L. Balzano , S. Rastogi , G.W.M. Peters Dutch Polymer Institute (DPI)

1. tailoring the molecular weight distribution of polyethylene for flow-enhanced self-nucleation L. Balzano, S. Rastogi, G.W.M. Peters Dutch Polymer Institute (DPI) Eindhoven University of Technology

2. polyolefins high dielectric properties barrier, transparency lightweight mechanical properties, durability breakthroughs 1980s metallocene 2000s 1930s branched PE 1950s linear PE and isotactic PP • explore the ultimate properties of existing polymers by controlling: • additives • processing conditions polypropylene (PP) polyethylene (PE)

3. process morphology properties without flow a with flow b cooling rate c pressure d a) Basset, D.C.et al. Phyl Trans Roy Soc London A 1994 b) Hobbs, J.K. et al. Macromolecules 2001 c) Androsch, R. Macromolecules, 2008

4. motivation understand structure formation at molecular level design materials that after processing have morphology (=properties) tailored for their application physical processes polymer molecules properties • crystallization • glass formation • physical aging processing conditions

5. process morphology properties without flow a with flow b cooling rate c pressure d a) Basset, D.C.et al. Phyl Trans Roy Soc London A 1994 b) Hobbs, J.K. et al. Macromolecules 2001 c) Androsch, R. Macromolecules, 2008

6. self-nucleation: introduction

7. self-nucleation: introduction Fillon, B. et al Journal of Polymer Science Part B: Polymer Physics 1993, 31, (10), 1383-1393 Banks, W. et al Polymer 1963, 4, 289-302 Blundell, D. J. et al. J. Polym. Sci., Polym. Letters 1966, 4, 481-486

8. self-nucleation: introduction iPP crystal fragments, obtained with partial melting, are used as nucleating agents Fillon, B. et al Journal of Polymer Science Part B: Polymer Physics 1993, 31, (10), 1383-1393 Banks, W. et al Polymer 1963, 4, 289-302 Blundell, D. J. et al. J. Polym. Sci., Polym. Letters 1966, 4, 481-486

9. our goal: self-nucleation with flow can we generate crystal fragments (at high temperature) with flowthat can be used as nucleating agent? what are the controlling parameters? what is their efficiency (Tc)?

10. our goal: self-nucleation with flow coils deformation fibrillar crystallites

11. our goal: self-nucleation with flow coils deformation fibrillar crystallites

12. preparation of bimodal PE blends synthetic route Cr catalyst → low Mw Fe catalyst → high Mw Kukalyekar, N. et al. Macromolecular Reaction Engineering 2009, 3, (8), 448 - 454

13. preparation of bimodal PE blends synthetic route Cr catalyst → low Mw Fe catalyst → high Mw Kukalyekar, N. et al. Macromolecular Reaction Engineering 2009, 3, (8), 448 - 454

14. preparation of bimodal PE blends synthetic route Cr catalyst → low Mw Fe catalyst → high Mw [Cr catalyst] [Fe catalyst] Kukalyekar, N. et al. Macromolecular Reaction Engineering 2009, 3, (8), 448 - 454

15. specimens Cr Cr+Fe LMW Mw=5.5·104 g/mol Mw/Mn=3.4 Mw=7.0·104 g/mol Mw/Mn=3.5 HMW Mw=1.1·106 g/mol Mw/Mn=2.3 7 wt% (C*=0.5 wt%) Balzano L et al., Macromolecules 2011, ASAP Kukalyekar, N. et al. Macromolecular Reaction Engineering 2009, 3, (8), 448 - 454

16. T effect on crystallization isothermal crystallization after pulse of shear 30s-1 for 2s unimodal bimodal with HMW molecules, crystallization can take place at higher T (under the influence of flow) Linkam Shear Cell (CSS-450) Balzano L et al., Macromolecules 2011, ASAP

17. flow induced crystallization near T0m 120s-1 for 1s at 142ºC Balzano L. et al. Physical Review Letters 2008, 100, 048302

18. flow induced crystallization near T0m 120s-1 for 1s at 142ºC fibrillar scatterers only Balzano L. et al. Physical Review Letters 2008, 100, 048302

19. size-dependent dynamics of fibrils • fibrillar scatterers • decreasing equatorial SAXS • increasing crystallinity dissolution crystallization melt melt precursor propagation (1 D) precursor nucleation shish

20. self-nucleation with flow 120s-1 for 1s at 142ºC • shishes are excellent for heterogeneous nucleation • increase Tc • template orientation

21. our goal: self-nucleation with flow can we generate crystal fragments (at high temperature) with flowthat can be used as nucleating agent? what are the controlling parameters? what is their efficiency?

22. peculiarity: critical strain shear rate shear time shear at 142ºC 100s-1 1s 50s-1 2s 25s-1 4s 5s-1 20s 50s-1 1s 25s-1 2s 10s-1 5s 5s-1 10s 25s-1 1s 5s-1 5s 2s-1 12.5s because of the high concentration of long molecules, the formation of shishes is governed by strain Balzano L et al., Macromolecules 2011, ASAP

23. self-nucleation with flow strain 100 at 142ºC inverse space real space cooling at 5°C/min Balzano L et al., Macromolecules 2011, ASAP

24. self-nucleation with flow strain shish-kebab isotropic strain more oriented ↔ higher Tc cooling at 5°C/min Balzano L et al., Macromolecules 2011, ASAP

25. room temperature morphology more oriented ↔ higher Tc ↔ thicker lamellae Balzano L et al., Macromolecules 2011, ASAP

26. room temperature morphology Balzano L et al., Macromolecules 2011, ASAP

27. flow 200 μm room temperature morphology specimen sheared at 142°C with 100s-1 for 1s and cooled at 5°C/min 0.5μm distance between shishes between 300 and 800 nm Balzano L et al., Macromolecules 2011, ASAP

28. room temperature morphology specimen sheared at 142°C with 100s-1 for 1s and cooled at 5°C/min 0.2μm 0.5μm distance between shishes between 300 and 800 nm Balzano L et al., Macromolecules 2011, ASAP

29. conclusions MWD can be tailored for flow-enhanced self-nucleation with incorporation of HMW molecules • with HMW molecules, shishes can be formed around T0m • shishes formed around T0m are an excellent substrate for heterogeneous nucleation of bulk molecules • with an excess (~10·C*) of HMW molecules, morphology during cooling (after step shear) is ruled by macroscopic strain (i.e. minimum strain/shear time for oriented morphology) a ‘smart’ combination of materials and processing conditions can be used for self-nucleation of polymer melts reducing the need for additives for nucleation and morphology control

31. X-ray scattering experiments Linkam CSS-450 performed at the beamlines ID02 and BM26

32. self-nucleation: rationale nucleation is the limiting step in polymer crystallization kinetics crystal growth only possible when ΔG<0 surface positive negative σi critical size! volume

33. self-nucleation: rationale nucleation is the limiting step in polymer crystallization kinetics crystal growth only possible when ΔG<0 surface positive negative σi σi/2 critical size! volume heterogeneous nucleation smaller critical size

34. self-nucleation: rationale nucleation is the limiting step in polymer crystallization kinetics crystal growth only possible when ΔG<0 surface positive negative σi σi/2 critical size! volume heterogeneous nucleation higher Tc smaller critical size

35. melting of shish-kebabs shishes melt at higher temperature increased stability result of the ECC structure