ultrasonic treatment of pen/lcp blends during extrusion march27 08.pdfultrasonic treatment of...
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Ultrasonic treatment of Ultrasonic treatment of PEN/LCP blends PEN/LCP blends during extrusionduring extrusion
by
Kaan Gunes and A. I. Isayev
Presented at
Conference on Graduate and Undergraduate ResearchThe University of Akron
March 27, 2008
22
OutlineOutline
� Objectives
� Liquid crystalline polymers (LCP)
� Blends of LCP/thermoplastics
� Compatibilization of LCP blends
� Effect of Ultrasound
� Materials
� Ultrasound assisted extrusion
� Experimental methods
� Results and discussion
� Summary
33
ObjectivesObjectives
Problem:Problem:� Blends of wholly aromatic LCPs with thermoplastics not fully
utilized� Optimum degree of compatibilization necessary to preserve
fibrillar LCP structure and improve interfacial adhesion
Research Objectives: Research Objectives: � To design a new ultrasonic single screw extrusion process to
effectively mix blends and induce in situ compatibilization at low residence times
� To study the effect of processing parameters in ultrasonic extrusion on PEN/LCP blends in order to create in situ polymer composites with enhanced mechanical properties
44
Liquid Crystalline PolymersLiquid Crystalline Polymers
Lyotropic: solution processible
e.g. poly(p-phenylene-terephtalamide)
C
O
C
O
N
H
N
H
n
Origin of liquid crystallinity
� Rod like structure� Mesogenic groups in backbone/side chains
Greater rigidityMelting temperature ↑
Stiffness and strength ↑
Processibility ↓
Thermotropic: melt processible
HBA/PET
HBA/HNA
Kevlar ®
1 Wissbrun, K. F., Journal of Rheology, 25(6), 619-662 (1981)
e.g.
55
LCP/Thermoplastic BlendsLCP/Thermoplastic Blends
Desirable properties of LCP blends� High tensile strength and modulus� Toughness� Dimensional stability� Chemical resistance� Low gas permeability
To achieve these properties:� Fine uniform fibrils� Good interfacial adhesion
In situ fiber reinforced composites�Low melt viscosity�LCP fibrillar structure�Fibrils created by elongation flows:
•Fiber spinning / injection molding
LCP fibrils in fiber spinning2
2 Sawyer, L.C. and Jaffe M., Journal of Materials Science, 21 (6), 1897-1913 (1986)
66
Application of LCPs and Application of LCPs and their blendstheir blends
� Typical applications of LCPs, and their blends include3
� Electronics interconnects
� Medical technology
� Automotive engineering
� Chemical process equipment
� Fuel cells
� Weathering-resistant fibers
� Packaging
3 Vectra LCP Application Database, Ticona.com
77
Compatibilization of LCP/Polyester Compatibilization of LCP/Polyester BlendsBlends
Traditional methods:�Addition of block copolymers�Transesterification by internal mixing or annealing for long times
OO
OHA
C
∆, ))))
B
O O
OH
A
B
O
Transesterification of polyesters
Heat / Mechanochemistry
Generation of copolymers through transesterification in the interface of polymer blends promotes compatibility through improved interfacial adhesion4
4 Porter, R. S., Wang, L-H, Polymer 33(10), 2019-2030 (1992)
88
Mechanism of UltrasoundMechanism of Ultrasound
Ultrasonic cavitation� High amplitude alternating pressure created by ultrasound.
� Oscillating forces nucleate bubbles at sites of material defects
5 Price, G. J. in “New Methods of Polymer Synthesis,”Edbon, J. R., Eastmond, G, Eds.,Chapman Hall: NY (1995)
Defects can be:
•Dissolved gasses
•Cryst. lattice imperfections
•Polymer/filler interface
•Immiscible blend interface
Mechanism of Cavitation5
99
In situ Ultrasonic CompatibilizationIn situ Ultrasonic Compatibilization
Ultrasonic cavitation in polymer melts
� Ultrasonic cavitation in melts can lead to� Chain scission� Formation of reactive end groups� Formation of interfacial graft/block copolymers� Creation of high MW species� Mn ↓, Mw ↑
� Recorded improvements in� Tensile strength� Elongation at break� Young’s modulus� Toughness
� Benefits:� Single step, continuous and fast operation, can be scaled up� Residence time is ultrasonic zone controlled
6Gunes, K., Isayev, A. I., ANTEC-SPE, 1533-1537 (2007)7 Lin, H., Isayev, A. I., Journal of Applied Polymer Sci., 102(3), 2643-2653 (2006) 8 Isayev, A. I., Ghose, S. in Rubber Recycling, De, S. K., Isayev, A. I., Khait, K eds., Boca Raton, FL: Taylor & Francis/CRC Press (2005)
Studied blends include: 6,7,8
�PET/LCP�PA6/PP�PP/NR�PP/EPDM�PP/EPDM�HDPE/NR�HDPE/EPDM�HDPE/SBR
1010
MaterialsMaterials
LCP: Vectra A950, Ticona (Tm=275oC)� Wholly aromatic copolyester containing 73% HBA and 27% HNA
PEN: VFR 40046, Shell Chemical Company (Tm=275oC)
1111
The Ultrasonic ExtruderThe Ultrasonic Extruder
Screw flightsScrew flightsScrew flightsScrew flights
•7 s residence time
•Frequency: 20 KHz
•Amplitude: 0-10 µm
PEN and PEN/LCP blends:
•260°C Feed, 300°C other zones
•10 rpm screw speed
•1 kg/hr flood feeding
Pure LCP was processed at 260°C feed, 285°C other zones, 15 rpm, 1 kg/hr flood feeding6
1212
Animation of Animation of copolymer copolymer formation in formation in ultrasonic extrusionultrasonic extrusion
1313
Experimental MethodsExperimental Methods
Injection molding: Van Dorn 55 HP-2.8F� Impact (ASTM D 256-05) & mini tensile bars (ASTM D 638-03)� 260°C Feed/ 285°C other zones; 27oC mold, 150 mm/s, 55 ton Clamping force, 4 MPa holding
pressure for 5 s, 25 s cooling
Rheological measurement: RH7 Advanced Capillary Rheometer, Bohlin Instruments� 300oC, 1:24 die, Ф=1 mm. Apparent shear rate: 20-2877 s-1 in 10 logarithmic steps, 69 MPa PTMorphological studies: Hitachi S-2150 SEM � Cryofractured injection molded mini tensile bars, skin-core micrographsMechanical tests:� Instron 5567 tensile tester
� 10 kN load; 5 mm/min crosshead speed; extensometer with 7.62 mm gauge length� Average of 6 samples
� Izod impact tester (Testing Machines Inc.) � Unnotched; Blends: 907 g load, LCP and PEN: 4536 g load� Average of 20 samples
Dynamic mechanical thermal analysis:� Elmer Pyris Diamond
� Oscillatory tension, frequency 1 Hz, Heating 20 to 150oC at 2oC/min
1414
Results and Discussion
1. Process characteristics2. Rheology3. Mechanical properties4. Microscopic Analysis
1515
Process CharacteristicsProcess CharacteristicsPressure (PEN & blends)
Pressure ↓ w/ ultrasonic amplitude due to:
Acoustic cavitation in melt:
�Permanent and thixotropicviscosity change
�Possible slip of polymer melt along the solid surface
Pressure greater in blends:
�Greater viscosity of blends with and without treatment for the low shear rate in extrusion of ~10 s-1
�Higher pressure at 7.5 µm indicates less degradation with presence of LCP
Pressure before ultrasonic treatment zone vs. ultrasonic amplitude
Ultrasonic amplitude (µm)
-2 0 2 4 6 8 10 12
Pre
ssu
re b
efo
re u
ltras
ou
nd z
one
(M
Pa)
0
1
2
3
4
5
6
PEN 90/10 PEN/LCP 80/20 PEN/LCP
1616
Process CharacteristicsProcess CharacteristicsUltrasonic Power Consumption (PEN & blends)
�Power consumption ↑ with ultrasonic amplitude
�Similar effect of ultrasound on PEN and blends
Ultrasonic power consumption vs. ultrasonic amplitude
Ultrasonic amplitude (µm)
0 2 4 6 8 10
Ultr
aso
nic
po
wer
co
nsu
mpt
ion
(W
)
0
50
100
150
200
250
PEN 90/10 PEN/LCP 80/20 PEN/LCP
1717
Process CharacteristicsProcess CharacteristicsUltrasonic Power Consumption & Pressure for LCP 6
Ultrasonic Amplitude
0 2 4 6 8 10
Pre
ssur
e (M
Pa)
0.8
1.0
1.2
1.4
1.6
1.8
2.0
2.2
2.4
2.6
2.8
Ultr
aso
nic
Po
wer
Con
sum
ptio
n (
W)
0
20
40
60
80
100
120
140
160
180
200
PressureUltrasonic power consumption
�Pressure greater due to processing at 15 RPM
�Pressure decreases at 5 µm and is similar at higher amplitudes
�Similar change in power consumption as in PEN and blends
Values shifted along abscissa for clarity
6Gunes, K., Isayev, A. I., ANTEC-SPE, 1533-1537 (2007)
1818
ViscosityViscosityPEN and LCPPEN and LCP
γ& γ&
γ&
•Viscosity of PEN ↓ w/ ultrasonic treatment � Degradation of PEN•Degradation of virgin PEN by extrusion without treatment•PEN: Newtonian, LCP: shear thinning•Less significant effect of extrusion and ultrasonic treatment on viscosity of LCP•Low �LCP viscosity highest at 7.5 µm. High �overlap, oriented domains.
Apparent shear rate (s-1)
10 100 1000 10000
App
aren
t vis
cosi
ty (
Pa
*s)
10
100
1000
PEN 0 µm PEN 5 µm PEN 7.5 µm PEN 10 µmPEN virgin
Apparent shear rate (s-1)
10 100 1000A
pp
are
nt V
isco
sity
(P
a*s
)10
100
LCP 0 µm LCP 5 µm LCP 7.5 µm LCP 10 µm LCP virgin
γ& γ&
1919
ViscosityViscosityPEN/LCP blendsPEN/LCP blends
Apparent shear rate (s-1)
10 100 1000
Ap
par
ent V
isco
sity
(P
a*s)
10
100
1000
90/10 PEN/LCP 0 µm 90/10 PEN/LCP 5 µm 90/10 PEN/LCP 7.5 µm 90/10 PEN/LCP 10 µm
Apparent shear rate (s-1)
10 100 1000
Ap
pare
nt V
isco
sity
(P
a*s
)
10
100
1000
80/20 PEN/LCP 0 µm 80/20 PEN/LCP 5 µm 80/20 PEN/LCP 7.5 µm 80/20 PEN/LCP 10 µm
•Viscosity of 80/20 PEN/LCP > that of 90/10 PEN/LCP•Blend viscosities do not decrease until 10 µm � different effect than for PEN•Blend more shear thinning with increasing LCP content•Slight increase in viscosity of 90/10 PEN/LCP with treatment at 5 µm
2020
DMADMAPENPEN
Storage (A) and loss (B) modulus vs. temperature for PEN without and with ultrasonic treatment
Temperature (oC)
60 80 100 120 140
E' (
Pa)
1e+6
1e+7
1e+8
1e+9
1e+10
PEN 7.5 µm
PEN 10 µm
PEN 5 µm
Virgin PEN
PEN 0 µm
(A)
Temperature (oC)
60 80 100 120 140
E"
(Pa)
1e+6
1e+7
1e+8
1e+9
PEN 7.5 µm
PEN 10 µm
PEN 5 µm
Virgin PEN
PEN 0 µm
(B)
2121
DMADMAPEN tan PEN tan δδ
Tg of PEN (tan δ peaks)
tanδ (oC) PENVirgin 1300um 1315um 1307.5um 12910um 126
Temperature (oC)
60 80 100 120 140
tan
δ
0.01
0.1
1
10
PEN 7.5 µm
PEN 10 µm
PEN 5 µm
Virgin PEN
PEN 0 µm
Severe degradation of PEN at 10 µm
2222
Mechanical PropertiesMechanical PropertiesTensile strength & Young’s modulus
�Tensile strength and Young’s moduli ↑ w/ LCP content. �With ultrasonic treatment, increase for 90/10 PEN/LCP at 7.5 µm and decrease for PEN and blends at 10 µm
Ultrasonic Amplitude (µm)
0 2 4 6 8 10
Ten
sile
str
engt
h (
MP
a)
20
40
60
80
100
120
140
160
180
200
220
Pure PEN 90/10 PEN/LCP 80/20 PEN/LCP Virgin PEN
Ultrasonic Amplitude (µm)
0 2 4 6 8 10
Yo
un
g's
mo
du
lus
(GP
a)
0
2
4
6
8
10
Pure PEN 90/10 PEN/LCP 80/20 PEN/LCPVirgin PEN
2323
�Elongation ↓ with LCP content and at 10 µm for PEN and blends� Impact strength more sensitive to polymer degradation� Improvement in impact strength at 7.5 µm for 90/10 blends.
Mechanical PropertiesMechanical PropertiesElongation & Impact strength
Ultrasonic amplitude (µm)
0 2 4 6 8 10
Elo
ngat
ion
at y
ield
(%
)
1
2
3
4
5
6
7
8
9
Pure PEN 90/10 PEN/LCP 80/20 PEN/LCP Virgin PEN
Ultrasonic Amplitude (µm)
-2 0 2 4 6 8 10 12
Imp
act s
tre
ng
th (
kJ/m2 )
0
20
40
60
80
100
120
140
160
180
200
Unextruded PENPure PEN 90/10 PEN/LCP 80/20 PEN/LCP
2424
Mechanical PropertiesMechanical PropertiesEffect of ultrasound on LCP 5
� Impact strength 261 kJ/m2 untreated LCP ↑ to 346 kJ/m2 at 7.5 µm. � Tensile strength 262 MPa untreated LCP ↑ to 273 MPa at 7.5 µm. � Ultrasound could have led to structural changes of LCP melt
Ultrasonic Amplitude ( µµµµm)
0 2 4 6 8 10
Impa
ct S
treng
th (kJ
/m2 )
220
240
260
280
300
320
340
360
Ten
sile
Stre
ngth
(M
Pa)
240
250
260
270
280
You
ng's
Mod
ulus
(G
Pa)
8.0
8.5
9.0
9.5
10.0
10.5
11.0
Young's modulus
Impact strength
Tensile strength
5Gunes, K., Isayev, A. I., ANTEC-SPE, 1533-1537 (2007)
2525
Microscopic AnalysisMicroscopic Analysis
�LCP droplets in core&fibrils in skin—Larger at 10 µm due to low η of PEN
90/10 7.5 µm 90/10 10 µm90/10 0 µm
Skin
Core
2626
Microscopic AnalysisMicroscopic Analysis
80/20 7.5 µm 80/20 10 µm80/20 0 µm
Skin
Core
�LCP droplets/fibrils in core/skin larger in 80/20 than in 90/10 and also at 10 µm
2727
Microscopic AnalysisMicroscopic AnalysisInterfacial thicknessInterfacial thickness
Ultrasonic Amplitude (µm)
0 2 4 6 8 10 12
Inte
rfac
ial t
hick
ness
( µm)
0.04
0.06
0.08
0.10
0.12
0.14
90-10 PEN-LCP80-20 PEN-LCP
90/10 PEN/LCP 7.5 µm
�Decrease in interfacial thickness suggests improved interfacial adhesion through possible copolymerization reactions.
2828
SummarySummary
�The novel ultrasonic extrusion method has been used to study compatibilization of PEN/LCP blends with the possibility of improving their mechanical properties.
�Ultrasonic treatment leads to competition between fibrillation and compatibilization
�PEN viscosity decreases with extrusion and with ultrasonic treatment, its Tg is lower with treatment at an amplitude of 10 µm
�Slight increase in LCP viscosity occurs with treatment at 7.5 µm, but otherwise there is little effect of ultrasound on its viscosity.
�Increases in Young’s modulus, tensile strength and impact strength of 90/10 PEN/LCP suggest improved interfacial adhesion with minimal change in LCP fibrillation through possible copolymerization during ultrasonic treatment
2929
Thank you for your attention