Download - Flame Retardant Polymer Nanocomposites
Jeffrey W. GilmanGroup Leader
Materials and Products GroupNIST
Flame Retardant Polymer Nanocomposites
General Flame Retardant Approaches for Polymers
I- Gas Phase Flame Retardants- Reduce Heat of Combustion (ΔHc ) resulting in incomplete combustion.- Inherent Drawbacks: Negative Public Perception!
II- Endothermic Flame Retardants- Function in Gas Phase and Condensed Phase- Via endothermic release of H2 O, polymer cooled and gas phase diluted.- Inherent Drawback: High loadings (30-50%) degrade mechanical properties.
III- Char Forming Flame Retardants- Operate in Condensed Phase- Provides thermal insulation for underlying polymer and a mass transport
barrier, preventing or delaying escape of fuel into the gas phase.- Inherent Drawback: High loadings (20-50%) degrade mechanical properties.
Goal: develop cost effective, environmentally friendly approacheGoal: develop cost effective, environmentally friendly approaches to s to reduce flammability reduce flammability andand improve physical propertiesimprove physical properties
Polymer clay NanocompositePolymer clay NanocompositeMaterials:Layered silicates, organic modifier, polymer matrix
Processing Techniques:•Solution mixing and film casting•Melt mixing (extrusion, injection molding)•In situ polymerization
Morphologies (Simplified picture):
Properties:•Flame resistance•Improved gas permeability•Higher stiffness•Scratch resistance•Higher glass transition•Improved thermo-mechanical response
Usuki et al. 2001, Nano LettersL. F. Drummy -AFRL
PPPP--clay Nanocomposite: TEMclay Nanocomposite: TEM
Gilman, et al, Chemistry of Materials; 2000; 12; 1866-1873
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PP intercalated + delaminated (mass fraction 2 % silicate) PP-g-MA (mass fraction 0.4 % MA)
PP intercalated + delaminated (mass fraction 4 % silicate) H
eat R
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(kW
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Time (seconds)
Flux = 35 kW/m 2
PPPP--clay Nanocomposite: Cone Calorimetryclay Nanocomposite: Cone Calorimetry
Gasification of Polystyrene LayeredGasification of Polystyrene Layered--silicate Nanocompositessilicate Nanocomposites
Char or
Coke Formation
Critical criteria for formation of homogeneous char
Kashiwagi et al., Polymer, 2004
Homogeneous clay dispersion in polymer
Unstable and inhomogeneous clay dispersion in polymer
Pyrolysis and phase separation
homogeneous char:thermal barrier
discontinuous char:Poor thermal protection
Depends on: clay loading, dispersion, polymer Mw, viscosity, degradation mechanisms, carbonaceous char formation
Nanocomposite + Conventional Flame Retardant Approach
Nanocomposites + additional flame retardants have resulted in fiNanocomposites + additional flame retardants have resulted in final nal materials that pass regulatory tests and have superior balances materials that pass regulatory tests and have superior balances of of properties. properties.
Successful commercial approaches remove some of existing FR Successful commercial approaches remove some of existing FR package, replace with nanocomposite. package, replace with nanocomposite.
DupontDupont 1980s 1980s ––PBT + PBT + OMMtOMMt + + OrganoOrgano BrBr-- UL94 V0UL94 V0Showa Denko Showa Denko –– PBT PBT SynMicaSynMica + + MealmineCYMealmineCY-- UL94V0UL94V0KabelwerkKabelwerk EupenEupen: EVA + : EVA + OrganomontmorilloniteOrganomontmorillonite + Al(OH)+ Al(OH)33. . ––UL1666UL1666PolyOne: (polyolefin nanocomposite PolyOne: (polyolefin nanocomposite –– ULUL--94 V94 V--0 @ 3.0mm) 0 @ 3.0mm) StrathclydeStrathclyde ––PU Foam + PU Foam + OMMtOMMt + FR + FR –– pass cribpass crib--5 5 NanocorNanocor –– PhosPhos. Clay . Clay -- UL94 V0UL94 V0U mass Lowell U mass Lowell –– ClayClay-- ELO as substitute for ELO as substitute for PbPb in PVCin PVC
ChallengesChallenges1)1) Furniture and mattress firesFurniture and mattress fires
still causestill cause~1000 deaths/yr and cost $ 500 M/yr~1000 deaths/yr and cost $ 500 M/yr
1)1)
Objective:Objective:
to evaluate the effectiveness of to evaluate the effectiveness of nanoadditive based flame retardantsnanoadditive based flame retardants
in reducing in reducing the flammability of flexible foams.the flammability of flexible foams.
2)2)
Objective :Objective :
To improve the ability of barrier To improve the ability of barrier fabrics to prevent flame spread in mattresses and fabrics to prevent flame spread in mattresses and furniture using furniture using nanoadditivesnanoadditives..
Melt Pool Fires During Foam Burning
240 kW in 540 sec240 kW in 540 sec
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Time Since Start of Ignition (s)
Polypropylene fabric
Cotton fabric
Cal 117 PU Foam
550 kW in 280 sec550 kW in 280 sec
Nano-additives
Layered Double Hydroxide
Mg(OH)64-
Al(OH)63
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POSSCarbon nanotubes
Coughlin-U MassBellayer - NIST
Zammerano-Chimteclab
Layered Silicates
Nano silica
Kashiwagi - NIST
Flame Retardant MechanismHigh aspect ratio nanoadditives (e.g. CNF) properly dispersed in the polymeric matrix form a percolated jammed structure, due to particle- particle interactions, so that the melt behaves rheologically like a gel
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Inhibition of dripping
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C30B CNF POSS
6.6 parts of Br-P FR in the standard formulation are replaced by 6.6 parts inorganic additive (e.g., CNF, Na+ MMT, LDH and Boehmite)
When organo-modified additive are used (e.g., OMMT) the amount of additive is increased in order to keep constant the inorganic fraction of the additive.
Modified/Nano Formulations
Br-P FR (wt.%)
Nano-additive (wt.%)
Br-P FR (Control 1) 6.2 0Talc (Control 2) 2.3 3.9CNF 2.3 3.9Boehmite 2.3 3.9LDH 2.3 3.9OMMT (C30B) 2.3 5.1POSS 2.3 5.1
Foam Processing Optimization
Control POSSFire-
quench Boehmite C30B
Non-optimized foam samples with various additives.
Each formulation needsto be individually tuned to match the control formulation.
1. Adjustment of the polyol – nanoparticle dispersion viscosity by coupling agents.
2. Optimization of the curing and blowing reaction through suitable catalysis ratios.
3. Prevention of collapse and shrinkage by appropriate surfactants and cell openers.
4. Monitoring of the foam rise and curing with a FOAMAT foam qualification system.
5. Evaluation of the foam quality by optical analysis, density and air flow measurements.
Characterization of Nanoparticles Dispersions
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3.8 nm
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q (nm-1)
Cloisite 30B in liquid polyol Cloisite 30B Foam
Median Size (μm)
Cloisite
30B 100Boehmite 0.2POSS 8CNF -
Small Angle X-Ray ScatteringAggregate size estimation by means of Static Laser Scattering
Foam Characterization
POLYOL
FOAM
OPTICAL MICROSCOPY
SEM
Talc OM-Clay CNF
Br-P FR OM-Clay CNF
CNF
Cloisite 30B FoamCNF Foam
Modified Cone Calorimetry
Nanoadditive Flame Retardants for Polyurethane Foam
Tom Ohlemiller, Richard Harris, J. Randy Shields, Tom Ohlemiller, Richard Harris, J. Randy Shields, Mauro Mauro ZammaranoZammarano (GR), Roland (GR), Roland KrKräämermer (GR)(GR)
PoolPool--fire fire
PU FRPU FR--foam controlfoam controlnono
PoolPool--fire fire
PU FRPU FR--foam + 4% Carbon Nanofoam + 4% Carbon Nano--Fibers:Fibers:
Catch Pan
ViscosityNano-Graphite
HRR by Modified Cone Calorimetetry
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Cloisite 30B POSS Talc
35% reduction in PHRR with CNF
External Heat Flux: 11 kW/m2
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Talc Br-P FR CNF
Flame Retardant Mechanism of CNF
*Takashi Kashiwagi, BFRL, NIST
High aspect ratio nanoadditives (e.g. CNF) properly dispersed in the polymeric matrix form a percolated jammed structure, due to particle- particle interactions, so that the melt behaves rheologically like a gel*.
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Inhibition of dripping-
Heat shield effects of network structured protective layer
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Residue of CNF foam after Cone
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C30B CNF POSS
CNF Foam Residue - SEM
1 mm1 mm1 mm
Residue of CNF foam after Cone
b) 4 μm
10 μmc)
Environmentally Friendly, Nano-based Polyurethane Fire Retardant Systems
Professor Richard A. Pethrick,
Department of Pure and Applied Chemistry, University of Strathclyde, Thomas Graham
Building, 295 Cathedral Street Glasgow G1 1XL.
"Pollution Prevention through Nanotechnology" September 25-26, 2007, in Arlington , VA
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Shear thinning of sonicated glycol blends of Strath A / Strath B
1% Strath B 2% Strath B 3% Strath B 1% Strath A 2% Strath A 3% Strath A
Vis
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Shear Rate (1/s)
Effect of dispersion methods -study of PU monomers
Alignment of Platelets Due to Shear
Applied Shear
Alignment of the platelets in the shear field leadsto a lowering of the viscosity.
Flame Retardancy in Polymer Foams.
Nano platlets compositestructures within cellwalls to inhibit volatilediffusion and enhancethe viscoelasticity ofthe melt phase .
Flexible Foam Systems
• A series of flexiblefoam system have beenproduced with therequired flexibilityand incorporatingnanocompositeorganically modifiedclay materials.{Patents have beenapplied for thesesystems}
What do the materials look like?
• Electron microscopy has been performed and they show the nano material is present in the foam walls and has effected the rheology in the foam formation
• The materials have comparable mechanical properties to current flexible foam formulations
Electron Micrograph of PU foam
Electron Micrography of PU Foam Structure
CL592 CL594
Daly, Lewicki, Liggat, McCulloch, MacRitchie, Pethrick, Rhoney
The Challenge:
The Process:Formulation design
Toavoid this
Obtain this
Escalating Self-extinguishing
Crib 5 Testing
From these
Nano Composites
I hope this short presentation has shown that by recognising the natural nano dimensions which exist in natural materials it is possible to enhance the properties of conventional materials which we produce and achieve a greater use of these materials.
Nano composites are not all about new exotic materials but can be about using traditional materials more effectively.
Acknowledgements
• Dr J.J. Liggat, Dr John Daly,• Dr Ian Rhoney, Dr Sharon Ingram, • EPSRC.• Scottish Enterprise. • Southern Clay.
Layer by layer assembly of nanoparticles
Collaborator: Jaime Grunlan, Texas A&M
University
Deposition of nanoparticles using layer by layer assembly technique.
Coated Control Foam: 2 wt. % coating
Movie Speed: 10x
Amphipholis squamata• Common echinoderm• Diet consists of particles• Bioluminescence under
nervous control, and produced only under stimulation
• Commonly used in the Deheyn lab to assess sub- lethal effect
Dimitri D. Deheyn, Ph.D. Marine Biology Research Division, Scripps Institution of Oceanography, University of California, San Diego
Methodologies to Determine Health and Methodologies to Determine Health and Environmental effects of Environmental effects of NanoNano--particlesparticles
Experimental setup in aquariums
Nanoparticles* Concentration (ppm) Abbreviations
Single-Wall Carbon Nanotubes 1 and 10 SNT
Multi-Wall Carbon Nanotubes 10 MNT
Surfactant: Carboxymethyl cellulose 0.1 CMC
Layered Double Hydroxide Colloidal 1 and 10 CLD
Micro Layered Double Hydroxide 10 MLD
Surfactant: Sodium acetate ~10 SA
* Received from Jeff Gilman group at NIST, National Institute for Standard and Technology
Time variation of the spontaneous light Nanoparticles
Time variation of the spontaneous light Nanoparticles
Parameter Space for Polymer Nanocomposites
Polymer Nano-additive
Organic Treatment
Processing Conditions
Other additives
Flame Retardant
PE PP PS
PA6 PU
PVC PC PEO
PMMA EVA
Epoxy . .
clay POSS
Carbon Silica LDH
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AlkylammoniumImidazolium
Chelates Silated Alkyl
Carboxylate . . . . . . .
Temperature Shear
Residence time sonication
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Stabilizers Processing
UV Antioxidant
Fillers Pigments
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Phosphate Halogenated Silicon Based
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• We will use a small-scale automated high throughput liquid handling equipment with the capability of mixing dozens of polyol, nanoadditive combinations to screen for nanoscale mixing with polyols.
NanoNano--dispersiondispersion
ConclusionsAn An important applicationimportant application of polymer clay nanocomposites is of polymer clay nanocomposites is as a flame retardant in polymers. as a flame retardant in polymers.
flame retardant mechanism of polymer clay nanocomposites flame retardant mechanism of polymer clay nanocomposites appears to be the maintenance of a appears to be the maintenance of a homogeneous homogeneous dispersiondispersionStrathclydeStrathclyde -- Clay in Foam passes crib 5Clay in Foam passes crib 5 test for UK test for UK upholstered furnitureupholstered furniture
Carbon Carbon NanoNano FibersFibers inhibit melt dripping and reduce the inhibit melt dripping and reduce the flammabilityflammability
GrunlanGrunlan -- LBLLBL Coating can be used to remove dripping in Coating can be used to remove dripping in foamsfoams
DeheynDeheyn/Scripps preliminary data show /Scripps preliminary data show possiblepossible toxic effects toxic effects from surfactants and from surfactants and nanotubesnanotubes
Acknowledgments
Dimitri
D. Deheyn, Marine Biology Research Division,
Scripps Institution of Oceanography, University of California, San DiegoRoland Krämer
School of Chemical Science and Engineering, Fibre and Polymer Technology,Royal Institute of Technology, SE-100 44 Stockholm, Sweden
Jeffrey W. Gilman, Richard Harris, Jr., Thomas J. Ohlemiller, Sameer
S. Rahatekar, John R. Shields, Takashi Kashiwagi
Building and Fire Research Laboratory, NIST, Fire Research Division, Gaithersburg, MD
Jaime C. GrunlanDepartment of Mechanical Engineering & Polymer Technology Center (PTC)
Texas A&M University, College Station, TX
Professor Richard A. PethrickDepartment of Pure and Applied Chemistry, University of Strathclyde, Thomas
Graham Building, 295 Cathedral Street Glasgow G1 1XL
Methane ice burning http://http://www.geomar.dewww.geomar.de
Thank you