Journal
POLYMER DEGRADATION AND STABILITY
Volume 96, Issue 3, Pages 256-269Publisher
ELSEVIER SCI LTD
DOI: 10.1016/j.polymdegradstab.2010.12.006
Keywords
Flame retarding PA6; Synergism; Time of ignition; Migration; Rate of heat release; Pentabromobenzyl acrylate
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Three systems of FR treatments of polyamide 6 with conventional flame retarding additives in the absence and in the presence of nanoparticles are discussed: I. ammonium sulfamate (AS) and dipentaerythritol (Di) II. melamine cyanurate (MC) Ill. pentabromobenzyl acrylate in the monomeric (PMA) and the polymeric (PPA) form. Depending on the concentration of the nanoparticles; synergism, antagonism, and cooperation in flame retardancy as well as in mechanical properties are observed. Cooperation between the OMMT in the concentration range of 0.5-1.0 wt% and the FR in all three systems is observed. The decrease in PHRR (Delta PHRR) is different for the three systems. In system III the brominated FR behaves similarly to OMMT with respect to Delta PHRR. The interaction between the molten polymeric matrix and the nanoparticles increases the viscosity in all three systems, which slows down the supply of the flame retarding moieties to the flame and lowers the FR rating, as measured by the UL-94 and OI tests. A new approach for assessing the viscosity of the pyrolyzing nanocomposite is presented by determining the size and mass of the drops formed during the UL-94 test. Dispersion of the nanoparticles in the polymer decreases the HRR and MRR and decreases the UL-94, OI ratings, and the mechanical properties, as evidenced by the different behavior of OMMT and Na(+)MMT. The time of ignition decreases markedly by the addition of the nanoparticles, due to the low thermal conductivity and heat transfer of the protective barrier on the surface of the pyrolyzing nanocomposite in the pre-ignition phase. A possibility of restoring the high FR rating in the presence of higher concentrations of nanoparticles is indicated. The significance of the results obtained for the future of the use of nanoparticles in FR is discussed. (c) 2010 Elsevier Ltd. All rights reserved.
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