Journal of Fire Sciences

This article studied the dripping behavior of eight polymers under UL94 vertical test conditions. The results suggested two different dripping behaviors: Type I, dripping with uniform- and small-sized drops with the short first dripping time, and Type II, dripping with irregular- and large-sized drops with the long first dripping time. Polymers of Type I dripping had dominant decomposition mechanism of random-chain scission, low activation energy of viscous flow, and high ratio of effective heat of combustion to heat of gasification. Otherwise, Type II dripping dominates. The surface tension at ambient temperature and the melt flow index at processing temperatures were not as important to dripping as expected. It was found that talc could convert the dripping of low-density polyethylene from Type I to Type II at a critical talc loading level of 20 wt%, which was ascribed to the reduction in the burning rate and the formation of an integral residue. Finally, a generalized model was presented, and a derived correlation showed that the drop mass was a power law function of the dripping time.

In this study, experiments are carried out to assess the influence of igniter location on the ignition characteristics of horizontally oriented and vertically oriented polymethylmethacrylate. Some new and significant conclusions are drawn from the study, including the linear relation between ignition time and the height of igniter and the U-shape curve of mass flux at ignition when the specimen is horizontally oriented. On the other hand, compared with the horizontally oriented condition, the mass flux at ignition of the vertically oriented specimen is larger. As the pilot igniter is moved perpendicularly with respect to the vertically oriented polymethylmethacrylate, its position, together with heat flux and solid boundary, influence the ignition time. The position of shortest ignition time is experimentally observed and as the igniter is moved horizontally, ignition time increases with increasing distance between the igniter and the surface of the vertically oriented specimen. The distance for nonignition also increases with increasing heat flux.

Many useful correlation equations derived for estimating the heat release rate for a postflashover room fire were applied in performance-based design. A postflashover room fire is very hazardous as demonstrated by several big accidents in the past few years. The authorities are starting to challenge the use of such equations as fire engineering design tools. Additional justification of the results with experiments in fire hazard assessment is now required. Two correlation equations on heat release rates with gas temperature for postflashover fire are commonly used. One was reported by Babrauskas and Williamson and the other by McCaffrey et al., denoted as BW and MQH equations, respectively. Both equations were justified in this article by reported experimental data. Two sets of reported experimental results on postflashover room fires with transient heat release rates measured by oxygen consumption calorimetry were used. One set was reported by Chow et al. on studying flashover in a compartment fire with gasoline pool fires up to 2.8 MW. The other set was the experimental data on cable fires in a long cavity reported by Hietaniemi et al. Direct comparison indicated that heat release rates estimated using the BW equation are lower than measured values of both sets of the experiments. This point should be watched while applying the BW equation in fire hazard assessment. Better agreement was observed in the equation by MQH. A possible reason is that the empirical constants in the MQH equation were deduced by fitting with experimental data.

Polyamide 6,6 is used in many industrial fields such as housing materials, transport or electrical engineering applications. Due to its chemical composition, this polymer is easily flammable. As far as the main applications concern electrical and electronic equipments, its flame-retardant properties become an important requirement. The most discriminating tests are the limiting oxygen index, UL94 and glow wire flammability index. The aim is to obtain high limiting oxygen index values, V0 rating at UL94 test for 1.6- or 0.8-mm-thick samples and a validation at 960°C of the glow wire flammability index. The usual way to fire retard polyamide 6,6 consists of incorporating an important loading of fire-retardant additives, which often reduce the intrinsic properties of the polymer. It is also difficult to combine a thin polymer thickness (e.g. 0.8 mm) and a high amount of additives because of processing issues. In this article, we first carried out a rapid screening to determine the best fire retardant for polyamide 6,6 and its optimized amount to achieve the previously defined fire retardant properties. It was shown that an amount of 23% of aluminium diethylphosphinate Exolit OP1230 allows reaching the requirements. Then, carrying out two different surface treatments (coating of polysiloxanes by plasma-enhanced chemical vapour deposition and use of an intumescent waterborne varnish), we have tried to reach the same results. It was shown that the use of surface treatment alone does not allow reaching the objectives. As a consequence, the combination of the bulk approach at low loadings with the surface treatment was investigated. This new route allows the combination of the condensed phase mechanism of the intumescent barrier with the gas phase mechanism of the OP1230 and leads to very good results: the use of 5% of the flame-retardant additives combined with a 100-µm-thick waterborne intumescent varnish leads to better results than a 23% of additive loading.

In this article, a study is reported on the ignition of timber board by an incandescent light. A set of experimental tests were conducted to demonstrate the possibility of such an event. Inference was then made to the possible cause of a fire incident that occurred at a building construction site a few years ago. Theoretical analysis was also conducted based on an ignition model. The model is able to correlate the time to ignition with the distance between the light bulb with a given power output and the timber board.

Flame-retardant additives used in plastics are based on halogen, phosphorus, inorganic compounds, and minerals. In this study, the use of bismuth trioxide as synergistic agent with brominated flame retardant is investigated and compared to formulations with antimony trioxide. Decabromodiphenyl ether and metal trioxide were incorporated in a polymer matrix via single-screw extrusion. The samples were classified with the UL 94 vertical burning protocol and studied with thermogravimetric analysis. The general combustion and heat release behaviors were studied via cone calorimeter. Results showed that 4% (wt) Bi₂O₃ displayed a synergistic effect with 12% (wt) of the halogen compound to achieve V-0.