  8 Influence moisture on Tg of PA6 -20 0 20 40 60 0 2 4 6 8 10 Tg[°C] moisture content [%]
  9. 9. Page  9 Influence temperature on modulus of PA6 0 1000 2000 3000 0 50 100 150 200 250 E-modulus[MPa] temperature [°C]
  10. 10. Page  10 Moisture induced crystallization Tg of PA6 • dry ~ 55 °C • wet ~ -10 °C Effects of moisture on PA6 film • lower stiffness • increased flexibility • improved stretchability • easier thermoforming • lower O2 barrier at high RH When Tg drops below ambient conditions, crystallization will occur
  11. 11. Page  11 Polyamide crystal structures Structure α phase β phase γ phase Crystal structure Monoclinic Pseudo hexagonal Monoclinic Melting point 220 °C 214 °C How created Slow cooling Quenching Specific nucleants
  12. 12. Page  12 Tensile behaviour crystal PA6 structures 0 20 40 60 80 0 1 2 3 4 5 Nominalstress[Mpa] Extension ratio Alpha Beta Gamma
  13. 13. Page  13 13 Transformations of the pure crystal phases α β γ αT αT γT αλ αλαλ Influence of temperature & stretching on the 3 crystal structures of PA6
  14. 14. Page  14 Conclusions • PA6 crystallizes: - from the melt at moderate cooling rate - when Tg > ambient temperature • α-phase is most stable • β-phase is a mesomorphous state • γ-phase is optimal for stretching
  15. 15. Page  15 Contact Ted Brink Email: ted.brink@extrusionist.com Internet: www.extrusionist.com Tel.: +31 651109899
  • mincao3

    Mar. 8, 2021
  • TalalNaseer

    Jun. 23, 2019
  • RafaelTeroba

    Aug. 1, 2017
  • FranzScheidl

    Oct. 11, 2015

Crystal structures of polyamide

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