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The 228The 228thth ACS National MeetingACS National MeetingPhiladelphia, PAPhiladelphia, PA
August 22August 22--26, 200426, 2004
D. MarchantD. Marchant11, J.H. Koo, J.H. Koo22, R.L. Blanski, R.L. Blanski33, , E.H. WeberE.H. Weber33, P.N. Ruth, P.N. Ruth11, A. Lee, A. Lee44, and C.E. Schlaefer, and C.E. Schlaefer33
1 1 Air Force Research Laboratory, Propulsion Materials, ERC Inc., 1Air Force Research Laboratory, Propulsion Materials, ERC Inc., 10 0 Saturn Blvd., Bldg 8451, Edwards AFB, CA 93524Saturn Blvd., Bldg 8451, Edwards AFB, CA 93524
22 The University of Texas at Austin, Department of Mechanical The University of Texas at Austin, Department of Mechanical EngineeringEngineering--C2200, Austin, TX 78712C2200, Austin, TX 78712
3 3 Air Force Research Laboratory, Propulsion Materials, AFRL/PRSM, Air Force Research Laboratory, Propulsion Materials, AFRL/PRSM, 10 Saturn Blvd., Bldg 8451, Edwards AFB, CA 9352410 Saturn Blvd., Bldg 8451, Edwards AFB, CA 93524
44Michigan State University, Department of Chemical Engineering anMichigan State University, Department of Chemical Engineering and d Materials Science, 2527 Engineering Bldg, East Lansing, MI 48824Materials Science, 2527 Engineering Bldg, East Lansing, MI 48824
Flammability and Thermophysical Flammability and Thermophysical Characterization of Thermoplastic Elastomer Characterization of Thermoplastic Elastomer
NanocompositesNanocomposites
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1. REPORT DATE AUG 2004 2. REPORT TYPE
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4. TITLE AND SUBTITLE Flammability and Thermophysical Characterization of ThermoplasticElastomer Nanocomposites
5a. CONTRACT NUMBER F04611-99-C-0025
5b. GRANT NUMBER
5c. PROGRAM ELEMENT NUMBER
6. AUTHOR(S) D Marchant; J Koo; R Blanski; E Weber; P Ruth
5d. PROJECT NUMBER 4847
5e. TASK NUMBER 0249
5f. WORK UNIT NUMBER
7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES) ERC, Inc,AFRL/PRS,10 E. Saturn Blvd.,Edwards AFB,CA,93524
8. PERFORMING ORGANIZATION REPORT NUMBER E04-082
9. SPONSORING/MONITORING AGENCY NAME(S) AND ADDRESS(ES) 10. SPONSOR/MONITOR’S ACRONYM(S)
11. SPONSOR/MONITOR’S REPORT NUMBER(S)
12. DISTRIBUTION/AVAILABILITY STATEMENT Approved for public release; distribution unlimited
13. SUPPLEMENTARY NOTES
14. ABSTRACT N/A
15. SUBJECT TERMS
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37
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Standard Form 298 (Rev. 8-98) Prescribed by ANSI Std Z39-18
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Collaborators
• AFRL/PRSM
– S. Barker
– M. Fernandez
– T. Jones
• 21st Century Polymers
– G. Wissler
• Texas A&M University
– Z.P. Luo
• Michigan State University
– M. Namani
• Southern Clay Products
– D. Hunter
• Applied Sciences Inc.
– J. Glasglow
• Omega Point Laboratories
– S. Romo
Financial Support: Air Force Office of Scientific Research
Air Force Research Laboratory, Propulsion Directorate
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OUTLINEINTRODUCTION
EXPERIMENTAL APPROACH
WHAT IS NANOTECHNOLOGY?
SELECTION OF MATERIALS
OVERVIEW OF NANOPARTICLES
DISCUSSION OF RESULTS
• Processing of Materials
• Microstructure Analyses of Pre-Test Materials
• Thermophysical Properties
• Flammability Properties
• Microstructure Analyses of Post-Test Materials
SUMMARY AND CONCLUSIONS
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INTRODUCTION
The introduction of inorganic nanomaterials as additives into polymer systems has resulted in polymer nanostructured materials exhibiting multifunctional, high performance polymer characteristics beyond what traditional polymer composites possess
Selective thermoplastic elastomers have been used with montmorillonite organoclays, POSS®, carbon nanofibers to develop a flame resistant material
Thermophysical and flammability properties of these polymer nanocomposites will be presented
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EXPERIMENTAL APPROACH
A 30 mm Werner Pfleider co-rotating twin screw extruder was used and was configured for a wide variety of materials for polymer melt blendingThe extruder length/diameter (L/D) ratio can be varied from 21 to 48, with options of multiple feeds and ventsThe energy profile of the screw is optimized to meet the needs of the target productLong residence time screw designs are available for reactive productsVarieties of feeders are available to accommodate the material handling characteristics of the raw materialsStrand pelletization with low temperature chilled fluids allows processing of very soft or rubbery materialsApproximately 5 lbs of each formulation were producedSpecimens were injection molded in various configurations for measuring flammability and thermophysical properties
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What “Nano” Really Means?
10 000nmhuman red blood cells
Courtesy of Vaia
bacteria E.coli1 000nm
QD 7nm.
Q-rods 30nm 10:1 aspect ratio
virus 100nm
polymer 40nm
A nanometer (nm) is one billionth of a meter (10-9 m) about 4 times the diameter of an atom
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Nanocompositel = 1 nm
10 nm
Nanostructured MaterialsUniqueness
Ultra-large interfacial area per volumeHigh fraction interfacial (interphase)
materialShort distances between components
NanoPolymer NanoInorganic
Characteristics
Reinforcement1>>h
lInterfacial Region
gRz <<0
Macrocompositel = 1 µm
BulkgRz >
10 µm
HierarchicalMorphology
ControlNano, Meso, Micro
Courtesy of Vaia
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10 µm
Novamet 60 and ASI Nanotubes (inset shows ~500 tubes)
Alexander et al.
Micro versus Nano
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SELECTION OF MATERIALS
Thermoplastic Elastomers – PELLETHANE™ 2102-90A thermoplastic polyurethane elastomer (TPU) is a polyester polycaprolactone elastomer manufactured by Dow Chemical. Its typical applications include seals, gaskets, belting, and others.Montmorillonite Nanoclays – Cloisite® 30B is a surface treated montmorillonite [Tallow bishydroxyethyl methyl, T(EOH)2M] manufactured by Southern Clay ProductsCarbon Nanofibers (CNFs) – CNFs are a form of vapor-grown carbon fibers, which is a discontinuous graphitic filament produced in the gas phase from the pyrolysis hydrocarbons manufactured by Applied Sciences. PR-19-PS CNF and PR-24-PS CNF were used.Polyhedral Oligomeric Silsesquioxane (POSS®) – Representing a merger between chemical and filler technologies, POSS nanostructured materials can be used as multifunctional polymer additives, acting simultaneously as molecular level reinforcements, processing aids, and flame retardants. Hybrid Plastics’ SO1458 Trisilanolphenyl-POSS® (C42H38O12Si7) was used.
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Montmorillonite Clays
Na1/3(Al5/3Mg1/3)Si4O10(OH)2
Na+
Octahedral alumina layer Tetrahedral
silicate layer
Layer thickness is 0.96 nm
11DISTRIBUTION A. Approved for public release; distribution unlimited
Nanocomposite Classification
U n m ix e d
D
E x fo lia te d
In te rc a la te d
d
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Processing Challenge of Nanoclay
8µm Particle >1 Million Platelets
Courtesy of Southern ClayProducts
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Dispersion Mechanism
8 µm Particle~1MM Platelets
Chemistry Chemistry/Processing Processing
Dispersion
Dispersion
Tactoids/Intercalants
Partial Dispersion
Tactoids/Intercalants
Tactoids/Intercalants
Tactoids/Intercalants
Courtesy of Southern ClayProducts
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Carbon Nanofibers
Carbon nanofibers (CNFs) are a unique form of vapor-grown carbon fiber that bridges the gap in physical properties between larger, conventional PAN or pitch-based carbon fibers (5 to 10 µm in diameter) and smaller single-wall and multi-wall carbon nanotubes (1 to 10 nm in diameter)
Pyrograf®-III is a very fine, highly graphitic carbon nanofiber manufactured by Applied Sciences Inc. that has an average diameter between 70 to 200 nm and a typical length of 50 to 100 µm
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Vapor-Grown Carbon Fiber
Pyrograf-III Carbon Nanofiber Pyrograf-I VGCF
Courtesy of Applied Sciences
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Pyrograf®-III TEMs
PR-24-PS with an average diameter of 65 nm
Courtesy of Applied Sciences
PR-19-PS with an average diameter of 128 nm
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Polyhedral OligomericSilsesquioxane (POSS®)
Represents a merger between chemical and filler technologies, POSS® nanostructured materials can be used as multifunctional polymer additives, acting simultaneously as molecular level reinforcements, processing aids, and flame retardants
They have two unique structural features: (1) the chemical composition is a hybrid, intermediate (RSiO1.5) between that of silica (SiO2) and silicones (R2SiO); (2) POSS® molecules are nanoscopic in size, ranging from approximately 1 to 3 nm
18DISTRIBUTION A. Approved for public release; distribution unlimited
Si
Si
O
O
Si
Si
Si
Si
O
O
O
O
SiO
Si
O
OO
OO
R R
R
R
R
R
R X
Anatomy of a POSS® Molecule
May possess one or moreMay possess one or morefunctional groups suitable forfunctional groups suitable for
polymerization or graftingpolymerization or grafting
Thermally and chemicallyThermally and chemicallyrobust hybridrobust hybrid
(organic(organic--inorganic) frameworkinorganic) framework
Nanoscopic in size with anNanoscopic in size with anSiSi--Si distance of 0.5 nmSi distance of 0.5 nm
and a Rand a R--R distance of 1.5 nmR distance of 1.5 nm
Nonreactive organic (R)Nonreactive organic (R)groups for solubilizationgroups for solubilization
and compatibilizationand compatibilization
Precise threePrecise three--dimensional structure for molecular leveldimensional structure for molecular levelreinforcement of polymer segments and coilsreinforcement of polymer segments and coils
Courtesy of Hybrid Plastics
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Key Aspects of POSS®Technology
Hybrid (inorganic/organic) CompositionHybrid (inorganic/organic) Composition Nanostructured™ Chemical ReinforcementNanostructured™ Chemical Reinforcement
POSSPOSS®® technology does not technology does not require manufacturers to require manufacturers to retool or alter existing retool or alter existing processes.processes.
Lichtenhan et. al. Macromolecules 1993, 26, 2141.Lichtenhan, Polym. Mater. Encyclopedia 1996, 10, 7768.
Si
SiO
O
Si
Si
Si
Si
O
O
O
OSi O
Si
O
O
O
O
O
R
R
R
R
RR
OO
CH 3
O
CH 3
R
Si
Si
O
O
Si
Si
Si
Si
O
O
O
O
SiO
Si
O
OO
OO
RR
R
R
R
R
O O
RTHFCatalyst
Si
Si
O
O
Si
Si
Si
Si
O
O
O
O
SiO
Si
O
O
O
O
O
RR
R
R
RR
O
R
O
Si
Si
O
O
Si
Si
Si
Si
O
O
O
O
SiO
Si
O
O
O
O
O
RR
R
R
RR
O
R
CH 3
Use
Tem
pera
ture
&O
xida
tion
Res
ista
nce
Toughness, Lightweight &Ease of Processing
Polymers
Ceramics
HYBRIDPROPERTIES
Courtesy of Hybrid Plastics
20
POSS®-Molecular Silica BlendsBlended into 2 million MW Polystyrene
Courtesy of A. LeeMichigan State University
50 wt% loadingand transparent!
Phase inversion
Partial compatibilityDomain formation
Si
Si
O
O
Si
Si
Si
Si
O
O
O
O
SiO
Si
O
OO
OO
R R
R
R
R
R
R R
R = cyclopentyl
Si
Si
O
O
Si
Si
Si
Si
O
O
O
O
SiO
Si
O
OO
OO
R R
R
R
R
R
R
R = cyclopentyl
Si
Si
O
O
Si
Si
Si
Si
O
O
O
O
SiO
Si
O
OO
OO
R R
R
R
R
R
R
R = styrenyl
Si
Si
O
O
Si
Si
Si
Si
O
O
O
O
SiO
Si
O
OO
OO
R R
R
R
R
R
R
R = Phenethyl
Cp8T8 CP7T8Styrenyl
Styrenyl8T8
Phenethyl8T8
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Thermoplastic Elastomer Nanocomposites (TPUN)
15% PR-24-PS CNF2102-90A (85%)7
15% PR-19-PS CNF2102-90A (85%)6
5% PR-24-PS CNF2102-90A (95%)5
5% PR-19-PS CNF2102-90A (95%)4
5% Trisilanolphenyl-POSS®
2102-90A (95%)3
5% Cloisite® 30B2102-90A (95%)2
None2102-90A (100%)1
NanoparticlesPellethane™ TPUExperiments
22DISTRIBUTION A. Approved for public release; distribution unlimited
Microstructures Analyses of Pre-Test Materials
TEM analyses were conducted on all 7 blends to examine the degree of dispersion of each type of nanoparticles in 2102-90A TPU
PR-24-PS CNFs and PR-19-PS CNFs dispersed very well in 2102-90A TPU forming TPUNs
In addition to TEM, the Cloisite® 30B modified materials were analyzed using WAXD
Tests showed that the Cloisite® 30B dispersed very well in 2102-90A TPU forming intercalated/exfoliated TPU nanocomposites (TPUNs)
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TEMs of TPUN:5 wt% PR-19-PS CNF/95 wt% 2102-90A TPU
24DISTRIBUTION A. Approved for public release; distribution unlimited
TEMs of TPUN:15 wt% PR-19-PS CNF/85 wt% 2102-90A TPU
25DISTRIBUTION A. Approved for public release; distribution unlimited
TEMs of TPUN:5 wt% PR-24-PS CNF/95 wt% 2102-90A TPU
500 nm 200 nm
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TEMs of TPUN:15 wt% PR-24-PS CNF/95 wt% 2102-90A TPU
500 nm 200 nm 100 nm
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WAXDs of 5 wt% Cloisite® 30B in 2102-90A TPU
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TEMs of TPUN:5 wt% Cloisite® 30B/95 wt% 2102-90A TPU
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Properties for TPUNs
• Thermophysical – coefficient of thermal expansion (CTE), heat capacity, thermal conductivity
• Flammability – Cone calorimeter data
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Correlations of CTE of CNF and Nanoclay TPUNs
150
200
250
300
350
400
0 5 10 15 20 25 30
PR 19 PS PR 24 PS Cloisite 30B
CTE
(mic
rons
/m K
)
Weight % nanofiller
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Heat Capacity of TPUN
0
0.5
1
1.5
2
2.5
none 30B PR19PS PR24PS POSS
Cp @ 45 (J/g/ C)Cp @ 55 (J/g/ C)
Hea
t Cap
acity
(J/g
/ o C)
Nanofiller
0
0.5
1
1.5
2
2.5
none PR19PS PR24PS
Cp @ 45 (J/g/ C)Cp @ 55 (J/g/ C)
Hea
t Cap
acity
(J/g
/ o C)
Nanofiller
5 wt% Nanofiller 15 wt% Nanofiller
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Thermal Conductivities of Thermoplastic Polyurethane Nanocomposites
5 wt% Nanofiller 15 wt% Nanofiller
0.15
0.2
0.25
0.3
0.35
none 30B PR19PS PR24PS POSS
k @ 45 C (W/ m-K)k @ 55 C (W/ m-K)
Ther
mal
Con
duct
ivity
(W/ m
-K)
NanoFiller
0.15
0.2
0.25
0.3
0.35
none PR19PS PR24PS
k @ 45 C (W/(m-K)k @ 55 C (W/(m-K)
Ther
mal
Con
duct
ivity
(W/ m
-K)
Nanofiller
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Cone Calorimeter Data at Irradiance Heat Flux of 50 kW/m2
Material tig (s) PHRR (kW/m2)
Avg. HRR, 60s (kW/m2)
Avg. HRR, 180s (kW/m2)
Avg. Eff, Hc (MJ/kg)
Avg. SEA (m2/kg)
Pellethane TPU 32 2,290 406 653 30 237 Pellethane-5% Cloisite 30B TPUN
34 664 (71% reduction)
560 562 25 303
Pellethane-5% PR-19-PS CNF TPUN
27 624 (73% reduction)
532 456 22 295
Pellethane-5% PR-24-PS CNF TPUN
30 911(60% reduction)
407 554 25 283
Pellethane-5%-Trisilanolphenyl-POSS TPUN
31 1,637 (29% reduction)
334 591 25 339
tig = Time to sustained ignition PHHR = Peak heat release rate Avg. HRR = Average heat release rate after ignition Avg. Eff, Hc = Effective heat of combustion Avg. SEA = Average specific extinction area
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Heat Release Rate of TPUN
0
500
1000
1500
2000
2500
0 50 100 150 200 250 300
Pellethane 21025% 30_21025% PR-19-PS_21025% PR-24-PS_21025% POSS_2102
Hea
t Rel
ease
Rat
e (k
W/m
2 )
Time (s)
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Cone Calorimeter samples after testing
Pellethane
Pellethane w/ 30B
Pellethane w/ PR19PS
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SUMMARY AND CONCLUSIONS
Blending of 5 wt% of nanoclay, CNF, and POSS® and 15 wt% of CNF in Dow’s PELLETHANE™ 2102-90A TPU were conductedThermophysical and flammability properties of these TPUNs were measuredTEM analyses have demonstrated to be a very efficient way to study the degree of dispersion of nanoparticles in polymer matrixTo obtain enhanced thermophysical and flammability properties, good dispersion of the nanoparticles in the polymer matrix is essentialDow’s polyester polycaprolactone elastomer is very compatible with Cloisite® 30B nanoclay, PR-24-PS CNF, and PR-19-PS CNF as shown by TEMsTrisilanolphenyl-POSS® is not compatible with the PELLETHANE™ TPU and may actually degrade the material during process. Further investigation is underway.CTE of nanoclay TPUN increases with nanoclay to greater than 2x for 10 wt% nanoclay; and CTE of CNF TPUN goes through a maximum (~15 wt% loading) Correlations of CTE with Cloisite® 30B, PR-24-PS CNFs, and PR-19-PS CNFs were obtained as a function of nanofiller loading
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SUMMARY AND CONCLUSIONS (cont’d)
Thermal conductivity increases with the addition of nanoparticlesSignificant reduction of PHRR was shown by 5 wt% PR-19-PS CNF (73%), 5 wt% Cloisite® 30B (71%), and 5 wt% PR-24-PS CNF (60%) than baselineTime to sustained ignition of Pellethane was 32s with a slight increase of tig of 34s for 5% Cloisite® 30B, all other TPUNs have a slight decrease of tig
Avg. HRR, 180s was lowered for all TPUNsAvg. effective heat of combustion was lowered for all TPUNsAvg. specific extinction area was slightly higher for all TPUNs