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L. Balzano, S. Rastogi, G.W.M. Peters Dutch Polymer Institute (DPI) Eindhoven University of Technology tailoring the molecular weight distribution of polyethylene.

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Presentation on theme: "L. Balzano, S. Rastogi, G.W.M. Peters Dutch Polymer Institute (DPI) Eindhoven University of Technology tailoring the molecular weight distribution of polyethylene."— Presentation transcript:

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

2 1930s branched PE 1950s linear PE and isotactic PP 2000s explore the ultimate properties of existing polymers by controlling: additives processing conditions 1980s metallocene breakthroughs polyolefins polyethylene (PE) polypropylene (PP)

3 without flow with flow pressure a b c d process morphology properties cooling rate 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 polymer molecules properties  crystallization  glass formation  physical aging physical processes processing conditions

5 without flow with flow pressure 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 a b c d cooling rate process morphology properties

6 self-nucleation: introduction

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

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

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

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

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

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

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

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

15 CrCr+Fe LMW M w =5.5·10 4 g/mol M w /M n =3.4 HMW M w =1.1·10 6 g/mol M w /M n =2.3 M w =7.0·10 4 g/mol M w /M n =3.5 7 wt% (C*=0.5 wt%) Balzano L et al., Macromolecules 2011, ASAP Kukalyekar, N. et al. Macromolecular Reaction Engineering 2009, 3, (8), specimens

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

17 flow induced crystallization near T 0 m 120s -1 for 1s at 142ºC Balzano L. et al. Physical Review Letters 2008, 100,

18 flow induced crystallization near T 0 m 120s -1 for 1s at 142ºC fibrillar scatterers only Balzano L. et al. Physical Review Letters 2008, 100,

19 crystallizationdissolution melt precursor nucleation propagation (1 D) shishprecursor melt size-dependent dynamics of fibrils fibrillar scatterers decreasing equatorial SAXS increasing crystallinity

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

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

22 peculiarity: critical strain Balzano L et al., Macromolecules 2011, ASAP because of the high concentration of long molecules, the formation of shishes is governed by strain 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 s shear rate shear time shear at 142ºC

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

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

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

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

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

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

29 conclusions with HMW molecules, shishes can be formed around T 0 m shishes formed around T 0 m 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 MWD can be tailored for flow-enhanced self-nucleation with incorporation of HMW molecules

30

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

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

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

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

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


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