Pressure Quench of flow-induced crystallization

transcript

Zhe Ma, Luigi Balzano, Gerrit W M Peters

Materials Technology

Department of Mechanical Engineering

Eindhoven University of Technology

Putting values to a model for Flow Induced Crystallization (DPI #714,VALFIC)

Z. Ma, G.W.M. Peters

Materials Technology Department of Mechanical Engineering Eindhoven University of Technology

structures

properties

motivation

[1] Swartjes F.H.M (2001) PhD thesis, Eindhoven University of Technology, NL

[2] Hsiao B.S et al. (2005) Physical Review Letter, 94, 117802

flow strength

mild strong

depending on the molecular mobility

more point-like nuclei

oriented

nuclei

quiescent

(no flow)

point-like nuclei, f(T)

nuclei

structure

Limitation: precursors without electron density difference

(or very little concentration)

SAXS electron density difference

Limitation: non-crystalline precursors

WAXD crystalline structure

How to observe nuclei:

Small Angle X-ray Scattering (SAXS)

Wide Angle X-ray Diffraction (WAXD)

……

objective

point-like

nuclei

oriented nuclei

crystallization after flow

formation during flow

row nuclei -- No

shish nuclei – Yes

observable

objective

point-like

nuclei

oriented nuclei

(kinetics)No

row nuclei -- No

observable

colored large nucleation density

Microscopy no no yes

Dilatomery yes yes no

DSC yes yes no

Rheometry yes yes yes

objective

develop a method which is (more) reliable, simple, also works with flow.

suspension-based model[1]

linear viscoelastic three dimensional generalized self-consistent method[2]

Relative dynamic modulus, f*G=G*/G*0

[1] R.J.A. Steenbakkers et al. Rheol Acta (2008) 47:643

[2] R.M. Christensen et al. J.Mech.Phys.Solids (1979) 27:315

A*, B* and C* determined by ratio of the complex moduli of the continuous phase and dispersed phase, Poisson ratio of both phases: all known,

A*, B* and C* then depend on space filling only.

measure G*(T) space filling nucleation density N(T)

Avrami Equation?

method suitable for combined effect of NA and flow

Z Ma et al. Rheol Acta (2011) DOI 10.1007/s00397-010-0506-1

suspension-based model

iPP and U-Phthalocyanine (145oC)

objective

point-like

nuclei

oriented nuclei

(orientation and kinetics)

row nuclei -- No

observable

increase Tequilibrium by pressure

decrease Texp by fast cooling --- Temperature quench difficult for large devices

Undercooling is expected to start crystallization

--- Pressure quench!

crystallization:

1. morphology (isotropic or oriented)

2. kinetics (compared with quiescent case)

objective

Pressure-quench

Set-up

Multi-Pass Rheometer (MPR)

Protocol

Erase history at 190oC and cool to 134oC

A apparent wall shear rate: 60 1/s

shear time: 0.8s

300barreference 50bar

highly oriented

crystals

row nuclei

Pressure-quench

Pressure Quench

twisted lamellae

t=0s t=17s

Pressure-quench

Set-up

Multi-Pass Rheometer (MPR)

Protocol

Erase history at 190oC and cool to 134oC

A apparent wall shear rate: 60 1/s

shear time: 0.8s

300barreference 50bar

annealing after flow, ta=22min

results

0s 8.5s 34s 93.5s

annealing (ta=22min)

Pressure Quench

0s 8.5s 17s 102s

no annealing

experimental theoretical (tube model)

results

relaxation of orientation

experimental

3 1.513 1D eZ

theoretical (tube model)

For HMW tail (1,480,000 g/mol) at 134 oC

results

Long lifetime of orientation

Besides molecular mobility, other effect exists.

3 1.513 1D eZ

results

iPP[1]

Besides molecular mobility, other effect exists.

[1] H An et al. J. Phys. Chem. B 2008, 112, 12256

3 1.513 1D eZ

results

Interaction between PE chains (or segments) at 134oC

[1] H An et al. J. Phys. Chem. B 2008, 112, 12256

iPP[1]

annealing (ta=22min)no annealing

results

average nuclei density

specific (200) diffraction

(equatorial, off-axis or meridional)

randomization of c-axes

content of twisting overgrowth

(nuclei density)

annealing (ta=22min)no annealing

results

average nuclei density

lower nuclei density some nuclei relax within annealing

specific (200) diffraction

(equatorial, off-axis or meridional)

randomization of c-axes

content of twisting overgrowth

(nuclei density)

0s 8.5s 34s 93.5s

results

Pressure Quench with annealing (ta=22min)

Using Pressure Quench,

it is found that nuclei orientation survives but average nuclei density decreases within annealing.

orientation

kinetics – apparent crystallinity

Z Ma et al. to be submitted

diamondwindow

sample

results

flow field in the slit

WAXD results after flow the whole sample

in situ characterization the first formation outer layer (strongest flow)

objective

point-like

nuclei

oriented nuclei

formation during flow

row nuclei -- No

observable

combining rheology (Multi-pass Rheometer ,MPR) and X-ray

DUBBLE@ESRF Pilatus

experimental

to track shish formation during flow

(30 frame/s)

DUBBLE@ESRF Pilatus

experimental

Pressure difference and shish during flow

flow time 0.25s

combining rheology and X-ray

rheology

iPP (HD601CF) at 145oC

bottom topP P P

wall stress

results

For ≥ 240 , pressure difference deviates from the steady state and shows an “upturn”.

“upturn”

rheology

results

iPP (PP-300/6) at 141oC[1]

[1] G Kumaraswamy et al Macromolecules 1999, 32, 7537

approach steady state after start-up of flow

birefringence

rheology

results

“upturn”

iPP (PP-300/6) at 141oC[1]

[1] G Kumaraswamy et al Macromolecules 1999, 32, 7537

birefringence “upturn”[1]

oriented precursors

∆P “upturn” precursory objects

form faster at higher shear rate

∆P “upturn” precursors during flow.

1). formation of precursor

apparent shear rate of 400s-1 and T = 145oC

time for precursor formation is around 0.1s

results

2). from precursor to shish

2D SAXS

streak

results

flow stops at 0.25s

results

2D SAXS

flow shish

SAXS equatorial Intensity

0.2 10

0.018 10( , ) az qI az q d d

(1/ )q nm

shish formation around 0.23s

2). from precursor to shish

rheological response

∆P “upturn” around 0.1s

results

shish formation around 0.23s

Precursors develop into shish

t = 0.13s

t = 0.17s

t = 0.20s

results

Shish forms during flow, faster at 560s-1 than 400s-1.

t = 0.26s

t = 0.33s

t = 0.37s

results

Shish precursors form during flow and shish forms after flow.

results

SAXS results linked to the FIC model

Nucleation and growth model[1]

[1] F. Custodio et al. Macromol. Theory Simul. 2009, 18, 469

growth rate number of nuclei ,( , )high MwN N T eB

length growth ,( , )average MwL L T eB

4 40 0

( ') 1 ' ( ) 1crit t

tot T L T N HMW avgL a g a g t dt t dt

total length of shish

conclusions

point-like

nuclei

oriented nuclei

row nuclei -- No

observable

Suspension-based model

innovation

• Formation of row nuclei is visualized.• Stable nuclei can survive within 22-min annealing.• Unstable ones relax within 22-min annealing.

Pressure Quench

Combining rheology and synchrotron X-ray

• Shish formation is tracked during flow.• The shish precursors are formed during flow and further develop into

shish.• Formation times of shish precursors and shish both depend on the

flow conditions.

• The combined effect of nucleating agent and flow on the nucleation density can be assessed.

conclusions

Acknowledgements

Prof. Gerrit Peters

Dr. Luigi Balzano

Ir. Tim van Erp

Ir. Peter Roozemond

Ir. Martin van Drongelen

Dr. Giuseppe Portale

Thank you for your attention

Pressure Quench of flow-induced crystallization

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