Fire Growth Index Research Articles

Increase of bridge length by ingenious grafting of ester chains, imparting epoxy resins superb thermal, smoke suppression, gas-phase flame retardancy, and mechanical properties

While bifunctional synergistic flame retardants have demonstrated efficacy in enhancing the fire safety of epoxy resins (EPs), the grafting of specific functional monomers into flame retardant molecules, elucidating their mechanisms of action through comparative analysis, and concurrently achieving a delicate balance among flame retardancy, heat resistance, and mechanical toughness remains a significant challenge. Herein, this research present an innovative strategy to derive a novel sulfur-based bifunctional flame retardant, DSTA, based on the structure of the original flame retardant, DST, by grafting the ester chains to increase the bridge length of the molecular structure. As expected, the addition of flexible ester chains enabled DSTA to have a very high initial decomposition temperature and the heat-resistance index. DSTA can be used in low dosage compared to DST, enabling EP to achieve UL-94 V-0 rating. Combustion behavior showed that DSTA had the best ability to heat and smoke suppression for EP, and had faster response speed and higher fire growth index. Notably, pyrolysis volatiles tested on DSTA revealed that the ester chains can pyrolysis to release large amounts of CO2, which occurs in the early stages of pyrolysis and works together with other N-containing inert gases and P-containing radicals in the gas-phase to efficiently extinguish flames. Meanwhile, DSTA improves all mechanical properties of EP, which was attributed to the presence of ester chains. In summary, this work presents a new strategy for examining the impact of specific functional groups on the flame retardant mechanisms of EP.

Flame retardant and mechanically enhanced polyacrylonitrile fibers prepared by amination and phosphorylation

To improve the flame retardancy of polyacrylonitrile (PAN) fibers, PAN fibers were firstly modified through amination with diethylenetriamine (DETA) to obtain ammoniated PAN fibers (A-PAN). Then, A-PAN underwent phosphorylation modification via phosphorus-containing flame retardant, i.e., tetrakis (hydroxymethyl) phosphonium sulfate (THPS) to fabricate flame retardant PAN fibers (THPS-A-PAN). XPS and FTIR confirmed the covalent bonding of DETA and THPS with PAN fibers. TGA showed improved thermal stability, particularly in increased char residue at high temperatures. The modified PAN fibers exhibited enhanced flame retardancy in vertical burning tests and MCC analysis, with LOI values increasing from 17% to 32.5% and maintaining at 26.5% after 30 laundering cycles (LCs). Fire safety parameters such as heat release capacity (HRC), total heat release (THR), and the fire growth index (FGI) decreased by 51.5%, 46.9%, and 41.9%, respectively. In addition, the tensile strength and elongation at break of THPS-A-PAN increased from 2.69 cN/dtex and 28.6% to 3.08 cN/dtex and 30.1% respectively, indicating enhanced mechanical properties. This work develops a feasible strategy to improve the flame retardancy of PAN fibers while endowing them with reinforced mechanical properties, which provides a possible research direction for the practical application of flame retardant PAN fibers.

Multi‐objective optimization of hybrid polypropylene composites for enhanced mechanical, thermal, and flame‐retardant properties

AbstractOptimizing composite materials is crucial for engineering advancements because it allows for the creation of materials tailored to specific functional requirements, thereby enhancing efficiency, safety, and sustainability. This study examines both the combined and individual effects of long flax fiber (LFF) bundles, short basalt fibers (BF), and rice husk powder (RHP) on the properties of polypropylene (PP) hybrid composites. LFF primarily provides mechanical strength, BF enhances mechanical, thermal, and flame‐retardant properties by filling gaps, and RHP reinforces and improves the overall composite. Contrary to previous studies that relied on random combinations, this research employs a systematic Box–Behnken design (BBD) for three variables: LFF plies, BF, and RHP by weight percentage. This approach facilitated the development of a new second‐order regression equation via response surface methodology (RSM), clarifying the contribution of each component, with R2 values exceeding 0.85, indicating high predictability. Optimization, conducted using a non‐dominated sorting genetic algorithm (NSGA‐II), demonstrated that the optimal composites significantly outperformed the non‐optimized ones in mechanical strength, thermal stability, and flame retardancy. Compared to the average values before optimization, improvements post‐optimization included increases of 49.86% in tensile strength (TS), 38.82% in TS modulus, 73.93% in char yield (YC), and 29.81% in peak heat release rate (pHRR). Specifically, the fire performance index improved by 237.5% and the fire growth index by 101.33%, compared to pure PP, highlighting significant advancements in fire safety. This study shows that mathematical equations can predict composite properties, helping to select balanced compositions without sacrificing flammability.Highlights Multi‐filler approach technique used for manufacturing of PP composites. LFF, BF & RHP optimize mechanics & flammability. Box–Behnken design predicts optimal composition for superior properties. NSGA‐II optimization improves tensile, thermal & flame retardant properties.

Cascade computational model for prediction impact of transient depth change on combustion parameters of certain timber species under continuous heating rate

The purpose of this research is to examine the effects of depth variation and exposure duration on the combustion characterization of the Maple wood species (Acer platanoides L.) and Walnut (Juglans regia L.) according to ISO 5660–1 in case of exposing the specimens to a constant heating rate 50 kWm−2. The delivered experimental data by cone calorimeter apparatus is used to train, test, and validate the optimized cascade forward artificial neural network with topology 2–8–8–12–2. This structure is simulated to predict the target parameters: the heat release rate (HRR) and the mass burning rate (MBR). With real systems, it is possible to achieve a reasonable performance and the closest approximations for the cascade model. The experimental combustion parameters: time of flame out, average specific mass burning rate, total heat release, maximum average rate of heat emission, and fire growth index are considered to make a systematic analysis and assessment with change depth. Three regions are considered for investigation of output target curves, thermally thin (d ≤ 1.1 cm), thermally medium (1.1 cm < d< 1.5 cm), thermally thick (d≥ 1.5cm). The findings demonstrate that independent of exposure period, an increase in depth change causes a sizable reduction in the HRR and MBR. Beyond 1.5 cm of depth in thermally thick regions, there is no discernible effect of time instant on changes in target parameters. In contrast, HRR and MBR gradients across depth in thermally thin regions are striking.

Preparation of a Flame-Retardant Curing Agent Based on Phytic Acid-Melamine Ion Crosslinking and Its Application in Wood Coatings.

To broaden the applications of wood, it is necessary to prepare flame-retardant coatings that can protect wood substrates during combustion. In this study, a bio-based, intumescent, flame-retardant phytic acid-melamine polyelectrolyte (PM) was prepared using phosphorus-rich biomass phytic acid and nitrogen-rich melamine as raw materials through an ion crosslinking reaction. Subsequently, a series of bio-based, flame-retardant wood coatings were prepared by optimizing the structure of urea-formaldehyde resin with the addition of melamine, sodium lignosulfonate, and PM as a flame-retardant curing agent. Woods coated with PM-containing coatings displayed significantly improved flame-retardant performances in comparison to uncoated woods. For PM-cured woods, the measured values of total heat release and total smoke production were 91.51% and 57.80% lower, respectively, compared with those of uncoated wood. Furthermore, the fire growth index decreased by 97.32%, indicating a lower fire hazard. This increase in flame retardancy and smoke suppression performance is due to the dense expanded carbon layer formed during the combustion of the coating, which isolates oxygen and heat. In addition, the mechanical properties of the flame-retardant coatings cured with PM are similar to those cured with a commercial curing agent, NH4Cl. In addition, the prepared flame-retardant coating can also stain the wood. This study proves the excellent flame-retarding and curing effect of ammonium phytate in urea-formaldehyde resin coatings and provides a new approach for the application of bio-based flame retardants in wood coatings.

Effect of flame retardant hexafluorocyclotriphosphazene on combustion characteristics of electrolyte for lithium-ion batteries

Hexafluorocyclotriphosphazene (HFPN) is a promising flame retardant to be applied in lithium-ion batteries (LIBs) to decrease the fire risk during the treatment of electrolyte. In this manuscript, the influence of HFPN on the combustion characteristics of LIB electrolyte was investigated, the combustion behaviors and flame retardancy of the electrolyte with or without HFPN were systematically studied by using cone calorimeter, flash point meter and a series of standard equipment, as well as self-made water spray fire extinguishing platform. The flash points of 3 kinds of control group as base solution and 3 kinds of flame-retarded electrolyte were measured and obtained by SCKB3000 closed cup automatic flash point tester. The combustion characteristics of 6 types of electrolytes were analyzed by a cone calorimeter. The heat release rate (HRR), fire growth index (FGI), fire magnitude index (FMI) and other important combustion parameters of the electrolytes were studied. Based on the self-made water mist fire extinguishing platform, the fire extinguishing effect on 6 kinds of electrolytes under the same water mist condition was compared, and the influence of flame retardants in the fire extinguishing process was analyzed. The results showed that the change of flash point was obviously related to the composition of electrolyte. Flame retardant could reduce the peak HRR (pHRR) during electrolyte fire to a large extent, while it could also prolong the combustion duration of electrolyte pool fire. Under the action of fine water mist, the electrolyte pool fire would quickly extinguish, but there would remain a lot of smoke.

Fully‐Recyclable Green and Fire‐Resistant Triboelectric Elastomer via Geometrical Synergistic Fillers and Its Applications for Smart Firefighting Boots

AbstractWearable sensors for high temperatures (WSHT) applications pose a significant challenge in the electronics field due to the inherent inability of most electronics to function in harsh environments. Triboelectric nanogenerators (TENG) present a substantial potential for applications in such challenging conditions. Herein, a fully‐recyclable flame‐retardant triboelectric elastomer is developed, which exhibits superior charge stability under high temperature conditions and proposes the specially designed synergistic fillers that play a dual role by trapping more charges into the interface and stabilizing the char layers via layer‐ball‐layer structure. An efficient flame‐retardant system is presented, which exhibits a 31% lower fire growth index than the individual components. The maximum surface charge density of this triboelectric elastomer can reach 361 µC m−2, while this surface charge density can be preserved to 70.9% after 16 s of combustion (≈520 °C) and to 37.9% by continuously working at 130 °C. At last, utilizing this flame‐retardant triboelectric elastomer, smart firemen's boots featuring gait analysis for identification and second level early warning systems have been developed. This work paves the way for the development of triboelectric materials and intelligent wearable devices suitable for applications in harsh environments.

Simple modification of phenylphosphonic acid to construct polyester-cotton fabrics with high flame retardancy

Polyester-cotton fabrics (PTCO) have excellent properties and are ubiquitous in daily life, but their serious flammability brings great safety hazards to people's lives. This study used phenylphosphonic acid (PPOA) and urea as raw materials to prepare a flame retardant named POU. PTCO/POU was prepared by the pad-dry-cure technique, and the performance was compared with that of PTCO/PPOA, revealing many interesting phenomena. Based on the gas phase and condensed phase flame-retardant mechanism brought by P/N synergy, PTCO/POU had better flame retardancy than PTCO/PPOA did. The damaged length was 6.7 cm, and the limiting oxygen index (LOI) value was 30.1%. The char residues after burning were complete and denser with a higher degree of graphitization. Thermogravimetric analysis showed that POU can significantly reduce the Rmax of PTCO, and improve its thermal stability in high temperature zones. The CCT results showed that PTCO/POU had the longest time to ignition and the smallest fire growth index, which was of great significance for reducing fire risk. The TG-FTIR results showed that the volatile products of PTCO/POU were greatly reduced, and during the burning process, NH3 was produced to dilute the concentration of combustible gases. In addition, PTCO/POU also had better whiteness performance than PTCO/PPOA did. This work greatly improved the flame retardancy of PTCO in a simple way and expanded its application prospects.

Thermal Stability, Flame Retardancy and Flame Retardant Mechanisms of Hollow Glass Microspheres/Montmorillonite/Epoxy Sheet Molding Compound Composites

Epoxy sheet molding compound (ESMC) composites have excellent mechanical properties, dimensional stability and electrical insulation, and are widely used in the automotive industry. In our previous work silane coupling agent modified, hollow glass microspheres (SiHGM) and montmorillonite (MMT) were incorporated to enhance the mechanical properties of the ESMC composites. It was found that the ESMC composites containing MMT (EP/SiHGM/MMT-1) exhibited excellent mechanical strength. However, the flammability of the epoxy resin (EP) limits the use of ESMC composites for applications that require good flame retardancy. In this paper we describe our research in which MMT was used to increase the flame retardancy of ESMC composites. The results showed that the addition of MMT made the ESMC composites have excellent flame retardancy. The limiting oxygen index (LOI) of the ESMC composites containing 1 phr MMT (EP/SiHGM/MMT-1) was 26.8%, which was 8.94% higher than that of the ESMC composites without MMT (EP/SiHGM/MMT-0). In addition, the peak heat release rate (PHRR), average heat release rate (AHRR) and total heat release (THR) of the EP/SiHGM/MMT-1 were 322.8 kW/m2, 95.3 kW/m2 and 38.6 MJ/m2, respectively, which were 22.6%, 8.2% and 8.0% lower than those of EP/SiHGM/MMT-0. The carbon monoxide production (COP) and carbon dioxide production (CO2P) of EP/SiHGM/MMT-1 were 0.0092 g/s and 0.2071 g/s, respectively, which were 34.3% and 22.8% lower than those of EP/SiHGM/MMT-0. The fire growth index (FGI) of EP/SiHGM/MMT-1 was 2.4, which was a decrease by 29.4% compared to EP/SiHGM/MMT-0. In addition, the flame retardant mechanisms were revealed. We suggest that MMT promoted dehydration and charring of the epoxy resin and helped construct an intact physical barrier, which had good blocking effects. The prepared composite has great application prospects for those occasions that require high flame retardancy. Thus, this work provides an innovative strategy for preparing low density epoxy composites with excellent flame retardancy and high mechanical properties.

Replacing Harmful Flame Retardants with Biodegradable Starch-Based Materials in Polyethylene Formulations.

The addition of toxic flame retardants to commercially available polymers is often required for safety reasons due to the high flammability of these materials. In this work, the preparation and incorporation of efficient biodegradable starch-based flame retardants into a low-density polyethylene (LDPE) matrix was investigated. Thermoplastic starch was first obtained by plasticizing starch with glycerol/water or glycerol/water/choline phytate to obtain TPS-G and TPS-G-CPA, respectively. Various LDPE/TPS blends were prepared by means of melt blending using polyethylene graft maleic anhydride as a compatibilizer and by varying the content of TPS and a halogenated commercial flame retardant. By replacing 38% and 76% of the harmful commercial flame retardant with safe TPS-G-CPA and TPS-G, respectively, blends with promising fire behavior were obtained, while the limiting oxygen index (LOI ≈ 28%) remained the same. The presence of choline phytate improved both the charring ability and fire retardancy of starch and resulted in a 43% reduction in fire growth index compared to the blend with commercial flame retardant only, as confirmed by means of cone calorimetry. Standard UL 94 vertical tests showed that blends containing TPS exhibited dripping behavior (rated V2), while those with commercial flame retardant were rated V0. Overall, this work demonstrates the potential of starch as a natural flame retardant that could reduce the cost and increase the safety of polymer-based materials.

Flame-retardant phytic acid–decorated thermoplastic starch/halloysite nanotube composite films with enhanced mechanical strength and excellent barrier properties

Thermoplastic starch (TPS), a green and fully biodegradable composite, is considered the most viable option for replacing petroleum-based polymers. However, the poor mechanical properties, high flammability and moisture absorption susceptibility of TPS severely restrict its large-scale applications. Through PA phosphorylation and blending with halloysite nanotubes (HNTs), phytic acid (PA)-phosphorylated HNT/TPS composite films (HNTPSFs) were fabricated with enhanced mechanical strength, excellent flame retardancy, and improved barrier properties. The introduction of HNTs substantially increased the mechanical properties (tensile strength increased 54.3 % and elongation at break decreased 37.0 %) of TPS films and reduced the diffusion of water vapor (decreased 34.1 %). Thermogravimetric analysis studies demonstrated that the HNTPSFs had exceptional thermal stability at their anticipated working temperatures. Furthermore, when the PA content in the composite films increased, the peak heat release rate, total heat release and fire growth index of the HNTPSFs all decreased substantially, demonstrating the improved flame retardancy of HNTPSFs. Hence, the synthesized fully biodegradable TPS composites show enormous potential in the field of renewable biopolymers.

Flammability and explosion characteristics of softwood dust

In technical terms, wood is a natural composite material with a polymer matrix, reinforced with fibres made of uniaxially oriented longitudinal cells. Due to the ease of obtaining and relatively low technological requirements related to its processing, wood is a common material used for various types of construction materials. An experimental investigation was carried out to determine the evolution of the ignition sensitivity and the explosion of three types of softwood dusts. Two of those dusts come from conifers and one from a deciduous tree. Complete fire characteristic requires several parameters describing wood dust behaviour under fire conditions including heat release rate (HRR), ignition time, or fire growth index. To determine those parameters, a cone calorimeter was used. Explosion characteristic was tested for representative wood as a dust sample in 20-L spherical vessel. Minimum ignition energy (MIE) was tested on MINOR II apparatus, which is a modified Hartman’s tube. Minimum ignition temperatures were tested with the use of layer ignition temperature apparatus and Godbert–Greenwald apparatus for minimum ignition temperature of a dust layer and dust cloud (MIT), respectively. Dust with the highest KST value, lowest MIE in the widest concentration range, and lowest MIT was pine wood dust. It also shows the shortest ignition time and a timespan between ignition and HRR peak.

In-situ synthesis of copper phytate-hierarchically porous MOF-199 hybrid in wood towards multifunctional flame-retardant wood composite

The modern society pays growing attention on global environmental issues, public safety, and individual health, which highlights the necessity of exploring sustainable, energy-saving, flame-retardant, and anti-mildew materials for building applications. Herein, by in-situ preparing copper phytate-hierarchically porous MOF-199 hybrid (PCuM) in natural wood (W) via simple phytate induced defect engineering strategy, we reported a multifunctional low fire-hazard wood composite (PCuM-W). The phytate anion not only acted as a modulator to generate hierarchical porosity in MOF-199, but also offered high flame retardancy due to its six phosphorus groups. The copper phytate anchored on the cell wall exhibited charring and graphitizing effects and enhanced the flame retardancy and smoke suppression performance of wood. By pyrolysis, a hierarchically porous MOF-199-derived carbon formed and offered a considerably enhanced catalytic activity towards the conversion of CO. With a weight percent gain of only 13.5%, the fire growth index, total smoke production, and maximum CO production rate of PCuM-W were 74.2%, 85.4%, and 33.3% lower than that of W, respectively, showing outstanding fire-hazard-reducing efficiency that surpassed most of its counterparts. Furthermore, due to the hierarchical porosity and antimicrobial property of PCuM, PCuM-W showed excellent moisture-buffering ability and mildew resistance. This work brings guidelines for fabricating hierarchically porous MOFs to realize multifunctional materials via phytate induced defect engineering.

In-situ polymerized zinc phytate chelated Si-C-P geopolymer hybrid coating constructed by incorporating chitosan oligosaccharide and DOPO for flame-retardant plywood

Zinc phytate (ZnPA) chelated geopolymer and in-situ polymerized chitosan oligosaccharide (COS)/DOPO explored a challenging and exciting flame retardant organic–inorganic hybrid coating via sol–gel method to find halogenated high-efficiency bio-flame retardants are widely used as decorative materials for flame-retardant plywood. Herein, the results show that the appropriated ZnPA (0.5 wt%) enhances the flame retardancy of the geopolymer coating, the peak of heat release rate (p-HRR) decreases from 136.09 to 99.39 kW·m−2, the fire growth index (FGI) dropped from 0.47 to 0.28 kW m−2 s−1, the fire performance index (FPI) climbs from 1.00 to 2.52 s·m2·kW−1, and the flame retardancy index (FRI) climbs from 1.00 to 2.52. Meanwhile, through the microstructural analysis of the residual layer, a strong, compact and non-flammable resilient residues is obtained after combustion; Moreover, the pyrolysis kinetics show that the Z.-L.-T. three-dimensional diffusion reaction model governs the pyrolysis of hybrid coatings. Appropriated ZnPA increases the pyrolysis Eα from 138.95 kJ·mol−1 to 160.75 kJ·mol−1 at 741 ∼ 890 ℃ and improves the thermal stability of the coating. The Si-C-P structure improves the formaldehyde adsorption rate by 46.5%. Therefore, this study, by preparing COS-pretreated ZnPA and DOPO to co-construct alkali-excited cenospheres-based Si-C-P coating, reveals the sustainable development of modified bio-based geopolymer flame-retardant coatings in the construction industry.

A reversibly flame-retardant thermal regulation material inspired by leaf transpiration

The demand for advanced fire-retardant wearable materials has increased with a rise in fire disasters in modern society. However, traditional fabrics have some drawbacks including non-temperature regulation, non-recyclability and contaminated products. Here, inspired by leaf transpiration, we prepared a reversibly flame-retardant thermal regulation material (LPWH). Wood cellulose skeleton is expected to be a reinforced mechanical scaffold by imitating the role of leaf vein for water collection and transportation. In parallel, to mimic the mesophyll cells around leaf vein, a hydrophilic and porous phase-change hydrogel aggregation is prepared by anchoring polyethyleneglycoldiacrylate-co-sodium vinylsulfonate copolymer on cellulose fibers and subsequent in-situ assembly of sodium alginate. This precise combination creates an artificial transpiration tissue, achieving effective heat dissipation and temperature regulation via water transpiration and phase-change behavior of hydrogel aggregation. LPWH shows a longer ignited time of 150 s (71% extension), a lower total smoke release of 22.3 m2/m2 (76% reduction), together with an ultralow fire growth index of 2.4 compared to commercial fire-retardant cotton fabric. Moreover, reversible fire retardancy (30 cycles) and great mechanical property (351 times higher than pure phase-change hydrogel) are demonstrated, suggesting LPWH can be the next generation of the pollution-free, recyclable temperature-regulated fireproof suit.

Silane coupling agent and carboxymethyl chitosan co‐modified boron nitride for preparing silicone acrylic emulsion‐based flame‐retarding coatings

AbstractHerein, the synergistic effect of the silane coupling agent (KH550) and carboxymethyl chitosan (CMCS) co‐modified boron nitride (BN) on the fireproof property of silicone acrylic emulsion‐based composite is investigated to explore halogen‐free coatings for flame‐retarding plywood. Firstly, KH550 and CMCS co‐modified BN improves its compatibility with the silicone acrylic emulsion. The results show that an appropriate loading of BN (2 wt%) enhances flame retardancy. The peak‐heat release rate decreases from 86.01 to 54.95 kW m−2, with the reduced fire growth index decreasing from 0.31 to 0.16 kW m−2 s−1, and the average effective heat of combustion drops from 0.99 to 0.85 kW g−1. Meanwhile, the x‐ray diffraction results demonstrate that the co‐modified BN reacts with the phosphoric acid generated by APP decomposition and transforms into BPO4, enhances the thermal insulation of the coating. The pyrolysis kinetics confirms that the co‐modified BN increases Eα at 300–380°C by 23.4% and Eα at 380–430°C by 21.5%. The water contact angle clarifies that the co‐modified BN significantly imparts higher water resistance to the coating. Generally, the high thermal conductivity of co‐modified BN effectively achieves heat dissipation and facilitates the uniform charring of the composite coating, leading to the as‐formed resilient residues for blocking flame development.

Functionalised biochar in biocomposites: The effect of fire retardants, bioplastics and processing methods

Fire retardants, although can impart fire-safety in polymeric composites, are detrimental to the mechanical properties. Biochar can be used, in conjunction with fire retardants, to create a balance between fire-safety and mechanical performance. It is possible to thermally dope fire retardants into the pores of biochar to make it functionalised. Thus, the current work is intended in identifying a composite having the combination of the most desirable fire retardant, bioplastic, and a suitable processing method. A comparison was made between two fire retardants (lanosol and ammonium polyphosphate), bioplastics (wheat gluten and polyamide 11), and composite processing methods (compression and injection moulding). It was found that wheat gluten containing ammonium polyphosphate-doped biochar made by compression moulding had the best fire-safety properties with the lowest peak heat release rate (186 kW/m2), the highest fire performance index (0.6 m2s/kW), and the lowest fire growth index (1.6 kW/ms) with acceptable mechanical properties compared to the corresponding neat bioplastic. Thus, for gluten-based polymers, the use of ammonium polyphosphate thermally doped into biochar processed by compression moulding is recommended to both simultaneously improve fire-safety and conserve the mechanical strength of the resulting biocomposites.

Fire-safe epoxy composite realized by MXenes based nanostructure with vertically arrayed MOFs derived from interfacial assembly strategy

In this contribution, Ni-based metal organic frameworks (Ni-MOF) nanosheets with high specific surface area are grown on transition metals carbides (MXenes, denoted as MX) surface via vertical alignment, gestating the flame retardant of MX@MOF-B. With the addition of 2.0 wt% MX@MOF-B, the peak heat release rate, peak smoke production rate, peak CO production rate, peak CO2 production rate are reduced by 42.5 %, 26.7 %, 37.8 %, 54.9 %, while the peak concentrations of C2H6, CH4, HCN, NO, N2O are impaired by 91.3 %, 94.3 %, 89.6 %, 90.3 %, 60.9 %, suggesting the enhanced fire safety. Meantime, the fire performance index is elevated by 83.0 % and fire growth index is reduced by 37.2 %, demonstrating the promoted fire safety. Of note, the using of MX@MOF-B induces the promotion of 787.1 % in char yield after combustion, which shows higher graphitized degree and thus enables better protection for basal matrix. Flame retardation contrast with previous works also manifests the strength of MX@MOF-B in hindering the heat release and toxicants emission. This work offers a new paradigm for forging fire-safe polymer composites with low toxicity.

Preparation of an integrated P–N–Si tube containing phosphazene-triazine-silica structure: An efficient flame retardant agent for epoxy resin

To reduce the fire risk of EP, an amino-silica functionalized triazine-rich polyphosphazene tube (MTP@NH2–SiO2) was designed and prepared. With low addition of MTP@NH2–SiO2 (0.5 wt% and 1.5 wt%), the peak value of heat release rate (PHRR) of EP/MTP@NH2–SiO20.5 and EP/MTP@NH2–SiO21.5 decreases by 55.1% and 72.4%, respectively. The total smoke production (TSP) of EP/MTP@NH2–SiO21.5 is of 52.8% reduction. And the fire growth index (FGI) and the fire performance index (FPI) of EP/MTP@NH2–SiO21.5 are 2.74 kW/(m2s) and 0.19 (m2s)/kW, which means EP/MTP@NH2–SiO21.5 is of the lowest fire risk properties. Therefore, the fire safety properties of EP/MTP@NH2–SiO2 can be improved by designed MTP@NH2–SiO2 indeed. MTP@NH2–SiO2 is with high-efficiency of condensed phase flame retardant effect on EP. EP/MTP@NH2–SiO2 can form a glass-like protective char layer rich in phosphorus-nitrogen-silicon (P–N–Si), so as to suppress the transmission of volatile products, oxygen and heat in combustion zone of EP, thus improving the fire safety of EP.

A rational design of functionalized black phosphorus cooperates with piperazine pyrophosphate to significantly suppress the fire hazards of polypropylene

The flammability of polypropylene (PP) not only has negative effects on human health but also causes environmental pollution. Herein, from the molecular polarity point of view, rationally designed hyperbranched charring foaming agents (HCFA) modified black phosphorus nanosheets by in situ polymerization to solve the fire hazards of PP. Based on the UL-94 test V-0 rating, the conventional flame retardant of piperazine pyrophosphate (PAPP) is substituted partly by the BP@PPC. Surprisingly, compared with 27 wt% of PAPP/PP, composites consisting of only 2 wt% of BP@PPC and 20 wt% PAPP/PP also passes the V-0 rating. The results of the cone calorimeter test confirmed that adding BP@PPC decreases the total heat release (THR) and peak heat release (PHRR) by a large amount, which are decreased by 23.4%, 85.8% respectively compared with PP. Moreover, it is uncommon for the fire growth index of BP@PPC composites to be 66.7% lower than that of PAPP/PP composites. In addition, the incorporation of BP@PPC has almost no impact on the mechanical characteristics of PP composites. This study offers a reference for combining established flame retardants with novel compounds to modify the burning behaviors of PP.