This paper reports on studies relating to the unstressed residual compressive strengths of geopol... more This paper reports on studies relating to the unstressed residual compressive strengths of geopolymer pastes that are heated up to 800 °C, behavior of reactive powder concrete before and after exposure to elevated temperatures and thermal behavior of novel reactive powder geopolymer-based concretes. For this purpose, 10 geopolymer pastes and three reactive powder concrete mixtures were tested for residual strengths. Gladstone fly ash was used as the primary binder for both geopolymer pastes and reactive powder geopolymer concretes. In addition, four novel reactive powder geopolymer concrete mixes were prepared with zero cement utilization. While reactive powder concretes achieved the highest seven-day compressive strengths of approximately 140 MPa, very poor thermal behavior was observed, with explosive spalling occurring at a temperature of ca. 360 °C. The reactive powder geopolymer concretes, on the other hand, displayed relatively high thermal properties with no thermal cracking ...
Geopolymer concrete is a valuable and alternative type of concrete that is free of traditional ce... more Geopolymer concrete is a valuable and alternative type of concrete that is free of traditional cement. Generally, geopolymer concretes require a source material, which is rich in silicon and aluminum. Furthermore, fly ash-based geopolymer concretes have been proven to have superior fire resistance, primarily due to their ceramic properties, and are inherently environmentally-friendly given their zero-cement content. This paper presents the effects on initial evaporation on the performance of fly ash-based geopolymer pastes after exposure to elevated temperatures of 400 °C and 800 °C. The fly ash (FA) samples used in the present study included: Gladstone and Gladstone/Callide. The results for sealed samples placed in the oven during curing were much more consistent than the samples that were not kept covered. In addition, Gladstone fly ash-based geopolymer samples that were sealed recorded an initial maximum compressive strength reading of ca. 75 MPa, while sealed Gladstone/Callide f...
Given that existing fire risk models often ignore human and organizational errors (HOEs) ultimate... more Given that existing fire risk models often ignore human and organizational errors (HOEs) ultimately leading to underestimation of risks by as much as 80%, this study employs a technical-human-organizational risk (T-H-O-Risk) methodology to address knowledge gaps in current state-of-the-art probabilistic risk analysis (PRA) for high-rise residential buildings with the following goals: (1) Develop an improved PRA methodology to address concerns that deterministic, fire engineering approaches significantly underestimate safety levels that lead to inaccurate fire safety levels. (2) Enhance existing fire safety verification methods by incorporating probabilistic risk approach and HOEs for (i) a more inclusive view of risk, and (ii) to overcome the deterministic nature of current verification methods. (3) Perform comprehensive sensitivity and uncertainty analyses to address uncertainties in numerical estimates used in fault tree/event trees, Bayesian network and system dynamics and their ...
Polymers are increasingly being used in domestic, commercial and public environments as component... more Polymers are increasingly being used in domestic, commercial and public environments as components of fabrics, surface coatings and moulded articles. Most of these polymeric components are synthetic, are based on hydrocarbon intermediates, and are highly flammable, thus resulting in unwanted fires. Fire fatalities are essentially due to the evolved smoke and toxic gases, exacerbated in some cases by poisonous fumes emitted from synthetic organic polymers. In addition, many of the thermoplastic materials tend to melt and flow under heat/fire, and this can constitute a very serious secondary hazard in fire scenarios involving them. Combustion of polymeric materials is a complex phenomenon that involves the solid phase, gaseous phase and the interphase.
The isothermal crystallization of poly(l-lactide) (PLLA) has been investigated by in-situ wide an... more The isothermal crystallization of poly(l-lactide) (PLLA) has been investigated by in-situ wide angle X-ray diffraction (WAXD) and polarized optical microscopes (POM) equipped with a hot-stage accessory. Results showed that the spherulites of PLLA were formed at high temperature, whereas irregular morphology was observed under a low temperature. This can be attributed to the varying rates of crystallization of PLLA at different temperatures. At low temperatures, the nucleation rate is fast and hence the chains diffuse very slow, resulting in the formation of imperfect crystals. On the other hand, at high temperatures, the nucleation rate is slow and the chains diffuse fast, leading to the formation of perfect crystals. The change in the value of the Avrami exponent with temperature further verifies the varying trend in the morphological feature of the crystals.
Polymeric materials often exhibit complex combustion behaviours encompassing several stages and i... more Polymeric materials often exhibit complex combustion behaviours encompassing several stages and involving solid phase, gas phase and interphase. A wide range of qualitative, semi-quantitative and quantitative testing techniques are currently available, both at the laboratory scale and for commercial purposes, for evaluating the decomposition and combustion behaviours of polymeric materials. They include, but are not limited to, techniques such as: thermo-gravimetric analysis (TGA), oxygen bomb calorimetry, limiting oxygen index measurements (LOI), Underwriters Laboratory 94 (UL-94) tests, cone calorimetry, etc. However, none of the above mentioned techniques are capable of quantitatively deciphering the underpinning physiochemical processes leading to the melt flow behaviour of thermoplastics. Melt-flow of polymeric materials can constitute a serious secondary hazard in fire scenarios, for example, if they are present as component parts of a ceiling in an enclosure. In recent years,...
This paper reports on the enhancement of the thermal transport properties of nanocomposite materi... more This paper reports on the enhancement of the thermal transport properties of nanocomposite materials containing hexagonal boron nitride in poly (vinyl alcohol) through room-temperature atmospheric pressure direct-current microplasma processing. Results show that the microplasma treatment leads to exfoliation of the hexagonal boron nitride in isopropyl alcohol, reducing the number of stacks from >30 to a few or single layers. The thermal diffusivity of the resulting nanocomposites reaches 8.5 mm2 s-1, 50 times greater than blank poly (vinyl alcohol) and twice that of nanocomposites containing non-plasma treated boron nitride nanosheets. From TEM analysis, we observe much less aggregation of the nanosheets after plasma processing along with indications of an amorphous carbon interfacial layer which may contribute to stable dispersion of boron nitride nanosheets in the resulting plasma treated colloids.
In this paper, we report on the thermal degradation behaviours and combustion attributes of some ... more In this paper, we report on the thermal degradation behaviours and combustion attributes of some polymers based on polystyrene (PSt). Here, both additive and reactive strategies were employed, through the bulk polymerization route, where the modifying groups incorporated P-atom in various chemical environments. These included oxidation states of III or V, and the loading of phosphorus was kept at ca. 2 wt.% in all cases. The characterization techniques that were employed for the recovered products included spectroscopic, thermal, and calorimetric. It was found that the presence of different modifying groups influenced the degradation characteristics of the base polymer, and also exerted varying degrees of combustion inhibition. In all cases, the modification of the base matrix resulted in a noticeable degree of fire retardance as compared to that of the virgin material. Therefore, some of the modifications presented have the potential to be explored on a commercial scale.
Styrene (ST) and methyl methacrylate (MMA) have been copolymerized with a variety of comonomers c... more Styrene (ST) and methyl methacrylate (MMA) have been copolymerized with a variety of comonomers containing covalently-bound phosphorus-containing groups, including vinyl phosphonic acid, several dialkyl vinyl phosphonates, and various vinyl and allyl phosphine oxides. ...
In the present paper we report on our preliminary investigations on the passive fire protection p... more In the present paper we report on our preliminary investigations on the passive fire protection property of potato starch on cellulosic substrates, such as on hard and soft wood. The primary aim of the study was to identify the effectiveness of the starch component of a novel and commercially available fire-fighting agent, based on starch, named Gel Feu, which is a product from a commercial firm based in France. Their in-house experiments have demonstrated the effectiveness of several formulations, made from Gel Feu, both a an active and as a passive fire fighting agents, especially, for protecting cellulosic materials, thus highlighting their potential as an environmentally-friendly alternative to compact wild land fires. The fire retardancy properties of potato starch formulations, when applied on wood materials, were evaluated using TGA, DSC and a Bench-cone calorimeter (BS 476-13: 1987). In the former tests, the fundamental physio-chemical processes accompanying the thermal degr...
The present paper reports the preliminary results relating to the development, subsequent applica... more The present paper reports the preliminary results relating to the development, subsequent application, and testing of environmentally benign starch-based formulations for passive fire protection of wood substrates. This study evaluated the effectiveness of starch colloid coatings applied onto the wood surface with a view to improving its performance when exposed to the external heat flux (35 kW/m2) during cone calorimetric tests. The formulations were prepared from aqueous colloid solutions of either starch alone, or in combination with inorganic salts, such as: sodium carbonate, Na2CO3, potassium carbonate, K2CO3, and diammonium hydrogen phosphate, (NH4)2HPO4. The fire performance of Taeda pine wood samples, where their top surfaces were treated with these formulations, was compared with the control sample. The thermal and combustion characteristics of the tested samples were determined with the aid of thermo-gravimetric analysis (TGA), bomb and cone calorimetric techniques, and a ...
The combustion behaviour of polystyrene flame retarded by the incorporation of phosphorus-contain... more The combustion behaviour of polystyrene flame retarded by the incorporation of phosphorus-containing compounds has been studied by LOI and cone calorimetry. Both ‘reactive’ and ‘additive’ approaches to the incorporation of the phosphorus have been applied and assessed. The data obtained show that the reactive approach results in enhanced char formation during combustion due to a condensed phase mechanism. Flame retardation by the additive systems occurred exclusively in the vapour phase via both chemical and physical interactions. The main advantage of the reactive approach was the maintenance of the physical and chemical properties similar to those of the homopolymer. The phosphorus environment was also a significant factor in terms of the level of flame retardance achieved. Phosphonate species were more effective than were phosphate species.
The aspects of fire retardation in some phosphorus-modified polymethyl methacrylate (PMMA) and po... more The aspects of fire retardation in some phosphorus-modified polymethyl methacrylate (PMMA) and polystyrene (PSt) polymers are reported in the present paper. Both additive and reactive strategies were employed to obtain the desired level of loading of the phosphorus-bearing compound/moiety (2 wt.% of P in each case). Test samples were obtained using bulk polymerization. The modifying compounds contained the P-atom in various chemical environments, as well as in an oxidation state of either III or V. With a view to gain an understanding of the chemical constitution of the gaseous products formed from the thermal decomposition of liquid additives/reactives, these materials were subjected to GC/MS analysis, whereas the decomposition of solid additives was detailed using the pyrolysis-GC/MS technique. Other investigations included the use of: Inductively-coupled Plasma/Optical Emission Spectroscopy (ICP/OES), solid-state NMR and FT-IR spectroscopy. In the case of PMMA-based systems, it w...
This paper reports on studies relating to the unstressed residual compressive strengths of geopol... more This paper reports on studies relating to the unstressed residual compressive strengths of geopolymer pastes that are heated up to 800 °C, behavior of reactive powder concrete before and after exposure to elevated temperatures and thermal behavior of novel reactive powder geopolymer-based concretes. For this purpose, 10 geopolymer pastes and three reactive powder concrete mixtures were tested for residual strengths. Gladstone fly ash was used as the primary binder for both geopolymer pastes and reactive powder geopolymer concretes. In addition, four novel reactive powder geopolymer concrete mixes were prepared with zero cement utilization. While reactive powder concretes achieved the highest seven-day compressive strengths of approximately 140 MPa, very poor thermal behavior was observed, with explosive spalling occurring at a temperature of ca. 360 °C. The reactive powder geopolymer concretes, on the other hand, displayed relatively high thermal properties with no thermal cracking ...
Geopolymer concrete is a valuable and alternative type of concrete that is free of traditional ce... more Geopolymer concrete is a valuable and alternative type of concrete that is free of traditional cement. Generally, geopolymer concretes require a source material, which is rich in silicon and aluminum. Furthermore, fly ash-based geopolymer concretes have been proven to have superior fire resistance, primarily due to their ceramic properties, and are inherently environmentally-friendly given their zero-cement content. This paper presents the effects on initial evaporation on the performance of fly ash-based geopolymer pastes after exposure to elevated temperatures of 400 °C and 800 °C. The fly ash (FA) samples used in the present study included: Gladstone and Gladstone/Callide. The results for sealed samples placed in the oven during curing were much more consistent than the samples that were not kept covered. In addition, Gladstone fly ash-based geopolymer samples that were sealed recorded an initial maximum compressive strength reading of ca. 75 MPa, while sealed Gladstone/Callide f...
Given that existing fire risk models often ignore human and organizational errors (HOEs) ultimate... more Given that existing fire risk models often ignore human and organizational errors (HOEs) ultimately leading to underestimation of risks by as much as 80%, this study employs a technical-human-organizational risk (T-H-O-Risk) methodology to address knowledge gaps in current state-of-the-art probabilistic risk analysis (PRA) for high-rise residential buildings with the following goals: (1) Develop an improved PRA methodology to address concerns that deterministic, fire engineering approaches significantly underestimate safety levels that lead to inaccurate fire safety levels. (2) Enhance existing fire safety verification methods by incorporating probabilistic risk approach and HOEs for (i) a more inclusive view of risk, and (ii) to overcome the deterministic nature of current verification methods. (3) Perform comprehensive sensitivity and uncertainty analyses to address uncertainties in numerical estimates used in fault tree/event trees, Bayesian network and system dynamics and their ...
Polymers are increasingly being used in domestic, commercial and public environments as component... more Polymers are increasingly being used in domestic, commercial and public environments as components of fabrics, surface coatings and moulded articles. Most of these polymeric components are synthetic, are based on hydrocarbon intermediates, and are highly flammable, thus resulting in unwanted fires. Fire fatalities are essentially due to the evolved smoke and toxic gases, exacerbated in some cases by poisonous fumes emitted from synthetic organic polymers. In addition, many of the thermoplastic materials tend to melt and flow under heat/fire, and this can constitute a very serious secondary hazard in fire scenarios involving them. Combustion of polymeric materials is a complex phenomenon that involves the solid phase, gaseous phase and the interphase.
The isothermal crystallization of poly(l-lactide) (PLLA) has been investigated by in-situ wide an... more The isothermal crystallization of poly(l-lactide) (PLLA) has been investigated by in-situ wide angle X-ray diffraction (WAXD) and polarized optical microscopes (POM) equipped with a hot-stage accessory. Results showed that the spherulites of PLLA were formed at high temperature, whereas irregular morphology was observed under a low temperature. This can be attributed to the varying rates of crystallization of PLLA at different temperatures. At low temperatures, the nucleation rate is fast and hence the chains diffuse very slow, resulting in the formation of imperfect crystals. On the other hand, at high temperatures, the nucleation rate is slow and the chains diffuse fast, leading to the formation of perfect crystals. The change in the value of the Avrami exponent with temperature further verifies the varying trend in the morphological feature of the crystals.
Polymeric materials often exhibit complex combustion behaviours encompassing several stages and i... more Polymeric materials often exhibit complex combustion behaviours encompassing several stages and involving solid phase, gas phase and interphase. A wide range of qualitative, semi-quantitative and quantitative testing techniques are currently available, both at the laboratory scale and for commercial purposes, for evaluating the decomposition and combustion behaviours of polymeric materials. They include, but are not limited to, techniques such as: thermo-gravimetric analysis (TGA), oxygen bomb calorimetry, limiting oxygen index measurements (LOI), Underwriters Laboratory 94 (UL-94) tests, cone calorimetry, etc. However, none of the above mentioned techniques are capable of quantitatively deciphering the underpinning physiochemical processes leading to the melt flow behaviour of thermoplastics. Melt-flow of polymeric materials can constitute a serious secondary hazard in fire scenarios, for example, if they are present as component parts of a ceiling in an enclosure. In recent years,...
This paper reports on the enhancement of the thermal transport properties of nanocomposite materi... more This paper reports on the enhancement of the thermal transport properties of nanocomposite materials containing hexagonal boron nitride in poly (vinyl alcohol) through room-temperature atmospheric pressure direct-current microplasma processing. Results show that the microplasma treatment leads to exfoliation of the hexagonal boron nitride in isopropyl alcohol, reducing the number of stacks from >30 to a few or single layers. The thermal diffusivity of the resulting nanocomposites reaches 8.5 mm2 s-1, 50 times greater than blank poly (vinyl alcohol) and twice that of nanocomposites containing non-plasma treated boron nitride nanosheets. From TEM analysis, we observe much less aggregation of the nanosheets after plasma processing along with indications of an amorphous carbon interfacial layer which may contribute to stable dispersion of boron nitride nanosheets in the resulting plasma treated colloids.
In this paper, we report on the thermal degradation behaviours and combustion attributes of some ... more In this paper, we report on the thermal degradation behaviours and combustion attributes of some polymers based on polystyrene (PSt). Here, both additive and reactive strategies were employed, through the bulk polymerization route, where the modifying groups incorporated P-atom in various chemical environments. These included oxidation states of III or V, and the loading of phosphorus was kept at ca. 2 wt.% in all cases. The characterization techniques that were employed for the recovered products included spectroscopic, thermal, and calorimetric. It was found that the presence of different modifying groups influenced the degradation characteristics of the base polymer, and also exerted varying degrees of combustion inhibition. In all cases, the modification of the base matrix resulted in a noticeable degree of fire retardance as compared to that of the virgin material. Therefore, some of the modifications presented have the potential to be explored on a commercial scale.
Styrene (ST) and methyl methacrylate (MMA) have been copolymerized with a variety of comonomers c... more Styrene (ST) and methyl methacrylate (MMA) have been copolymerized with a variety of comonomers containing covalently-bound phosphorus-containing groups, including vinyl phosphonic acid, several dialkyl vinyl phosphonates, and various vinyl and allyl phosphine oxides. ...
In the present paper we report on our preliminary investigations on the passive fire protection p... more In the present paper we report on our preliminary investigations on the passive fire protection property of potato starch on cellulosic substrates, such as on hard and soft wood. The primary aim of the study was to identify the effectiveness of the starch component of a novel and commercially available fire-fighting agent, based on starch, named Gel Feu, which is a product from a commercial firm based in France. Their in-house experiments have demonstrated the effectiveness of several formulations, made from Gel Feu, both a an active and as a passive fire fighting agents, especially, for protecting cellulosic materials, thus highlighting their potential as an environmentally-friendly alternative to compact wild land fires. The fire retardancy properties of potato starch formulations, when applied on wood materials, were evaluated using TGA, DSC and a Bench-cone calorimeter (BS 476-13: 1987). In the former tests, the fundamental physio-chemical processes accompanying the thermal degr...
The present paper reports the preliminary results relating to the development, subsequent applica... more The present paper reports the preliminary results relating to the development, subsequent application, and testing of environmentally benign starch-based formulations for passive fire protection of wood substrates. This study evaluated the effectiveness of starch colloid coatings applied onto the wood surface with a view to improving its performance when exposed to the external heat flux (35 kW/m2) during cone calorimetric tests. The formulations were prepared from aqueous colloid solutions of either starch alone, or in combination with inorganic salts, such as: sodium carbonate, Na2CO3, potassium carbonate, K2CO3, and diammonium hydrogen phosphate, (NH4)2HPO4. The fire performance of Taeda pine wood samples, where their top surfaces were treated with these formulations, was compared with the control sample. The thermal and combustion characteristics of the tested samples were determined with the aid of thermo-gravimetric analysis (TGA), bomb and cone calorimetric techniques, and a ...
The combustion behaviour of polystyrene flame retarded by the incorporation of phosphorus-contain... more The combustion behaviour of polystyrene flame retarded by the incorporation of phosphorus-containing compounds has been studied by LOI and cone calorimetry. Both ‘reactive’ and ‘additive’ approaches to the incorporation of the phosphorus have been applied and assessed. The data obtained show that the reactive approach results in enhanced char formation during combustion due to a condensed phase mechanism. Flame retardation by the additive systems occurred exclusively in the vapour phase via both chemical and physical interactions. The main advantage of the reactive approach was the maintenance of the physical and chemical properties similar to those of the homopolymer. The phosphorus environment was also a significant factor in terms of the level of flame retardance achieved. Phosphonate species were more effective than were phosphate species.
The aspects of fire retardation in some phosphorus-modified polymethyl methacrylate (PMMA) and po... more The aspects of fire retardation in some phosphorus-modified polymethyl methacrylate (PMMA) and polystyrene (PSt) polymers are reported in the present paper. Both additive and reactive strategies were employed to obtain the desired level of loading of the phosphorus-bearing compound/moiety (2 wt.% of P in each case). Test samples were obtained using bulk polymerization. The modifying compounds contained the P-atom in various chemical environments, as well as in an oxidation state of either III or V. With a view to gain an understanding of the chemical constitution of the gaseous products formed from the thermal decomposition of liquid additives/reactives, these materials were subjected to GC/MS analysis, whereas the decomposition of solid additives was detailed using the pyrolysis-GC/MS technique. Other investigations included the use of: Inductively-coupled Plasma/Optical Emission Spectroscopy (ICP/OES), solid-state NMR and FT-IR spectroscopy. In the case of PMMA-based systems, it w...
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