Smoke Suppression Research Articles

Nanostructured poplar wood via delignification and ammonium dihydrogen phosphate-SiO2 modification towards remarkable flame retardant performance: Synergistic effect and enhanced mechanism

Developing efficient methods to prepare high-performance flame retardant and smoke suppression wood is crucial for the application. Herein, nanostructured poplar wood (DWI-4) with remarkable flame retardant and smoke suppression performance was fabricated by impregnating ammonium dihydrogen phosphate (ADP) and nano-silica (SiO2) into delignified wood (DW-4). With the delignification treatment, lignin was partially removed, and numerous pores and cracks were developed on the cell wall of wood, allowing more ADP-SiO2 particles to be impregnated into wood. As a result, ADP-SiO2 particle was not only anchored in the lumens (pores) of wood, but also was penetrated and embedded into the cell wall, achieving the synergistic modification of the lumen and cell wall of wood. As anticipated, the produced DWI-4 featured outstanding flame retardant and smoke suppression performance. The peak heat release rate (pHRR) of DWI-4 was as low as 38.2 kW m−2, which was only 8 % of that of natural wood (NW). And the total heat release (THR) and total smoke production (TSP) demonstrated reductions of 73.9 % and 64.4 % comparing to NW. Moreover, the compressive strength of DWI-4 increased by 31.4 % comparing to NW. The structure of residual char of DWI-4 was more stable and the gas intensity produced by the combustion of DWI-4 decreased remarkably. Therefore, the synergy of delignification and ADP-SiO2 impregnation significantly enhanced the flame retardant and smoke suppression performance of wood and the enhanced mechanism was revealed. The nanostructured poplar wood with excellent flame retardant and smoke suppression performance was prepared, providing an effective method for the functional improvement of wood and expanding the fields of application.

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.

Study on flame retardant and smoke suppression of EPDM by sepiolite expansion flame retardant system

AbstractA large amount of smoke will be produced during the combustion of ethylene propylene diene monomer(EPDM), which seriously endangers the environment and personal safety. In this study, K‐SEP was obtained by modifying sepiolite with KH550, and two bio‐based flame retardant and smoke suppression systems AEGS and PEGS were prepared by combining ammonium polyphosphate intumescent flame retardant system (AEG) and piperazine pyrophosphate intumescent flame retardant system (PEG), respectively. The flame retardant and smoke suppression properties of AEGS and PEGS on EPDM matrix composites were investigated. The experimental results show that the LOI values of EPDM/AEGS3 and EPDM/PEGS3 composites with 3 phr K‐SEP are 8.1% and 5.5% higher than those of the blank samples without sepiolite. TSP decreased by 26.3% and 14.3% respectively, which proved that sepiolite has important research value in the field of flame retardant and smoke suppression of polymer materials.

Staggered distribution structure Cu-Mn catalysts for mitigating smoke and gas toxicity in combustion: Unravelling mechanistic insight through operando studies

The integration of flame retardancy and environmental friendliness can be achieved by designing cost-effective, stable, and efficient catalysts to reduce smoke and toxicity during the combustion of polymeric materials. This work reports the development of non-precious metal catalysts for thermoplastic polyurethanes (TPU), which exhibit a significant reduction in smoke and gases toxicity while providing flame retardancy. The use of MgB2 as a support enables the in-situ growth of highly efficient Cu-Mn based catalysts, resulting in a remarkable 51.5 % decrease in total smoke release and a 49.1 % reduction in peak rate of CO generation of TPU according to cone calorimeter test results. Furthermore, Cu-Mn/MgB2 demonstrates an impressive 83.1 % reduction in total CO production rate during the steady-state tube furnace test. Additionally, density functional theory is employed to analyze the binding energy between catalysts and TPU as well as the adsorption energy of gases. This elucidates the rational reaction mechanism behind the catalyst and smoke inhibiting process. By combining transition metal oxide catalyzed CO oxidation reaction with polymeric material combustion, this study presents a promising approach for efficient smoke suppression with potential applications.

Hierarchical Nano/Micro-Array Structured CuMgAl-LDH/rGO Hybrids for Remarkably Improved Flame Retardancy and Smoke Suppression Performance of Flexible Polyvinyl Chloride.

In this study, we explored the rational integration of layered double hydroxides (LDHs) with reduced graphene oxide (rGO) to create a hierarchical nano/microarray structured CuMgAl-LDH/rGO hybrid aimed at enhancing the flame retardancy and smoke suppression properties of polymer nanocomposites. The results indicated that the limiting oxygen index (LOI) value of the G-CuMgAl/polyvinyl chloride (PVC) composite reached 35.8%, reflecting a 6.4% increase compared to pristine PVC (29.4%), and achieved a UL-94 V-0 rating. Furthermore, in comparison to pristine PVC, the peak heat release rate (PHRR) of the G-CuMgAl/PVC composite was significantly reduced by 40.2%; the total heat release rate (THR) decreased by 24.3%; the maximum average heat release rate (MARHE) diminished by 41.6%; the peak smoke production (PSPR) decreased by 37.8%; the total smoke production (TSP) was reduced by 31.3%; and the average effective heat of combustion (av-EHC) decreased by 15.2%. The enhanced flame retardancy and reduced smoke production can primarily be attributed to the multiple synergistic interactions among the highly dispersed constituents and the nano/microstructures, which effectively impede the transfer of heat, mass, and O2 from various directions while preventing further combustion of the underlying matrix by creating a tortuous path in the condensed phase. Additionally, this study provides a novel perspective on the design and synthesis of structured LDHs/rGO hybrids, with the potential to enhance flame retardancy and smoke suppression properties across a broad spectrum of polymer materials.

High rubber elasticity and thermal conductivity in plasticized polyvinyl chloride film with flame retardancy and smoke suppression properties

AbstractFor hydrogenated nitrile‐butadiene rubber (HNBR) modified polyvinyl chloride (PVC), magnesium hydroxide and antimony trioxide are frequently employed as flame retardants. Fume silica is thought to be useful reinforced agent for rubber as well as efficient flame retardant for polymer‐based composites. The plasticized PVC and HNBR blend in this work were combined with three fillers mentioned above to create rubber‐plastic composites that performed well overall, with a notable improvement in combustion. The limiting oxygen index of the composites increased from 23.7% to 33.8% with no droplets falling during combustion, the smoke density rating decreased from 23.8% to 7.9%, and the maximum smoke density dropped from 95.5% to 15.5%. The cone calorimetry test findings revealed that the three fillers simultaneously prevented the emission of smoke and heat from combustion. High thermal conductivity is typically linked to excellent flame retardancy. The thermal conductivity of composites rose from 0.193 to 0.583 W m−1 K−1 with the addition of fillers. Furthermore, the low glass transition temperature and permanent set of improved composites reflect its softness and rubber elasticity. Thermogravimetric analysis was used to examine the thermal stability of the composites in nitrogen and air, and the results indicated the addition of fillers improved the thermal stability.

Catalyst-free sustainable epoxy vitrimers with fire safety offered by phosphorus-containing compounds

In this study, we designed and incorporated a phosphorus-rich compound, DPT, which possesses inherent catalytic properties, into a typically sustainable epoxy vitrimer. This innovative strategy enables the fabrication of flame retarded epoxy vitrimers that require no additional catalysts. DPT was synthesized through a reaction between triethanolamine (TEA) and dibenzyl chlorophosphonate (DPCP). The successful synthesis of DPT is attested to by FTIR and NMR analyses. DPT effectively accelerated the curing process of the epoxy vitrimers, yielding materials with exceptional mechanical strength and inherent self-healing abilities. Notably, the pHRR of epoxy vitrimer incorporated with DPT is reduced to 296.3 kW/m2, showing a remarkable 54% reduction compared to that of the epoxy vitrimer catalyzed by conventional catalysts. The THR is also decreased from 84.3 to 42.4 MJ/m2. Comprehensive analyses using cone calorimetry and TG-FTIR revealed that DPT effectively inhibits the emission of toxic gases. Crucially, the presence of DPT in the epoxy matrix facilitated the formation of a dense and stable phosphorus-laden carbon layer, which not only enhanced flame retardancy but also imparted exceptional smoke suppression capabilities. These findings underscore the potential of DPT for developing high-performance, catalyst-free, flame-retardant epoxy vitrimers.

Co Hybrids modified piperazine pyrophosphate towards efficient flame retardancy, smoke suppression, and high mechanical properties of styrenic thermoplastic elastomer

The highly flammable nature of thermoplastic elastomers (TPE) results in poor fire safety performance. The large addition of flame retardants leads to a significant decrease in mechanical properties. To solve above challenges, we design a multilayer core-shell flame retardant, piperazine pyrophosphate@ tannic acid@ Co amorphous hybrids (PAPP@TA@Co-2-MIM) and add it to TPE to enhance the fire safety and mechanical performance simultaneously. It was found that the addition of 32 wt% PAPP@TA@Co-2-MIM achieved a UL-94 V-0 rating of TPE composites, with a limiting oxygen index of 27 %. Compared to pure TPE, the peak heat release rate, total heat release, total smoke production, and peak CO release rate of TPE/PAPP@TA@Co-2-MIM were reduced by 79.8 %, 37.1 %, 42.9 %, and 82.5 %, respectively, effectively suppressing the release of heat, smoke, and toxic gases. Besides, the flame-retardant mechanism was also explained. In terms of mechanical performance, benefiting by the bridging effect of the core-shell structure, the tensile strength of TPE/PAPP@TA@Co-2-MIM increased by 52.7 %, compared to TPE/PAPP. This study designed a TPE composite material that showed good thermal stability, high fire safety performance and enhanced mechanical properties.

CoFe Oxides-Coated 2D Black Phosphorus for Flame-Retardant Nanocoatings with Tunable Mechanical Strength and Efficient Elimination of Toxic Gases.

2D black phosphorus (BP) degrades irreversibly into phosphate compounds under ambient conditions, which limits its application in a variety of fields. In this study, by coating amorphous ferric-cobalt oxides (CoFeO)on BP nanosheets, a multifunctional CoFeO@2D BP is successfully developed that effectively inhibited combustion and catalyzed CO oxidation to eliminate toxic gases. Strong affinity between transition-metal cations and BP allowed the uniform growth of amorphous ferric‒cobalt oxides on the BP surface, which effectively prevented the spontaneous degradation of 2D BP. By combining CoFeO@2D BP with gelatin and kosmotropic salts, the as-obtained nanocoatings are used for surface treatment of flammable polyurethane foam (PU). Kosmotropic ions induced strong hydrophobic interactions and bundling within the gelatin chains which significantly enhanced the mechanical performance of the PU. BP accelerates the carbonization of gelatin to inhibit the combustion of PU, and CoFe oxides, which act as true active centers to accelerate the oxidation of CO, effectively inhibiting the production of harmful gas. The release rate of CO decreases by 73% and the limiting oxygen index (LOI) increases from 17% to ≈32% during PU combustion. The developed novel 2D material opens the way for multifunctional coatings with integrated durability, flame retardancy, and high smoke suppression efficiency.

Functionalized LDH via intercalation of gluconate anion and surface assembly of ultrafine copper hydroxide for improving mechanical properties and the fire safety of epoxy resin

To impart epoxy resin (EP) with outstanding mechanical properties and fire safety, LDH was systematically functionalized through gluconate anion (GA) intercalation followed by surface assembly of ultrafine Cu(OH)2, resulting in the LDH-GA@Cu(OH)2 hybrid. Comprehensive characterizations confirmed the successful synthesis of the desired product, with a uniform distribution of ultrafine Cu(OH)2 nanoparticles on the GA-intercalated LDH surface. The findings revealed that LDH-GA@Cu(OH)2 improved the mechanical properties of EP due to the increased LDH layer spacing, facilitating EP chain insertion, and the hydrogen bonding between the –OH of GA and the EP matrix. Fire retardancy tests indicated that the EP composite containing 7.5 wt% LDH-GA@Cu(OH)2 achieved a limiting oxygen index (LOI) of 30.1%. Furthermore, compared to pure EP, the composite demonstrated significant reductions in the peak heat release rate (PHRR) and peak CO production rate (PCOP) by 47.4% and 60.5%, respectively, underscoring its superior flame-retardant and toxic smoke suppression capabilities. Mechanistic studies further indicated that ultrafine Cu(OH)2 enhanced char formation through catalytic charring at the interface, which promoted compact and cohesive char layers. Overall, this work proposes a promising functionalization strategy for LDH to endow EP with excellent comprehensive performance.

Multi‐component coupling synergistic effect of resourced gold tailings on intumescent flame‐retardant polypropylene

AbstractAddressing the challenge of resource utilization of gold tailings. A high performance flame‐retardant fillers (K‐GTF) were prepared from gold tailings (GTF) by coupling and condensation for application to intumescent flame‐retardant polypropylene (PP). K‐GTF enhances the flame‐retardant, thermal stability, smoke suppression and mechanical properties of flame‐retardant PP through synergistic approach. The results show that K‐GTF demonstrates good flame‐retardant synergism, with PP composites containing 3% additive (PP/G3) exhibiting substantial flame‐retardant and smoke suppression characteristics. Notably, PP/G3 boasts a limiting oxygen index (LOI) of 36.1%, which is substantially higher than the 33.6% LOI of the flame‐retardant PP without added K‐GTF (PP/G0). Furthermore, the peak heat release rate (PHRR), peak smoke production rate (PSPR), total heat release rate (THR), and total smoke production (TSP) of PP/G3 were decreased by 32.5%, 26.9%, 31.6%, and 21.5%, respectively, as compared to PP/G0. According to the synergistic mechanism analysis, K‐GTF exerts a multi‐component coupling synergistic effect, which promotes the production of phosphorus‐rich cross‐linking structures in flame‐retardant PP materials during the combustion, thereby promotes the formation of stable, dense and intumescent char to further enhances the flame‐retardant performance of the PP materials. In terms of mechanical effects, the introduction of K‐GTF alleviates the issue of a substantial decline in mechanical properties typically caused by flame retardants in PP materials. This indicates that K‐GTF improves the compatibility between the flame retardants and the PP matrix, thereby enhancing the mechanical properties of the flame‐retardant PP materials.Highlights Successfully synthesis a flame‐retardant synergist (K‐GTF). K‐GTF has good synergistic flame‐retardant effect. K‐GTF substantially enhances char formation and thermal stability of flame‐retardant PP. K‐GTF exerts a multi‐component coupling synergistic effect. K‐GTF enhances the compatibility between the PP matrix and the flame retardants.

Constructing piperazine pyrophosphate@LDH@rGO with hierarchical core-shell structure for improving thermal conductivity, flame retardancy and smoke suppression of epoxy resin thermosets

The integration and miniaturization development of electronic devices placed the great demand for epoxy resin (EP) thermosets with excellent thermal management, flame retardancy and electrical insulation. Herein, a multifunctional additive piperazine pyrophosphate@layered double hydroxide@reduced graphene oxide (PPAP@LDH@rGO) with hierarchical core-shell structure was constructed by solvothermal and electrostatic self-assembly methods to meet the above requirements. Profiting from the distinct structure of PPAP@LDH@rGO, the thermal conductivity of EP/PPAP@LDH@rGO reached 0.951 W m−1 K−1 at 7 wt% addition (3 wt% rGO containing), which is 320.8 % increment compared to pristine EP. Meanwhile, when 4 wt% PPAP@LDH@rGO was added, the EP thermoset reached UL-94 V-0 rating during vertical burning tests with the limiting oxygen index of 29.8 % due to the synergistic effect of PPAP, LDH and rGO. The release of hazard products including smoke and carbon monoxide for EP/PPAP@LDH@rGO visibly declined during combustion. Besides, the EP thermosets also well-maintained the electrical insulation and mechanical properties. This work provided an alternative approach for preparing high performance EP thermosets which was suitable to be applied in electronics and electrical fields.

MOF-derived strategy for in-situ assembly of nickel phyllosilicate nanoflowers: Enhancing smoke suppression, flame retardancy and mechanical properties of epoxy resins

Epoxy resin (EP) is a highly versatile polymer extensively used in high-end applications, including aerospace components, electronics encapsulation and adhesives. To custom-design flame retardant materials for high-performance epoxy resins, a MOF-derived zeolitic imidazolate framework-8@nickel phyllosilicate (ZIF@Ni-PS) was synthesized through the in-situ assembly of nickel phyllosilicate nanoflowers. The results showed that the smoke suppression, flame retardancy, and mechanical properties of the EP composites containing 5 wt% ZIF@Ni-PS were significantly enhanced. The peak heat release rate (pHRR) and the peak smoke production rate (pSPR) were reduced by 33.2% and 12.7%, respectively. The presence of ZIF@Ni-PS promoted the formation of a dense, high-quality carbon layer that isolated heat and oxygen transfer, effectively reducing heat release during combustion and suppressing smoke generation. Furthermore, the imidazole ring and Zn ions on the surface of ZIF@Ni-PS facilitated the formation of coordination and hydrogen bonds with the epoxy (EP), thereby enhancing the dispersion, compatibility, and mechanical properties of the epoxy resin matrix. This study presents a straightforward preparation method for high-performance EP composites, providing a novel pathway for EP research.

Preparation and characterization of HNTs@ZIF enhanced intrinsic flame retardant RTV silicone rubber

Phenylphosphonyl dichloride (BPOD) and 3-aminopropyltriethoxysilane (APTES) were used to prepare phosphorus-nitrogen hexaethoxysilane (BPTES). BPTES was then used for cross-linking and curing hydroxyl-terminated room-temperature vulcanized (RTV) silicone rubber, providing intrinsic flame retardancy. In addition, halloysite (HNTs) is a kind of tubular silicate, taking advantage of its large aspect ratio, HNTs were used as a template to load ZIF67 on the surface of halloysite to obtain HNTs@ZIF tubular filler. It was added to the above system as a reinforcing and flame-retardant filler by physical blending, and the RTV elastomer with excellent performance was prepared. The successful preparation of phosphorus-containing crosslinkers (BPTES) was demonstrated by FT-IR. After the introduction of the new crosslinker, RTV not only has improved flame retardant performance, but also improved mechanical properties. The tensile strength and elongation at break of RTV with 20 wt.% BPTES are increased by 151% and 211%, respectively. The peak heat release rate (pHRR) and the peak of smoke production rate (pSPR) are reduced by 55.9% and 48.6%, respectively, and the thermal stability is also improved. In addition, the successful preparation of HNTs@ZIF was confirmed by FT-IR, XRD, XPS, and TEM. By introducing 2 wt.% HNTs@ZIF into 20 wt.% BPTES cured RTV, the intrinsically flame-retardant RTVs with enhanced performance were prepared. It is worth noting that when 2 wt.% HNTs@ZIF is added, the flame retardant and smoke suppression properties of phosphorus-containing silicone rubber are further improved. Because the ZIF contains cobalt metal ions that can be catalyzed into carbon. The pHRR and pSPR decrease by 18.3% and 16.3%, respectively, and the total heat release (THR) and total smoke production (TSP) decrease by 23.6% and 24.4%, respectively. This work will provide enlightenment for the study of intrinsic flame-retardant RTVs enhanced by modified halloysite.

Linear polydichlorophosphazene and Ti3C2Tx MXene nanohybrids: Synthesis and application to epoxy resin to improve the fire safety and mechanical properties

Enhancing the fire safety of epoxy resins (EPs) typically requires a significant amount of flame retardants, which often results in considerable degradation of their mechanical properties. To address this issue, a novel flame retardant known as PDCP@DPA@MXene was synthesized and integrated into EP to achieve notable improvements in flame retardancy, smoke suppression, and mechanical strength. By incorporating 1.5 wt% PDCP@DPA@MXene, the impact strength, tensile strength, and elongation at break of the resulting PDM-1.5 %/EP composite reached 12.1 kJ/m2, 57.4 MPa, and 13.0, respectively, reflecting enhancements of 63.5 %, 18.4 %, and 17.1 % compared to the pure EP. The enhancement in tensile strength may be attributed to the high rigidity of Ti3C2Tx MXene, which reinforces the EP matrix. Additionally, the intertwined structure of PDCP@DPA@MXene chains effectively mitigates material fracturing and absorbs impact forces, thus toughening the EP. The presence of phosphorus, nitrogen, and titanate in PDCP@DPA@MXene contributes to the formation of a more compact char layer. The PDM-1.5 %/EP sample achieved a V-0 rating in the vertical UL-94 test and exhibited a high limiting oxygen index of 32.0. Furthermore, the sample containing 2 wt% PDCP@DPA@MXene showed a significant reduction in peak heat release rate (p-HRR) and total heat release (THR), recording values of 689 kW/m2 and 71.9 MJ/m2, which are decreases of 45.1 % and 26.9 %, respectively, compared to pure EP. Additionally, the incorporation of PDCP@DPA@MXene led to a reduction in CO production. These flame-retarded EPs demonstrate strong potential for various applications due to their elevated glass transition temperature and robust thermal stability.

Multi-scale ceramic self-extinguishing fire retardant coating based on scale armor layer

Currently, designing an efficient and broadly applicable (suitable for foams, wood, steel, plastic) fire-retardant coating remains a significant challenge. This work introduces a multi-scale micro-nanostructured hybrid fireproof coating. The composite features basic fillers that include ceramic glass microspheres, while its interior comprises an inorganic aerogel made from nano black phosphorus and silicon dioxide nanofibers for reinforcement, with a phosphorus-containing acrylic polymer serving as the base. Upon exposure to elevated temperatures, the coating’s surface transforms into a solid char layer resembling scale armor, effectively functioning as a robust fire barrier to protect the underlying substrate. The coating treated rigid polyurethane foam achieved an exceptionally high Limiting Oxygen Index of 45 %, outperforming comparable products. In terms of flame retardancy and smoke suppression, this innovative coating significantly reduces Peak Heat Release Rate (50.3 %) and Total Smoke Production (54.9 %). Notably, it exhibits rapid self-extinguishing capabilities within seconds during butane flame tests at temperatures exceeding 1100 °C, demonstrating remarkable resistance to high-temperature flames. This research offers a straightforward methodology for developing high-performance fireproof coatings, with promising applications across various industrial settings.

Multi-functional flame-retardant epoxy resin featuring diverse crosslinking networks

High-performance epoxy resins (EPs) with ultimate flame retardancy, particularly in terms of smoke suppression (as asphyxiation is the primary cause of death in fires), remain a significant challenge. To address this issue, we propose a feasible multiple crosslinking strategy by incorporating an additive flame retardant (abbreviated as BPPDN) containing self-crosslinking groups to construct multi-crosslinking networks during the curing of EPs. Using this strategy, the BPPDN/EP flame-retardant samples achieved a V-0 rating in the UL-94 test in the absence of conventional flame-retardant elements such as halogens or phosphorus. Among the rest, 15BPPDN/EP had remarkable low fire hazards, with total smoke production and peak heat release rate reduced by 38.7 % and 22.2 %, respectively. Surprisingly, the 15BPPDN/EP material maintained its high transparency, excellent ultraviolet shielding, and dielectric properties (specifically, the dielectric constant decreased from 5.19 to 3.46; the dielectric loss decreased from 0.0066 to 0.0045), as well as its ultrahigh tensile strength (increased by 63 %), flexural strength (by 48 %) and impact strength (by 75 %). This paper investigates in detail the effects of BPPDN on the curing process, thermal properties, mechanical properties, dielectric properties, and flame retardancy of EPs, providing a new direction for the design of highly transparent, multifunctional high-performance flame-retardant thermosetting resins without the need for conventional flame-retardant elements.

Facile preparation of heptazine-covered Fe2O3 and its synergistic effect on the enhanced flame retardance of silicone rubber composite

The flammability of silicone rubber (SR) significantly limits its broad use in areas that require high flame retardancy. In this study, heptazine-covered Fe2O3, which exhibits effective flame retardancy, was prepared using simple ball milling and heat treatment, which are advantageous for large-scale production. The prepared filler was incorporated into SR. The addition of 7.02 wt% FM filler increased the thermal degradation onset temperature at 5 % weight loss from 492.5 °C for neat SR to 502.7 °C (FM 1:1 composite). Moreover, the peak heat release rate and peak smoke production rate of the FM 1:1 composite significantly decreased by 43.15 % and 68.42 %, respectively, indicating a significant enhancement in the fire safety and smoke suppression of the FM composites. The chemical, morphological, and electronic structures of the FM fillers, pyrolysis gas production, and char residue were thoroughly investigated to reveal the possible flame-retarding mechanisms of the SR composites.

Synthesis of a novel biomass-based flame retardant featuring vinyl-terminated chemical cross-linking and application in flame retardancy, smoke suppression, toxicity reduction and mechanical enhancement of PAN composite fibers

To develop green and efficient polyacrylonitrile (PAN) fibers with excellent fire safety properties, a new biomass-based flame retardant (PPC@VA) with vinyl-terminated groups was prepared based on the reaction of hexachlorocyclotriphosphonitrile, teat polyphenols, ethylenediamine and vinylphosphonic acid. Subsequently, it was mixed with spinning solution to obtain PPC@VA/PAN through wet spinning, which were then chemically cross-linked via thermal initiation to achieve CC-PPC@VA/PAN fibers. CC-PPC@VA/PAN showed a significant improvement in flame retardancy with a limiting oxygen index value of 32.5 %. The peak of smoke production rate, total smoke production and CO production rate were lowered by 81.9 %, 77.8 % and 91.3 %. Besides, the hazardous gas HCN was greatly suppressed. Owing to the macromolecular entanglement, hydrogen bonding and covalent cross-linking, CC-PPC@VA/PAN improved elongation at break and tensile strength by 19.2 % and 72.1 %. Also, chemical cross-linking contributed to decrease the migration of P/N-based flame retardants, lower the potential risk of water eutrophication and increased the service life of the fibers.

Developing flame retardant, smoke suppression and self-healing polyvinyl alcohol composites by dynamic reversible cross-linked chitosan-based macromolecule

With the increasing threat of white pollution to the public health and ecosystem, functional materials driven by green and sustainable biological macromolecule are attracting considerable attention. Inspired by the double-helix structure of DNA, a P–B–N ternary synergistic chitosan-based macromolecule (PBCS) was constructed to prepare flame retardant, smoke suppression and self-healing polyvinyl alcohol composite (PVA@PBCS) via dynamic reversible interactions. The limiting oxygen index value of PVA@PBCS increased from 19.6 % to 28.7 %, whereas the peak heat release rate and total heat release decreased by 47.04 % and 43.37 %, respectively. Besides, the peak smoke production rate and total smoke production of PVA@PBCS also decreased by 45.31 % and 54.98 %. With the presence of borate ester-based covalent and multiple hydrogen bonds, the tensile strength and elongation at break of PVA@PBCS increased by 19.50 % and 16.85 % compared to the control sample, and the healing efficiency for tensile strength and elongation at break was as high as 93.86 % and 90.57 %, respectively. This work developed an eco-friendly and effective scenario for fabricating flame retardant and smoke suppression PVA materials, stimulating the substantial potential of chitosan-based biomacromolecule and dynamic reversible cross-linked tactics in self-healing field.