Institute for Polymer Research 27 th Annual Symposium Symposium documents for Costas Tzoganakis Abstract Presentation
Institute for Polymer Research 27th Annual Symposium
Symposium documents for
Costas Tzoganakis
Abstract
Presentation
PROCESSING OF POLYMERS WITH SUPERCRITICAL CO2
Professor Costas Tzoganakis Department of Chemical engineering
University of Waterloo 200 University Avenue West Waterloo, Ontario N2L 3G1
CANADA E-mail: [email protected]
ABSTRACT
Supercritical fluids (SCF) have recently achieved a widespread attention in the synthesis and
processing of thermoplastic polymers. A supercritical fluid (SCF) is a substance that is
compressed beyond the critical pressure and heated above the critical temperature (see figure). At
these conditions, the vapour and liquid phases become
indistinguishable and the substance behaves as a single
phase. Although the SCF remains as a single phase, its
density can be easily “tuned” from gas to liquid values
merely by changing the pressure of the fluid. While the
density of an SCF is liquid like, the diffusivity and
viscosity are intermediate between the gas and liquid
values. The motivation for using SCFs in polymer
processing stems not just from the environmental impetus for their use as benign solvents.
Sorption of SCFs into polymers results in their swelling and changes in mechanical and physical
properties of these polymers. The higher diffusivities of SCFs provide a means of improving mass
transfer characteristics, while lower viscosities assist in reduced energy for pumping. In polymer
extrusion, SCFs are injected in extruders for the purpose of plasticizing a polymer, reducing the
melt viscosity and increasing diffusion rates. This leads to reduced pumping requirements and
thermal degradation as well as it provides interesting potential for chemical modification in
reactive extrusion operations.
In this presentation, results will be presented from studies in four different areas. In the first one,
the effect of supercritical CO2 on the viscosity and elasticity of polymer melts during extrusion
will be highlighted for polyethylene and polystyrene resins. In the second one, the effect of
supercritical CO2 on the morphology of binary blends will be addressed in view of the influence of
scCO2 on the interfacial tension. In the third study, we will address the role of supercritical CO2 in
reactive extrusion processes by discussing results from grafting and reactive blending experiments.
In the fourth study, the application of scCO2 in an extrusion process for the devulcanization of
rubber crumb will be presented. Finally, current research efforts on the development of a scCO2-
assisted fibre spinning processes will be highlighted.
PROCESSING OF POLYMERSPROCESSING OF POLYMERSWITH SUPERCRITICAL COWITH SUPERCRITICAL CO22
Prof. Costas TzoganakisProf. Costas TzoganakisInstitute for Polymer ResearchInstitute for Polymer Research
Department of Chemical EngineeringDepartment of Chemical EngineeringUniversity of WaterlooUniversity of Waterloo
Waterloo, OntarioWaterloo, OntarioCANADACANADA
•• IntroductionIntroduction•• Supercritical Fluids (Supercritical Fluids (SCFsSCFs) / Applications) / Applications
•• Polymer Extrusion ApplicationsPolymer Extrusion Applications•• Plasticization / Effects on Plasticization / Effects on viscoelasticviscoelastic behaviorbehavior•• Polymer Blending / Interfacial tension and morphologyPolymer Blending / Interfacial tension and morphology•• Reactive ExtrusionReactive Extrusion•• Rubber Rubber DevulcanizationDevulcanization
•• Closing RemarksClosing Remarks•• AcknowledgementsAcknowledgements
OUTLINEOUTLINE
INTRODUCTIONINTRODUCTIONSupercritical Fluids (Supercritical Fluids (SCFsSCFs) / Applications) / Applications
•• vapour and liquid phases are indistinguishablevapour and liquid phases are indistinguishable•• SCF density can be easily SCF density can be easily ““tunedtuned”” from gas to liquid values from gas to liquid values
merely by changing the pressure of the fluidmerely by changing the pressure of the fluid•• density is liquid like / diffusivity and viscosity are density is liquid like / diffusivity and viscosity are
intermediate between the gas and liquid valuesintermediate between the gas and liquid values
INTRODUCTIONINTRODUCTIONSupercritical Fluids (Supercritical Fluids (SCFsSCFs) / Applications) / Applications
Motivation for using sc COMotivation for using sc CO2 2 in polymer extrusionin polymer extrusion
•• Benign solventBenign solvent•• Changes in mechanical and physical properties of polymersChanges in mechanical and physical properties of polymers•• Higher diffusivities improve mass transfer characteristicsHigher diffusivities improve mass transfer characteristics•• Lower viscosities assist in reduced energy for pumpingLower viscosities assist in reduced energy for pumping
ReferencesReferencesA.I. Cooper, A.I. Cooper, J.Mat. Chem.J.Mat. Chem., , 1010, 207, 207--234 (2000).234 (2000).S.G. S.G. KazarianKazarian, , Polymer Science, Ser.C.Polymer Science, Ser.C., , 4242, 78, 78--101 (2000).101 (2000).P.G. P.G. JessopJessop and W. and W. LeitnerLeitner, , ““Chemical Synthesis Using Supercritical FluidsChemical Synthesis Using Supercritical Fluids””, , WeinheimWeinheim, Wiley, Wiley--VCH (1999).VCH (1999).J.L Kendall, D.A. J.L Kendall, D.A. CanelasCanelas, J.L. Young and J.M. , J.L. Young and J.M. DeSimoneDeSimone, , Chem. Rev.Chem. Rev., , 9999, 543 (1999)., 543 (1999).C.A. Eckert, B.L. Knutson and P.G. C.A. Eckert, B.L. Knutson and P.G. DebenedettiDebenedetti, , NatureNature, , 382382, 313 (1996)., 313 (1996).
POLYMER EXTRUSION APPLICATIONSPOLYMER EXTRUSION APPLICATIONS
Extrusion with SCF
Injection of SCF Mixing and dissolution of SCF
On-line measurementof rheological properties
POLYMER EXTRUSION APPLICATIONSPOLYMER EXTRUSION APPLICATIONSPlasticization / Effects on Plasticization / Effects on viscoelasticviscoelastic behaviorbehavior
•• Supercritical COSupercritical CO22 (scCO(scCO22))•• Research StudiesResearch Studies
Capillary, Slit, Wedge Dies
Free Volume Scaling Model
Shear Viscosity
EntranceFlow
Entrance Pressure Drop
Elongational Viscosity
( )2
,,, COCTPγηη &=
POLYMER EXTRUSION APPLICATIONSPOLYMER EXTRUSION APPLICATIONSPlasticization / Effects on Plasticization / Effects on viscoelasticviscoelastic behaviorbehavior
Viscosity of PS/COViscosity of PS/CO22 SolutionsSolutions
Gearbox
Extruder
Positive Displacement
Pump
Valve Valve
Pressure Transducers
Control Panel
Opto 22 Data Acquisition System
Feeder
CO2Cylinder
Wedge Die
SecondaryDie
Thermocouples
50 rpm200 C
Polymer(PS)
Twin-screw Extruder
POLYMER EXTRUSION APPLICATIONSPOLYMER EXTRUSION APPLICATIONSPlasticization / Effects on Plasticization / Effects on viscoelasticviscoelastic behaviorbehavior
Shear Rate (1/s)0.001 0.01 0.1 1 10 100 1000 10000
Visc
osity
(Pa-
s)
10
100
1000
10000
Cone-Plate Rheometer(220oC-260oC)Capillary Rheometer(220oC-260oC)
Wedge Die Rheometer(203oC-271oC)
Viscosity of PS/COViscosity of PS/CO22 SolutionsSolutions
Shear Rate (1/s)30 40 50 60 70 8090 200 300 400100
Visc
osity
(Pa-
s)
200
300
400
500600700800900
2000
100
1000
PS viscosity dataPS viscosity data PS/COPS/CO22 viscosity dataviscosity data
POLYMER EXTRUSION APPLICATIONSPOLYMER EXTRUSION APPLICATIONSPlasticization / Effects on Plasticization / Effects on viscoelasticviscoelastic behaviorbehavior
Viscosity of PS/COViscosity of PS/CO22 SolutionsSolutions
η0γ
1e+1 1e+2 1e+3 1e+4 1e+5 1e+6 1e+7 1e+8 1e+9
η/η
0
1e-4
1e-3
1e-2
1e-1
1e+0
Experimental values2nd order C-C model
POLYMER EXTRUSION APPLICATIONSPOLYMER EXTRUSION APPLICATIONSPlasticization / Effects on Plasticization / Effects on viscoelasticviscoelastic behaviorbehavior
Viscosity of PS/COViscosity of PS/CO22 SolutionsSolutions
- Dissolution of 1.0 wt% of CO2 ≈ Decreasing pressure by 9.8 MPa- T-P and T-C interactions depend on the absolute temperature.
Increasing Temperature
Increasing CO2 content
Decreasing Pressure
200°C 210°C
260°C 270°C
1.35 wt%
0.9 wt%
13.3 MPa
8.7 MPa
POLYMER EXTRUSION APPLICATIONSPOLYMER EXTRUSION APPLICATIONSPlasticization / Effects on Plasticization / Effects on viscoelasticviscoelastic behaviorbehavior
Entrance Pressure Drop of PS/COEntrance Pressure Drop of PS/CO22 SolutionsSolutions
18
1
52 24 24 24 24 52PT #1 PT #2 PT #3 PT #4 PT #5
TS
Flow
PT — Pressure TransducerTS — Temperature Sensor
Die width is 22All dimensions are in mm
POLYMER EXTRUSION APPLICATIONSPOLYMER EXTRUSION APPLICATIONSPlasticization / Effects on Plasticization / Effects on viscoelasticviscoelastic behaviorbehavior
Entrance Pressure Drop of PS/COEntrance Pressure Drop of PS/CO22 SolutionsSolutions
Pressure Profile within the Slit Die
∆ Pent
Pupstream
P
Flow Direction
2nd dieslit dieupstream
ionextrapolatupstreament PPP −=∆
POLYMER EXTRUSION APPLICATIONSPOLYMER EXTRUSION APPLICATIONSPlasticization / Effects on Plasticization / Effects on viscoelasticviscoelastic behaviorbehavior
Entrance Pressure Drop of PS/COEntrance Pressure Drop of PS/CO22 SolutionsSolutions
Upstream Pressure, MPa15 20 25 30 35 40
Ent
ranc
e P
ress
ure
Dro
p, M
Pa
0.1
1.0
200 oC, 0% CO2
210 oC, 0% CO2
220 oC, 0% CO2
220 oC, 2% CO2
220 oC, 4% CO2
γapp = 220 s-1
POLYMER EXTRUSION APPLICATIONSPOLYMER EXTRUSION APPLICATIONSPlasticization / Effects on Plasticization / Effects on viscoelasticviscoelastic behaviorbehavior
Entrance Pressure Drop of PS/COEntrance Pressure Drop of PS/CO22 SolutionsSolutions
Extension Rate, s-1
100 101 102
Ext
ensi
onal
Vis
cosi
ty, P
a.s
104
105
0% CO2
4% CO2
T = 220 oCPupstream = 27.6 MPa
POLYMER EXTRUSION APPLICATIONSPOLYMER EXTRUSION APPLICATIONSPlasticization / Effects on Plasticization / Effects on viscoelasticviscoelastic behaviorbehavior
Entrance Pressure Drop of PS/COEntrance Pressure Drop of PS/CO22 SolutionsSolutions
• Entrance pressure drop of PS and PS/CO2 increases with upstream pressure
• CO2 decreases the entrance pressure drop of PS melts. Entrance pressure drop, plotted versus wall shear stress, coincide on a master curve
• CO2 decreases both shear and extensional viscosities of PS
POLYMER EXTRUSION APPLICATIONSPOLYMER EXTRUSION APPLICATIONSPolymer Blending / Interfacial tension and morphologyPolymer Blending / Interfacial tension and morphology
PS/LDPE BlendsPS/LDPE Blends
Gearbox
Extruder
Positive Displacement
Pump
Valve Valve
Pressure Transducers
Control Panel
Opto 22 Data Acquisition System
Feeder
CO2Cylinder
Wedge Die
SecondaryDie
Thermocouples
50 rpm200 C
PolymerA+B
Twin-screw Extruder
POLYMER EXTRUSION APPLICATIONSPOLYMER EXTRUSION APPLICATIONSPolymer Blending / Interfacial tension and morphologyPolymer Blending / Interfacial tension and morphology
Shear Rate (1/s)
Visc
osity
(Pa-
s)
10 100 1000100
1000
10000
without CO2
2 wt% CO23 wt% CO24 wt% CO2
Shear Rate (1/s)
Visc
osity
(Pa-
s)
10 100 1000
100
1000
without CO2
3 wt% CO25 wt% CO27 wt% CO2
PS LDPE
PS/LDPE BlendsPS/LDPE Blends
POLYMER EXTRUSION APPLICATIONSPOLYMER EXTRUSION APPLICATIONSPolymer Blending / Interfacial tension and morphologyPolymer Blending / Interfacial tension and morphology
PS/LDPE BlendsPS/LDPE Blends
0 wt% (x1000)
Schematic
cellcell
cell
0 wt% (x500) 3wt% (x1000)
Schematic
3 wt% (x5000)
PE/PS=80/20
POLYMER EXTRUSION APPLICATIONSPOLYMER EXTRUSION APPLICATIONSPolymer Blending / Interfacial tension and morphologyPolymer Blending / Interfacial tension and morphology
0 wt% CO2 4 wt% CO2PS/LDPE=60/40
PS/LDPE BlendsPS/LDPE Blends
POLYMER EXTRUSION APPLICATIONSPOLYMER EXTRUSION APPLICATIONSPolymer Blending / Interfacial tension and morphologyPolymer Blending / Interfacial tension and morphology
0 wt% CO2 4 wt% CO2PS/LDPE=50/50
PS/LDPE BlendsPS/LDPE Blends
POLYMER EXTRUSION APPLICATIONSPOLYMER EXTRUSION APPLICATIONSPolymer Blending / Interfacial tension and morphologyPolymer Blending / Interfacial tension and morphology
PS/LDPE BlendsPS/LDPE Blends
mη
Γ
γ&
dη
Γ
POLYMER EXTRUSION APPLICATIONSPOLYMER EXTRUSION APPLICATIONSPolymer Blending / Interfacial tension and morphologyPolymer Blending / Interfacial tension and morphology
PS/LDPE BlendsPS/LDPE Blends
(a) t = 0.5 hr (b) t = 3 hr (c) t = 6 hr
(f) t = 9 hr(e) t = 8 hr(d) t = 7 hr
POLYMER EXTRUSION APPLICATIONSPOLYMER EXTRUSION APPLICATIONSPolymer Blending / Interfacial tension and morphologyPolymer Blending / Interfacial tension and morphology
Time (hr)0 1 2 3 4 5 6 7 8 9
IFT
(mN
/m)
4.0
4.5
5.0
5.5
6.0
6.5
7.0
7.5
8.0
Necking DropStable Drop
PS/LDPE BlendsPS/LDPE Blends
POLYMER EXTRUSION APPLICATIONSPOLYMER EXTRUSION APPLICATIONSPolymer Blending / Interfacial tension and morphologyPolymer Blending / Interfacial tension and morphology
PS/LDPE BlendsPS/LDPE Blends
CO2 Pressure (MPa)0 4 8 12 16 20
IFT
(mN
/m)
4
5
6
7
200 oC220 oC
Pc
POLYMER EXTRUSION APPLICATIONSPOLYMER EXTRUSION APPLICATIONSReactive ExtrusionReactive Extrusion
Grafting of Grafting of MahMah on PPon PP
CH
CH 3R orI
C
CH3
grafting
OO O
..
C
O
O
O
.CH 3
.
.RH
Rhydrogentransfer
C
O
O
O
.CH3 CH3
O
O
O
C
POLYMER EXTRUSION APPLICATIONSPOLYMER EXTRUSION APPLICATIONSReactive ExtrusionReactive Extrusion
Grafting of Grafting of MahMah on PPon PP
Die
CO2 2
Cylinder
PP/MAh Peroxide Solution
POLYMER EXTRUSION APPLICATIONSPOLYMER EXTRUSION APPLICATIONSReactive ExtrusionReactive Extrusion
Grafting of Grafting of MahMah on PPon PP
MAh Content (wt. %)
0.30 0.40 0.50 0.60
Mel
t Flo
w In
dex
(g/1
0 m
in)
10
20
30
40
50 2 % MAh Level without CO 2
2 % MAh Level with CO 2
4 % MAh Level without CO 2
4 % MAh Level with CO 2
T = 190 CLoad = 1.2 kg
POLYMER EXTRUSION APPLICATIONSPOLYMER EXTRUSION APPLICATIONSReactive ExtrusionReactive Extrusion
Interfacial Reaction (PEInterfacial Reaction (PE--MahMah / PA/ PA--6)6)
O OO
NH2(CH2)5CNHO
+
– H2O
O ON
(CH2)5CNHO
cyclic imide
POLYMER EXTRUSION APPLICATIONSPOLYMER EXTRUSION APPLICATIONSReactive ExtrusionReactive Extrusion
Interfacial Reaction (PEInterfacial Reaction (PE--MahMah / PA/ PA--6)6)
CO2 Concentration, wt%0 1 2 3 4
MA
Con
vers
ion,
%
0
20
40
60
80
100
30.0 / 00.0 / 70
47.5 / 47.5 / 5
45.0 / 45.0 / 10
40.0 / 40.0 / 20
PE-MA / LDPE / PA-6
POLYMER EXTRUSION APPLICATIONSPOLYMER EXTRUSION APPLICATIONSReactive ExtrusionReactive Extrusion
Rubber Rubber DevulcanizationDevulcanization
SY
SY
CO2
Vulcanized rubber Crosslink
POLYMER EXTRUSION APPLICATIONSPOLYMER EXTRUSION APPLICATIONSReactive ExtrusionReactive Extrusion
Rubber Rubber DevulcanizationDevulcanization
Gearbox
Extruder
Positive Displacement
Pump
Valve Valve
Pressure Transducers
Control Panel
Opto 22 Data Acquisition System
Feeder
CO2Cylinder
Wedge Die
SecondaryDie
Thermocouples
50 rpm200 C
POLYMER EXTRUSION APPLICATIONSPOLYMER EXTRUSION APPLICATIONSReactive ExtrusionReactive Extrusion
Rubber Rubber DevulcanizationDevulcanization
Soxhlet extraction
Two-step process to separate gelAcetone : Remove the low molecular weight contentToluene : Extract the sol content
Extrudate Soluble Gel
POLYMER EXTRUSION APPLICATIONSPOLYMER EXTRUSION APPLICATIONSReactive ExtrusionReactive Extrusion
Rubber Rubber DevulcanizationDevulcanization
Rubber flow rate (g/min) – CO2 concentration (wt%)Powder 15-1% 15-2% 15-3% 30-1% 30-2% 30-3%
Wei
ght p
erce
nt o
f who
le s
ampl
e
0.00
0.05
0.10
0.15
0.20
0.25
0.30
Circles: Screw 1Triangles: Screw 2
Soluble content
Sol content
Low molecular weight content
SBR80 / 250 oC
CLOSING REMARKSCLOSING REMARKS
• Highlights from our research work on polymer extrusion with supercritical CO2 have been presented
• Potential innovative applications are numerous
• Our current efforts are focused on membrane and fiber formation as well as on block copolymer and TPV preparation
ACKNOWLEDGEMENTSACKNOWLEDGEMENTS
Funding
Natural Sciences and Engineering Research Council of Canada (NSERC)Materials Manufacturing Ontario (MMO)DuPont Canada Inc.
Researchers
Dr. Minhee LeeDr. Anle XueDr. S. ZhuMs. Beth DorschtMs. Joy Zhang