Grace Chigwada

Synergy between conventional phosphorus fire retardants and organically-modified clays can lead to fire retardancy of styrenics

Abstract Polystyrene–clay nanocomposites combined with phosphorous-containing fire retardants have been prepared and used to explore the thermal stability and mechanical properties of the polymer formed. The amounts of fire retardants and clay used were varied to study the effect of each on thermal stability and mechanical properties of the polymer. The samples were prepared by bulk polymerization and analyzed by X-ray diffraction, thermogravimetric analysis, cone calorimetry, Fourier Transform infrared spectroscopy and the evaluation of mechanical properties. The thermal stability of the polymers is enhanced by the presence of the phosphorus-containing fire retardants.

High-throughput techniques for the evaluation of fire retardancy

As new flame retardant (FR) approaches are developed they must be evaluated with conventional FR additives, processing additives, stabilizers, and fillers. In most cases this is done in a number of polymers, and a variety of processing conditions also must be optimized. Thus the development of new FR methods is a multi-parameter problem. A full-factorial approach to developing the structure–property relationships of interest requires numerous experiments and is prohibitively labor intensive; additional methods in which the composition space can be rapidly sampled and evaluated are necessary. Several new high throughput approaches are described herein which have been correlated with conventional flammability tests.

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 of modified 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.