Fire safety and prevention of combustible materials are of paramount importance in modern society but have been a global challenge. Frequent fire disasters cause massive casualties and irreparable ...property losses and negatively impact the global environment. A recent increasing concern is to develop smart fire warning materials and sensors that combine traditional passive flame retardant strategies and active fire alarm response. However, there still lacks an incisive and comparative overview of such fire warning systems. This review comprehensively discusses passive flame retardant materials, traditional active fire warning sensors, and next-generation smart fire warning materials and sensors, in addition to the flammability of combustible materials. The conceptual design, synthesis, characterizations, and fabrication strategies of smart warning materials are systematically reviewed. Subsequently, the performance and applications of different fire warning sensor systems, including resistance-type, phase/shape change, thermoelectric responsive and colour-change observation, were reviewed and compared to understand their features and working mechanisms better. Finally, some key challenges associated with fire warning materials/sensors are highlighted, following which future perspectives and opportunities are proposed.
Macroscopic three-dimensional (3D) free-standing porous all-graphene aerogel with ultralight density and high compressibility is successfully fabricated through a mild in-situ self-assembly and ...thermal annealing processes. The formed interconnected 3D porous graphene network, high thermal stable all-graphene composition and large porosity of aerogels made it possible to remove heat quickly during combustion, exhibiting a conspicuous fire-retardancy. Meanwhile, excellent recoverable compressibility with high strain levels of up to 75% endowed the aerogel with high sensitive strain-responsive characteristic in volume electrical conductivity, thereby opening a new way for realizing the adjustment of internal free space and electrical conductivity of 3D architecture. Based on the results, the microwave absorption performance of the graphene aerogel was effectively self-adjusted via a simple mechanical compression. The optimal absorbing value was up to 61.09 dB with a broad qualified bandwidth of 6.30 GHz at the thickness of 4.81 mm when the compression strain ratio of the sample was controlled to be 30%.
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Frequent oil spillages and the industrial discharge of organic solvents have not only caused severe environmental and ecological damage, but also create a risk of fire and explosion. Therefore, it is ...imperative, but also challenging, to find high‐performance absorbent materials that are both effective and less flammable. Here we present a superior superhydrophobic sponge that exhibits excellent absorption performance through a combination of its superhydrophobicity, high porosity, and robust stability. More importantly, it inherits the intrinsic flame‐retardant nature of the raw melamine sponge, and is thus expected to reduce the risk of fire and explosion when being used as an absorbent for flammable oils and organic compounds. Moreover, the fabrication of this sponge is easy to scale up, since it does not use a complicated process or sophisticated equipment. These characteristics make the sponge a much more competitive product than the commercial absorbent, nonwoven polypropylene fabric.
Coming clean: A robust and flame‐retardant sponge has been prepared from the commercially available melamine sponge through a simple and mild two‐step strategy. The superhydrophobicity, high porosity, robust stability, and intrinsic flame‐retardant nature of the sponge enable the absorption and recycling of crude oil (see picture) as well as organic solvents. The fabrication of this sponge is easy to scale up.
A novel flame retardant (POCODA) was synthesized using the POC and ODA. The POCODA/APP as a synergistic flame retardant (FR) was incorporated into the poly(L-lactic acid) (PLA) to investigate effects ...of this synergistic FR on the thermal stability, combustion behavior and flame retardancy on the PLA. The limited oxygen index (LOI) value of the PLA-based composites gradually increased with an enhancement in the amount of the POCODA/APP. Except the PLA/5%APP, the V-0 level achieved for other composites. Both the POCODA and POCODA/APP exhibited the self-extinguishing effect on the PLA in the UL-94 test. The pHRR, THR, TSP and other combustion performance parameters of the composites reduced, compared to neat PLA, and the PLA/2%POCODA/10%APP composite exhibited the dense and continuous carbon residue after the CONE measurement and showed most excellent flame retardance. With combination of the results of the SEM, TG-IR and PY-GC/MS measurement, the flame retardant mechanism of the PLA/2%POCODA/10%APP composite was also proposed and discussed in detail.
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•A novel N/P-based compound was synthesized as a halogen-free flame retardant (FR) of PLA.•LOI value of PLA enhanced markedly with loading of FR.•The FR showed self-extinguishing effect on PLA.•The FR enhanced the flame retardance and fire safety of PLA.•The FR increased significantly the crystallizability of PLA.
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•Graphene considered as a promising carbon nanomaterials with unique properties.•Graphene and their composites present new generation of flame retardant materials.•Graphene sheets ...have effective ability to form protective char layer as flame retardants.•Graphene sheets have superior flame retardancy effect than clay and CNTs.•Graphene sheets present renewable smart generation of flame retardant materials.
Polymeric and textile based materials constitute the majority of market products, however, due to their low thermal stability and high flammability hazards, their uses are limited in some applications. Therefore, flame retardant materials have to be dispersed as fillers in polymer matrix and coated on textile fabrics to enhance their fire safety and thermal stability. Graphene is two-dimensional materials and considered as a promising carbon nanomaterials with sp2-hybridization and with unique properties. In this review article conventional flame retardant and different methods of synthesis of graphene layers were summarized. Also, the possibility of use graphene sheets alone as flame retardant material for polymeric materials was reviewed and compared with other common nanofillers. Graphene sheets and their composite as flame retardant nanofillers for polymers and flame retardant coating for textiles are discussed in details. Synergistic flame retardant effect of use of nanoparticles decorated graphene sheets as flame retardant for polymer nanocomposites are discussed.
Polyurethane (PU) sponge has a wide range of applications in our daily life. Unfortunately, the PU sponge is highly flammable and becomes a breeding ground for bacteria, thereby threatening human ...health and life. To date, it remains a challenge to improve the flame retardant and antibacterial properties of PU sponge simultaneously without destroying its inherent elasticity and flexibility. Here we report a novel composite coating on the PU sponge using bioderived phytic acid and sodium lignosulfonate via a facile soaking method. Compared to the pristine sponge, the coated PU sponge can reach a 32% reduction in peak heat release rate during cone calorimeter test, and prevent melt dripping after being ignited by a butane torch and the flame can be self-extinguished after the torch is removed. The resultant composite coating also demonstrates a killing rate of 99% against Staphylococcus aureus. Meanwhile, the coated PU sponge can retain the inherent elasticity and flexibility even after 500 cycles of compression. Furthermore, the coating materials are easily recyclable, which provide a useful reference for multifunctional treatment of sponge and cyclic utilization of resources.
Polyimide (PI) composite aerogels with enhanced flame-retardant performance have been fabricated with the addition of environmentally friendly flame-retardant additives (i.e. graphene (G) and ...montmorillonite (MMT)) via an eco-friendly freeze-drying method followed by a thermal imidization process. Through the strong interaction between the two components, graphene oxide/MMT hybrid can be synergistically dispersed in water, providing good dispersibility in PI matrix, thus endowing the composite aerogels with enhanced mechanical, thermal and flame-retardant properties. As a result, the obtained optimal PI/G/M aerogel exhibits a high compression modulus of up to 14.0 MPa, as well as a specific modulus as high as 155.5 MPa cm3 g−1. Furthermore, with the incorporation of G/MMT hybrids, the decomposition temperature at 10% weigh loss of PI/G/MMT aerogels is 574.3 °C, which is 20 °C higher than that of neat PI aerogels. Moreover, the PI/G/M aerogels exhibit enhanced flame retardant performance with the limiting oxygen index (LOI) value up to 55. Therefore, the G/MMT hybrids synergistically reinforced PI composite aerogels show great potential as high-performance flame-retardant materials.
A phosphorous‐nitrogen intumescent flame‐retardant, 2,2‐diethyl‐1,3‐propanediol phosphoryl melamine (DPPM), was synthesized and characterized by Fourier transform infrared spectroscopy and nuclear ...magnetic resonance. Flame‐retardant rigid polyurethane foams (RPUFs) with DPPM (DPPM‐RPUF) as fire‐retardant additive were prepared. Scanning electron microscope (SEM) and mechanical performance testing showed that DPPM exhibited a favorable compatibility with RPUF and negligibly negative influence on the mechanical properties of RPUF. The flame retardancy of DPPM on RPUF was investigated by the limiting oxygen index (LOI), vertical burning test and cone calorimeter. The LOI of DPPM‐RPUF could reach 29.5%, and a UL‐94 V‐0 rating was achieved, when the content of DPPM was 25 php. Furthermore, the DPPM‐RPUF exhibited an outstanding water resistance that it could still obtain a V‐0 rating after water soaking. Thermogravimetric analysis showed that the residual weight of RPUF was relatively low, while the charring ability of DPPM‐RPUF was improved greatly. Real‐time Fourier transform infrared spectroscopy was employed to study the thermo‐oxidative degradation reactions of DPPM‐RPUF. The results revealed that the flame‐retardancy mechanism of DPPM in RPUF was based on the surface charred layer acting as a physical barrier, which slowed down the decomposition of RPUF and prevented the heat and mass transfer between the gas and the condensed phases.
Separators play a pivotal role in the electrochemical performance and safety of lithium‐ion batteries (LIBs). The commercial microporous polyolefin‐based separators often suffer from inferior ...electrolyte wettability, low thermal stability, and severe safety concerns. Herein, a novel kind of highly flexible and porous separator based on hydroxyapatite nanowires (HAP NWs) with excellent thermal stability, fire resistance, and superior electrolyte wettability is reported. A hierarchical cross‐linked network structure forms between HAP NWs and cellulose fibers (CFs) via hybridization, which endows the separator with high flexibility and robust mechanical strength. The high thermal stability of HAP NW networks enables the separator to preserve its structural integrity at temperatures as high as 700 °C, and the fire‐resistant property of HAP NWs ensures high safety of the battery. In particular, benefiting from its unique composition and highly porous structure, the as‐prepared HAP/CF separator exhibits near zero contact angle with the liquid electrolyte and high electrolyte uptake of 253%, indicating superior electrolyte wettability compared with the commercial polyolefin separator. The as‐prepared HAP/CF separator has unique advantages of superior electrolyte wettability, mechanical robustness, high thermal stability, and fire resistance, thus, is promising as a new kind of separator for advanced LIBs with enhanced performance and high safety.
A new kind of highly flexible, porous, high‐wettability, fire‐resistant hydroxyapatite nanowire‐based separator with superior performance and high safety is prepared for advanced lithium‐ion batteries. The batteries with the hydroxyapatite nanowire‐based separators show better cyclability and enhanced rate capability compared with those with the commercial polypropylene separator. The as‐prepared batteries adopting the hydroxyapatite nanowire‐based separator can safely work at 150 °C.
