Effects of nanoadditives and different conventional flame redardants on the flammability of polystyrene

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2012
Sipahioğlu, Bengü Melike
In this thesis, there were four purposes. The first one was to investigate effects of nanoclays (NC) on the flammability behavior of polystyrene (PS). The second purpose was to investigate contribution of nanoclays to the flame retardancy performance of conventional phosphorus based flame retardant; triphenyl phosphate (TPP) and its synergist melamine cyanurate (MCA). For the third purpose contribution of nanoclays to the flame retardancy performance of another conventional halogenated flame retardant; brominated epoxy polymer (BE) and its synergist antimony trioxide (AO) was investigated. As the fourth purpose, effects of another nanoadditive; carbon nanotubes (CNTs) on the flammability behavior of PS with and without BE-AO flame retardant system was investigated. Materials were prepared via “solution mixing” method, while test specimens were shaped by compression and injection molding. Flammability behaviors were investigated by Mass Loss Cone Calorimeter (MLC), Limiting Oxygen Index (LOI) and UL-94 Vertical Burning tests. Other characterization techniques required in this thesis were; X-ray diffraction analyses, scanning and transmission electron microscopy, thermogravimetric analyses and tensile tests. It was revealed that use of nanoclays improved flame retardancy of PS significantly, mainly with “condensed phase” mechanism via formation of strong char barrier layers inhibiting mass and heat transfer. When nanoclays were used together with conventional flame retardant systems TPP-MCA and BE-AO, flame retardancy parameters improved further, this time due to the “synergistic action” of “condensed phase mechanism” of nanoclays and “gas phase mechanism” of the conventional systems. Use of carbon nanotubes also resulted in improvements in the flame retardancy of PS. However, “condensed phase mechanism” of CNTs were not as effective as the NCs, which might be due to the lower performance of 1D geometry (CNTs) compared to higher efficiency of 2D geometry (NC) in barrier formation. As an additional purpose, effects of mixing methods in the production of PS-Nanoclay composites were also investigated. It was seen that compared to “solution mixing” use of “in-situ polymerization” resulted in poorer flame retardancy parameters that might basically be due to residual monomers or oligomers left during polymerization.

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Citation Formats
B. M. Sipahioğlu, “Effects of nanoadditives and different conventional flame redardants on the flammability of polystyrene,” M.S. - Master of Science, Middle East Technical University, 2012.