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In this study, the challenges of brittleness and flammability in Polyamide 6/glass fiber (PA6/GF) composites, which are crucial for heat‐resistant and stress‐bearing structural parts, are addressed. Polyphosphazene (PZ) elastomers, known for their exceptional flame‐retardant properties, are introduced to enhance the robustness and safety of these composites. Specifically, poly(diaryloxy)phosphazene (PDAP) and poly(difluoroalkoxy)phosphazene (PDFP) are utilized, both contributing to the improved toughness and flame resistance of the PA6/GF composites. Experimental results show that PDAP mainly played the role of solid‐phase flame retardant, while PDFP mainly acted the role of gas‐phase flame retardant. For PA/PZs composites without adding GF, PDFP plays a more efficient flame retardant effect than PDAP. By introducing 15 Vol% of PDFP, the limiting oxygen index (LOI) of the composite reached 26.1%, while the notched impact strength increased by 297%. For PA/PZs/GF composites, PDAP plays a better flame retardant role than PDFP. Under the action of 30 vol% GF and 15 vol% PDAP, the LOI of PA6/PDAP/GF composite reached 26.8%, and the notch impact strength improved to 18.7 kJ/m2, which is 165% higher than that of PA6/GF, and the UL‐94 test reaches V‐0 level. The findings of the study highlight the potential of PDAP and PDFP to act as dual‐function modifiers. These modifiers can considerably ameliorate both the impact resistance and flame retardancy of PA6 and PA6/GF composites. Such dual enhancement surpasses the typical trade‐offs seen in conventional composites, indicating a constructive direction for future material innovation. Highlights: Polyphosphazenes simultaneously enhance PA6's toughness & flame resistance.Distinct flame retardant mechanisms found in PDAP and PDFP.GF presence alters PDAP and PDFP's flame retardant efficacy.PDAP shows superior flame resistance in GF‐reinforced PA6 composites.Without GF, PDFP outperforms PDAP in enhancing flame retardancy. [ABSTRACT FROM AUTHOR]

Highlights To enhance the flame retardant property of fiber‐reinforced polymer composites without adding more flame retardants, we prepared film stacking composites by maintaining a total flame retardant content of 20% and applying a gradient flame retardant strategy. The gradient composites have been designated as 3113FRPLA/F and 1331FRPLA/F, respectively. 3113FRPLA/F is characterized by an augmented concentration of fire‐resistant additives in the surface layer, while 1331FRPLA/F features a reduced content. 20%FRPLA/F is prepared with a homogeneously distributed flame retardant composition. Results derived from LOI test and cone calorimeter test unequivocally demonstrate that 3113FRPLA/F outperforms both 1331FRPLA/F and 20%FRPLA/F in improving flame retardancy. The LOI value of 3113FRPLA/F is 36.1%, exceeding that of 20%FRPLA/F and there is also a reduction in the pk‐HRR compared with 20%FRPLA/F. It is of interest to note that 3113FRPLA/F exhibits the most effective heat insulation properties while 20%FRPLA/F has the worst, which is reflected by the infrared thermal imaging results. It bears mention that the impact strength and tensile strength of 3113FRPLA/F surpasses that of 20%FRPLA/F. In summary, 3113FRPLA/F, characterized by its increased surface concentration of flame retardants, demonstrates the most superior overall performance. The characteristics of PLA/fiber composites using a gradient strategy were compared. The LOI value of 3113FRPLA/F is 36.1%, exceeding that of 20%FRPLA/F. 3113FRPLA/F has the best heat insulation effect while 20%FRPLA/F has the worst. The impact strength and tensile strength of 3113FRPLA/F surpasses 20%FRPLA/F. Improving the surface flame retardant concentration increases the overall property. [ABSTRACT FROM AUTHOR]

Inspired by the natural thermal charring capacity of lacquer tree bark, a novel halogen-free, bio-based and two-component synergistic flame retardant system has been constructed by introducing transition metal (Fe3+)-modified tannic acid (TA) as char source and ammonium polyphosphate (APP) as acid source, which was employed for overcoming the severe flammability problem for silicone rubber (SR). By systematically investigating the effect of APP/TA@Fe system on the flame retardancy of SR composites, it has been found that when 40 mass% APP and TA@Fe in a ratio of 3:1 are added, the limited oxygen index (LOI) and vertical combustion tests of SR composites can reach 30% and UL-94 V-0 rating with a rapid self-extinguishing capacity. Through the comprehensive analysis of the residues of SR composites after complete burning, a gas/condensed flame retardant mechanism is primarily proposed in detail. Among these, the ammonia and water vapor released by the decomposition of APP and TA@Fe during combustion can dilute the combustible gases and tannic acid will act via the free radicals scavenging ability. Besides, the continuous, intumescent and dense charring residues from the thermal interaction between APP and TA will exert a prominent role in restricting the heat/mass exchange process and inhibiting the SR matrix from further flame attacking. Surprisingly, the mechanical strength of SR system is attained even if the combination of APP and TA@Fe is blended. Consequently, this article has developed a bionic, eco-friendly and effective approach to settle the flammability problem of SR and broaden their applications in the fields of construction and decoration materials. [ABSTRACT FROM AUTHOR]

Flame-retardant behavior of flax fabric coated by calcium borate powders with clove-like and elongated morphologies was investigated by thermal analysis and cone calorimeter. PDA was used to form strong and uniform adhesion of calcium borate onto fabric. Thermal analysis showed a 20% of decrease in mass loss, while detected exothermic/endothermic peaks as a result of the degradation of fabric and PDA. Significant reductions in HRR, p-HRR, EHC and CO2 amount were observed for fabric coated by PDA and elongated calcium borate powder. PDA was carbonized at low temperatures and formed a char layer that prevented flame propagation. At the same time, calcium borate powder dilutes the flammable gases in the environment with the release of water within its body. Among the calcium borate powders, rod-like morphology showed the best flame-retardant performance. [ABSTRACT FROM AUTHOR]

Aerogel fibers, known for their lightweight and exceptional thermal insulation properties, provide an ideal material solution for fabricating triboelectric nanogenerators (TENGs) for self‐powered wearable electronics in extreme environments, such as firefighting gear. However, current aerogel fibers face limitations due to their poor mechanical properties and lack of performance stability under harsh conditions. Herein, a facile strategy for preparing silica/aramid nanofiber (ANF) composite aerogel fibers with interpenetrated dual networks and a silica‐dominant component (≈64 wt.%) is demonstrated; the unique structure and composition endow the composite aerogel fibers with high tensile strength (3.4 MPa), low thermal conductivity (0.033 W (m·K)−1), a large specific surface area (587 m2 g−1), and outstanding fire resistance at 95% porosity, combining the best properties of both ANF and silica aerogel. Moreover, the composite aerogel fibers exhibit excellent mechanical flexibility at extremely low temperatures (−196 °C) and maintain structural integrity even when exposed to flame for up to 5 min. Leveraging these exceptional properties, composite aerogel fiber‐based TENGs show high electrical output performance before and after combustion (>94% retention). The fabrication strategy offers promising opportunities for modulating the properties and functionalities of aerogel fibers on demand, holding great potential for future applications in wearable smart protective fabrics for extreme environments. [ABSTRACT FROM AUTHOR]

Nanocomposites containing impermeable two‐dimensional materials are of significant interest for protecting metals against corrosion. Incorporating 4‐aminobutyltriethoxysilane (ABES) functionalized tantalum nitride (TaN) into a coating matrix enhances the barrier effect due to TaN's notable chemical and thermal stability. When integrated with graphitic carbon nitride (GCN) in polyurethane (PU), functionalized TaN significantly improves corrosion resistance and fire‐retardant capabilities. Electrochemical evaluations of aluminum coated with varying amounts of functionalized TaN/GCN in PU demonstrated substantial enhancements in protective behavior in chloride environments. The PU nanocomposite exhibited superior flame retardancy, with significant reductions in peak heat release rate (PHRR), total heat release (THR), and total smoke production (TSP) compared to pure PU. Flame retardancy tests demonstrated increased thermal stability, attributed to the synergistic effects between GCN and silanized TaN. Electrochemical impedance spectroscopy (EIS) measurements showed a high coating resistance of 8.89×1011 Ω cm2 for PU/functionalized TaN/GCN, even after 40 days of electrolyte exposure. Additionally, the PU/functionalized TaN/GCN coating demonstrated exceptional water repellency, indicated by a water contact angle (WCA) of 164°. Mechanical tests revealed that PU/functionalized TaN/GCN exhibited favorable adhesion strength and hardness, maintaining integrity even under prolonged immersion. These findings suggest that this nanocomposite is a promising coating component for aerospace applications. The integration of functionalized TaN/GCN within the PU matrix presents a novel approach to developing multifunctional coatings with enhanced performance across various metrics essential for aerospace materials. [ABSTRACT FROM AUTHOR]

Cellulose aerogels are considered as ideal thermal insulation materials owing to their excellent properties such as a low density, high porosity, and low thermal conductivity. However, they still suffer from poor mechanical properties and low flame retardancy. In this study, mullite-fibers-reinforced bagasse cellulose (Mubce) aerogels are designed using bagasse cellulose as the raw material, mullite fibers as the reinforcing agent, glutaraldehyde as the cross-linking agent, and chitosan as the additive. The resulted Mubce aerogels exhibit a low density of 0.085 g/cm3, a high porosity of 93.2%, a low thermal conductivity of 0.0276 W/(m∙K), superior mechanical performances, and an enhanced flame retardancy. The present work offers a novel and straightforward strategy for creating high-performance aerogels, aiming to broaden the application of cellulose aerogels in thermal insulation. [ABSTRACT FROM AUTHOR]

Carbon fiber (CF)‐reinforced epoxy resin (EP) composites are lightweight materials with excellent comprehensive performance. However, the flammability of EP and the poor interfacial bonding between CF and EP are two key disadvantages that limit their further applications. Here, a kind of water‐soluble lignin‐based CF sizing agent (ELBEDK) is prepared through hydrophilic modification of enzymatic lignin, which can significantly enhance the interfacial interaction between CF and EP. Additionally, a highly efficient intumescent flame retardant (LMA) is prepared. The EP, enzymatic lignin, LMA and CF sized ELBEDK are compounded to obtain the fire‐safety CF reinforced composites (SCF/FEP/L). The flame retardancy of SCF/FEP/L with 7% LMA (SCF/FEP7) reached V‐0 rating. Moreover, SCF/FEP/L with 7% LMA and 15% lignin (SCF/FEP7/L15) present an limiting oxygen index (LOI)of 30.2% and V‐0 of UL‐94. Specifically, the total smoke production and the heat release rate are 47.8% and 46.81% lower than that of SCF/EP, respectively, indicating the improved smoke suppression and flame retardancy. The IFSS and flexural strength of SCF/FEP7/L15 are improved to be 59.4 MPa and 511.1 MPa, respectively. This study presents a simple approach to fabricate low‐cost high performance lignin‐based flame retardant CF/EP biocomposites with wide application potential. [ABSTRACT FROM AUTHOR]

Mineral-based flame retardants are widely used worldwide as they are both effective and inexpensive solutions. Especially alumina trihydrate (ATH) and magnesium hydroxide (MDH) are the first mineral additives that come to mind industrially due to their environmental friendliness and easy availability. In this study, the effectiveness of huntite-hydromagnesite mineral, which is not as widely used as the other two minerals, and its differences from its counterparts were investigated. For this purpose, composites with polyethylene carrier were produced by extruder method using binders at various ratios, and various physical, mechanical, and combustion properties of these samples were investigated. According to the data obtained, the samples containing huntite-hydromagnesite showed UL94 V0 class flame retardant performance with 5% less filler than their counterparts. The same samples showed superior mechanical properties in tensile strength between 23.4% and 70.8% and elongation at break between 60.7% and 73.1%. [ABSTRACT FROM AUTHOR]

In this article, the optimal conditions for synthesizing a new flame retardant based on pentaerythritol, phosphoric acid, and magnesium hydroxide are studied. In this case, the molar ratio of the initial substances was 3.64:1, and the synthesis duration was four hours. After the completion of this process, different (1, 3, and 5%) solutions of magnesium hydroxide were added at a temperature of 90 ºC for 3 hours. The yield of this reaction was 85%. Applying this obtained flame retardant to textile materials increases the fire resistance of textile materials. The composition of synthesized antiperine and antiperine applied textile fabrics was studied by IR spectrum, and the thermal decomposition of antiperine applied fabric was investigated by TGA and DTA analysis, and 100 μm sections of flame retardant treated fabrics were measured by scanning electron microscope. The fire resistance and physical mechanical properties of these materials were studied based on the requirements of GOST 50810-95. The oxygen index of the fabric treated with synthesized flame retardant was 35.6%. [ABSTRACT FROM AUTHOR]

Fireproof coatings are the simplest, most efficient, and oldest method for protecting a wide range of flammable products, such as wood. Furthermore, surface ignition is the initial phase, so surface protection is essential to reduce fire propagation. Furthermore, delaying the spread of flames can help to save someone when a fire starts. This project synthesized flame-resistant resin starting from tetraallyloxysilane monomer as a halogen-free monomer, an intrinsic flame retardant co-curing agent. The following step synthesized polyester resin using terephthalic acid as a heat-resistant resin. Unsaturated polyester was used by bulk radical polymerization. FT-IR and 1H-NMR analysis showed the successful synthesis of the desired monomer and polymeric compound. The thermal degradation and flame retardancy of pure unsaturated polyester resin (UPE) and allyloxysilane-unsaturated polyester (AUPE) were investigated by thermogravimetric analysis (TGA/DTG/DSC). The burning test and the thermal stability of the coating layers were evaluated using standard UL 94. Physical properties of resins were evaluated using Heat Deflection Temp tests (HDT) ISO 75-A, ASTM 648, Hardness ASTM D2583, Volumetric shrinkage ASTM 3521, and Water absorption ASTM D570. The results of the tests show the successful synthesis and their flame retardant properties. [ABSTRACT FROM AUTHOR]

Dibutyl phosphate-bound natural rubber (DBNR) was prepared by reacting epoxidized natural rubber with 20 mol% (ENR-20) with dibutyl phosphate in a latex medium. Fourier transform infrared spectroscopy (FTIR) was used to confirm the molecular structures of ENR-20 and DBNR and to quantify the epoxide contents. The shear flows and thermal properties of DBNR were then characterized and compared with ENR-20 and natural rubber (NR). The DBNR exhibited the lowest viscosity curves, but it depicted the highest glass transition temperature (Tg) and residue from thermogravimetric evaluation, indicating higher thermal resistance. Subsequently, different NR/DBNR blend ratios were compounded, with and without flame resistance additives, compared with unmodified NR and chloroprene rubber (CR) compounds. We found that all natural rubber compounds exhibited reversion behavior due to the breakage of newly formed sulfidic bonds. However, chloroprene rubber showed marching cured curves, as evidenced by the increasing torque with prolonged testing time. Additionally, antimony trioxide retarded the curing reaction of NR, while tris(2-ethylhexyl) phosphate accelerated it. Therefore, the combination of these additives synergists with the intrinsic flame retardant properties of DBNR. The study revealed that the burning rate of NR/DBNR blends, exhibited very high flame resistance capability compared to gum NR and NR compounded with flame resistance additives. [ABSTRACT FROM AUTHOR]

Polybenzoxazines (PBz) are a new type of resin belonging to the category of phenolic resins. As polybenzoxazines are addition-curable polymers, this obviates many of the shortcomings associated with conventional phenolic resins while endowing them with excellent thermal, physical, and thermo-physical properties and surpass the features of many conventional and state-of-the-art polymers. They even possess excellent design flexibility. In this study, a benzoxazine monomer was successfully synthesized from eugenol (Eu), ethylenediamine, and paraformaldehyde utilizing a solventless approach. The synthesized benzoxazine resin was characterized for its structural elucidation via FTIR, 1H, and 13C NMR spectroscopy and was used for crosslinking a petroleum-based epoxy and a gallic acid-based epoxy. The effects of the presence of benzoxazine on the thermal and flame retardant properties of the films were evaluated using TGA and DSC analysis and the LOI and UL 94 tests, respectively. It was found that the benzoxazine in the epoxy systems led to an increase in thermal stability and flame retardancy. The gallic acid-based epoxy system showed better thermal and flame retardant properties compared to the petroleum-based epoxy system, thus showing potential to replace the petroleum-based epoxy for high-performance applications. [ABSTRACT FROM AUTHOR]

Black phosphorus and black phosphorus nanosheets are widely used in the flame retardant field because of their excellent properties, but the immature preparation methods have resulted in extremely high preparation cost, which greatly limits their development and application. In this paper, various preparation methods of black phosphorus and black phosphorus nanosheets are described in detail, the advantages and disadvantages of each method are analyzed in depth, the flame-retardant mechanism and application of black phosphorus and black phosphorus nanosheets in flame retardants are discussed, and the subsequent development direction of black phosphorus and black phosphorus nanosheets is proposed. [ABSTRACT FROM AUTHOR]

Over the past few decades, the development of highly efficient phosphorus-based flame retardants has become one of the research focuses in the field of halogen-free flame-retardant polymer technology. In this work, three kinds of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO)-based derivatives were synthesized through integrating multiple phosphorous oxidation states into one molecular structure. The influence of DOPO-based derivatives on the thermal decomposition and flame-retardant properties of EP composites were investigated. DOPO-based derivatives promoted the slightly earlier decomposition of the epoxy matrix, resulting in better thermal stability at high temperatures and higher char yield. The unmodified EP showed a LOI value of 27.0% and no UL-94 rating, while all the EP composites containing 2 wt.% DOPO-based derivatives passed the UL-94 V-0 rating and achieved a LOI value of higher than 30.0%. Among the three DOPO-based derivatives, TDCA-DOPO-2 behaved the best flame-retardant efficiency owing to the highest synergistic effect. Specifically, the peak of heat release rate, total heat release and average effective heat combustion (av-EHC) of EP/TDCA-DOPO-2 was 62.0%, 54.2% and 39.9% lower than those of the unmodified EP, respectively. The high flame-retardant efficiency of DOPO-based derivatives was ascribed to the synergism between the barrier effect in the condensed phase (proved by the high yield and stability of char residues) and the flame inhibition effect in the gaseous phase (proved by the decreased av-EHC values). [ABSTRACT FROM AUTHOR]

Weak bonds usually make macromolecules stronger; therefore, they are often used to enhance the mechanical strength of polymers. Not enough studies have been reported on the use of weak bonds in flame retardants. A water-soluble polyelectrolyte complex composed of polyethyleneimine (PEI), sodium tripolyphosphate (STPP) and melamine (MEL) was designed and utilized to treat bio-based polyamide 56 (PA56) by a simple three-step process. It was found that weak bonds cross-linked the three compounds to a 3D network structure with MEL on the surface of the coating under mild conditions. The thermal stability and flame retardancy of PA56 fabrics were improved by the controlled coating without losing their mechanical properties. After washing 50 times, PA56 still kept good flame retardancy. The cross-linking network structure of the flame retardant enhanced both the thermal stability and durability of the fabric. STPP acted as a catalyst for the breakage of the PA56 molecular chain, PEI facilitated the char formation and MEL released non-combustible gases. The synergistic effect of all compounds was exploited by using weak bonds. This simple method of developing structures with 3D cross-linking using weak bonds provides a new strategy for the preparation of low-cost and environmentally friendly flame retardants. [ABSTRACT FROM AUTHOR]

In recent years, MXene 2D materials have shown good performance in enhancing the flame retardant properties of composite materials, but it is still tricky to improve the compatibility with the polymer matrix. This work explores a simple method for the synthesis of MXene based nanohybrids (CoMn‐LDH@MXene) by hydrothermal synthesis using MXene and layered double hydroxides (CoMn‐LDH) to construct a flame retardant system with excellent performance. The results show that the MXene nanosheets are less built up and more dispersed in the TPU collective due to the inclusion of LDH, giving the TPU composites excellent flame retardant and smoke suppressant properties. Compared to TPU without flame retardant, TPU composites with 2 wt% CoMn‐LDH@MXene reduced PHRR by 33.7 % and THR by 28.7 %. The TPU/2wt %CoMn‐LDH@MXene composites also showed better flame and smoke suppression performance, PSPR, TSP, PCO and PCO2 were reduced by 44.4 %, 22.7 %, 37.7 % and 27.2 % respectively, the production of Hydrocarbons and HCN were also reduced. Barrier effect of transition metal oxide catalysed carbon layer formation, combustion blocking effect of hybrid material nanosheets, cooling effect of water vapour from thermal decomposition of LDH and the gas phase dilution effect are the main reasons for the increased fire safety of TPU composites. [ABSTRACT FROM AUTHOR]

In this study, a nanocomposite based on a heterophasic polypropylene copolymer containing 5 wt% of nanoclays and 3 wt% of compatibilizer was formulated via melt compounding to obtain a material suitable for Fused Filament Fabrication (FFF) processing with enhanced flame-retardant properties. From rheological analyses, the nanocomposite showed an important increase in the non-Newtonian behavior, and, therefore, improved FFF printability compared to the pristine PP COPO. A filament with suitable characteristics for FFF was produced using a single-screw extruder and subsequently 3D printed. Finally, cone calorimeter and UL94 tests were carried out on both 3D-printed and compression-molded specimens. The obtained results showed that the 3D-printed samples exhibited even better flame-retardant properties than the compression-molded ones, thus demonstrating not only the possibility of successfully developing and using functionalized PP-based filaments in 3D printing but also the possibility of obtaining enhanced flame-retardant properties compared to conventional compression molding. [ABSTRACT FROM AUTHOR]

[Display omitted] • FC@NF and T@CF were prepared by LBL self-assembly and soaking methods, respectively. • Fire-retardant performance and mechanism of FC@NF were investigated. • FCF-TENG was fabricated for self-powered sensing in fire scenarios. The fabrics commonly used in architectural decorative materials pose significant fire hazards due to their flammability and rapid fire spread. Moreover, the traditional fire-alarm systems may fail to function properly in complex fire environments owing to power supply disruptions. In this study, we developed a low-cost and eco-friendly flame-retardant conductive fabric-based triboelectric nanogenerator (FCF-TENG) by integrating flame-retardant conductive nylon fabric and polytetrafluoroethylene soaked cotton fabric. This nanogenerator exhibits excellent flame-retardant properties and remarkable energy-harvesting capabilities. The nylon fabric, treated with layer-by-layer self-assembly method, possesses outstanding self-extinguishing capability and melt-dripping resistance. Additionally, the electrical performance of FCF-TENG significantly improves, with a 10-fold boost in conductivity, and the open-circuit voltage increases by 84% to 92 V. Besides, by incorporating the rectifier circuit, the FCF-TENG is capable of completely charging a 1 μF capacitor within 30 s. Furthermore, the FCF-TENG was successfully applied as a self-powered sensor in the fire-alarm system and served as a safety exit indicator for evacuees and fire rescue. This work presents an effective and innovative application of multifunctional smart textiles for energy harvesting and self-powered sensing. [ABSTRACT FROM AUTHOR]

• Flammability limits of azeotropic mixtures consist of R1243zf are tested for the first time. • A brief mechanism for flame-retardant effect of R13I1, R227ea and R134a is analyzed. • CSCs of R1243zf mixtures are tested and compared with calculation results by 3 methods. 3,3,3-trifluoropropene (R1243zf) is a low climate change effect refrigerant that has great development potential. However, R1243zf is flammable and its safety classification is A2 as per ISO standard 817. To reduce its risk of flammability, the method of using mixed refrigerants in practical applications is an effective approach. In this paper, an experimental system was established according to the ASHRAE standard 34 to measure the flammability limits of four azeotropic mixtures containing R1243zf. First, the critical suppression ratio (CSR) of R13I1/R1243zf was tested out that is 0.353. Further measurements were made to determine the lower flammability limits (LFLs) and critical suppression concentrations (CSCs) of three ternary mixtures consisted of R1243zf, thermodynamic performance enhancer (RE170) and flame retardants (R13I1, R134a or R227ea), at various compositions. The experimental non-flammable proportions of R1243zf/RE170/R13I1, R1243zf/RE170/R134a, and R1243zf/RE170/R227ea were 31.81 %, 5.49 %, and 22.42 %, respectively. Besides, a comparison was made between the experimental data and the predicted results by means of three different theoretical methods (the equal effect method, thermal balance method, and group contribution method). The fresh experimental results will provide practical guidance for the applications that utilize the R1243zf blends in low flammability risk. [ABSTRACT FROM AUTHOR]

Unsaturated polyester resins (UPR) are broadly applied in chemical, construction, transportation and electrical fields, etc. However, UPR materials are extremely flammable. Through radiation, conduction and convection, the released heat brings serious thermal hazards to surrounding life and the environment. Meanwhile, the combustion of UPR also releases a vast of toxic pyrolysis gases and smoke, causing extremely serious non-thermal hazards, endangering life and health, reducing fire visibility and hindering escape and rescue efforts. Therefore, the flame retardant modification of UPR materials is an inevitable measure to reduce its flammability and broaden its application breadth. In this review, the flammability of UPR materials is firstly analyzed from the perspective of their compositions and structures. Meanwhile, based on the differences in preparation methods of flame retardant UPR (FR-UPR) in literature research, it is divided into additive flame retardant, intrinsic flame retardant and interfacial flame retardant methods. The relationship between the highly efficient flame retardant structures and the properties, and the gaseous-phase flame retardant and condensed-phase mechanisms in FR-UPR composites are analyzed. Compared with traditional additive flame retardants, polymeric flame retardants, nanosheet flame retardants and intrinsic flame retardant method are important directions for the future development of FR-UPR composites. In addition, the interfacial flame retardant method can effectively improve the interfacial adhesion and flame retardant properties of fiber-reinforced UPR composites, and also has application prospects. This review analyzes the current challenges faced by FR-UPR, and looks forward to its possible future development directions to guide the preparation and application of high-performance FR-UPR. [ABSTRACT FROM AUTHOR]

In this study, in order to expand the engineering application range of thermoplastic corrugated sheets, flame-retardant thermoplastic corrugated sheets were prepared by the thermoplastic molding method. Based on our previous research results, we prepared flame-retardant prepreg tapes with the flame retardant addition accounting for 15%, 20%, and 25% of the resin matrix. Then, we prepared flame-retardant thermoplastic corrugated sandwich panels with corresponding flame retardant addition amounts. The limiting oxygen index test, vertical combustion test, cone calorimetry test, and mechanical property test were carried out on each group of samples and control group samples. The results showed that when the flame retardant was added at 25%, the flame retardant level could reach the V0 level. Compared with the control group, the flexural strength and flexural modulus decreased by 2.6%, 14.1%, and 19.9% and 7.3%, 16.1%, and 21.9%, respectively. When the amount of flame retardant was 15%, 20%, and 25%, respectively, the total heat release decreased by 16.3%, 23.5%, and 34.1%, and the maximum heat release rate decreased by 12.5%, 32.4%, and 37.4%, respectively. [ABSTRACT FROM AUTHOR]

For many years, efforts have been made to reduce the flammability of unsaturated polyester resins (UPRs), which are often used in the rail, shipbuilding, and construction industries. Without modification, they often fail to meet fire safety standards. Despite a rich history of flame retardants (FRs) applied to UPRs, researchers seek new solutions that will provide lower flammability and smoke density, as well as attaining a lower environmental impact from the composites. The objective of the study is to highlight the most important recent research on promising nano FRs in order to promote their further development. Mechanisms of action of several groups of nano FRs, such as clay-based, carbon-based, transition metal compounds, layered double hydroxides, polyhedral oligomeric silsesquioxanes, and others, including bio-based, have been studied. Particular emphasis has been laid on nano FRs applied to UPRs, and their influences on thermal stability, flammability, and mechanical properties. Moreover, the environmental impact and toxicity of nano FRs have been discussed. Results have proved that nano FRs applied at low loadings may significantly improve thermal stability, with a simultaneous increase or only a slight decrease in mechanical properties. However, attention on related environmental issues has highlighted the necessity of carefully selecting novel nano FRs. [ABSTRACT FROM AUTHOR]

A series of pentaerythritol derived flame retardant additives (FRs labeled FR1, FR2, FR3, and FR4) were synthesized and blended with thermoplastic polyurethane (TPU) to enhance its flame retardancy. The chemical structures of the FRs were established by FTIR, 1H, 13C and 31P NMR spectroscopy. The flammability of the TPU blends was analyzed through UL-94 vertical burning and limiting oxygen index (LOI) test. It is found that for FR4-TPU blends with 2% of phosphorus content, the LOI value reached up to 31.2%, and no melt dripping with a V-0 rating was obtained by UL-94, indicating its superior flame retardant properties. Thermogravimetric analysis (TGA) of TPU blends showed that the char yield increases from 3.9% in neat TPU to 20% with the addition of 2% of FR3 in TPU. Based on findings from scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDX), a possible mechanism for the flame retardant property of blends has been proposed. The improved flame retardant properties of TPU blends can be attributed to the formation of a continuous and highly entangled char. This work provides a suitable approach for synthesizing promising phosphorus-based flame retardants from readily available raw materials that can be used to enhance the flame retardancy of TPU. [ABSTRACT FROM AUTHOR]

Bamboo powder has a high risk of fire and dust explosion during production, manufacturing, transportation and storage. It is of great significance to study the combustion characteristics of bamboo powder and its influencing factors for finding suitable flame retardants. So far, the relative study is more focused on bamboo rather than bamboo powder. In this paper, the combustion characteristics of bamboo powder were measured by TGA. Ignition temperature, burnout temperature, combustion rate and comprehensive combustion index were used as evaluation criteria. The influence of particle size and heating rate was quantitatively analyzed. The results showed that the ignition and burnout temperature increased with the increase in heating rate. The S value at the heating rate of 40 °C min−1 was 22 times of that at 5 °C min−1. The finer the particle size, the higher the S value, and the S value of 400-mesh bamboo powder can reach 2.0 × 10–5. The flame retardant properties of six inorganic compounds on bamboo powder were studied. According to the S value, the order of flame retardant properties at the best concentration was CaCl2 ˃ NH4H2PO4 ˃ MgCl2 ˃ Na3PO4 ˃ NH4Cl ˃ APP. Among them, 33% CaCl2 had the best flame retardancy. [ABSTRACT FROM AUTHOR]

Achieving high mechanical performance in a polymer composite is one of the primary concerns when using mineral-based flame retardants. Mineral-based flame retardants should be added to the matrix at 50%–70% to achieve a high level of flame retardancy. High mineral content increases the modulus of elasticity and reduces the ductility of the material. This can be disastrous in applications where flexibility is critical. To overcome this problem, minerals can be used in combination with other effective flame retardants. In this study, the combination of halogen-free mineral-based huntite/hydromagnesite (H/H) and phosphorus-nitrogen-based intumescent flame retardants was investigated to improve the flame retardancy and maintain the flexibility of polypropylene (PP). For this purpose, PP carrier composites were prepared by extrusion by decreasing the mineral concentration in the active formulations and increasing the ratio of phosphorus-based flame retardants. These composites were subjected to mechanical, morphological (SEM), color, and flammability (UL94) tests. As a result, composites with UL94 V0 flammability and 18% to 104% higher tensile strength than equivalent H/H-based flame retardants were obtained. [ABSTRACT FROM AUTHOR]

The presence of massive amounts of toxic volatiles and smoke during combustion is a very serious problem facing epoxy resin (EP) composites. Therefore, flame retardants (FRs) can simultaneously enhance flame retardancy and reduce the release of smoke and fatal gases. Herein, a novel sulfur–phosphorous reactive flame retardant (SPMS) was synthesized for epoxy resin. The high efficiency of smoke suppression and flame retardancy of the EP/SPMS-APP hybrid was investigated using a cone calorimeter, a vertical burning test, and limited oxygen index measurements. Compared with those of pure EP, the composite with 20 wt% SPMS-APP reduced the peak heat release rate (pHRR), the peak smoke production rate (SPR), and total smoke production rate (TSR) by 82%, 94%, and 84%, respectively. The results showed a remarkable suppressed effect of alleviating the fire hazard of EP using a sulfur–phosphorus flame retardant. [ABSTRACT FROM AUTHOR]

Purpose: This paper aims to study a new halogen-free fame-retardant curing agent 1-aminoethylidenediphosphonate (AAEDP). Design/methodology/approach: The AAEDP was synthesized by phosphoric acid, acetonitrile and ammonia. The chemical structures of AAEDP were characterized by proton nuclear magnetic resonance, mass spectrometry and Fourier transform infrared spectrometer. Thermal gravimetric analysis (TGA) and scanning electron microscope (SEM) would study the thermal properties and the char residues of AAEDP/EP. The thermal stability, mechanical and flame properties and morphology for the char layer of composite materials were separately investigated using TGA, tensile and charpy impact tests, limiting oxygen index (LOI), UL-94 HB flammability standard (UL-94) and SEM. Findings: The results showed that the AAEDP had been prepared successfully. When the intumescent flame retardant was added into the EP, the LOI of composite material was improved. Research limitations/implications: The AAEDP can be prepared successfully and can improve the flame resistance of composite material. Practical implications: The AAEDP has excellent flame-retardant properties and produce no toxic fumes when burnt in case of fire. Originality/value: The results showed that the phosphorus content of AAEDP was 2.958 Wt.%; the impact and tensile strength of the composite material were 6.417 kJ m−2 and 38.0 MPa, respectively; and the LOI and UL-94 were 29.7% and V-0 ranking, respectively. The TGA results indicated that the carbon residue ratio can be increased by 1000°C in air. The denser and more uniform structure of residual carbon prevents heat transfer and diffusion, restricts the production of combustible gas and reduces the rate of heat release. [ABSTRACT FROM AUTHOR]

The commercial application of lithium–sulfur (Li–S) batteries is severely impeded by abominable shuttle effects, sluggish redox kinetics, and poor safety performance under high loading conditions. Herein, a novel adsorption‐mediator synergistic polymer binder (PAT) is reported to regulate the conversion of lithium polysulfides (LiPSs) through close intermolecular synergy. The abundant polar groups provide strong anchor ability for LiPSs to effectively inhibit the shuttle effect, and the anchored LiPSs are accelerated by adjacent mediator catalytic sites to facilitate their redox kinetics. Moreover, PAT itself features excellent flame retardant properties, which effectively enhance the safety performance of Li–S cells. Benefiting from these attributes, PAT‐based Li–S cells exhibit outstanding rate performance with an average capacity of 617.34 mAh g−1 at 5 C and excellent cycling stability maintaining a capacity of 629.1 mAh g−1 after 800 cycles at 2 C. Even under the harsh conditions of high loading (9.84 mg cm−2) and lean electrolyte (E/S = 3.56 µL mg−1), PAT‐based cell delivers a high average areal capacity of 9.58 mAh cm−2 and an ultralow overpotential of 3 mV, confirming the application potential of adsorption‐mediator synergistic polymer binder in high performance Li–S batteries. [ABSTRACT FROM AUTHOR]

In this study, sodium alginate (SA) was oxidized with potassium periodate to produce an alginate-based tanning agent. Using OSA as a biodegradable tanning agent and a nano-hydroxyapatite (nano-HAp) low concentration suspension to give flame retardancy to leather, eco-design concepts were applied to establish a chrome-, aldehyde-, and phenol-free tanning process. Micro-DSC, 1H unilateral nuclear magnetic resonance (NMR), attenuated total reflection mode Fourier transform infrared spectroscopy (FTIR-ATR), and scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDS) were used to investigate the complex matrix collagen-OSA-nano-HAp. Micro-differential scanning calorimetry (micro-DSC) was used to assess OSA's ability to interact with collagen and stabilize the collagen-OSA matrix, while 1H unilateral (NMR) was used to investigate the aqueous environment and its limitations around collagen molecules caused by their association with OSA and nano-HAp. Industrial standard tests were used to assess the mechanical properties and fire resistance of the new leather prototype. The findings reported here indicate that both OSA and nano-HAp are suitable alternatives for cleaner tanning technologies and more sustainable leather. [ABSTRACT FROM AUTHOR]

Combining bio-based functional reagents and biopolymers has become a solution to address the needs of sustainability, health, and safety as society has grown. This study developed a waterproof and intumescent flame retardant system for epoxy resin (EP) by combining hexachlorocyclotriphosphazene and melamine with vanillin, synthesizing a ternary polymer flame retardant (HCPVM), combining carbon and gas sources, and using piperazine pyrophosphate (PAPP) as an acid source. The test results showed that HCPVM could participate in the curing reaction of EP and improve the mechanical properties of EP material. At the same time, the flame retardancy and water resistance of the material have been significantly improved. The peak heat release rate (PHRR) of EP/3.5 PAPP/0.5 HCPVM was 65.43% lower than that of pure EP. Additionally, the system's LOI and UL-94 did not significantly change after five days of boiling. In summary, this study's waterproof bio-based intumescent flame retardant solution broadens the application possibilities for EP. [ABSTRACT FROM AUTHOR]

Hybrid aluminum dialkylphosphinates were synthesized from mixed diethyl-, ethylisobutyl-, and diisobutylphosphinates and Al3+ in water. The XRD, DSC, and TGA results of these Al phosphinates established that phosphinate ligands are randomly distributed in the species. The thermal and thermoxidative stabilities of the hybrid phosphinates were easily adjustable by varying the ratio of phosphinate ligands, a desirable feature for efficient flame retardants. The hybrid aluminum dialkylphosphinates with a relatively low ratio of diethylphosphinate demonstrated higher efficiency than Al diethylphosphinate and Al diisobutylphosphinate in flame-retarding polyamide 66. Detailed investigations on the thermal and thermoxidative stabilities of Al dialkylphosphinates and the morphologies of char obtained in UL-94 tests revealed that timely vaporization of degradation products of hybrid dialkylphosphinates at a temperature which closely matches the degradation temperature of polyamides and their ability to promote char formation of polyamides are two key factors which contribute to the excellent performance of hybrid aluminum dialkylphosphinates. [ABSTRACT FROM AUTHOR]

In this study, the intermediate of SPDPC flame retardant curing agent was successfully synthesized through the reaction between phosphorus oxychloride and pentaerythritol under the catalysis of 4-dimethylaminopyridine. Using 1,2-propylenediamine and the prepared SPDPC, a novel phosphorus and nitrogen flame retardant curing agent named poly1,2-propylenediamine pentaerythritol diphosphate (PDS) was successfully synthesized. The target product was subjected to characterization using infrared spectroscopy, mass spectrometry, hydrogen NMR spectroscopy and thermogravimetric analysis. The molecular structure of the product was determined and its decomposition temperature curve obtained, leading to the conclusion that it could be cured at high temperatures. DDS was selected as the curing agent for epoxy E-51, the specific curing conditions were obtained by DSC test. Subsequently, E-51, DDS and PDS were mixed for high temperature curing resulting in obtaining test spline of PDS-E-51 flame retardant composite material. Then, the flame retardancy and mechanical properties of the spline were tested. It was observed that pure EP cured by DDS had an LOI of only 19.5%, indicating its flammability. However, upon addition of PDS as a flame retardant, the LOI significantly increased with 20 parts resulting in an LOI of 29.7%. The addition of 25 parts results in an increase in limiting oxygen index to 30.3%, while the tensile strength and impact strength are measured at 38.27 MPa and 5.087 kJ/m2 respectively. The CCT test shows that the addition of PDS can significantly reduce the HHR and THR of the system. CCT digital photos show that the addition of PDS can make the combustion residue of the system expand obviously, showing a good expansion and flame retardant effect. TG-FTIR gas phase infrared absorption indicates that the addition of PDS can reduce the concentration of combustible gas in the combustion process. Test results indicate that the mechanical properties of PDS-E-51 flame retardant composites experience a certain degree of decline, but with increasing amounts of PDS curing agent added, their flame retardancy is significantly enhanced. [ABSTRACT FROM AUTHOR]

To reduce the fire risk of epoxy (EP) resin, a renewable lignin-based flame retardant functionalized with a metal–organic framework (MOF) HKUST-1 (Cu3(BTC)2, BTC = benzene-1,3,5-tricarboxylate) was prepared by a facile and green method. The chemical structure of flame retardant was characterized by Fourier transform infrared (FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results showed that HKUST-1 was in-situ grown on the surface of phosphorus/nitrogen modified lignin, which was treated as an efficient flame retardant (termed PN-lignin@HKUST-1) for subsequent EP resin. The flame-retardant properties of EP composites were evaluated by the limiting oxygen index (LOI), vertical burning (UL-94), and cone calorimetry tests. As compared with neat EP thermoset, the presence of 15 mass% PN-lignin@HKUST-1 increased the LOI value from 28.5 to 33.2% and upgraded the UL-94 rating from V-2 to V-0. Besides, the peak heat release rate (PHRR) and total heat release (THR) were reduced by 41.2 and 33.8%, respectively. Observations of char residues could indicate that addition of PN-lignin@HKUST-1 contributes to a compact and dense char layer, which blocks the release and transfer of heat and harmful gases during combustion. [ABSTRACT FROM AUTHOR]

Intrinsic flammability significantly impedes practical applications of epoxy (EP), despite many merits. Intercalation‐functionalized graphene oxide (GO) has shown excellent performance in flame retardancy studies of polymers, but research investigating the effect of layer spacing on the flame‐retardant performance of polymers is still lacking so far. Therefore, three GO flame retardants with different layer spacing were prepared to flame retardant EP. When the layer spacing of GO is 1.09 nm, the heat and smoke release from EP composites is effectively suppressed. This is attributed to the barrier effect and maze effect of GO as well as the synergistic effect between the intercalator and GO. Analysis shows that the layer spacing of GO affects the flame retardancy of the composite by influencing the formation of protective char layer. [ABSTRACT FROM AUTHOR]

In this paper, a single-component intumescent flame retardant di-(3-aminopropyltriethoxysilane) spirocyclic pentaerythritol diphosphate (PDAP) was synthesized, imparting flame retardancy to polylactic acid (PLA), which using melt blending process. The chemical structure and thermal stability of PDAP were characterized by test methods such as Fourier transform infrared spectroscopy (FTIR) and thermogravimetric analysis (TGA). The fire retardancy of PLA/PDAP was evaluated by test methods such as limiting oxygen index (LOI) and vertical burning test (UL-94). The thermal stability of PLA/PDAP was studied by TGA and thermogravimetry-Fourier transform infrared spectrometry (TG-FTIR). According to the results of laser Raman spectroscopy (LRS) and FTIR, the possible flame retardant mechanism of PLA/PDAP was discussed. With only 20 wt% addition of PDAP, PLA/PDAP could achieve 11.98% char residues at 800 °C. The LOI value of PLA/PDAP achieved 37%, UL-94 test reached V-0 rating. And higher fireproof performance with 62.1% reduced peak heat release rate (PHRR), 36.8% reduced total heat release rate (THR) and 19.5% reduced average effective combustion heat (av-EHC) value than PLA. The results show that PDAP has remarkable flame retardant effect on PLA, which provides an excellent research case for flame retardant modification of PLA plastic products. [ABSTRACT FROM AUTHOR]

In this work, an effective flame retardant consisting of nanoscale zinc oxide doped on the surface of hexagonal lamellar magnesium hydrate (ZO@MH) has been successfully synthesized via a hydrothermal process. Approximately 3-methacryloxypropyltrimethoxysilane (KH-570) is chosen as a modifier of ZO@MH for the purpose of enhancing the interfacial interaction between ZO@MH and the polypropylene (PP) matrix and reducing the agglomeration of ZO@MH. Afterwards, ZO@MH and KH-570 modified ZO@MH (KZO@MH) filled PP (PP/ZO@MH and PP/KZO@MH) composites are respectively prepared via the melt blending method. The flame retardant and smoke suppression properties of PP/ZO@MH and PP/KZO@MH composites are estimated by a cone calorimetry test (CCT). The peak value of the heat release rate of the PP/40KZO@MH composite is 327.0 kW/m2, which is 6.1% and 31.2% lower than that of the PP/40ZO@MH and PP/40MH composites, respectively. The lowest peak values of CO and CO2 production, 0.008 and 0.62 g/s, also appeared in the PP/40KZO@MH composite, which are 11.1% and 10.1% lower than those of the PP/40ZO@MH composite. Analysis of char residues indicates that nanoscale ZO and modification of KH-570 improve the amount and quality of char residues, which should be the main reason for the good flame retardant and smoke suppression properties of KZO@MH. Impact strength and nominal strain at break results show that the PP matrix is toughened by ZO@MH rather than KZO@MH. Tensile properties and the quantitative interfacial interaction calculated by the Turcsányi equation both prove the reinforcement of KZO@MH on the PP matrix. [ABSTRACT FROM AUTHOR]

Effective insulation of buildings and other industrial objects requires the use of materials and system solutions that ensure maximum uniformity and density of insulation shells. The study focuses on the development of insulation systems based on expanded polyethylene and, in particular, on the development of modified polyethylene with reduced flammability containing a flame-retardant modified montmorillonite clay, which does not hinder gas formation, and silicate nanofillers in layered construction. Active experiments based on mathematical design methods allowed us to establish an analytical relationship between flame-retardant and modifier consumption and extruder pressure and response functions: average density of polyethylene foam and flammability criterion. The flammability criterion was taken as the oxygen index of the modified polyethylene foam. A foaming agent masterbatch was used as the flame retardant. Analytical optimization of mathematical models obtained as a result of active experiments allowed us to determine the optimal flame-retardant consumption, which was 3.7–3.8% of the polymer mass. Optimised systems for average density and oxygen index of flammability of modified polyethylene were obtained. A nomogram for predicting the material properties and selecting the composition, and an algorithm for a computer program for evaluating the properties of modified polyethylene foam as a function of the values of various factors, were developed. Taking into account the possible expansion of the scope of application of rolled polyethylene foam and seamless insulation shells based on it, possible solutions for insulation systems were studied using the program THERM, and a combined insulation system was adopted. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The combination of nitrogen and phosphorus compounds has synergistic flame retardant effect, but the addition of low phosphorus content compounds is large, which affects the mechanical properties of polymers. Phosphorus ammonium polyphosphate (APP) with high phosphorus content and graphitic carbon nitride (g-C3N4) doped with SiO2 were used for the flame retardant (CN-Si-APP) of polyamide 6 (PA6). CN-Si-APPs with different APP/CN mass ratio (1, 2.5 and 4) and dosage (7 and 12 wt%) were blended with PA6 via a twin-screw extruder, and their flame retardancy was investigated by limiting oxygen index (LOI), UL-94 test, muffle furnace carbonization test and raman spectroscopy. When only APP added, the coefficient of water absorption (CWA) of composites increased and its tensile strength greatly reduced by nearly 37.1% to 35.39 MPa. The addition of g-C3N4 inhibited the water absorption. When the addition dosage is 7%, the CWA of PA6/APP, PA6/CN-Si-APP2.5, PA6 and PA6/CN were 11.1, 6.86, 5.78 and 4.6%, respectively. SiO2 effectively improved the dispersion of g-C3N4 and the mechanical properties of composites. Thermogravimetric analysis (TGA) showed that the char residue of PA6 composites was improved significantly. The composite with 7 wt% CN-Si-APP4 passed the UL-94 V-0 rating. The LOI value and graphitization degree (ID/IG) of PA6/12 wt% CN-Si-APP2.5 reached 28.7% and 2.93 respectively. Under the same dosage, the graphitization degree of CN-Si-APP2.5 (3.51) was higher than that of g-C3N4 (3.98). The barrier protection of g-C3N4, catalytic effect of APP and SiO2 crosslinking network promoted PA6 to form a dense and stable char layer, which protected PA6 composites from the flame. The strategy of synergistic flame retardant in this paper provides a valuable solution for reducing the amount of flame retardant. [ABSTRACT FROM AUTHOR]

A tris(DOPO-grafted piperazine)-triazine phosphoramide (DOPO-TPT) was synthesized, and its structure was well characterized by Fourier transform infrared spectroscopy and nuclear magnetic resonance spectroscopy. DOPO-TPT was used as a flame retardant additive to modify the epoxy resin to obtain a series of flame retardant epoxy thermosets. The effects of DOPO-TPT on the thermomechanical properties, thermal stability and flame retardancy of the resulting epoxy thermosets were investigated. The results showed that when the addition of DOPO-TPT was 5 mass% (phosphorus content was 0.47 mass%), the limiting oxygen index of the epoxy thermoset reached 30.0%, and it passed the UL-94 V-0 classification. Compared with unmodified epoxy resin, the maximum heat release rate and total heat release of EP/DOPO-TPT-5.0 decreased by 28% and 20%, respectively. Additionally, the presence of DOPO-TPT did not deteriorate the thermomechanical properties of the resulting epoxy thermosets. TG-FTIR test confirmed that the incorporation of DOPO-TPT could significantly inhibit the release of gaseous products. The char layer analysis results showed that DOPO-TPT had good catalytic charring performance, which was conducive to decreasing the escape of combustible gas during combustion, thus improving the flame retardancy. [ABSTRACT FROM AUTHOR]

Polymer composites are widely used in various fields of production and life, and the study of preparing environmentally friendly and flame retardant clay/polymer composites has gradually become a global research hotspot. But how to efficiently surface modify clay and apply it to the field of flame retardant polymers is still a potential challenge. One of the most commonly used surface modification methods is the modification of clay with silane coupling agents. The hydrolysable groups of the silane coupling agent first hydrolyze to generate hydroxyl groups. These hydroxyl groups then undergo a condensation reaction with the hydroxyl groups on the surface of the clay, allowing for organic functional groups to be grafted onto the clay surface. The organic functional groups and polymer matrix react to generate chemical bonds so that the composite material's interface is more closely combined. Thus, the dispersion of clay in the organic polymer material and the compatibility of the two is better, which improves the flame retardant effect of the composite material. This paper introduces the classification of a silane coupling agent and the mechanism and process of silane coupling agent-modified clay, outlines the mechanism of silane coupling agent-modified clay flame retardant polymers, reviews the research results on flame retardant polymers of various clays after surface treatment with silane coupling agents in recent years, and highlights the synergistic flame retardant effect of clay and flame retardant organized by silane coupling agents. Finally, it is found that the current research in the field of silane coupling agent-modified clay in flame retardants is focused on the modification of montmorillonite, sepiolite, attapulgite, and kaolinite by KH-550, KH-560, and KH-570, and the development trends in this field are also prospected. [ABSTRACT FROM AUTHOR]

Modern polymer coatings possess tremendous multifunctionalities and have attracted immense research interest in recent decades. However, with the expeditious development of technologies and industries, there is a vast demand for the flame retardancy and electrical conductivity of engineered polymer coatings. Traditional functional materials that render the polymer coatings with these properties require a sophisticated fabrication process, and their high mass gains can be a critical issue for weight-sensitive applications. In recent years, massive research has been conducted on a newly emerged two-dimensional (2D) nanosize material family, MXene. Due to the excellent electrical conductivity, flame retardancy, and lightweightness, investigations have been launched to synthesise MXene-based polymer coatings. Consequently, we performed a step-by-step review of MXene-involved polymer coatings, from solely attaching MXene to the substrate surface to the multilayered coating of modified MXene with other components. This review examines the performances of the fire safety enhancement and electrical conductivity as well as the feasibility of the manufacturing procedures of the as-prepared polymer composites. Additionally, the fabricated polymer coatings' dual property mechanisms are well-demonstrated. Finally, the prospect of MXene participating in polymer coatings to render flame retardancy and electrical conductivity is forecasted. [ABSTRACT FROM AUTHOR]

Modern society relies heavily on producing commercial and industrial plastics to improve the quality and quantity of our lives. However, increased fire risks threaten commercial operations and the potential impact of high‐performance electronic and transportation technologies that utilize polymeric materials. Despite significant monitoring and reduction of commonly used halogenated flame retardants, their worldwide usage still poses environmental hazards. Many non‐halogenated flame‐retardant compounds are viable additives for synthetic polymers; however, their incorporation often results in reduced composite homogeneity and mechanical strength. This review focuses on reactive flame retardants and the effect of polymer structure on inherent flame retardance in recent studies. The synthesis and characterization of polymeric systems (e.g. polyurethanes, polyamides, polyimides, polyesters and epoxy resins) are discussed in terms of structure–flame‐retardant performance using a complement of analytical tools, including thermogravimetric analysis, cone calorimetry, limiting oxygen index and UL 94 testing. These commercially important polymeric systems represent a broad compositional space for future adaptation and the discovery of increasingly modular polymeric materials with, while also contributing to the fundamental understanding of unique combinations of gas‐ and condensed‐phase mechanisms of flame retardance. © 2024 Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

Although epoxy resin (EP) has been widely used in many fields, it is still urgent to effectively improve its flame retardancy by halogen‐free strategies. Herein, a silicon‐containing cyclotriphosphazene derivative (HEP‐Si) was synthesized by nucleophilic substitution and silicon–hydrogen addition reaction using eugenol, hexachlorophosphazene and triethylsilane as raw materials. Then it served as a halogen‐free flame retardant for an EP/4,4′‐diaminodiphenylmethane system, and its performance was compared with that of commercial flame retardant hexaphenoxycyclotriphosphazene (HPP). The results showed that although the initial thermal decomposition temperature (T5%) of the cured products of EP/HEP‐Si was slightly lower than that of pure EP, T5% did not decrease further as the amount of HEP‐Si increased, indicating that good thermal stability was maintained. In addition, the char yield of the cured products of EP/HEP‐Si was significantly increased (more than 20 wt%) compared to that of pure EP. The cured EP with the addition of HPP and HEP‐Si both achieved a V‐0 rating in UL‐94 vertical burning test at 0.5 wt% phosphorus content, while the limiting oxygen index of the EP/HEP‐Si system was higher, reaching 33.2%. From cone calorimetric test results, the peak heat release rate, total heat release and total smoke production of the cured products of EP/HEP‐Si decreased by 61.5%, 37.1% and 26.2%, respectively, compared with that of pure EP. The cured EP/HEP‐Si materials also exhibited good thermomechanical and mechanical properties. Therefore, HEP‐Si is suggested to be a promising P/N/Si‐containing halogen‐free flame retardant for EP. © 2024 Society of Industrial Chemistry. [ABSTRACT FROM AUTHOR]

Densified wood (DW) is a carbon-negative and energy-saving structural material with promising applications in high-rise timber buildings. However, its fire safety issues restrict its applications. In this paper, a bio-material, phytic acid, based flame retardant PPBNOH was prepared to improve the flame retardancy of DW. The structure characteristics, thermal stability, flammability, combustion behavior and mechanical performance of flame-retardant DW (PPBNOH/DW) were studied. Results show that the decomposition of PPBNOH catalyzes char formation and enhances thermal stability. Thus, PPBNOH/DW has a 57% reduced peak mass loss rate and a 27.9% increased char yield. Both the wood dense structure and PPBNOH catalyzation synergistically promote the formation of phosphorus-containing, crosslinked and aromatic char during wood combustion, which hinders heat/mass transfers and enhances flame retardancy. Thus, PPBNOH/DW has a 53.2% limiting oxygen index, a V-0 rating of UL-94 test. It presents delayed ignition time, reduced heat release characteristics and lower heat of combustion (5.37 MJ kg−1) in the cone calorimeter test. BNOH improves the smoke suppression performance of PPBNOH/DW with a 38.6% reduced total smoke production. The compatible and thermally insulating char also enhances the high-temperature heating resistance of PPBNOH/DW as it has the highest remaining mechanical strengths after heating. [ABSTRACT FROM AUTHOR]

In this study, the influence of flame-retardant materials on the rheological properties of warm-mix asphalt was investigated. The rheological properties of base asphalt and styrene–butadiene–styrene-modified (SBS) asphalt modified with 2% Sasobit and flame-retardant materials, such as alumina trihydrate and organic montmorillonite (OMMT) in a proportion of 3:1 (AM), were systematically explored. The investigation was carried out under three dosages of AM; i.e., 4%, 8%, and 12%. Experiments including dynamic shear rheological tests, multiple stress creep recovery tests, bending beam rheometer tests, Fourier transform infrared (FTIR) spectroscopy tests, gel permeation chromatography (GPC) tests, and fluorescence microscopy (FM) tests were conducted to evaluate the rheological properties and micromechanism of warm-mix flame-retardant asphalt under different AM dosages. The results showed that the rheological properties of warm-mix flame-retardant SBS asphalt (SOA) at high and low temperatures were better than those of warm-mix flame-retardant asphalt (POA) at the same AM dosage. The increase in AM dosage improved the high-temperature rheological properties and decreased the low-temperature rheological properties. Based on the combined analysis of FTIR spectroscopy, GPC results, and FM results, the reason for this phenomenon was speculated to be the occurrence of wax-crystal structure and filler–asphalt interaction between asphalt and AM. Furthermore, organic cations in OMMT adsorbed the lightweight components present in asphalt, which reduced their proportion and improved the high-temperature and rheological properties. Moreover, the increase in AM led to the increase in physical volume filling, which increased the mechanical properties and brittleness of asphalt. The stress concentration led to the worsening of the stress-diffusion capacity of POA and SOA and eventually led to the decrease in the low-temperature rheological properties of POA and SOA. [ABSTRACT FROM AUTHOR]

Polylactic acid has good biodegradability and processability, but its flammability and serious droplet characteristics limit its development and application. Therefore, developing safer flame‐retardant PLA materials is crucial. This research develops a novel flame‐retardant polylactic acid (PLA) material blend, utilizing aluminum diethylphosphinate (AlPi), piperazine pyrophosphate (PAPP), and β‐cyclodextrin. Optimal synergy occurs at a 5:1 PAPP/β‐CD mass ratio with 4 wt.% AlPi. This combination significantly reduces the heat release peak from 294.89 to 144.21 kW·m−2 and generates non‐combustible residues. The sample forms a stable, uniform carbon layer during combustion due to hydrogen bond crosslinking and Lewis acid–base reactions. The activation energy (Eα) is raised from 264.99 to 281.08 kJ·mol−1 between 312 and 402°C. Thus, an AlPi‐PAPP‐β‐CD based P‐C‐N composite flame retardant is investigated, offering a promising research direction for developing fire‐safe polylactic acid materials. This research may yield valuable insights for diverse applications. [ABSTRACT FROM AUTHOR]

This article aims to prepare a nitrogen, silicon, and phosphorus multiple synergistic high-efficiency flame retardant and study its application performance. Firstly, allyl substituted melamine was synthesized by melamine powder and allyl bromide. After copolymerizing it with vinyltrimethoxysilane, a nitrogen-silicon containing melamine copolymer was obtained. Using the equal volume impregnation method, a certain mass of Type I ammonium polyphosphate (I-APP) powder is mixed with an equal volume of nitrogen-silicon containing melamine copolymer solution to prepare nitrogen silicon flame retardant copolymer coated I-APP flame retardant (MAPP). Pre mix polypropylene(PP) with a certain mass fraction of I-APP or MAPP flame retardant, and then perform melt blending, extrusion, and granulation in a twin-screw extruder to prepare PP flame retardant composites. Mechanical and vertical combustion tests were conducted on PP flame-retardant composites. The results showed that when MAPP was added up to 20%, it could reach the V-0 flame retardant level, while pure I-APP, even with 30% addition, remained below the V-0 level and had lower mechanical properties. It can be seen that the compatibility of I-APP coated with nitrogen silicon copolymer is better, and the synergistic flame retardant efficiency among nitrogen, silicon, and phosphorus is higher. [ABSTRACT FROM AUTHOR]

Integrating flame‐retardant additives into epoxy resins is an essential strategy for improving their fire resistance. However, introducing flame‐retardant groups often compromises the processability and mechanical integrity of such resins. In this research, we synthesized a novel, biobased flame retardant, referred to as DPN, using naringenin and chlorodiphenylphosphine as precursors via a straightforward single‐step process. The addition of DPN markedly decreased the viscosity of hydantoin epoxy resin, from 7468 to 1285 mPa s. Furthermore, when cured with 4,4‐diaminodiphenylmethane, the composite containing five equivalents of DPN (DPN‐5) exhibited a marked improvement in mechanical strength, reaching 190 MPa, significantly outperforming the pure thermoset (DPN‐0: 104 MPa), while preserving high transparency. Combustion tests further confirmed that DPN significantly boosts the flame resistance of the thermoset, with DPN‐5 achieving a limiting oxygen index of 37% and securing a UL‐94 V‐0 rating. Cone calorimetry analysis showed that DPN‐5 effectively reduced heat and smoke production during combustion, achieving a 13.4% reduction in peak heat release rate and a 28.2% decrease in total heat release compared to DPN‐0. This study underscores the potential of multifunctional biobased flame retardants derived from renewable resources in advancing the development of high‐performance materials. © 2024 Society of Industrial Chemistry. [ABSTRACT FROM AUTHOR]