Engineering Sulfur-Containing Polymeric Fire-Retardant Coatings for Fire-Safe Rigid Polyurethane Foam.

With the advantages of lightweight and low thermal conductivity properties, polymeric foams are widely employed as thermal insulation materials for energy-saving buildings but suffer from inherent flammability. Flame-retardant coatings hold great promise for improving the fire safety of these foams without deteriorating the mechanical-physical properties of the foam. In this work, four kinds of sulfur-based flame-retardant copolymers are synthesized via a facile radical copolymerization. The sulfur-containing monomers serve as flame-retardant agents including vinyl sulfonic acid sodium (SPS), ethylene sulfonic acid sodium (VS), and sodium p-styrene sulfonate (VSS). Additionally, 2-hydroxyethyl acrylate (HEA) and 4-hydroxybutyl acrylate are employed to enable a strong interface adhesion with polymeric foams through interfacial H-bonding. By using as-synthesized waterborne flame-retardant polymeric coating with a thickness of 600 µm, the coated polyurethane foam (PUF) can achieve a desired V-0 rating during the vertical burning test with a high limiting oxygen index (LOI) of >31.5 vol%. By comparing these sulfur-containing polymeric fire-retardant coatings, poly(VS-co-HEA) coated PUF demonstrates the best interface adhesion capability and flame-retardant performance, with the lowest peak heat release rate of 166 kW m-2 and the highest LOI of 36.4 vol%. This work provides new avenues for the design and performance optimization of advanced fire-retardant polymeric coatings.

The Effect of Flame-Retardant Additives DDM-DOPO and Graphene on Flame Propagation over Glass-Fiber-Reinforced Epoxy Resin under the Influence of External Thermal Radiation.

The flammability of various materials used in industry is an important issue in the modern world. This work is devoted to the study of the effect of flame retardants, graphene and DDM-DOPO (9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide-4,4'-diamino-diphenyl methane), on the flammability of glass-fiber-reinforced epoxy resin (GFRER). Samples were made without additives and with additives of fire retardants: graphene and DDM-DOPO in various proportions. To study the flammability of the samples, standard flammability tests were carried out, such as thermogravimetric analysis, the limiting oxygen index (LOI) test, and cone calorimetry. In addition, in order to test the effectiveness of fire retardants under real fire conditions, for the first time, the thermal structure of downward flame propagation over GFRER composites was measured using thin thermocouples. For the first time, the measured thermal structure of the flame was compared with the results of numerical simulations of flame propagation over GFRER.

Functionally Active Microheterogeneous Systems for Elastomer Fire- and Heat-Protective Materials.

Elastomeric materials are utilized for the short-term protection of products and structures operating under extreme conditions in the aerospace, marine, and oil and gas industries. This research aims to study the influence of functionally active structures on the physical, mechanical, thermophysical, and fire- and heat-protective characteristics of elastomer compositions. The physical and mechanical properties of elastomer samples were determined using Shimazu AG-Xplus, while morphological research into microheterogeneous systems and coke structures was carried out on a scanning electronic microscope, Versa 3D. Differential thermal and thermogravimetric analyses of the samples were conducted on derivatograph Q-1500D. The presence of aluminosilicate microspheres, carbon microfibers, and a phosphor-nitrogen-organic modifier as part of the aforementioned structures contributes to the appearance of a synergetic effect, which results in an increase in the heat-protective properties of a material due to the enhancement in coke strength and intensification of material carbonization processes. The results indicate an 8-17% increase in the heating time of the unheated surface of a sample and a decrease in its linear burning speed by 6-17% compared to known analogues. In conclusion, microspheres compensate for the negative impact of microfibers on the density and thermal conductivity of a composition.

Burn Intensity Drives the Alteration of Phenolic Lignin to (Poly) Aromatic Hydrocarbons as Revealed by Pyrolysis Gas Chromatography-Mass Spectrometry (Py-GC/MS).

High-intensity wildfires alter the chemical composition of organic matter, which is expected to be distinctly different from low-intensity prescribed fires. Herein, we used pyrolysis gas chromatography/mass spectrometry (Py-GC/MS), in conjunction with solid-state 13C nuclear magnetic resonance (NMR) and Fourier transform infrared (FT-IR) spectroscopy, to assess chemical alterations from three wildfires and a long-term frequent prescribed fire site. Our results showed that black ash formed under moderate intensity burns contained less aromatic (ArH), polyaromatic hydrocarbon (PAH), and nitrogen-containing compounds (Ntg) but more lignin (LgC) and phenol compounds (PhC), compared to white ash formed under high intensity burns. Both 13C NMR and FT-IR confirmed a higher relative percentage of carboxyl carbon in white ash, indicating the potential for higher water solubility and more mobile carbon, relative to black ash. Compared to wildfires, ash from low-intensity prescribed fire contained less ArH, PAH, and Ntg and more LgC and PhC. Controlled laboratory burning trials indicated that organic matter alteration was sensitive to the burn temperature, but not related to the fuel type (pine vs fir) nor oxygen absence/presence at high burn temperatures. This study concludes that higher burn temperatures resulted in higher (poly)aromatic carbon/nitrogen and lower lignin/phenol compounds.

The development of a tool to predict temperature-exposure of incinerated teeth using colourimetric and hydroxyapatite crystal size data.

This study presents a novel tool to predict temperature-exposure of incinerated pig teeth as a proxy for understanding impacts of fire on human teeth. Previous studies on the estimation of temperature-exposure of skeletal elements have been limited to that of heat-exposed bone. This predictive tool was developed using a multinomial regression model of colourimetric and hydroxyapatite crystal size variables using data obtained from unheated pig teeth and teeth incinerated at 300 °C, 600 °C, 800 °C and 1000 °C. An additional variable based on the observed appearance of the tooth was included in the tool. This enables the tooth to be classified as definitely burnt (600 °C-1000 °C) or uncertain (27 °C/300 °C). As a result, the model predicting the temperature-exposure of the incinerated teeth had an accuracy of 95%. This tool is a holistic, robust and reliable approach to estimate temperature of heat-exposed pig teeth, with high accuracy, and may act as a valuable proxy to estimate heat exposure for human teeth in forensic casework.

Forensic Analysis and Identification Processes in Mass Disasters: Explosion of Gun Powder in the Fireworks Factory.

A mass disaster is a situation that involves criticality between the number of victims and resources, in terms of both men and means, present on the site of an event that is mostly unexpected and sudden. In the multidisciplinary teams that intervene, the role of forensic pathologists, who are responsible for the direction and coordination of post-mortem operations, is central, and must remain so. The authors report the case of an explosion of a pyrotechnic artifice factory, as a result of which numerous victims and injuries are recorded. So, the team completed the autopsies and created a protocol to obtain biological samples (bones, blood, teeth, muscles), while the forensic pathologists contacted the families of the alleged victims and each provided a blood sample that was collected for the DNA. The geneticist, using the method of gene extraction and amplification, obtained the DNA from each bone, tooth, and muscle of blood taken from the victims and then compared it with that extracted from the blood samples of the relatives; the electropherograms showed at least one allele for each genetic marker of the "Combined DNA Index System" in common between the victims and the families, thus allowing to establish the identity of all the subjects involved in the event. Having established the identity of all workers, it was possible to determine their whereabouts in the environment at the time of the location of fires and explosions. The results of the various forensic analyzes (autopsies, genetic investigations and even traumatological investigations) have allowed us to validate a scientific method useful in all mass disasters even when any type of anthropological or forensic dental research is difficult.

Moisture Resistance, Thermal Stability and Fire Behavior of Unsaturated Polyester Resin Modified with L-histidinium Dihydrogen Phosphate-Phosphoric Acid.

In this paper, the fire behavior of unsaturated polyester resin (UP) modified with L-histidinium dihydrogen phosphate-phosphoric acid (LHP), being a novel intumescent fire retardant (IFR), was investigated. Thermal and thermomechanical properties of the UP with different amounts of LHP (from 10 to 30 wt. %) were determined by thermogravimetric analysis (TG) as well as dynamic mechanical thermal analysis (DMTA). Reaction to small flames was studied by horizontal burning (HB) test, while fire behavior and smoke emission were investigated with the cone calorimeter (CC) and smoke density chamber. Further, the analysis of volatile products was conducted (TGA/FT-IR). It was observed that the addition of LHP resulted in the formation of carbonaceous char inhibiting the thermal decomposition, burning rate and smoke emission. The most promising results were obtained for the UP containing 30 wt. % of LHP, for which the highest reduction in maximum values of heat release rate (200 kW/m2) and total smoke release (3535 m2/m2) compared to unmodified polymer (792 kW/m2 and 6895 m2/m2) were recorded. However, some important disadvantage with respect to water resistance was observed.

The use of gelling agents to preserve burnt teeth within the dental alveoli for dental human identification - a study utilising sheep mandibles.

Dental comparison is one of the primary methods of scientific identification of severely incinerated human remains. However, due to the fragile nature of the remains dental structures may be lost or damaged during recovery and transportation, limiting the amount of evidence available for examination. In addition to protecting the head, stabilization of the oral structures with an adhesive substance that will not interfere with the dental examination is ideal. A number of materials have been described in previous studies, however, no optimal method has yet to be indicated. Many of these materials contain petrochemicals, which have been shown to be a contamination risk. Wheatpaste solution has been demonstrated to be a viable alternative but has demonstrated handling issues and is not optimal in some environments. This study explores the stabilization of burnt teeth utilizing gelatin and agar solutions as alternatives to wheatpaste. Like wheatpaste solution, these materials are inexpensive, simple to use and are free from petrochemicals. Anterior sections of sheep mandibles were incinerated and subsequently solutions of agar, gelatin or wheatpaste were applied. The jaw fragments were then subjected to vibration and the number of teeth retained within the bone was recorded and compared to untreated incinerated jaw fragments. Although agar solution demonstrated serious handling issues, gelatin solution provided stabilization equivalent to that of wheatpaste. Gelatin also performed well at lower temperature conditions under which wheatpaste has been shown to perform poorly.

Simple, Frequent Indicator for Personal Identification-Postmortem and Antemortem Abdominal Computed Tomography Findings of a Charred Body.

Postmortem personal identification in forensic science is performed using various methods. However, severely burnt bodies are hard to identify using odontological or skeletal features because of carbonization, and sometimes DNA profiling is impracticable because of the unavailability of the relatives. We present a case of a burn victim found after a house fire. Personal identification was attempted, but the body was heavily charred to the bones and the use of physical appearance was impracticable. There were no known relatives or personal belongings of the deceased for comparison of DNA typing. We obtained a series of abdominal computed tomography (CT) scans taken antemortem and found bilateral multiple renal cysts, left renal artery calcification, and a big right inguinal hernia, which matched the deceased's postmortem CT findings and autopsy findings. To date, studies of identification by CT have acted for a rise in precision, but they require complicated calculation or high graphical methods. Calcification of the arteries or renal cysts seen in our case are very common lesions present in many adults with abundant variation; thus, they may be helpful as simple indicators for identification.

Organo-Inorganic Hybrid Intumescent Fire Retardant Coatings for Thermoplastics Based on Poly(Vinylphosphonic Acid).

Thin coatings of crosslinked poly(vinylphosphonic acid), PVPA, display good adhesion and excellent intumescent, fire-retardant barrier properties when applied to the surfaces of a typical thermoplastic, such as poly(methyl methacrylate), but perform relatively poorly in water-soak tests. To strengthen and further improve the barrier properties of the intumescent char and to make the coating more hydrophobic, PVPA has been complexed with various inorganic and organic species. The chars formed from coatings of some of these hybrid materials are less friable than chars from coatings synthesized from crosslinked PVPA alone, and show higher levels of water tolerance with no significant reduction in dry adhesion to the substrate.

Enhanced Fire Safety of Rigid Polyurethane Foam via Synergistic Effect of Phosphorus/Nitrogen Compounds and Expandable Graphite.

In order to explore highly efficient flame-retardant rigid polyurethane foam (RPUF), phosphorus/nitrogen compounds and expandable graphite (EG) were successfully incorporated into RPUF by a free one-spot method. The combustion results showed that the fire safety of the RPUF samples was remarkably improved by the addition of phosphoric/nitrogen compounds and EG. With the incorporation of 22.4 wt.% phosphorus/nitrogen compounds and 3.2 wt.% EG, the RPUF composites achieved UL-94 V-0 rating. Besides, the total heat release and total smoke release of RPUF composites were reduced by 29.6% and 32.4% respectively, compared to those of the pure RPUF sample. PO• and PO2• together with nonflammable gaseous products were evolved from phosphoric/nitrogen compounds in the gas phase, which quenched the flammable free radicals in the matrix and diluted the concentration of combustible gaseous products generated from PRUF during combustion. The compact char residues which acted as excellent physical barriers were formed by catalysis of EG and phosphoric/nitrogen compounds in the condense phase. The fire hazard of RPUF was significantly reduced by the synergistic effect of phosphorus-nitrogen compounds and EG. This work provides a promising strategy to enhance the fire safety of RPUF.

Reactive and Additive Modifications of Styrenic Polymers with Phosphorus-Containing Compounds and Their Effects on Fire Retardance.

Polystyrene, despite its high flammability, is widely used as a thermal insulation material for buildings, for food packaging, in electrical and automotive industries, etc. A number of modification routes have been explored to improve the fire retardance and boost the thermal stability of commercially important styrene-based polymeric products. The earlier strategies mostly involved the use of halogenated fire retardants. Nowadays, these compounds are considered to be persistent pollutants that are hazardous to public and environmental health. Many well-known halogen-based fire retardants, regardless of their chemical structures and modes of action, have been withdrawn from built environments in the European Union, USA, and Canada. This had triggered a growing research interest in, and an industrial demand for, halogen-free alternatives, which not only will reduce the flammability but also address toxicity and bioaccumulation issues. Among the possible options, phosphorus-containing compounds have received greater attention due to their excellent fire-retarding efficiencies and environmentally friendly attributes. Numerous reports were also published on reactive and additive modifications of polystyrene in different forms, particularly in the last decade; hence, the current article aims to provide a critical review of these publications. The authors mainly intend to focus on the chemistries of phosphorous compounds, with the P atom being in different chemical environments, used either as reactive, or additive, fire retardants in styrene-based materials. The chemical pathways and possible mechanisms behind the fire retardance are discussed in this review.

Factors affecting dental DNA in various real post-mortem conditions.

Post-mortem DNA degradation is still the real challenge of DNA-based identification in forensic practise. It is a complicated multifactorial process occurring as a result of the combination of several different environmental effects along with the crucial effect of the elapsed post-mortem interval (PMI). The main purpose of the present study is to evaluate the effect of ante- and post-mortem factors on dental DNA in real forensic cases. Ninety-five teeth extracted from 39 corpses, whose bodies were subject to 6 different post-mortem conditions, were used to evaluate dental DNA amount. In total, 179 DNA extracts isolated from the root of the teeth were examined after removing the crown and sectioning each root into apical and cervical portions. DNA concentration was measured using real-time polymerase chain reaction DNA quantitation kit (PowerQuant™ System/Promega). Our results indicate that the post-mortem interval (PMI) is the most important influential factor on dental DNA quantification (p < 0.001). However, in the actual data set, it was confounded with several ante- and post-mortem factors, rendering its actual net effect difficult. The time period of the first 10 days after death yielded the best DNA results from all analysed dental samples. Afterwards, a dramatic decrease in dental DNA was observed in the following time period. Teeth extracted from burnt and fresh corpses yielded the highest amount of DNA, while skeletonized exhumed corpses resulted in the lowest DNA amount. Indeed, dry and indoor conditions demonstrated better results than those in water, outdoors, or buried in the ground. On the other hand, ante-mortem factors including sex, age, tooth type, and tooth root portions did not reveal significant effect on dental DNA yield. We suggest that ante-mortem factors are considerably more subjected to individual variations. Post-mortem factors including PMI, post-mortem conditions, and the relevant surrounding environments have substantial influence on the dental DNA amount yielded.

The use of liquid latex for detecting traces of blood following thermal exposure.

In cases of crimes involving blood, the perpetrators often attempt to remove the traces they have left behind. Setting fire to the crime scene, aside from cleaning measures, seems to achieve this goal and presents a major challenge for crime scene investigators. There is only very little published information available on the effect of fire and extreme heat on blood and the detection thereof. After exposure to high temperatures of or exceeding 1.000 °C, blood is deemed to be undetectable. This study exposed 11 different potentially crime-relevant objects using a standardized and controlled procedure to temperatures of 300 °C, 700 °C, and 1.000 °C documenting the influence of heat on bloodstains and the detection of blood. The results of the forensic collection of blood traces with and without liquid latex confirmed the advantage of using the latex method. Almost all objects showed a clear luminescence-caused visualization of traces of blood after removing the soot with a latex lift. There were also fewer false positive results than in tests not using latex.

Use of XRD and SEM/EDX to predict age and sex from fire-affected dental remains.

In fire scenarios, the application and accuracy of traditional odontological methods are often limited. Crystalline studies and elemental profiling have been evaluated for their applicability in determining biological profiles (age and sex) from human dentition, particularly fire- and heat-affected dental remains. Thirty-seven teeth were paired according to tooth type and donor age/sex for the analysis of crown and root surfaces pre- and post-incineration using X-ray diffraction (XRD) and scanning electron microscopy (SEM/EDX). In unburned crowns, carbon (C) content showed a positive correlation with age, whereas phosphorus (P) and calcium (Ca) contents showed a negative correlation with age. In unburned roots, C, P and Ca contents also showed significant changes that were opposite of those observed in the crowns. In relation to sex, females exhibited a higher C ratio than males, whereas males showed significantly higher levels of oxygen (O), P and Ca in unburned roots. Incineration resulted in an increase in the crystallite size that correlated with increasing temperature. No differences in hydroxyapatite (HA) crystallite size were found between age groups; however, unburned teeth from females exhibited a larger crystallite size than did those from males. The challenges of using XRD with a 3D sample were overcome to allow analysis of whole teeth in a nondestructive manner. Further studies may be useful in helping predict the temperature of a fire.

The circles of life: age at death estimation in burnt teeth through tooth cementum annulations.

Age at death estimation in burnt human remains is problematic due to the severe heat-induced modifications that may affect the skeleton after a burning event. The objective of this paper was to assess if cementochronology, which focuses on the cementum incremental lines, is a reliable method of age estimation in burnt remains. Besides the classical approach based on the counting of incremental lines, another approach based on the extrapolation of incremental lines taking into account the cement layer thickness and the incremental line thickness was investigated. A comparison of the performance of the two techniques was carried out on a sample of 60 identified monoradicular teeth that were recently extracted at dentist offices and then experimentally burnt at two maximum temperatures (400 and 900 °C). Micrographs of cross-sections of the roots were taken via an optical microscope with magnification of ×100, ×200 and ×400. Incremental line counting and measurements were carried out with the ImageJ software. Age estimation based on incremental line counting in burnt teeth had no significant correlation with chronological age (p = 0.244 to 0.914) and led to large absolute mean errors (19 to 21 years). In contrast, age estimation based on the extrapolation approach showed a significant correlation with known age (p = 0.449 to 0.484). In addition, the mean absolute error of the latter was much smaller (10 to 14 years). The reason behind this discrepancy is the heat-induced dimensional changes of incremental lines that affect their visibility and individualization thus complicating line counting. Our results indicated that incremental lines extrapolation is successful at solving this problem and that the resulting age estimation is much more reliable.

Intra-oral ignition of monopolar diathermy during transnasal humidified rapid-insufflation ventilatory exchange (THRIVE).

We present the case of unanticipated airway ignition during hard palate biopsy. Transnasal humidified rapid-insufflation ventilatory exchange (THRIVE) and monopolar diathermy were utilised for the procedure, during which an arc arose from the diathermy tip to a titanium implant, causing a brief ignition on the monopolar diathermy grip. This case highlights the need for maintained awareness of fire risk when using diathermy in the presence of THRIVE during airway surgery.

Flammability testing of 22 conventional European pediculicides.

Lice have been parasitizing humans for at least 10,000 years. Since then, humans have tried to rid themselves of these unpleasant and potentially disease-carrying insects. Despite various plant extracts and chemical compounds being used to combat recurring infestations to this date, several lice populations have developed resistance to some of the abundantly used compounds. This resulted in the development of anti-louse products that physically kill the different lice stages. Today, a widely used group of delousing agents are dimethicones (polydimethylsiloxane PDMS) which function by suffocating the lice. However, many dimethicones and related products are highly flammable which makes them potentially dangerous for treatment. In the present study, we tested the flammability of 22 delousing agents in order to shed some light onto this currently unresolved problem in the product design of pediculicides. Thirteen products were easily ignitable, some even by distant contact with a sparkler.