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

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)

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

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

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

self-nucleation: introduction

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

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

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 )?

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

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

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

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

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]

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

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)

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

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,

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

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

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?

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

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

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

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

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

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

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

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

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

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

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

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

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