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Thermal Degradation Chemistry of Alkyl Quaternary Ammonium Montmorillonite

Wei XieWestern Kentucky UniversityZongming GaoThermal Analysis Laboratory, Material Characterization Center, Department of Chemistry, Western Kentucky University, Bowling Green, Kentucky 42101; Southern Clay Products, Inc., 1212 Church Street, Gonzales, Texas 78629; Triton Systems, Inc., 200 Turnpike Road, Chelmsford, Massachusetts 01824; and AFRL/MLBP, BLDG 654, 2941 P Street, Wright-Patterson AFB, Ohio 45433Wei-Ping PanThermal Analysis Laboratory, Material Characterization Center, Department of Chemistry, Western Kentucky University, Bowling Green, Kentucky 42101; Southern Clay Products, Inc., 1212 Church Street, Gonzales, Texas 78629; Triton Systems, Inc., 200 Turnpike Road, Chelmsford, Massachusetts 01824; and AFRL/MLBP, BLDG 654, 2941 P Street, Wright-Patterson AFB, Ohio 45433Doug HunterThermal Analysis Laboratory, Material Characterization Center, Department of Chemistry, Western Kentucky University, Bowling Green, Kentucky 42101; Southern Clay Products, Inc., 1212 Church Street, Gonzales, Texas 78629; Triton Systems, Inc., 200 Turnpike Road, Chelmsford, Massachusetts 01824; and AFRL/MLBP, BLDG 654, 2941 P Street, Wright-Patterson AFB, Ohio 45433Anant Kumar SinghThermal Analysis Laboratory, Material Characterization Center, Department of Chemistry, Western Kentucky University, Bowling Green, Kentucky 42101; Southern Clay Products, Inc., 1212 Church Street, Gonzales, Texas 78629; Triton Systems, Inc., 200 Turnpike Road, Chelmsford, Massachusetts 01824; and AFRL/MLBP, BLDG 654, 2941 P Street, Wright-Patterson AFB, Ohio 45433Richard A. VaiaThermal Analysis Laboratory, Material Characterization Center, Department of Chemistry, Western Kentucky University, Bowling Green, Kentucky 42101; Southern Clay Products, Inc., 1212 Church Street, Gonzales, Texas 78629; Triton Systems, Inc., 200 Turnpike Road, Chelmsford, Massachusetts 01824; and AFRL/MLBP, BLDG 654, 2941 P Street, Wright-Patterson AFB, Ohio 45433

2001fi

ABI

Annotatsiya

The thermal stability of organically modified layered silicate (OLS) plays a key role in the synthesis and processing of polymer-layered silicate (PLS) nanocomposites. The nonoxidative thermal degradation of montmorillonite and alkyl quaternary ammonium-modified montmorillonite were examined using conventional and high-resolution TGA combined with Fourier transform infrared spectroscopy and mass spectrometry (TG−FTIR−MS) and pyrolysis/GC−MS. The onset temperature of decomposition of these OLSs was approximately 155 °C via TGA and 180 °C via TGA−MS, where TGA−MS enables the differentiation of water desorbtion from true organic decomposition. Analysis of products (GC−MS) indicates that the initial degradation of the surfactant in the OLS follows a Hoffmann elimination reaction and that the architecture (trimethyl or dimethyl), chain length, surfactant mixture, exchanged ratio, or preconditioning (washing) does not alter the initial onset temperatures. Catalytic sites on the aluminosilicate layer reduce thermal stability of a fraction of the surfactants by an average of 15−25 °C relative to the parent alkyl quaternary ammonium salt. Finally, the release of organic compounds from the OLS is staged and is associated with retardation of product transfer arising from the morphology of the OLS. These observations have implications to understanding the factors impacting the interfacial strength between polymer and silicate and the subsequent impact on mechanical properties as well as clarifying the role (advantageous or detrimental) of the decomposition products in the fundamental thermodynamic and kinetic aspects of polymer melt intercalation.

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DOI: 10.1021/cm010305s

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