Flame Retardant Nanocomposites
Christophe Swistak
Valentin Chapuis
Alexandre Durussel
Composites technology 16.12.2008
Outline
• Applications
• Introduction– Fire hazards
– Combustion of polymers
• Flame-Retardant composites
• Nanofillers
• Flame retardancy mechanism
• Processing
Applications
• Flame retardant wall panels
• Flame retardant doors
• Airplanes & trains
Applications / Introduction / Flame retardant composites / Nanofillers /
Flame retardancy mechanism / Processing
!!! Flame retardant ≠ Fireproof
Dangers due to fire
• Heat release (HR)– Control intensity and speed of combustion
• « Black » smokes– Difficult orientation of rescue squads and
victims
• Toxic gazes released during combustion– Can lead to death
Applications / Introduction / Flame retardant composites / Nanofillers /
Flame retardancy mechanism / Processing
Combustion of polymers
• Process in two stages
1. Thermo-oxidative degradation• Heat transfer
• Decomposition leading to generation of flammable volatile products
• Diffusion of gazes through the matrix
2. Normal burning• Combustion involving volatiles products and
oxygen
Applications / Introduction / Flame retardant composites / Nanofillers /
Flame retardancy mechanism / Processing
Flame-retardant composites (I)
• Conventional composites– Polymer matrix (PP, PE, PA, …)– Fillers
• Aluminium trihydrate AlH3
• Magnesium hydroxide MgOH• Organic brominated compounds
– AdvantagesWell knownNo problem of dispersion of the filler
– DrawbacksX Requires gf ~ 30-60%wt to obtain good flame retardancyX High density, small flexibilityX Toxicity of flame retardant compounds (e.g. Br)
Applications / Introduction / Flame retardant composites / Nanofillers /
Flame retardancy mechanism / Processing
Flame-retardant composites (II)
• Nanocomposites– Polymer matrix (PP, PE, PA, PS, EVA, epoxy, …)
– Nanofillers• Layered silicates (mostly Monmorillonite (MMT))• Spherical nanoparticles of silica• Carbon nanotube
– AdvantagesSame flame-retardant properties with a smaller volume
fraction of filler (gf~2-10%wt) Easier to process (especially in injection)Better mechanical properties and smaller density
– DrawbacksX Compatibility between matrix and fillerX Dispersion
Applications / Introduction / Flame retardant composites / Nanofillers /
Flame retardancy mechanism / Processing
Nanofillers (I)• Structure
– Layered structure with thickness ~1nm
– High ratio length/thickness ~ 1000
– “Agglomerated” structure
Applications / Introduction / Flame retardant composites / Nanofillers /
Flame retardancy mechanism / Processing
MMT structure from wikipedia.org
Nanofillers (II)
• Dispersion– Determine flame-retardant property
Kashiwagi et al., Polymer, 2004
Applications / Introduction / Flame retardant composites / Nanofillers /
Flame retardancy mechanism / Processing
Nanofillers (III)• Dispersion
– Big challenge
S. Bourbigot et al, 2008, [7]
TEM pictures of PP/clay nanocomposite
Günter Beyer et al, 2002, [1]
Maximization of Matrix/filler interaction Leads to the better flame-retardancy
Applications / Introduction / Flame retardant composites / Nanofillers /
Flame retardancy mechanism / Processing
Nanofillers (IV)
• Dispersion
– Chemical process1. Expansion2. Compatibilization3. Mixing / Polymerization
– Specific system for each couple of clay and polymer matrix
W.S. Wang et al, 2008, [9]
Applications / Introduction / Flame retardant composites / Nanofillers /
Flame retardancy mechanism / Processing
Nanofillers (V)• Dispersion
– Mechanical process (separating the layers with a high shear stress)
– Directly in the production process– Addition of a stabilization / compatibilization
agent may be necessary
F. Samyn, S. Bourbigot et al, 2008, [7]
Applications / Introduction / Flame retardant composites / Nanofillers /
Flame retardancy mechanism / Processing
Flame retardancy mechanism (I)
Applications / Introduction / Flame retardant composites / Nanofillers /
Flame retardancy mechanism / Processing
• Formation of a thermal insulating and low permeability char
• The char acts as a physical and chemical barrier between the polymer and the burning surface
Heat release rate (HRR) decrease
Less smoke/gazes formation
Flame retardancy mechanism (II)
G. Beyer et al, 2002, [1]
Reduction of the HRR of 47%with only 5%wt of filler
Applications / Introduction / Flame retardant composites / Nanofillers /
Flame retardancy mechanism / Processing
Flame retardancy mechanism (III)
F. Laoutid et al. 2008, [5]
Reduction of the HRR up to 70 %with 10%wt of filler
Applications / Introduction / Flame retardant composites / Nanofillers /
Flame retardancy mechanism / Processing
Processing• In-situ Polymerization
• Polymerization in solvent
• Molten processing1. Polymer melting
2. Add fillers
3. Physical dispersion
– Allows injection / extrusion
– Industrial process
Applications / Introduction / Flame retardant composites / Nanofillers /
Flame retardancy mechanism / Processing
Summary• Important parameters to control
– Heat release rate– Thermal and diffusion barrier
• Nanocomposites (layered silicates)
Same or better flame-retardancy for a lower gf
better mechanical propertiesImprovements in processability and matrix/filler
interactionFillers that are non-toxic
Problems of dispersion and compatibility
References[1] Nanocomposites : a new class of flame retardants for polymers, in Plastics Additives &
Compounding, October 2002[2] Nanocomposites offer new way forward for flame retardants, in Plastics Additives &
Compounding, September/October 2005[3] Flame retardant mechanism of polymer/clay nanocomposites based on polypropylene, H. Qin
and al., Polymer 46 (2005), pp. 8386-8395[4] Characterization of the dispersion in polymer flame retarded nanocomposites, F. Samyn and
al., European Polymer Journal 44 (2008), pp. 1631-1641[5] New prospects in flame retardant polymer materials: From fundamentals to nanocomposites,
F.Laoutid, et al., Mater. Sci. Eng. R(2008), doi:10.1016/j.mser.2008.09.002[6] Flame retardant mechanism of polyamide 6-clay nanocomposites, T. Kashiwagi and al. Polymer
45, 2004, pp. 881-891.[7] Crossed characterisation of polymer-layered silicat nanocomposite morphology: TEM, X-ray
diffraction, rheology and solid-state nuclear magnetic resonance measurements. F. Samyn, S. Bourbigot and al. European Polymer Journal 44, 2008, pp. 1642-1653
[8] Synergism between flame retardant and modified layered silicate on thermal stability and fire behavior of polyurethane nanocomposite foams, M. Modesti and al., Polymer Degradation and Stability (2008), pp. 1-6
[9] Properties of novel epoxy/clay nanocomposites prepared with reactive phosphorous containing organoclay, W.S. Wang and al., Polymer (2008), pp. 1-11
[10] A novel phosphorus-containing copolyester/monmorillonite nanocomposites with improved flame retardancy, X.G. Ge and al., European Polymer Journal 43 (2007), pp. 2882-2890
[11] http://www.epp.goodrich.com/fyreroc/[12] http://www.cfoam.com/fireproofcore.htm