Harald Pasch

1
Advanced Fractionation Techniques for Complex
Polyolefins
Harald Pasch SASOL Chair of Analytical Polymer
Science Department of Chemistry and Polymer
Science, University of Stellenbosch, South Africa
2
Polyolefin Analysis
Complex Structures
New Applications
New Copolymers
Fractionation Techniques ?
Chemical composition
Molecular size
HT-SEC
TREF CRYSTAF
3
Polyolefins The Most Common Polymers
polyethylene
Where are the problems ?
polypropylene
4
Polyolefins just CH, CH2 and CH3 .... ?????
Isotactic polypropylene (high crystallinity)
Narrower PDI (Metallocene)
Syndiotactic polypropylene
Atactic polypropylene (low crystallinity)
Broader PDI (Ziegler-Natta)
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Polyolefins just CH, CH2 and CH3 .... ?????
2
Morphology
Crystal size, crystal size distribution tie molecules interfacial order
Instrumentation required
DSC, DMA NMR, Microscopy AFM, SEM
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Physical Properties
haze,gloss, clarity, tear strength, tensile strength,impact strength
Instrumentation required
Different test equipment
1
Molecular structure
MM,MMD SCB distribution SCB content
Instrumentation required
HT-SEC CRYSTAF, TREF DSC NMR, FTIR
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Why does chain structure influence properties?
Branch type influences the crystal
structure Distribution of the branches ???
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Results SEM
Change in Crystal Morphology as a Result of
Blending
LDPE
60 LDPE 40 Plastomer poly(ethylene-1-octene)
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• Molar Mass Analysis

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High-Temperature SEC Polymer Labs Model PL GPC 220
Stationary phase Cross-linked PS Mobile
phase Trichlorobenzene Temperature 140
oC Calibration PS, PE Detectors RI, ELSD, IR,
LS, Vis
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HT-SEC and FTIR of an Oxidized Polyethylene
?
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Universal LC-FTIR Coupling
pump injector
RI-detector
Separation
HPLC / GPC

Identification
FTIR spectrometer
series of spectra
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SEC-FTIR of an Ethylene-Methacrylic Acid Copolymer
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SEC-FTIR Analysis of a Polyolefin Blend
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Separation by Crystallizability Chemical
Heterogeneity
CRYSTAF TREF
HT-SEC

• Temperature Rising Elution Fractionation (TREF)
• Crystallization Analysis Fractionation (CRYSTAF)

? separation with regard to chemical composition
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Separation by Crystallizability Chemical
Heterogeneity

• Based on Flory-Huggins expression for
  polymer-diluent mixtures
• diluent solvent, comonomer
• melting point depression is a function of
  non-crystallizable comonomer content
• chemical composition separation separation by
  crystallizability

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Temperature Rising Elution Fractionation
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TREF Separation Mechanism
The slow cooling rate is the most important
factor in achieving good separation The slow
cooling rate minimizes the effects of
co-crystallization and molar mass
influences. Typical cooling rates would be about
2C/hour It takes about 2-3 days to cool!!
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Temperature Rising Elution Fractionation
Comparison of typical LLDPE and LDPE
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Temperature Rising Elution Fractionation
Hypothetical samples with same MMD and
crystallinity distribution but different
dependency on each distribution
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Temperature Rising Elution Fractionation
Automatic Cross-Fractionation System TREF-SECS.
Nakano, Y. Goto, J. Appl. Polym. Sci. 26 (1981)
4217
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Temperature Rising Elution Fractionation
TREF-SEC Analysis of a Blend of Two
Polyethylenes S. Nakano, Y. Goto, J. Appl.
Polym. Sci. 26 (1981) 4217
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Crystallization Analysis Fractionation
IR detector
dW/dT
W
100
6
80
4
60
dW/dT
W
40
2
20
0
0
20
30
40
50
60
70
80
90
Temperature C
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Crystallization Analysis Fractionation
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Crystallization Analysis Fractionation
Typical temperature cycle
Typical crystallization curve
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Crystallization Analysis Fractionation
Crystaf analysis of a PP blend
Comparison of TREF and CRYSTAF
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CRYSTAF Analysis of Copolymers and Blends
HDPE
LLDPE
HDPE/LDPE 496
HDPE/PP 50 50
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CRYSTAF Analysis of Copolymers and Blends
Propene-?-Olefin Copolymers
Propene-Octene
Propene-Octadecene
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CRYSTAF (in particular when coupled to IR
sensor) excellent technique but very time
consuming
Fast and selective techniques are required liquid
chromatography is a good candidate
Polyolefins are soluble only at high
temperatures unconventional stationary and mobile
phases ???
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Elution Behaviour of Polyolefins in High
Temperature Chromatography (HT-HPLC) Using
Interactive Stationary Phasespolyolefin must
dissolve in the mobile phase screening of
solubility polyolefin must interact with the
phase system screening of mobile and stationary
phases
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Solvents and Columns

• Decaline
• Trichlorobenzene
• Cyclohexanone
• Dimethylformamide
• normal phase systems SiO2 (ZrO2, TiO2, Al2O3)
  
• reversed phase systems
• Diol CN Phenyl C8 C18

polarity
polarity
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Screening of Stationary Phases for HT-HPLC
Stationary phase dimethylsiloxane-modified
silica gel
? Benzylalcohol x Cyclohexylacetate ? DMF ?
Cyclohexanone
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Screening of Stationary Phases for HT-HPLC
Stationary phase dimethylsiloxane-modified
silica gel, solvent TCB
SEC conditions with regard to PP (?)
Limiting conditions with regard to PE (?)
mobile phase EGMBE
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Screening of Stationary Phases for HT-HPLC
Stationary phase dimethylsiloxane-modified
silica gel, solvent TCB
PP SEC PE Limiting conditions
PP 36k PE 34k PP 57k PE 66k PP 438k PE 500k
mobile phase EGMBE
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Analysis of PE-PMMA Block Copolymers SEC and FTIR
PE
PMMA
?
Multimodal distribution blend or copolymer ?
MMA and ethylene units can be identified, but is
it a copolymer or a polymer blend ?
Chemical composition as a function of molar mass ?
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Analysis of PE-PMMA Block Copolymers Coupled
SEC-FTIR
PE
PMMA
Chemical composition as a function of molar mass
is visualized ! Homopolymers and copolymers can
be identified !
PE-b-PMMA
PE
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Analysis of PE-PMMA Block Copolymers
What about interaction chromatography ?
SEC
molar mass separation
LC-CC
chemical composition separation
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Analysis of PE-PMMA Block Copolymers Gradient
HPLC
Column Nucleosil 300 C18
Temperature 140?C Mobile phase
gradient from100 DMF
to 100 TCB
PE
PMMA
PE-b-PMMA
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Analysis of PE-PMMA Block Copolymers Gradient
HPLC-FTIR
---- PMMA 1730 cm-1 ----- PE 720 cm-1
PE
High-Temperature Gradient HPLC as a New Tool for
the Analysis of Olefin Copolymers
PMMA
PE-b-PMMA
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Polymer Labs High-Temperature Gradient HPLC
System
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Separation System for PE-PP Blends
PP
PE
M
TCB
signal
Time min
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Separation System for PE-PP Blends
PE
PP
propylene-rich
ethylene-rich
PP
column Nucleosil 500 mobile phase EGMBE-TCB T
140oC detector ELSD sample solvent TCB
EP copolymer with 48 ethylene
L.-C. Heinz, H. Pasch, High-Temperature Gradient
HPLC for the Separation of Polyethylene-Polypropyl
ene Blends.Polymer 46 (2005) 12040
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Separation System for EVA Copolymers
stationary phase silica gel mobile phase
gradient of decaline-cyclohexanone
PVAc
PE
A. Albrecht, R. Brüll, T. Macko, H. Pasch
Separation of Ethylene-Vinyl Acetate Copolymers
by High-Temperature Gradient Liquid
Chromatography. Macromolecules 40 (2007) 5545
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Separation of Polyolefins by Tacticity
stationary phase carbon-based mobile phase
gradient of 1-decanol-TCB
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Schematic Protocol for 2D Separations
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Two-Dimensional Chromatography (HPLC vs. SEC)
1. Dimension HPLC/LCCC
Degasser Pump Injector HPLCColumn
2. Dimension GPC
Degasser Pump
Detector
SEC Column
Waste
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High-Temperature 2D-HPLC in Stellenbosch
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High-Temperature 2D-HPLC

• Chromatographic conditions
• Stationary phase Hypercarb
• Mobile phase gradient of decanol-TCB
• Operating temperature 160 oC

Ginsburg, A., Macko, T., Dolle, V., Bruell, R.,
Europ. Polym. J. 47 (2011) 319-329
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High-Temperature LC-NMR
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High-Temperature LC-NMR
ELSD
Transfer line
HT Stop-flow valve
HT-SEC
Transfer line
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polyethylene
polymethyl methacrylate
copolymer EtMMA
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On-flow High-Temperature SEC-NMR
T130C
TCB Impurities
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On-flow High-Temperature SEC-NMR
Solvent subtraction of impurities
T130C
PE Mn1.100
Et-MMA Mn10.600
PMMA Mn263.000
flow rate 0.5mL/min, conc. 222 mg/mL, 300 µL
injection volume, 5 Waters columns, 24 scans per
FID, 1.24s repetition delay
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On-flow High-Temperature SEC-NMR
1H traces of the on-flow run
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On-flow High-Temperature SEC-NMR
on-flow HT-SEC-NMRof PE-PMMA Block Copolymer
E
MMA