Anna A. Stec

Synthesis of Mesoporous Silica@Co–Al Layered Double Hydroxide Spheres: Layer-by-Layer Method and Their Effects on the Flame Retardancy of Epoxy Resins

Hierarchical mesoporous silica@Co-Al layered double hydroxide (m-SiO2@Co-Al LDH) spheres were prepared through a layer-by-layer assembly process, in order to integrate their excellent physical and chemical functionalities. TEM results depicted that, due to the electrostatic potential difference between m-SiO2 and Co-Al LDH, the synthetic m-SiO2@Co-Al LDH hybrids exhibited that m-SiO2 spheres were packaged by the Co-Al LDH nanosheets. Subsequently, the m-SiO2@Co-Al LDH spheres were incorporated into epoxy resin (EP) to prepare specimens for investigation of their flame-retardant performance. Cone results indicated that m-SiO2@Co-Al LDH incorporated obviously improved fire retardant of EP. A plausible mechanism of fire retardant was hypothesized based on the analyses of thermal conductivity, char residues, and pyrolysis fragments. Labyrinth effect of m-SiO2 and formation of graphitized carbon char catalyzed by Co-Al LDH play pivotal roles in the flame retardance enhancement.

Fabrication of Ce-doped MnO2 decorated graphene sheets for fire safety applications of epoxy composites: flame retardancy, smoke suppression and mechanism

Ce-doped MnO2–graphene hybrid sheets were fabricated by utilizing an electrostatic interaction between Ce-doped MnO2 and graphene sheets. The hybrid material was analyzed by a series of characterization methods. Subsequently, the Ce-doped MnO2–graphene hybrid sheet was introduced into an epoxy resin, and the fire hazard behaviors of the epoxy nanocomposite were investigated. The results from thermogravimetric analysis exhibited that the incorporation of 2.0 wt% of Ce-doped MnO2–graphene sheets clearly improved the thermal stability and char residue of the epoxy matrix. In addition, the addition of Ce–MnO2–graphene hybrid sheets imparted excellent flame retardant properties to an epoxy matrix, as shown by the dramatically reduced peak heat release rate and total heat release value obtained from a cone calorimeter. The results of thermogravimetric analysis/infrared spectrometry, cone calorimetry and steady state tube furnace tests showed that the amount of organic volatiles and toxic CO from epoxy decomposition were significantly suppressed after incorporating Ce–MnO2–graphene sheets, implying that this hybrid material has reduced fire hazards. A plausible flame-retardant mechanism was hypothesized on the basis of the characterization of char residues and direct pyrolysis-mass spectrometry analysis: during the combustion, Ce–MnO2, as a solid acid, results in the formation of pyrolysis products with lower carbon numbers. Graphene sheets play the role of a physical barrier that can absorb the degraded products, thereby extend their contact time with the metal oxides catalyst, and then promote their propagate on the graphene sheets; meanwhile pyrolysis fragments with lower carbon numbers can be easily catalyzed in the presence of Ce–MnO2. The notable reduction in the fire hazards was mainly attributed to the synergistic action between the physical barrier effect of graphene and the catalytic effect of Ce–MnO2.

Self-Assembly Fabrication of Hollow Mesoporous Silica@Co–Al Layered Double Hydroxide@Graphene and Application in Toxic Effluents Elimination

Here, we propose a self-assembly process to prepare hierarchical HM-SiO2@Co-Al LDH@graphene, with the purpose of combining their outstanding performance. Hollow mesoporous silica was first synthesized as the core, using a novel sonochemical method, followed by a controlled shell coating process and chemical reduction. As a result of the electrostatic potential difference among HM-SiO2, Co-Al LDH, and graphene oxide, the HM-SiO2 spheres were coated by Co-Al LDH and graphene. Subsequently, the HM-SiO2@Co-Al LDH@graphene spheres were introduced into an epoxy resin (EP) matrix for investigation of their toxic effluents capture and elimination effectiveness during combustion. The amount of toxic CO and volatile organic compounds from the epoxy resin decomposition significantly suppressed after incorporating the HM-SiO2@Co-Al LDH@graphene hybrids, implying a reduced toxicity.

Double In Situ Approach for the Preparation of Polymer Nanocomposite with Multi-functionality

A novel one-step synthetic route, the double in situ approach, is used to produce both TiO2nanoparticles and polymer (PET), and simultaneously forming a nanocomposite with multi-functionality. The method uses the release of water during esterification to hydrolyze titanium (IV) butoxide (Ti(OBu)4) forming nano-TiO2in the polymerization vessel. This new approach is of general significance in the preparation of polymer nanocomposites, and will lead to a new route in the synthesis of multi-functional polymer nanocomposites.

Hydrogen Chloride in Fires

ISO 13571:2007 describes the calculation of safe escape time using yields of asphyxiant and irritant gases for performance based design. Hydrogen chloride (HCl) gas is an incapacitating irritant, reported to be intolerable at concentrations above 100 ppm, but lethal to rats only at concentrations around 5000ppm for a 30 minute exposure. It is evolved from burning PVC, and other chlorine containing plastics. The experimental evidence of the concentration/dose effects on a range of animal species has been reviewed, and concludes that the HCl concentration leading to incapacitation of 1000 ppm, used in ISO 13571, is rather too high to ensure safe escape. Experimental data is presented from burning unplasticised PVC, plasticized PVC cable, and LDPE to show that HCl interferes with the flame chemistry, particularly the conversion of CO to CO2, further increasing the hazard from the fire effluent. The product yields are used to estimate the fire effluent toxicity, comparing the standard based on rat lethality, ISO 13344 with the newer standard, which also takes the effect of incapacitating irritants into account, showing the large contribution of HCl to the fire hazard. Finally, the relationship between the toxicity and a simple analysis of effluent acidity (EN 50297-2-3) is discussed.

Analysis of toxic effluents released from PVC carpet under different fire conditions

Abstract A large number of investigations have been reported on minimising the PAH and PCDD/F yields during controlled combustion, such as incineration. This study is an attempt to quantify acute and chronic toxicants including PAH and PCDD/F in conditions relating to unwanted fires. This paper investigates distribution patterns of fire effluents between gas and aerosol phase, and the different particle size-ranges produced under different fire conditions. PVC carpet was selected as the fuel as a precursor for both PAH and PCDD/F. In order to generate fire effluents under controlled fire conditions, the steady-state tube furnace, was chosen as the physical fire model. Fire scenarios included oxidative pyrolysis, well-ventilated and under-ventilated fires. Fire effluent measurements included: carbon monoxide, carbon dioxide, hydrogen chloride, polycyclic aromatic hydrocarbons, chlorinated dibenzo-dioxins and furans and soot. The distribution patterns between gas and particle phase, and the size-ranges of the particles produced in these fires together with their chemical composition is also reported. Significant quantities of respirable submicron particles were detected, together with a range of PAHs. Lower levels of halogenated dioxins were detected in the fire residue compared with those found in other studies. Nevertheless, the findings do have implications for the health and safety of fire and rescue personnel, fire investigators, and other individuals exposed to the residue from unwanted fires.

Experimental results of a residential house fire test on tenability: Temperature, smoke, and gas analyses

A fire experiment conducted in a British 1950s‐style house is described. Measurements of temperature, smoke, CO, CO2, and O2 were taken in the Lounge, stairwell, and front and back bedrooms. The front bedroom door was wedged open, while the door to the back bedroom was wedged closed. Contrary to expectations and despite the relatively small fire load, analysis and hazard calculations show permeation of toxic fire gases throughout the property with lethal concentrations of effluent being measured at each sampling point. A generally poor state of repair and missing carpets in the upper story contributed to a high degree of gas and smoke permeation. The available egress time was calculated as the time before the main escape route became impassable. Given known human responses to fire, such an incident could have caused fatalities to sleeping or otherwise immobile occupants.

A Comparison of Toxic Product Yields Obtained From Five Laboratories Using the Steady State Tube Furnace (ISO TS 19700)

The steady state tube furnace has been developed from BS 7990 into the first internationally recognized standard for assessment of fire gas toxicity, ISO TS 19700. The apparatus has been shown to reliably replicate different fire stages, and is capable of generating toxic product yields as a function of the equivalence ratio φ. Work is reported from 5 laboratories currently using the steady state tube furnace where it has been used to assess the toxic product yields from a range of generic polymer materials, as a function of equivalence ratio. For the polymers tested, (LDPE, PP, PVC, Nylon, and PS) a high degree of reproducibility is observed across the range of ventilation conditions. In particular, the carbon monoxide yield, which is most susceptible to fire conditions shows consistent behaviour, which is independent of a particular laboratory.

Classification and identification of soot source with principal component analysis and back-propagation neural network

Identification of soot sources is significant in fire investigation and forensic science. In this paper, principal component analysis (PCA) and a back-propagation (BP) neural network model have been used to classify and identify the soot samples from three different kinds of combustible material. Diesel, polystyrene and acrylonitrile butadiene styrene were burnt under the controlled combustion conditions in small-scale burn tests. Based on the matrix data from the GC-MS analysis data, two principal components have been obtained from PCA analysis with the cumulative energy content of 90.21%. Three different kinds of soot sample can be classified with 100% accuracy. A BP neural network model for predicting and identifying the soot source has been further developed. Accurate identification of the unknown samples has been achieved with this trained BP model. This pilot study indicates that PCA and BP neural network methods have potential in the analysis of soot to identify its principle pre-combustion source material.

Carbon Monoxide Generation in Fires: Effect of Temperature on Halogenated and Aromatic Fuels

Carbon monoxide is widely regarded as the major toxicant in fire effluents. It is produced as a result of incomplete combustion, by low temperatures, flame quenching, or under-ventilation. Polymers containing halogens and aromatic rings give higher carbon monoxide yields in well-ventilated conditions, when burnt in the steady state tube furnace (ISO 19700) at a furnace temperature of 650 °C. This is believed to result from flame quenching by hydrogen halides or the enhanced stability of aromatic rings in flames, respectively. This work investigates the effect of ventilation condition and furnace temperature on the yield of carbon monoxide from burning mixtures of polyvinyl chloride and polyethylene, polyamide 6 containing a brominated flame retardant and an antimony synergist, and polystyrene. In each case, the high carbon monoxide yields in well-ventilated burning reduced at higher furnace temperatures, showing a diminution of fire toxicity above 850 °C.