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BCC Research in cooperation with Dr. Menachem Lewin presents The 19th Annual Conference Recent Advances in Flame Retardancy of Polymeric Materials Monday, June 9, 2008 Session I: General Papers and Reviews Chairman: Charles A. Wilkie, Department of Chemistry, Marquette University, Milwaukee, WI 8:15-8:30 a.m. Introduction Professor Menachem Lewin, Polymer Research Institute, Polytechnic University, Brooklyn, NY 8:30-9:00 a.m. Statistical Model of Flame Resistance of Plastics Richard E. Lyon, Richard N. Walters, Stanislav I. Stoliarov, Federal Aviation Administration, William J. Hughes Technical Center, Atlantic City International Airport, NJ
The Underwriters Laboratory Test for Flammability of Plastics (UL 94) is modeled as a binary (no burn, burn) event by assigning a value of 0 to UL 94 ratings of V-0 or 5V and a value of 1 to ratings of V-1, V-2, NR, or HB. The probability of burning, considered to be the dependent variable in the analysis, was calculated as the fraction of burn results for 3 mm thick specimens in a narrow range (bin) of the independent variable obtained by microscale combustion calorimetry (MCC) for nearly 200 samples. The logistic response function was fit to the probability of burning using binned MCC heat release capacity as the sole explanatory variable with an accuracy of about 75%. More accurate predictions are obtained when multiple MCC indicator variables are used in the regression analysis.
9:00-9:30 a.m. Modeling the Dispersion and Agglomeration of Carbon Nanotubes in Polymers Marc R. Nyden, Building and Fire Research Laboratory, National Institute of Standards and Technology, Gaithersburg, MD; Stanislav I. Stoliarov, SRA International, Egg Harbor Twp., NJ; Venkat Ganesan, Landry Khounlavong, Department of Chemical Engineering, The University of Texas at Austin, Austin, TX.
The improvement in properties due to the incorporation of nanostructured materials, such as carbon nanotubes (CNTs), in polymers is most effective when they are uniformly dispersed with minimal agglomeration. Good dispersion results in large interfacial surface areas that facilitate strong interactions between the nanoadditive and polymer. When nanocomposite materials are subjected to thermal and mechanical stress, these interactions transfer the strain to the nanoadditives, which are typically stronger and more rigid than polymer chains, thereby reinforcing the host material.
The dispersion of nanoadditives in polymers above a critical concentration is marked by a transition from liquid-like to solid-like flow behavior, due to the formation of a nanoparticle network. It is usually accompanied by significant enhancements in the properties of the host material. This is especially true with respect to flammability performance. Thus, it is known that the reduced heat release rates exhibited by many nanocomposite materials depends, in large part, on the ability of the nanoadditives to form a protective layer that insulates the unburnt polymer in the interior of the burning object from thermal energy incident on its surface. As the polymer (in a nanocomposite) decomposes in a fire, the network structure formed by the nanoadditives is left behind. Although it consists primarily of free volume, it must be sufficiently strong to withstand thermal motions that might otherwise break it apart. In poorly dispersed nanocomposites, the network structure has less free volume (because the nanoadditives are agglomerated) and the thermal protection of the unburnt polymer is correspondingly less effective. The extent to which it is possible to achieve and sustain good dispersion of the CNTs, especially at the high temperatures experienced during burning, depends on the nature of the interactions between the nanoadditives and polymer.
The unique properties of polymer nanocomposites arise from interactions between nanoadditives and polymers that are limited to a range of about 10 nanometers. This is too small to be captured by continuum mechanics, but beyond the capabilities of conventional atom based molecular mechanics (MM) and dynamics. Problems that fall into this domain (commonly referred to as the mesoscale) can be handled by stochastic dynamics, such as dissipative particle dynamics (DPD), which require force fields that are resolved over length scales intermediate between atomic and continuum dimensions. In this talk, I will summarize progress made in the development of a stochastic dynamics model of the dispersion and agglomeration of CNTs in polymers. 9:30-10:00 a.m. Fire Properties of Alloys and Composites Based on Recycled Polyethylene Terephthalate Benjamin Swoboda, Eric Leroy, Laurent Ferry, Nadra Kerboua, José Marie Lopez-Cuesta, Centre des Matériaux de Grande Diffusion (C.M.G.D), Pôle matériaux polymères avancés, Ecole des Mines d'Alès, Alès Cedex, France
Thermal stability and fire behaviour of recycled plastics are generally poor in comparison with those of the corresponding commercial ones, in which thermal stabilizers and flame retardant amounts are optimized. In order to recycle PET from bottles in engineering applications, several strategies have been developed. The blending with PC as a minor component was shown to improve fire behaviour, mainly by the control of morphology and blending conditions. The results also depend on the use of catalysts, able to form PET/PC copolymers. Moreover, the use of TriPhenylPhosphite (TPP), acting as chain extender as well as flame retardant allowed improving both fire behaviour and mechanical properties. Other strategies concern the incorporation in PET/PC blends of organomodified montmorillonite or kaolinite in combination with TPP. More recently, the blending of PET with recycled ABS issued from electrical waste was studied. The fire performance of blends is connected to the nature and percentage of flame retardants present in ABS as well as the morphology and processing. 10:00-10:30 a.m. Coffee Break Chairman: Gerald Kirshenbaum, Polytechnic University, Brooklyn, NY 10:30-11:00 a.m. Nitrogen oxides - accelerators of oxidation and combustion of polymers. Mechanism of Radical Conversions on Exposure to Nitrogen Oxides G. E. Zaikov, G. B. Pariiskii, I. S. Gaponova, T. V. Pokholok, A. P. Vorotnikov, E. Ya. Davydov, N.M. Emanuel Institute of Biochemical Physics, Russian Academy of Sciences, Moscow, Russia
LOI is important criterion of polymer (material) combustibility. Unfortunately, this factor is useless if temperature of combustion is more then 3000oC because nitrogen becomes active in this conditions. Polymers (materials) will burn in this situation in atmosphere of nitrogen (combustion in nitrogen). These reactions are very exothermic (more exothermic then reactions of oxidation) and nitrides will be products of combustion in nitrogen.
If temperature is elevate (high) enough reactions of nitrogen with oxygen will take place with accumulation of nitrogen oxides. It is well know that nitrogen oxides are initiators of reactions of oxidation. We should expect that nitrogen oxides will also accelerate the combustion of polymers (materials).
The goal of this report is investigation of kinetics and mechanism of reactions between polymers and nitrogen oxides. These results are very important not only for investigation of combustion of polymers in extremal conditions but also for understanding of behavior of polymers in polluted atmosphere.
11:00-11:30 a.m. Recycling of PP/EPR Blends From End of Life Vehicles: Thermal Properties and Reaction to Fire Mathilde Casetta, Damien Delaval, Serge Bourbigot, René Delobel, Laboratoire Procédés d'Elaboration des Revêtements Fonctionnels (PERF), LSPES - UMR/CNRS 8008, Ecole Nationale Supérieure de Chimie de Lille (ENSCL), Avenue Dimitri Mendeleïev, Villeneuve d'Ascq Cedex, France
This study deals with the thermal characterization and the reaction to fire of different PP/EPR blends issue from end of life vehicles. Reference materials have been prepared contaminating the polymer with small quantities of motor oil and/or ethylene glycol. Moreover, these samples have been extruded several times to simulate recycling. The influence of pollutants and of the recycling process on the thermal degradation of the PP/EPR blends has been examined by TGA and a kinetic analysis has been performed. An intumescent product has been incorporated in the systems and the fire retardant properties have been evaluated through specific fire tests (LOI, UL-94) and also by cone calorimetry. The different results and the influence of each pollutant and of the recycling will be discussed in the talk.
11:30 a.m.-12:00 noon Flame Retardancy Mechanisms of Aluminum Phosphinate in Glass Fiber Reinforced Thermoplastics Bernhard Schartel, U. Braun, BAM Federal Institute for Materials Research and Testing, Berlin, Germany
Halogen-free V0 performance of glass fiber reinforced thermoplastics is of great commercial interest such as for polyamides and polyesters. Recently combinations of aluminum phosphinate and melamine containing flame retardants have been proposed as novel approach in this field. A systematic investigation of the pyrolysis (TG, TG-FTIR, FTIR-ATR, NMR, SEM-EDX, etc.) flammability (LOI, UL 94) and fire behavior (cone calorimeter at different heat fluxes) is presented. Pyrolysis pathways are worked out. The flammability and fire behavior is characterized. The flame retardancy mechanism of aluminum phosphinate and aluminum phosphinate in combination with melamine polyphosphate or with melamine cyanurate is analyzed. The influence of metal cation is discussed.
12:00 noon-12:30 p.m. From Pyrolysis Kinetics to Models of Polymer Burning Guillermo Rein, BRE Centre for Fire Safety Engineering, The University of Edinburgh, UK
The last decade has seen a surge of computational modelling been applied to
solve fire protection engineering. The use of fire modelling tools is only expected
to grow at even faster rates in the short and long terms. But the robustness of the
state-of-the-art of fire modelling is currently stalled by our poor capability to
model the burning of solid fuels.
Fire simulations required submodels of the solid phase to predict flame spread
and fire growth over solid fuels. These submodels allow calculating the pyrolyzate
rate based mainly on two factors, the heat transfer into the solid and a pyrolysis
kinetic mechanism. The heat transfer problem was solved long ago and solutions
are available in the literature. But the pyrolysis part suffers from our limited
ability to understand and quantify the kinetic parameters. This precludes fire
models from calculating the reaction rates, and thus fire growth, from first
principles.
A few methodologies have been proposed in the past to extract the kinetics
governing the thermal degradation of polymers using thermogravimetric (TG)
data. These methodologies stem from the same fundamental idea consisting in
assuming a mechanism and then extracting the parameters from the experimental
results. These parameters can then be used as input to the fire models. The few
applications available until now offer promising results.
However, the selection of the underlying chemical mechanism and the
expression for the reaction rates are assumptions that compromises the quality of
the predictions. In this work, the kinetic parameters resulting from different
mechanisms are investigated at different heating rates and conditions. Two
polymers are explored, cellulose and polyurethane foam. At the lie of the result,
the key elements in the procedure are identified, the uniqueness of the solution is
investigated and conclusions are made on the robustness of the methodologies.
12:30-1:30 p.m. Lunch |
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