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

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

Enhanced Fire Retardancy of Vinyl Ester Resins by Combination of Additives

In pursuit of fire-retardant materials, vinyl ester resins were combined with commercially available fire retardants at lower loadings than that at which they are usually effective when used alone. The thermal stability and flammability of the various combinations of fire retardants were evaluated by thermogravimetric analysis and cone calorimetric analysis. With some combinations, the 50% degradation temperature was improved by about 5-10ºC Different additives affected the flammability to varying extents and some combinations resulted in an enhanced fire retardancy compared to the additives used alone. The combinations that showed the best reductions in the peak heat release rate (PHRR) were further used to prepare glass reinforced resins and the flammability of those systems was also evaluated using cone calorimetry

Polystyrene Nanocomposites Based on Quinolinium and Pyridinium Surfactants

In this paper pyridine and quinoline-containing salts were employed to modify montmorillonite. TGA analysis shows that the quinolinium modified clay has a higher thermal stability than the pyridinium modified clay. Polystyrene nanocomposites were prepared by in situ bulk polymerisation and direct melt blending using both clays. The X-ray diffraction and transmission electron microscopy results show the formation of intercalated structures. The 50% degradation temperature of the nanocomposites is increased and so is the amount of char from TGA analysis compared to the virgin polymer. Cone calorimetric results indicate that clay reduces the peak heat release rate and average mass loss rate and thus lowers the flammability of the polymer

Polystyrene Nanocomposites based on Carbazole-Containing Surfactants

New organically-modified clays containing a carbazole unit were prepared and the number of long alkyl chains on the surfactant was varied. The clay was used to prepare polystyrene nanocomposites by both bulk polymerization and melt blending. The dispersion of these clays in the polymer matrix was evaluated using X-ray diffraction (XRD) and transmission electron microscopy (TEM). The thermal stability of the clays and the nanocomposites were analyzed by thermogravimetric analysis (TGA) while the fire properties were evaluated by cone calorimetry. If more than two alkyl chains were present, the gallery spacing is apparently overcrowded, leading to poor dispersion. Bulk polymerization gave nanocomposites with better dispersion and reduced flammability when compared to the melt blending process

Styrenic Nanocomposites Prepared using a Novel Biphenyl-Containing Clay

Montmorillonite was organically modified using an ammonium salt containing 4-acetylbiphenyl. This clay (BPNC16 clay) was used to prepare polystyrene (PS), acrylonitrile butadiene styrene (ABS) and high impact polystyrene (HIPS) nanocomposites. Polystyrene nanocomposites were prepared both by in situ bulk polymerisation and melt blending processes, while the ABS and HIPS nanocomposites were prepared only by melt blending. X-ray diffraction and transmission electron microscopy were used to confirm nanocomposite formation. Thermogravimetric analysis was used to evaluate thermal stability and the flammability properties were evaluated using cone calorimetry. By thermogravimetry, BPNC16 clay was found to show high thermal stability, and by cone calorimetry, a decrease in both the peak heat release rate and the mass loss rate was observed for the nanocomposites

Fire Retardancy of Vinyl Ester Nanocomposites: Synergy with Phosphorus-Based Fire Retardants

Vinyl ester (PVE) nanocomposites were prepared using both clay and polyhedral oligosilsesquioxanes (POSS) as the nano-dimensional material. From cone calorimetric data, it was shown that both POSS and clay affect the flammability of the nanocomposites to the same extent. To improve on the flame retardancy, the nanocomposites were combined with phosphorous-containing fire retardants (FRs) and the result compared to the benchmark halogen-containing system. The use of the cone calorimeter to investigate the fire properties of these nanocomposites showed a great reduction in peak heat release rate (PHRR) in the presence of phosphate and slight improvements in average mass loss rate (AMLR) while thermogravimetric analysis showed improvement in char yield in the presence of phosphate. Several different organically modified clays were used and they affected the flammability to different extents. The time that the resin and clay were mixed and the atmosphere in which the reaction was carried out do not have an effect on the flammability and thermal stability of the nanocomposites. The effect of curing temperature on the clay dispersion and flammability was also investigated

Synergy Between Nanocomposite Formation and Low Levels of Bromine on Fire Retardancy in Polystyrenes

An organically-modified clay has been prepared using ammonium salts which contain an oligomeric material consisting of vinylbenzyl chloride, styrene and dibromostyrene. The presence of dibromostyrene enhances the flame retardancy of polystyrene nanocomposites compared to both the virgin polymer and polystyrene nanocomposites prepared from non-halogen-containing organically-modified clays. The nanocomposites were prepared both by bulk polymerization and melt blending and they were evaluated by X-ray diffraction, transmission electron microscopy, thermogravimetric analysis and cone calorimetry measurements. Bulk polymerization produced nanocomposites with reduced peak heat release rate, reduced total heat release and improved thermal stability. It is noteworthy that all these improvements were obtained with clay loading as low as 3% and bromine content less than 4%

Nanostructured Layered Copper Hydroxy Dodecyl Sulfate: A Potential Fire Retardant for Poly(vinyl Ester) (PVE)

Composites of poly(vinyl ester) (PVE) with copper hydroxy dodecyl sulfate (CHDS) were prepared by thermal curing. The efficiency of the additive, CHDS, in reducing flammability is demonstrated via cone calorimetry and thermogravimetric analysis (TGA). The addition of 1-10% by mass of the CHDS additive resulted in significant increments in char formation (~4-11%) from thermogravimetric analysis (TGA). Incorporation of the CHDS into the polymer matrix at these low concentrations leads to substantial reductions in the total heat release (~20-30%) but no significant change in the peak heat release rate. The composite materials generally ignite more quickly, however, the flame extinguishes faster for the composites relative to the virgin polymer. X-ray diffraction (XRD) and infrared spectroscopic analyses of the residues collected at various stages during thermal decomposition of the composities, suggest the participation of copper-containing species in promoting enhanced thermal stability of PVE

Effects of additives and structure of surfactants on fire retardancy of polymer nanocomposites

Nanocomposites are know to enhance flame retardancy (FR) and result in reduced PHRR compared to the virgin polymer, which is good, but on the other hand the total heat produced is the same as that of the virgin polymer, which means that eventually everything burns. Phosphorous-containing compounds are also used as additives and they reduce flammability. However, like any other additives large amounts have to be used. The advantage of using phosphorous-containing compounds is that they are not hazardous to the environment. So with these facts in mind the objective of this study is to develop a small-scale system that can be used for the preliminary analysis of nanocomposites containing phosphate additives and then study the synergism between nanocomposites and phosphorous-containing fire retardants (FRs) for large samples. This goal was achieved by first developing a high throughput system that was used to evaluate phosphorous-containing additives that are compatible with nanocomposites and do not burn after exposure to a flame. Large samples of the Polymer/Fire retardant/clay systems were prepared using the phosphates that passed the first analysis. The amounts of both the clay and FR were varied. In the second part we investigated the synergism in vinyl ester (VE) nanocomposites. The vinyl ester studied was Derakane 441-400. In the VE/FR/clay systems, apart from varying the amounts of fire retardant and clay, we also investigated the effects of using different clays, varying mixing times and varying the curing conditions to see effect on the clay dispersion in the nanocomposites. In these systems we hope to lower the flammability of the systems and also not adversely impact the mechanical properties. The effect of varying the structure of surfactants on nanodispersion and fire retardancy of clay nanocomposites was also investigated