Composites Flame Retardant

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The flame-retardant mechanisms involved in the polymer-clay nano-composites are described.

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Composites Flame Retardant

  1. 1. Composites technology 16.12.2008 Flame Retardant Nanocomposites Christophe Swistak Valentin Chapuis Alexandre Durussel
  2. 2. Outline • Applications • Introduction – Fire hazards – Combustion of polymers • Flame-Retardant composites • Nanofillers • Flame retardancy mechanism • Processing
  3. 3. Applications • Flame retardant wall panels • Flame retardant doors • Airplanes & trains ! !! Flame retardant ≠ Fireproof Applications / Introduction / Flame retardant composites / Nanofillers / Flame retardancy mechanism / Processing
  4. 4. 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
  5. 5. 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
  6. 6. Flame-retardant composites (I) • Conventional composites – Polymer matrix (PP, PE, PA, …) – Fillers • Aluminium trihydrate AlH3 • Magnesium hydroxide MgOH • Organic brominated compounds – Advantages  Well known  No problem of dispersion of the filler – Drawbacks X Requires gf ~ 30-60%wt to obtain good flame retardancy X High density, small flexibility X Toxicity of flame retardant compounds (e.g. Br) Applications / Introduction / Flame retardant composites / Nanofillers / Flame retardancy mechanism / Processing
  7. 7. 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 – Advantages  Same 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 – Drawbacks X Compatibility between matrix and filler X Dispersion Applications / Introduction / Flame retardant composites / Nanofillers / Flame retardancy mechanism / Processing
  8. 8. Nanofillers (I) • Structure – Layered structure with thickness ~1nm – High ratio length/thickness ~ 1000 – “Agglomerated” structure MMT structure from wikipedia.org Applications / Introduction / Flame retardant composites / Nanofillers / Flame retardancy mechanism / Processing
  9. 9. Nanofillers (II) • Dispersion – Determine flame-retardant property Kashiwagi et al., Polymer, 2004 Applications / Introduction / Flame retardant composites / Nanofillers / Flame retardancy mechanism / Processing
  10. 10. Nanofillers (III) • Dispersion – Big challenge Maximization of Matrix/filler interaction  Leads to the better flame- retardancy TEM pictures of PP/clay nanocomposite Günter Beyer et al, 2002, [1] S. Bourbigot et al, 2008, [7] Applications / Introduction / Flame retardant composites / Nanofillers / Flame retardancy mechanism / Processing
  11. 11. Nanofillers (IV) • Dispersion – Chemical process 1. Expansion 2. Compatibilization 3. 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
  12. 12. 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
  13. 13. Flame retardancy mechanism (I) • 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 Less smoke/gazes formation Heat release rate (HRR) decrease Applications / Introduction / Flame retardant composites / Nanofillers / Flame retardancy mechanism / Processing
  14. 14. 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
  15. 15. 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
  16. 16. Processing • In-situ Polymerization • Polymerization in solvent • Molten processing 1. Polymer melting 2. Add fillers 3. Physical dispersion – Allows injection / extrusion – Industrial process Applications / Introduction / Flame retardant composites / Nanofillers / Flame retardancy mechanism / Processing
  17. 17. 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 properties  Improvements in processability and matrix/filler interaction  Fillers that are non-toxic Problems of dispersion and compatibility
  18. 18. 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

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