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introduction: polymer crystallization

structure development and mechanical performance of oriented isotactic polypropylene 15th International Conference on DYFP 1-5 April 2012, Rolduc Abbey, The Netherlands T.B. van Erp , L.E. Govaert, G.W.M. Peters. introduction: polymer crystallization. quiescent. melt. pressure. fast cooling.

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introduction: polymer crystallization

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  1. structure development andmechanical performanceof oriented isotactic polypropylene15th International Conference on DYFP1-5 April 2012, Rolduc Abbey, The NetherlandsT.B. van Erp, L.E. Govaert, G.W.M. Peters

  2. introduction: polymer crystallization quiescent melt pressure fast cooling with flow

  3. introduction: injection molding typical cross section of injection molded semi-crystalline polymer part skin layer shear layer core layer rapid cooling (~100 °C s-1) flow induced crystallization (~1000 s-1) pressure induced crystallization (~1000 bar) beamspot 10μm, ID13 @ ESRF

  4. introduction: influence of processing

  5. deformation kinetics: influence of processing constant strain rate constant applied stress factor 500 in lifetime for different directions

  6. motivation rapid cooling (~100 °C s-1) flow induced crystallization (~1000 s-1) pressure induced crystallization (~1000 bar) need for controlled and homogeneous structure formation

  7. extended dilatometry (1) • Pirouette: a dedicated dilatometer that can perform experiments near processing conditions • Quantify influence of thermal-mechanical history on specific volume of (semi-crystalline) polymers sample weight: ~75 mg

  8. extended dilatometry (2) • Pirouette: a dedicated dilatometer that can perform experiments near processing conditions • Quantify influence of thermal-mechanical history on specific volume of (semi-crystalline) polymers Ts=193 °C Ts=133 °C M.H.E. van der Beek et al., Macromolecules (2006)

  9. processing protocol Annealing 10 min @ 250°C Compressed air cooling @ ~1°C/s Isobaric mode Pressures: 100 – 500 – 900 – 1200 bar Short term shearing of ts = 1s Shear rates: 3 - 10 – 30 – 100 – 180 s-1 Ts= Tm(p) – ∆Ts with ∆Ts = 30 - 60°C

  10. evolution of specific volume (1) effect of shear rate

  11. evolution of specific volume (2) effect of shear temperature pronounced effect of shear flow at lower shear temperature

  12. evolution of specific volume (3) effect of shear effect of pressure higher pressure enhances the effect of shear

  13. analysis crystallization kinetics dimensionlesstransition temperature

  14. analysis crystallization kinetics Weissenberg number (‘strength of flow’) WLF Temperature shift dimensionlesstransition temperature Pressure shift J. van Meerveld et al., Rheol. Acta (2004); M.H.E. van der Beek et al., Macromolecules (2006)

  15. flow regimes (1) dimensionlesstransition temperature

  16. flow regimes (1) dimensionlesstransition temperature

  17. flow regimes (2) from spherulitic morphology to oriented structures

  18. classification of flow regimes • No influence of flow • Flow enhanced (point-like) nucleation • Flow induced crystallization of oriented structures

  19. modeling quiescent crystallization space filling Schneider rate equations Avrami equation nucleation density growth rate ‘number’ ‘radius’ ‘surface’ ‘undisturbed volume’ ‘real volume’

  20. flow-induced crystallization model total nucleation density (flow-induced) nucleation rate shish length (L) growth rate equations Avrami equation ‘length’ ‘surface’ ‘undisturbed volume’ ‘real volume’ R.J.A. Steenbakkers and G.W.M. Peters, J. Rheol. (20011); P.C. Roozemond et al., Macromol. Theory Simul. (2011)

  21. flow-induced crystallization model total nucleation density (flow-induced) nucleation rate shish length (L) growth rate equations Avrami equation ‘length’ ‘surface’ ‘undisturbed volume’ ‘real volume’ R.J.A. Steenbakkers and G.W.M. Peters, J. Rheol. (20011); P.C. Roozemond et al., Macromol. Theory Simul. (2011)

  22. flow-induced crystallization model total nucleation density (flow-induced) nucleation rate shish length (L) growth rate equations Avrami equation ‘length’ ‘surface’ ‘undisturbed volume’ ‘real volume’ prediction of number, size, type and orientation of crystalline structures for pressure and flow-induced crystallization R.J.A. Steenbakkers and G.W.M. Peters, J. Rheol. (20011); P.C. Roozemond et al., Macromol. Theory Simul. (2011)

  23. prediction of flow regimes effects of pressure and shear flow on crystallization kinetics captured

  24. mechanical performance

  25. mechanical performance

  26. influence of orientation T.B. van Erp et al., J. Polym. Sci., Part B: Polym. Phys., (2009) T.B. van Erp et al., Macromol. Mater. Eng. (2012)

  27. influence of orientation relation between yield stress and orientation still an open issue

  28. conclusions • rheological classification of flow-induced crystallization of polymers by incorporating in a controlled way the effect of pressure, under cooling and the effect of flow. • a molecular stretch based model for flow induced crystallization provides detailed structure information in terms of number, size and degree of orientation • promising route for determining processing-structure- property relations

  29. structure developmentandmechanical performanceof oriented isotactic polypropylene T.B. van Erp, L.E. Govaert, G.W.M. Peters Mechanical Engineering Department Eindhoven University of Technology

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