Flame Retardant Mechanism Research Articles

One-step green synthesis durable flame-retardant, antibacterial and dyeable cellulose fabrics with a recyclable deep eutectic solvent.

The development of cellulose fabrics with good flame retardancy and durability has been a primary concern for in firefighting clothing. A recyclable ternary deep eutectic solvent (TDES) was used to prepare surface ammonium phosphate-modified cellulose fabrics (SACF). The incorporation of ammonium phosphate groups notably enhanced the durable flame retardancy of cellulose fabrics. The limiting oxygen index (LOI) of SACF could reach 48 %, and remain at 33.5 % even after 50 laundering cycles (LCs). And the TDES can be recovered and reused for 5 cycles and the SACF still remains flame retardancy. It also exhibited excellent antibacterial properties (with an antibacterial rate of 99.79 % against E. coli) and dyeability with cationic dyes. Moreover, the flame-retardant of the SACF did not decrease after dyed and showed both condensed-phase and gas-phase flame-retardant mechanisms during combustion. This method for producing flame-retardant cellulose fabrics with recyclable TDES effectively reduces the use of chemical reagents and holds promise for application in eco-friendly manufacturing and firefighting garments.

Preparation and flame retardancy of an Al2O3 infiltration layer on polycarbonate surface

Abstract In this study, the surface flame retardancy of polycarbonate (PC) was improved and the impact of flame retardants on the substrate were minimized by pre-mixing Al2O3 particles with dichloromethane, an infiltration promoter, to form a suspension, and then treating PC with the suspension to form an Al2O3 infiltration layer. For this layer, its structure and composition were characterized, its flame retardancy was evaluated, and its flame retardancy mechanism was investigated. The characterization results confirmed that an Al2O3 infiltration layer was successfully prepared on the PC surface under the aid of dichloromethane and that the involvement of dichloromethane induced certain microscopic pores and voids in the PC, with some dichloromethane remaining within the surface infiltration layer. The surface Al2O3 infiltration layer mainly served as a condensed-phase flame retardant. The infiltration layer prepared using a suspension with a dichloromethane-to-Al2O3 mass ratio of 24:1 not only exhibited a good overall performance but also achieved the best improvement in the PC flame retardancy, such as an increase in the vertical burning rating from HB to V-0, as well as the LOI increased from 24 to 31.3, and a 35% reduction in the peak heat release rate compared to those of pure PC.

Bio-based molecules with ionically bonded phosphorus toward ultra-high flame-retardant efficiency of PLA plastics.

The fire safety of polymer plastics has become a global consensus, and creating a more efficient flame-retardant network is in line with the trend. Here, a direct strategy for low usage of flame retardants and fire-resistant PLA plastics was proposed. The bio-based flame-retardant PDT, which was formed by ionic bonding of phytic acid and organic amine molecules, had high flame-retardant efficiency for PLA. PLA/PDT composite demonstrated excellent flame-retardant performance during service, achieving UL-94V-0 grade with only 2wt% of addition and a LOI of 29.3%, significantly better than previous work. In cone calorimeter test, heat release, CO2 production, and av-EHC were inhibited. And the flame-retardant mechanism was analyzed in detail through SEM, XPS, Raman, and TG-IR. Besides, the thermal stability and crystallinity of PLA composites were enhanced. It was expected that this work will provide a new approach for the development of sustainable flame-retardant PLA plastics.

Facial functionalization carbon fiber with MnO2 nanosheets for high‐performance epoxy composites with excellent flame retardancy and mechanical properties

AbstractThe carbon fiber (CF) reinforced epoxy composites possess exceptional and distinctive properties as advanced composite materials. However, the flammability of epoxy resin and inadequate interfacial bonding between the resin and CF often impose limitations on their broader application. Herein, in order to enhance the flame retardancy of EP composites effectively, a hierarchical reinforcement was developed by facilely growing MnO2 nanosheets onto CF surface through an in situ process. Owing to their synergistic effects of physical barrier and chemical catalytic behavior, the presence of MnO2 nanosheets can effectively retard the combustion process by facilitating charring formation and suppressing heat and smoke release. Specifically, compared to the Untreated CF, the modified fiber reinforced composites exhibited significantly improved fire safety with reduction of 76.23%, 51.5% and 23.1% in peak heat release rate, total heat release and peak smoke production rate, respectively. Additionally, incorporating MnO2 nanosheets significantly enhanced mechanical properties of the composites, leading to remarkable enhancements of 41.8% in flexural strength and 28.14% in interlaminar shear strength. This study proposes an effective strategy for achieving outstanding flame retardancy and mechanical performance, thereby introducing an innovative concept for the production of high‐performance CF reinforced polymer composites.Highlights Growth of MnO2 nanoparticles enhanced the mechanical properties of the CF/EP composites. The CF‐MnO2/EP composites showed excellent flame retardancy. The flame retardant mechanism of CF‐MnO2/EP composites were analyzed. Highlight the potential application of MnO2 in the field of flame retardancy.

Temperature-sensitive intelligent gel to prevent coal spontaneous combustion: Large-scale simulation fire extinguishing experimental study

Coal spontaneous combustion seriously endangers mine safety production. In this study, a temperature-sensitive intelligent gel was synthesised from methylcellulose (MC), polyethene glycol (PEG) and sodium chloride (NaCl). The flow characteristics of temperature-sensitive intelligent gel (abbreviated as TSIG) under different conditions were analyzed by viscosity test. An infrared spectrometer also analyzed the microscopic flame retardant mechanism of temperature-sensitive intelligent gel. A large-scale simulation fire extinguishing test bench was designed at the coal mine site to analyze the flame retardant effect of the temperature-sensitive intelligent gel on coal oxidation reaction at different injection temperatures. The results show that the temperature-sensitive intelligent gel undergoes a liquid–solid phase transition at a temperature higher than 60 °C. When MC: PEG: NaCl = 1: 6: 5, the temperature-sensitive intelligent gel showed the best flow characteristics. The large-scale simulation fire extinguishing experiments show that the CO concentration is significantly reduced after the temperature-sensitive intelligent gel is injected at the coal temperature of 300–900 ℃, and both show excellent fire extinguishing effects. The addition of temperature-sensitive intelligent gel can inhibit the number of free radicals in the process of coal oxidation, block the chain reaction of coal spontaneous combustion, and comprehensively inhibit the process of coal spontaneous combustion. The research results provided theoretical support for the application of temperature-sensitive intelligent gel in coal spontaneous combustion areas. Additionally, they guided the design of temperature-sensitive intelligent gel to prevent coal spontaneous combustion technology.

Synthesis of nitrogen and phosphorus-doped chitosan derivatives for enhanced flame retardancy, smoke suppression, and mechanical properties in epoxy resin composites.

Biomass-based flame retardants have attracted significant academic interest due to their environmental benefits and sustainability. Nevertheless, devising straightforward, eco-friendly, and mild methodologies to synthesize flame retardants of epoxy resins (EP) remains a formidable challenge. This paper reports the successful synthesis of a novel nitrogen and phosphorus-doped chitosan derivatives flame retardant (MMCA) utilizing phytic acid, chitosan, and melamine cyanurate via electrostatic self-assembly and physical encapsulation in an acidic aqueous solution. The incorporation of 5wt% MMCA into the EP readily achieved a UL-94V-0 rating. This improvement can be primarily attributed to the early formation of a continuous, dense, robust, and expanded char layer during combustion, coupled with the synergistic flame retardant mechanisms of radical scavenging and the dilution of non-combustible gases. Compared to pristine EP, EP/5MMCA exhibited significant reductions of 23.7%, 29.2%, and 24% in total smoke production rate, peak heat release rate, and peak smoke production rate, respectively. Moreover, the strategic introduction of MMCA also enhanced the glass transition temperature, storage modulus, and crosslinking density of EP, improving its tensile, compressive and impact properties. This study proposes a simple, viable, and environmentally sustainable strategy for the fabrication of biomass-based flame retardants, resulting in notable improvements the flame retardancy, smoke suppression, fire safety, and mechanical robustness of EP.

An innovative method for preparing durable flame-retardant cotton fabrics using tetrakis(hydroxymethyl)phosphonium sulfate without specialized equipment.

In this study, two phosphorus-based flame retardants diethylenetriamine trimethyl diphosphonate lysine (APTA) and a tetrakis(hydroxymethyl)phosphonium sulfate prepolymer with urea (DUPT) were synthesized. The structures of these compounds were characterized via nuclear magnetic resonance (NMR) and Fourier-transform infrared spectroscopy (FTIR). FTIR and scanning electron microscopy (SEM) analyses revealed that DUPT crosslinked APTA onto cellulose, which was pre-processed with diethylenetriamine dipropylene oxide (NAED) to introduce NH groups through PCN bonds. The APTA/DUPT-30 cotton exhibited a limiting oxygen index (LOI) of 36.4 % and a damaged length of 4.8 cm. After 50 washing cycles, the treated cotton maintained an LOI of 30.5 % and a damaged length of 5.4 cm. These results indicate the exceptional flame retardancy and washing resistance of the treated cotton fabrics. Moreover, the thermogravimetry (TG) curves indicated that APTA/DUPT altered the degradation process of the cotton fabrics. The TG-FTIR data and residue analysis from the vertical flame-retardant test confirmed that the treated cotton utilized a condensed-phase flame-retardant mechanism. Overall, this approach effectively imparts excellent durable flame retardancy to cotton fabrics through stable PCN bonds, eliminating the need for specialized equipment.

Effects of two phosphonamide flame retardants derived from biomass pyridine on flame retardancy and flame-retardant mechanism of Polyamide 6

Achieving favorable flame retardancy in polyamide 6 (PA6) without compromising its mechanical performance remains a challenge, with a notable gap in understanding the influence of flame-retardant structure on PA6 properties and mechanisms. In this study, two biomass-derived phosphonamide flame retardants, P,P-diphenyl-N-(pyridin-3-yl) phosphonamide (DPDA) and P,P-Diphenoxy-N-(pyridin-3-yl) phosphonamide (DPPA), were synthesized and incorporated into PA6 to develop flame retardant composites. Results demonstrated that the PA6-9DPDA, containing a P-C bond, achieved a UL-94 V-0 rating with a Limiting Oxygen Index (LOI) of 27.9 %, while PA6-9DPPA, containing a P-O-C bond, maintained the UL-94 V-2 rating of pure PA6 but with an increased LOI of 29.4 %. DPPA exhibited a more favorable impact than DPDA on enhancing the tensile performance of PA6. Mechanisms indicated that DPDA primarily operates through vapor phase flame retardancy, whereas DPPA utilizes condensed phase flame retardancy. Overall, this study proposes a sustainable approach for fabricating PA6 composites with enhanced comprehensive performance.

Improvement of fame retardancy and thermal stability of epoxy composites by modifying salen-based polyphosphazene microspheres with Co-based metal organic frameworks

A functionalized cross-linked polyphosphazenes microsphere (Salen-PZN-Ni@Co-MOF) was fabricated by enveloping Salen-Ni-based polyphosphazenes (Salen-PZN-Ni) with a type of hybrid flame retardant (Co-MOF) to enhance the flame retardant, smoke suppression properties and mechanical properties of epoxy (EP) composites. Thermogravimetric analysis indicated that the incorporation of Salen-PZN-Ni@Co-MOF significantly enhanced the thermal stability of the EP composites. The existence of Salen-PZN-Ni@Co-MOF enhanced both the vertical burning rating and resulted in a higher limiting oxygen index. The addition of 5 wt% Salen-PZN-Ni@Co-MOF conspicuously improved the fire safety of EP, as evidenced by the results of the cone calorimeter. For instance, the peak heat release rate and total heat release rate of the EP composites were decreased by 25.3% and 44.97%, respectively. In addition, the incorporation of Salen-PZN-Ni@Co-MOF significantly inhibited the generation of toxic carbon monoxide and other volatile compounds. Furthermore, a synergistic effect between Salen-PZN-Ni and Co-MOF was observed. The proposed flame retardant mechanism of Salen-PZN-Ni@Co-MOF is attributed to the synergistic catalytic carbonization effect and the formation of thermally stable components. Consequently, enhanced fire safety in EP composites is achieved through the synergistic interaction among various components (nickel and Co-MOF) with polyphosphazene microspheres. Meanwhile, the excellent compatibility between Salen-PZN-Ni@Co-MOF and EP enhances the mechanical properties of EP composites.

Preparation of eugenol-based flame retardant epoxy resin with an ultrahigh glass transition temperature via a dual-curing mechanism

Eugenol epoxy resin, as one of the most promising biobased epoxy resins, still faces problems of insufficient heat resistance, high flammability, and complicated synthesis processes. Based on the principles of the Diels–Alder (D-A) addition reaction and epoxy-amine open-loop crosslinking, the EUEP epoxy monomer (EUEP) was synthesized, and ternary cocuring (EUEP-BDM-DDS) was performed with bismaleimide (BDM) and the high-temperature curing agent 4,4′-diamino-diphenyl sulfone (DDS). The resulting system exhibited an exceptional glass transition temperature (Tg) of 306 °C, surpassing other eugenol epoxies and commercial bisphenol A epoxies. EUEP-BDM-DDS demonstrated superior mechanical properties with high moduli (up to 4.14 GPa for tensile and 4.10 GPa for flexural). Its processing characteristics were also favorable, featuring a long pot-life, low viscosity, and suitable for all operating processes of traditional DGEBA-DDS systems. In addition, the formation of rigid six-membered rings during curing and the higher cross-linking density gave the resin system excellent flame retardant properties, with a limit oxygen index of 33.5 % and passing the V-0 class test of UL-94. The system exhibited significantly lower peak heat release and smoke release rates compared to DGEBA-DDS, indicating enhanced fire safety. And the analysis revealed a coacervated flame retardant mechanism. Moreover, the composite material derived from EUEP-BDM-DDS displayed improved interlaminar shear strength, flexural strength, and high-temperature mechanical properties, outperforming the DGEBA-DDS system. This study paves the way for utilizing biobased eugenol epoxy resins in advanced composite materials, offering enhanced performance and fire safety. It holds significant implications for promoting the application of biobased materials in high-performance composites.

Phytic acid/cellulose nanofibers modified layered double hydroxides flame retardants: Synthesis, properties and applications

Layered double hydroxides (LDHs) tend to agglomerate and primarily exhibit a single condensed phase flame-retardant mechanism, limiting their application as flame retardants (FRs) for wood. In this paper, we prepared a composite FR by intercalating phytic acid (PA) into the LDH layers through anion exchange. Additionally, cellulose nanofibers (CNF) were incorporated to interact with the hydroxyl groups on the LDH surface, improving the dispersion and stability of LDH. LDH-PA-CNF exhibited excellent flame-retardant performance and good dispersibility, which was suitable for flame-retardant modification of wood. After impregnating the wood with LDH-PA-CNF, the total heat release (THR) and total smoke release (TSR) of Wood@LDH-PA-CNF decreased by 21.2 % and 56 %, respectively, compared with the untreated wood. The limited oxygen index (LOI) value of Wood@LDH-PA-CNF has been significantly improved from 21 % to 75.4 %. Based on the analysis of the composition and chemical structure of the residues and gases produced during the combustion of Wood@LDH-PA-CNF, the synergistic flame-retardant mechanism in both condensed and gas phases of LDH-PA-CNF was proposed. This study provides novel insights into the design of high-performance FRs and offers valuable clues for enhancing the homogeneous dispersion and synergistic effects of inorganic FRs.

A high-molecular-weight flame retardant derived from bis[tetrakis(hydroxymethyl)phosphonium] sulfate for cotton fabrics

A high-molecular-weight flame retardant, bis[tetrakis(hydroxymethyl)phosphonium] (THPS)-urean-(PO3)(NH4)2, was synthesized for cotton fabrics. Fourier-transform infrared spectroscopy, nuclear magnetic spectroscopy, scanning electron microscopy, and X-ray photoelectron spectroscopy analyses confirmed that (THPS-urea)n-(PO3)(NH4)2 effectively infiltrated the fibers and grafted onto cellulose through N–P(=O)–O–C covalent bonds. The fabric treated with 30 wt% of (THPS-urea)n-(PO3)(NH4)2 (C30) had a limiting oxygen index of 46.8 %. Even after 50 laundering cycles according to the AATCC 61-2013 3A standard, C30 maintained a limiting oxygen index of 39.8 %. Thermogravimetric-Fourier-transform infrared spectrometry, thermogravimetry, and cone calorimetry tests revealed that C30 exhibited excellent flame retardancy. Upon exposure to flame, C30 formed a stable char layer, which prevented the spread of heat and combustible gases. Additionally, C30 was free of formaldehyde, making it suitable for producing infant textiles. After grafting with the flame retardant, C30 retained its mechanical properties. The high-molecular-weight flame retardant enhanced the flame resistance and durability of cotton materials owing to its numerous N–P(=O) (ONH4)2 groups, which facilitated a condensed-phase flame retardancy mechanism.

The synthesis of an efficient titanium-based flame retardant with high dispersibility in polyamide 66

The preparation of high-performance flame retardants specialized for melt-spinning polyamide 66 (PA66) fibers remains a big challenge nowadays. This study has synthesized a highly dispersed, phosphorus-containing titanocene complex, namely Cp2Ti(DBA). The synthesized flame retardant possesses high dispersibility and compatibility in PA66. Flammability tests show that Cp2Ti(DBA) exhibits efficient flame retardancy in PA66. With the addition of 15 wt % of Cp2Ti(DBA) in PA66, a LOI value of 29.9 % is achieved, and the peak heat release rate (PHRR) and total heat release (THR) are reduced by 36 % and 26 %, respectively, as compared to pure PA66. Based on the py-GC MS study and char analysis, Cp2Ti(DBA) shows a dual-phase flame-retardant mechanism. In the gas phase, Cp2Ti(DBA) releases the phosphorus-containing free radicals, which capture the highly reactive free radicals. While in the condensed phase, titanium promotes the phosphaphenanthrene fragments to degrade and retains phosphorus in the form of titanium phosphates, which reinforce the barrier effect and stability of the char layer. This work may provide an efficient flame retardant with promising applications in PA66, especially for the melt-spinning of fibers.

A recyclable, toughening, extreme-condition resistant flame retardant for unsaturated polyester: Bridging performance and sustainability

Recycling thermosets presents significant economic benefits and social implications, and to date, a series of controllable recycling strategies have been proposed. However, prior research has primarily focused on neat polymers, neglecting the impact of the recycling process on composites whose additives may lose performance post-recycling. The paradigm shift towards sustainability necessitates the development of additives that not only exhibit high performance but also endure recycling conditions. Herein, taking flame-retardant unsaturated polyester (FRUP) as an example, we designed a new flame retardant (DPPONSi) with multiple flame-retardant elements and a low phosphorous oxidation state. FRUP with 16.7 wt% of DPPONSi achieves a V-0 rating in the UL-94 vertical burning test, and its limiting oxygen index (LOI) reaches 27.1%. Moreover, its peak heat release rate and total heat release are distinctively reduced by 65% and 42%, respectively. The high flame-retardant efficiency structure also protected DPPONSi from by-reactions. Without complex separation processes, FRUP degradation products were integrated with polyvinyl alcohol (PVA) to create flame-retardant aerogels with high flame retardancy. Additionally, we systematically studied the influence of flame retardants with varying oxidation states on FRUP, the corresponding flame-retardant mechanisms, and the degradation process of FRUP. This work realizes the organic combination of strategies to enhance the high efficiency of flame retardants with design methods for flame retardants that are resistant to existing unsaturated polyester degradation systems.

Preparation and performance of waterborne polyurethane coatings based on the intumescent flame retardant of boron, phosphorus, and nitrogen

AbstractPNB organic flame retardant was synthesized using 4‐formylphenylboronic acid, 4‐aminophenylthiophenol, 9,10‐dihydro‐9‐oxa‐10‐phos‐phaphenanthrene‐10‐oxide (DOPO), and then introduced into the hydroxyl‐terminated polybutadiene acrylonitrile (HTBN) molecular chain to successfully prepare a macromolecular flame retardant, which was used to prepare flame retardant waterborne polyurethane. The mechanical properties, thermal properties, and flame retardancy of waterborne polyurethane (FR‐WPU) were studied using thermogravimetic analysis (TGA), limiting oxygen index (LOI), scanning electron microscope (SEM), cone calorimeter, and universal testing machine, respectively, and the flame retardant mechanism of macromolecular flame retardants was explored. An LOI value of 29.76% and a UL‐94 V‐0 rating could be realized when the APFBH conjugation is 7.5 wt%, showing a significant improvement of melt dripping behavior and flame retardancy. It indicated that the fire resistance of FR‐WPU remarkably improved and displayed both gas and condensed phase mechanism. As the content of APBDH increased, the tensile strength and the elongation at break of FR‐WPU increased firstly and then decreased.

Fire-safe and mechanically robust polycarbonate composite enabled by novel copolymerization/macromolecular blending strategy

Polycarbonate is a widely used engineering plastic material, but its limited flame retardancy has restricted its application in high-end fields such as aviation and railways. In this study, we propose a novel copolymerization/macromolecular blending strategy to produce a high-performance, fire-safe polycarbonate composite. By copolymerizing with polydimethylsiloxane oligomer and blending with macromolecular polyarylate, the resulting PC-BPDMS5/PITR successfully achieved a UL-94 V-0 rating and a high limiting oxygen index value of 34.2 %. The peak heat release and total smoke release were significantly reduced by 45.2 % and 27.4 %, respectively, compared to pure PC. SEM, Raman, and XPS analyses confirmed the condensed-phase dominated flame-retardant mechanism, attributed to the char-forming ability of the polyarylate and polydimethylsiloxane segments. Polydimethylsiloxane segments can decompose to produce small molecules such as methane, and the left structure with silicon, which undergo cross-linking reactions with the substrate during combustion to promote char formation. The polyaromatic ring structure of PITR can also participate in the formation of a dense and stable char layer. The excellent compatibility between the polyarylate and the PC matrix, combined with the superior flexibility of polydimethylsiloxane, allowed the composite to maintain mechanical properties comparable to pure PC. Additionally, the increased molar volume resulted in a low dielectric constant for PC-BPDMS5/PITR. This work presents a promising approach for the development of high-performance polycarbonate composites.

The intramolecular aggregation of phosphaphenanthrene groups and benzene-terminated effect within linear phosphonate oligomers effectively enhanced the flame retardancy and toughness of epoxy resin

To explore the potential of a flame retardant molecular structure that simultaneously enhances the flame retardancy and physical properties of epoxy resin (EP), benzene-terminated linear phosphonate oligomers Bz-DQPC-n were synthesized. Compared with the previously prepared linear bisphenol phosphonate oligomers DQPC-n, the benzene-terminated effect of Bz-DQPC-n molecules endows EP composites with better flame retardancy and toughness. In the vertical combustion (UL 94) test, Bz-DQPC-n/EP reached a V-0 rating. For the Bz-DQPC-2 molecule, the results revealed that under the same phosphorus contents, the limiting oxygen index (LOI) value of the Bz-DQPC-2/EP reached 38.2 %, which was higher than that of DQPC-2/EP. Furthermore, the peak heat release rate (pk-HRR) and total heat release rate (THR) of Bz-DQPC-2/EP were 677 kW/m2 and 83 MJ/m2. These values decreased by 54.7 % and 27.2 % in comparison to pure EP, respectively. In addition, the incorporation of Bz-DQPC-n can enhance the glass transition temperature (Tg) of EP composites. The flame retardant mechanism research demonstrated that Bz-DQPC-n molecules produced phosphorus-containing free radicals and aromatic compound fragments during gas-phase pyrolysis. These phosphorus-containing free radicals can interrupt or inhibit the combustion chain reaction process. A proportion of the aggregated phosphaphenanthrene groups decomposed to produce aromatic compounds that remained in the condensed phase, thereby enhancing the quality of the char layer. The investigation of the impact of the end-capping effect within Bz-DQPC-n molecules on the flame retardant behavior of EP composites offers a valuable reference for designing phosphaphenanthrene compounds with high flame retardant efficiency.

A polysulfides adsorption strategy through cation-anion interactions for achieving high-safety lithium-sulfur batteries in multiple scenarios

The widespread application of lithium-sulfur batteries (LSBs) is hindered by challenges such as the shuttle effect of polysulfides (LiPSs), slow reaction kinetics, and fire safety concerns. In this study, surface-functionalized boron nitride nanosheets (ChBN) are prepared and employed as functional separator coatings, enabling multiple application scenarios of LSBs. Specifically, a creative strategy of cation-anion interactions is constructed through the strong chemisorption of N+ on the ChBN surface to Sn- in LiPSs. In addition, the boron nitride and N+ show synergistic effects on adsorption-catalysis, further facilitating the rapid and sufficient deposition of Li2S. The prepared LSBs with ChBN + SP/PP separators exhibit excellent cycle stability (an ultralow capacity degradation of 0.034 % per cycle over 500 cycles at 2C). These LSBs are available in a wide temperature range of −20 to 60 °C, offering a capacity of 1208 mA h/g at 60 °C and 919 mA h/g at −20 °C. Furthermore, the presence of ChBN effectively improves the fire-safety of pouch batteries through the condensed-phase flame retardant mechanism. This simple fabrication process of ChBN is effective and favorable for large-scale manufacturing, which provides a feasible method for the development of high-safety LSBs.

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.

Fabrication of Functionalized Graphene Oxide-Aluminum Hypophosphite Nanohybrids for Enhanced Fire Safety Performance in Polystyrene.

To enhance the fire safety performance in polystyrene (PS), a novel organic-inorganic hybrid material (FGO-AHP) was successfully prepared by the combination of functionalized graphene oxide (FGO) and aluminum hypophosphite (AHP) via a chemical deposition method. The resulting FGO-AHP nanohybrids were incorporated into PS via a masterbatch-melt blending to produce PS/FGO-AHP nanocomposites. Scanning electron microscope images confirm the homogeneous dispersion and exfoliation state of FGO-AHP in the PS matrix. Incorporating FGO-AHP significantly improves the thermal behavior and fire safety performance of PS. By incorporating 5 wt% FGO-AHP, the maximum mass loss rate (MMLR) in air, total heat release (THR), and maximum smoke density value (Dsmax) of PS nanocomposite achieve a reduction of 53.1%, 23.4%, and 50.9%, respectively, as compared to the pure PS. In addition, thermogravimetry-Fourier transform infrared (TG-FTIR) results indicate that introducing FGO-AHP notably inhibits the evolution of volatile products from PS decomposition. Further, scanning electron microscopy (SEM), FTIR, and Raman spectroscopy were employed to investigate the char residue of PS nanocomposite samples, elaborating the flame-retardant mechanism in PS/FGO-AHP nanocomposites.