probing polymer crystallization in processing conditions (using synchrotron radiation)
DESCRIPTION
Synchrotron Radiation in Polymer Science 5 San Francisco, 30 th March – 2 nd April 2012. PROBING POLYMER CRYSTALLIZATION IN PROCESSING CONDITIONS (using synchrotron radiation). D. Cavallo , L. Balzano, G. Portale, G.W.M. Peters, G.C. Alfonso. - PowerPoint PPT PresentationTRANSCRIPT
PROBING POLYMER CRYSTALLIZATION IN PROCESSING CONDITIONS
(using synchrotron radiation)
D. Cavallo, L. Balzano, G. Portale, G.W.M. Peters, G.C. Alfonso
Synchrotron Radiation in Polymer Science 5 San Francisco, 30th March – 2nd April 2012
Crystallization of polymers in “unperturbed” conditions
Unit cell ~1-10 Å
Chain folded lamellae ~10 nm
Spherulites ~10-100 μm
Hierarchical organization
Crystallization of polymers in “unperturbed” conditions
Crystallization kinetics
Growth of PLLA spherulites,
Optical Microscopy
Polymer processing
Combined application of:
HIGH COOLING RATES
( 101-103 K/s )
FLOW FIELDS
( 10-1-103 s-1 )
Crystallization of polymers in “real” conditions
Injection molded sample
Final structure depends on local
thermo-mechanical history
Outline
Crystallization under fast cooling conditions
Effect of flow on crystallization
Structure formation during real processing
“Model” experiments
Fast cooling: Continuous-Cooling-Transformation
diagrams
Very important for steel technology, (almost) neglected for semicrystalline
polymers
DUBBLE@ESRF, March 2010
Acq. time 0.05 s
Experimental method
Quenching devicecooling rate up to
≈200°C/s
Case 1: Polymorphism of quenched isotactic polypropylene
D. Mileva, et al. Polymer 2009, 50, 5482
Q. Zia et al.Polym. Bull. 2008, 60, 791
An actual experiment
Continuous-Cooling-Transformation diagram of i-PP
Prevailing mesophase
Prevailing alpha phase
Mixed structure
Effect of comonomer on CCT diagrams
Effect of comonomer on CCT diagrams
Case 2: Polymorphism of quenched polyamide 6
a-phase
mesophase
• monoclinic• themodynamically stable• sheet-like hidrogen bonding
• pseudo-hexagonal• metastable• irregular hidrogen bonding
a-phase
mesophase
amorphous
Continuous – Cooling –Transformation diagrams of PA6
PA6 18kDa
Flow induced crystallization:consequences
Flow induced crystallization:causes
melt
FLOW
dissolution of flow induced structures
nucleating effect on crystallization
cluster of (locally) oriented chain
segments
X-raydiamond windows
(30 frame/s)Multi-pass rheometer @ DUBBLE, ESRF
Flow induced crystallization: experimental methods
Pilatus
Rotational shearing device Linkam CSS 450 coupled with SAXS at Beamline A2 HASYLAB/DESY
Flow induced crystallization: experimental methods
i-PP, “apparent” shear rate of 560s-1 ; T = 145 °C
shish
SAXS WAXD
(110)(040
)(130)
(110)
(110)
time
0.17s
0.20s
0.27s
0.13s
What happens during flow
FLOW STOPS
Crystallization onset time in flow
10-1sQuiescient onset time
103s
Effect of flow induced structures on rheologyRheology
iPP , T = 145 °C
wall stress
DP = P bottom - P top
Huge increase in viscosity during shear: “suspension” of shishes
Dissolution of shear-induced nucleation precursors: indirect
evidencesRelaxation effect on
crystallization kineticsRelaxation effect on crystal orientation
Dissolution of shear-induced nucleation precursors: mechanism
Relaxation temperature
increases
Rate controlling step:detachment of segments from
the surface of oriented clusters
X-ray beam (fixed height)
Die exit
Take-up direction
2D WAXD detector
(fixed position)
Crystallization during real processing : in-situ study of film
blowing
X-ray beam (fixed height)
Die exit
Take-up direction
2D WAXD detector
(fixed position)
Crystallization during real processing : in-situ study of film
blowing
Film blowing at synchrotron facilities : experimental setup
Collin Blown Film Unit type 180
Die-extruder on a manually operated hydraulic lifter
Film blowing at synchrotron facilities : experimental setup
Data analysis: WAXD patterns vs. axial position
b
a
c
Results
BUR= final bubble
diameter/bubble diameter at the die
TUR= take-up
velcoity/velocity at the die exit
Bubble kinematics
Video tracker technique
Machine direction
Velocity profiles
“Corrected” results
Elongation in both machine and
transverse direction affects crystallization
kinetics
Acknowledgments(this work would not have been possible without...)
Wim Bras, BM26/DUBBLE - ESRF, Grenoble (France)
Daniel Hermida-Merino, BM26/DUBBLE - ESRF, Grenoble (France)
Florian Ledrappier, BM26/DUBBLE - ESRF, Grenoble (France)
Sergio Funari, A2 - HASYLAB, DESY (Germany)
Daniela Mileva, University of Halle (Germany)
Renè Androsch, University of Halle (Germany)
Zhe Ma, Eindhoven University of Technology (The Netherlands)
Roberto Floris , University of Genova (Italy)
Lorenza Gardella, University of Genova (Italy)