Showing papers in "Fire and Materials in 2018"

Waste‐derived low‐cost mycelium composite construction materials with improved fire safety

Abstract: Mycelial growth attracts academic and commercial interest because of its ability to upcycle agricultural and industrial wastes into economical and environmentally sustainable composite materials using a natural, low-energy manufacturing process able to sequester carbon. This study aims to characterise the effect of varying ratios of high silica agricultural and industrial wastes on the flammability of mycelium composites, relative to typical synthetic construction materials. The results reveal that mycelium composites are safer than the traditional construction materials considered, producing much lower average and peak heat release rates and longer time to flashover. They also release significantly less smoke and CO2, although CO production fluctuated. Rice hulls yielded significant char and silica ash which improved fire performance, but composites containing glass fines exhibited the best fire performance because of their significantly higher silica concentrations and low combustible material content. Higher concentrations of glass fines increased volume-specific cost but reduced mass-specific and density-specific costs. The findings of this study show that mycelium composites are a very economical alternative to highly flammable petroleum-derived and natural gas-derived synthetic polymers and engineered woods for applications including insulation, furniture, and panelling.

Study of fire behaviour of facade mock-ups equipped with aluminium composite material-based claddings, using intermediate-scale test method

Abstract: Efectis France, route de l'Orme des Merisiers, 91193 Saint Aubin Cedex, France Efectis UK‐Ireland, Jordanstown Campus Block 27, Shore Road, Newtownabbey BT 37 0QB, UK Ulster University, FIRESERT, Jordanstown Campus Block 27, Shore Road, Newtownabbey BT 37 0QB, UK Correspondence Eric Guillaume, Efectis France, route de l'Orme des Merisiers, 91193 Saint Aubin Cedex, France. Email: eric.guillaume@efectis.com

Three in one: β-cyclodextrin, nanohydroxyapatite, and a nitrogen-rich polymer integrated into a new flame retardant for poly (lactic acid)

Abstract: A new halogen‐free flame retardant was developed by integrating β‐cyclodextrin, triazin ring, and nanohydroxyapatite (BSDH) into a hybrid system. A β‐cyclodextrin was grafted to a commercially available SABO®STAB UV94 via an aromatic deanhydrate. The BSDH was prepared in situ in the presence of β‐cyclodextrin‐grafted nitrogen‐rich precursor. The resulting hybrid was applied as a flame retardant for poly(lactic acid) (PLA) and compared for performance with ammonium polyphosphate (APP). PLA composites containing BSDH and APP, individually or simultaneously, were examined for thermal degradation and flammability by TGA, cone calorimeter, and pyrolysis‐combustion flow calorimetry. TGA results confirmed enhancement of thermal stability of PLA with assistance of BSDH compared to APP. The gases evolved during thermal degradation were assessed by a thermogravimetric analysis and Fourier infrared spectroscopy device. APP revealed catalytic effect to initiate PLA degradation, while BSDH continued to release some gases at elevated temperatures. The flame retardancy of PLA/APP/BSDH blend containing only 10 wt.% of additives was significantly improved. In cone calorimetric tests, a significant fall in peak of heat release rate was observed for this sample, 49% more than that of neat PLA, which was indicative of more gas and condensed phase reflected in more char residue. The corresponding PLA/APP sample, however, showed 17% improvement, as compared to neat PLA. Also, total heat release rate of PLA/APP/BSDH was 45 MJ.m−2, whereas those of PLA and PLA/APP were 89 and 65 MJ.m−2, respectively. BSDH and APP showed a synergistic effect on improving the flame retardancy of PLA composites.

Cable tray fire tests in a confined and mechanically ventilated facility

Abstract: Cable fires are one of the main fire hazards in nuclear power plants. As part of the cable fire spreading (CFS) campaign of the OECD PRISME-2 programme, 3 real-scale cable tray fire tests were performed in open atmosphere (1 CFS support test, named CFSS-2) and in a confined and mechanically ventilated facility (2 CFS tests, named CFS-3 and CFS-4). This study aims at investigating the effects of confined and ventilated conditions on cable tray fires that used a halogen-free flame retardant cable-type. The CFS-3 and CFS-4 tests involved 2 ventilation renewal rates of 4 and 15 h−1, respectively. The confined conditions lead to decrease the fire growth rate and the peaks of mass loss rate and heat release rate, compared with open atmosphere. The reductions are larger for the lower ventilation renewal rate. Furthermore, it is shown that the CFS-4 test may be classified as a well-ventilated fire and the CFS-3 test as an under-ventilated fire. For this last one, its fire characteristics and its consequences in the fire room highlight an oscillatory behaviour, with the same low frequency, for about 30 minutes. These oscillations arise from successive combustions of unburnt gases.

Fire performance of charring closed‐cell polymeric insulation materials: Polyisocyanurate and phenolic foam

Abstract: Results are presented from 2 series of ad hoc experimental programmes using the cone calorimeter to investigate the burning behaviour of charring closed-cell polymeric insulation materials, specifically polyisocyanurate (PIR) and phenolic (PF) foams. These insulation materials are widely used in the construction industry due to their relatively low thermal conductivity. However, they are combustible in nature; therefore, their fire performance needs to be carefully studied, and characterisation of their thermal degradation and burning behaviour is required in support of performance-based approaches for fire safety design. The first series of experiments was used to examine the flaming and smouldering of the char from PIR and PF. The peak heat release rate per unit area was within the range of 120 to 170kW/m(2) for PIR and 80 to 140kW/m(2) for PF. The effective heat of combustion during flaming was within the range of 13 to 16kJ/g for PIR and around 16kJ/g for PF, while the CO/CO2 ratio was within 0.05 to 0.10 for PIR and 0.025 to 0.05 for PF. The second experimental programme served to map the thermal degradation processes of pyrolysis and oxidation in relation to temperature measurements within the solid phase under constant levels of nominal irradiation. Both programmes showed that surface regression due to smouldering was more significant for PF than PIR under the same heat exposure conditions, essentially because of the different degree of overlap in pyrolysis and oxidation reactions. The smouldering of the char was found to self-extinguish after removal of the external heat source.

The intumescent flame‐retardant biocomposites of poly(lactic acid) containing surface‐coated ammonium polyphosphate and distiller's dried grains with solubles (DDGS)

Abstract: Summary This work aims to develop the poly(lactic acid) (PLA) biocomposites with high flame-retardant performance, which can be applied in electronic and electrical devices as well as automotive parts. First, an intumescent flame retardant composed of ammonium polyphosphate (APP) as the acid source and the blowing agent, and the distiller's dried grains with solubles (DDGS) as the natural charring agent was designed. The surfaces of DDGS and APP were coated by degradable polymeric flame-retardant resorcinol di(phenyl phosphate) (RDP), and the coating effects were analyzed. And then the flame-retardant biocomposites of PLA with RDP-coated DDGS (C-DDGS) and RDP-coated APP (C-APP) were prepared. The limited oxygen index value of the biocomposites with loading of 15 wt% C-DDGS and 15 wt% C-APP reached 32.0%, and UL-94 V-0 was attained. The biocomposites also had good mechanical properties and the tensile strength of this sample reached about 57 MPa. Finally, the char residues after burning were analyzed and the flame-retardant mechanism was discussed.

Specimens size, aggregate size, and aggregate type effect on spalling of concrete in fire

Abstract: Summary This paper attempted to isolate variables that govern concrete spalling when exposed to a hydrocarbon fire. The influence of specimen size was investigated by studying 4 specimen sizes consisting of cylinders, columns, and panels. Three aggregate sizes, 7 mm, 14 mm, and 20 mm were used in the concrete mixes to determine their effect on concrete spalling. Influence of aggregate type on concrete spalling was also investigated. Forty-two different specimens were considered in this investigation. Concrete spalling was quantified as nominal spalling depth, which has been presented as a new way of quantifying the degree of concrete spalling. The results indicated that specimen size did have an effect on the spalling of concrete under hydrocarbon fire exposure and that nominal spalling depth of concrete increases as the specimen size increases. Aggregate size effect was evident when the maximum aggregate size increased from 7 mm to 20 mm, and explosive spalling was more severe for specimens with small size aggregates. Specimens with 14-mm aggregate size showed inconsistent results and the spalling behavior witnessed was more random and sporadic. The type of aggregate used has no clear bearing on concrete spalling given both aggregates had similar linear expansion profiles.

Thermal and residual mechanical profile of recycled aggregate concrete prepared with carbonated concrete aggregates after exposure to elevated temperatures

Abstract: Summary Thermal and residual mechanical performance of recycled aggregate concrete (RAC) prepared with recycled concrete aggregates (RCAs) after exposure to high temperatures has so far received less attention than that of conventional concrete prepared with natural aggregates (NAs). This study experimentally investigated thermal and residual mechanical performance of RAC prepared with different replacement percentages of non-carbonated and carbonated RCAs after exposure to high temperatures. The residual mechanical properties, including compressive strength, modulus of elasticity, and peak strain at the maximum strength, were measured for evaluating the fire resistance of RAC. The experimental results showed that although the fire-resistant ability of natural granite aggregates was high, thermal deterioration of the conventional concrete after exposure to 600°C, presented by thermal induced mesocracks, was more serious than that of RAC due to thermal incompatibility between NAs and mortar. Using the carbonated RCAs can reduce the width of thermal mesocrack in RAC. The residual mechanical properties of RAC after exposure to 600°C can be obviously improved by incorporating 20% to 40% of the carbonated RCAs. For the RAC made with the 100% carbonated RCAs, the ratio of residual to initial compressive strength after exposure to above 500°C was even higher than that of the conventional concrete.

The effect of the trimerization catalyst on the thermal stability and the fire performance of the polyisocyanurate‐polyurethane foam

Abstract: Summary In this work, 3 currently used trimerization catalysts, TMR-2 (quaternary ammonium), K-15 (potassium octoate), and PU-1792 (potassium acetate) were used to produce rigid polyisocyanurate (PIR) foams with certain amounts of isocyanurate contents. The results from Fourier transform infrared (FTIR) quantitative analysis showed that PU-1792 had the highest catalytic efficiency in isocyanurate formation. Then, the effect of different amounts of PU-1792 catalyst on isocyanurate ring output was further investigated, and the result showed that the highest amount of isocyanurate ring formation could be attained by the 5 pphp of PU-1792 catalyst. It was also found that the increased amount of isocyanurate ring could result in reduced cell size, improved compressive strength, and lowered thermal conductivity of PIR foam. The results from thermogravimetric analysis (TGA) and cone calorimeter (CONE) test revealed that the thermal stability and fire performance of PIR foam could be improved with the increased amount of isocyanurate ring. Furthermore, the CONE test indicated that the smoke production of PIR foam decreased approximately 51.7% in comparison to the reference polyurethane (PU) foam, and the SEM image of char morphology showed that the char of PIR foam was more compact than PU foam.

Modeling of fire exposure in facade fire testing

Abstract: In this paper a comparative simulation study on three large scale facade testing methods, namely the SP Fire 105, BS 8414 – 1 and the ISO 13785 – 2 methods, is presented. Generally good correspondence between simulations and experimental data has been found, provided that thermal properties of the facade material and heat release rates are known however the correspondence seems to deviate in close proximity of the fire source. Furthermore, a statistical ensemble for evaluating the effects stemming from uncertainty in input data is used. Here, it was found using a statistical ensemble the variability in input data could be assessed and that the variability was smaller in the ISO 13785 – 2 compared to the BS 8414 – 1 method. The heat release rates (HRR) used in the simulations were adopted from measurements except for the ISO method where the information in the standard was used to approximate the HRR. Furthermore, a quantitative similarity between the HRR in the ISO method and the British method was found.

Fire performance of brominated and halogen-free flame retardants in glass-fibre reinforced poly(butylene terephthalate)

Abstract: Summary This paper investigates the effects of brominated and halogen-free fire retardants on the fire performance of glass-fiber (GF) reinforced poly(butylene terephthalate) (PBT). Brominated polystyrene was used as the brominated fire retardant, whereas aluminum diethylphosphinate with/without nanoclay as halogen-free fire retardants (HFFRs). Tests were conducted by using thermogravimetric analysis, limiting oxygen index (LOI), UL94, and the cone calorimeter. Thermogravimetric analysis results show that decomposition of GF plus PBT (PBT + GF) starts earlier in the presence of all fire retardants (FRs). In the cone calorimeter, all FRs reduce significantly the heat release rate (HRR) compared with PBT + GF, with brominated polystyrene achieving lowest HRR primarily because bromine released in the pyrolysis gases inhibits combustion. Brominate polystyrene does not, however, affect the mass loss rate. Aluminum diethylphosphinate alone has significant effects on reduction of both HRR and mass loss rate, which become considerably more when combined with nanoclay. It was also found that the combustion efficiency of the brominated polystyrene compound is much lower than that of HFFRs, indicating that brominated polystyrene has higher gas phase flame retardant efficiency compared with HFFRs because the bromine radicals released during degradation of brominated polystyrene effectively quench the chemical reactions of the pyrolysis gases due to degradation of PBT.

Fire‐induced reradiation underneath photovoltaic arrays on flat roofs

Abstract: The impact of the reflection of fire-induced heat from a gas burner was studied experimentally to gain knowledge on the interaction between photovoltaic (PV) panels and a fire. The heat flux was measured in a total of eight points at the same level as the top of the gas burner. The gas burner was placed underneath the centre of a PV panel and the eight points were measured in symmetrical pairs of two at four different distances from the burner. The heat release rate from the gas burner was increased stepwise every four minutes. The measurements were made underneath a PV panel installed in a geometry similar to a commercial East-West orientated mounting system and was compared to a baseline test without the re-reflection from the PV panel. A significant increase of the received heat flux was noticed and the trend indicated an ascending percentage-wise difference as a function of an increased heat release rate. Contrary to the basic view factor theory, the received heat flux was higher underneath the most elevated part of the PV panel, and this occurred due to two important flame related reasons: 1) the deflection of the flame towards the most elevated part of the panel, resulting in an increased amount of radiation from the flame towards the surface; 2) A non-homogeneous distribution of the temperature on the PV panel surface, due to the deflected flame, and thereby a non-homogeneous emission from the heated PV panel. Finally, it was seen that two similar tests conducted with respectively a brand new PV panel and a PV panel tested for the fourth time, showed very comparable results, except during the period when the thin combustible film underneath the new PV panel was burning. This resulted in a higher heat flux during that period and implies that the results presented herein are conservative in that they are lower than what can be expected in case of a real fire hazard, where the PV panel is by definition involved in the fire for the first time. It can be concluded that PV panels can have a significant contribution in roof fires, as they stimulate fire spread over the roof on which they have been mounted. These findings emphasise that the risk related to the installation of PV panels is not only associated with the increased fire load and possibility of ignition, but largely also with the changed fire dynamic surroundings of the roof construction.