Probing synergism, antagonism, and additive effects in poly(vinyl ester) (PVE) composites with fire retardants

Potential fire retardants, including copper hydroxy dodecyl sulfate (CHDS), organically-modified montmorillonite (Cloisite 15A), and resorcinol di-phosphate (RDP), were added to pure poly(vinyl ester) (PVE) individually or in combinations at low concentration formulations. Thermogravimetric analysis and cone calorimetry were used to study the thermal stability and fire performance of the composites. Synergistic, antagonistic, and additive effects were observed depending on the specific formulation. Time to self-sustained combustion is greatly reduced, but the flame extinguishes faster, for the composites containing CHDS alone or in combination with either RDP or Cloisite 15A compared to the virgin polymer. The presence of copper in PVE composites containing additive, CHDS, may be responsible for the enhanced thermal stability and fire performanc

Thermal stability and degradation kinetics of polystyrene/organically- modified montmorillonite nanocomposites

Organically-modified montmorillonite (MMT) clays have been prepared using ammonium salts containing quinoline, pyridine, benzene, and styrenic groups. The nanocomposites were prepared by melt blending and the formation of nanocomposites was characterized using X-ray diffraction (XRD) and transmission electron microscopy (TEM). Thermal stability and flammability were evaluated by thermogravimetric analysis (TGA) and cone calorimetry measurements, respectively. The presence ofmodified MMT at 5% loading resulted in significant improvement in thermal stability compared to the virgin polymer. Effective activation energies for mass loss were determined via a model-free isoconversional approach from TGA data obtained under N2 and under air. The additives served to raise the activation energy, with a more significant impact observed under pyrolysis conditions. The onset temperature of degradation and temperature of maximum decomposition rate are increased, while the peak heat release rate and mass loss rates are significantly reduced in the presence of three of the modified clays. No reduction in the total heat released is observed

Keeping out of trouble: Female crack cocaine dealers in England

This paper offers a rare insight into women’s experiences dealing crack cocaine. Drawing on interviews with eight women, this research finds that, although the retail-level crack trade is male dominated, it is not simply a man’s world. This paper examines the strategies that successful female dealers employed, demonstrating that women reflexively took their gender into account to made cognizant choices about what, when and how to deal. Dealing strategies were a response not solely to the gendered nature of the drug market but also to women’s gendered social positions, relationships and identities. Performing respectable femininity was a key strategy for keeping dealing hidden and keeping out of trouble. This paper is underpinned by the concept of ‘doing gender’