- Thermal degradation characteristic and flame retardancy of polylactide-based nanobiocomposites
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Polylactide (PLA) is one of the most widely used organic bio-degradable polymers. However, it has poor flame retardancy characteristics. To address this disadvantage, we performed melt-blending of PLA with intumescent flame retardants (IFRs; melamine phosphate and pentaerythritol) in the presence of organically modified montmorillonite (OMMT), which resulted in nanobiocomposites with excellent intumescent char formation and improved flame retardant characteristics. Triphenyl benzyl phosphonium (OMMT-1)-and tributyl hexadecyl phosphonium (OMMT-2)-modified MMTs were used in this study. Thermogravimetric analysis in combination with Fourier transform infrared spectroscopy showed that these nanocomposites release a smaller amount of toxic gases during thermal degradation than unmodified PLA. Melt-rheological behaviors supported the conclusions drawn from the cone calorimeter data and char structure of the various nanobiocomposites. Moreover, the characteristic of the surfactant used for the modification of MMT played a crucial role in controlling the fire properties of the composites. For example, the nanocomposite containing 5 wt.% OMMT-1 showed significantly improved fire properties with a 47% and 68% decrease in peak heat and total heat release rates, respectively, as compared with those of unmodified PLA. In summary, melt-blending of PLA, IFR, and OMMT has potential in the development of high-performance PLA-based sustainable materials.
- Malkappa, Kuruma,Bandyopadhyay, Jayita,Ray, Suprakas Sinha
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- Thiocyanation of alkyl halides with alkyl thiocyanates in the presence of quaternary phosphonium halides
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Alkyl thiocyanates undergo simple SN2 reactions with the counter ions of quaternary phosphonium salts in nonpolar solvents and thiocyanate ions are liberated as the leaving ion. Depending on the nucleophile, the reaction proceeded irreversibly or reversibly. The reaction of benzyl thiocyanate with azide ions afforded a quantitative yield of benzyl azide. The reactions of alkyl thiocyanates with halide ions gave an equilibrium mixture where the reverse reaction of the alkyl halides produced with the liberated thiocyanate ions took place simultaneously. Thus, thiocyanate-halide exchange reactions between an alkyl thiocyanate and an alkyl halide were possible in the presence of a catalytic amount of a quaternary salt.
- Ohtani, Noritaka,Murakawa, Shigeki,Watanabe, Kohji,Tsuchimoto, Daisuke,Sato, Daiki
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p. 1851 - 1856
(2007/10/03)
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