Hybrid Flame Retardant Research Articles

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.

Impact of phosphonate and phosphoramidate in Si/P/triazine hybrid flame retardants on cotton flammability

Phosphorus and nitrogen-containing flame retardants are well-known for their high efficacy when used in combination, either as separate compounds or within the same molecule. However, a detailed examination of the chemical bonding of phosphorus is needed to understand the flame behavior. To this end, two different scenarios were examined and compared with a phosphorus-free benchmark. Both scenarios contain a triazine ring and a silane-based precursor. The first scenario involves a direct bond between phosphorus and triazine (phosphonate), while the second involves a bridging of phosphorus and triazine via nitrogen (phosphoramidate). This allowed to investigate the structural effect of phosphoramidate and phosphonate of triazine derivatives on the thermal and flame retardant behavior. The flame-retardant performance and mechanism of the treated samples were investigated by means of the vertical flame test (DIN EN ISO 15025), thermogravimetric analysis and microscale combustion calorimetry, amongst others. Our research shows that triazine-based phosphonate has a better flame retarding effect on cotton than phosphoramidate at the same phosphorus concentration. Self-extinguishing characteristics was observed at a low add-on value of 0.23 mmol/g for phosphonate-based flame retardant, while a higher add-one value of 0.24 mmol/g was required in the case of phosphoramidate. The comprehensive analysis demonstrated that both flame retardants undergo mechanisms in both the gas phase and condensed phase by releasing incombustible gases and promoting the carbonization of cotton fabrics.

Flame retardancy, thermal, and mechanical properties of flame retardant PA6/SGF and PPS/PA6/SGF composites

AbstractFlame retardant polyamide 6/short glass fiber (FR PA6/SGF) and polyphenylene sulfide/PA6/SGF (FR PPS/PA6/SGF) composites were prepared by melt extrusion blending using aluminum diethylphosphinate (ADPP) as flame retardant. The thermogravimetric analysis (TGA) indicated that the flame retardant composites showed good thermal degradation with increasing ADPP loading. Flame retardancy mechanisms were studied by analyzing the residue chars. ADPP provided better flame inhibition, promoted formation of carbonaceous char, and improved thermal stability of PA6/SGF. Meanwhile, due to the self‐extinguishing performance of PPS, the flame retardancy of PPS/PA6/SGF was greatly affected by only 3.0 wt% of ADPP. With increasing ADPP content, both storage and loss moduli of FR PA6/SGF and FR PPS/PA6/SGF were increased accompanied with a slight increase of tan δ peak as compared to PA6/SGF and PPS/PA6/SGF, respectively. Besides, notched impact strengths of FR PA6/SGF‐10.0 and FR PPS/PA6/SGF‐10.0 increased by 69% and 5%, while tensile strengths decreased by approximately 5% and 32%, as compared to PA6/SGF and PPS/PA6/SGF, respectively. It demonstrates that ADPP and PPS components are efficient inorganic–organic hybrid flame retardant system. This provides a novel and innovative method for preparing halogen‐free flame retardant reinforced polyamide composites.

Synergic effect between La-MOF and MXene: Revolutionizing TPU with improved mechanical strength and fire safety

Two-dimensional MXene nanosheets with lamellar structure and high specific surface area are considered promising flame retardants for polymers. However, MXene easily accumulates in polymer materials, resulting in the impairment of their mechanical properties. Metal-organic frameworks (MOFs) not only address this issue effectively but also improve compatibility with polymer materials due to their organic components. In this work, lanthanide rare-earth MOF (La-MOF) were successfully grown in-situ on the MXene surface to prepare hybrid flame retardants (La-MOF@MXene), then added to thermoplastic polyurethane (TPU). The La-MOF suppressed the accumulation of MXene in TPU, and the synergistic effect between them improved the fire safety and mechanical strength of TPU composites. The peak heat release rate of the TPU composites with the addition of 3 wt% La-MOF@MXene was 473.3 kW/m2, which represented a 49.4 % decrease compared to that of pure TPU. Besides, due to the synergic properties of MXene and La-MOF, La-MOF@MXene further reduced total smoke, CO2, and CO of TPU composites in fires. Moreover, with the addition of 3.0 wt% La-MOF@MXene, the tensile strength and elongation at break of TPU composites dramatically improved to 42.4 MPa and 686 %, respectively. Therefore, this study provides a novel paradigm for preparing hybrid flame retardants that can improve the fire safety and mechanical properties of TPU composites, exhibiting broad application prospects.

Interface chemistry-induced organic-inorganic phosphorus-based hybrid for high fire safety epoxy resin

The organic-inorganic phosphorus-based hybrid flame retardants are attractive owing to the high efficiency in promoting flame retardancy and suppressing the smoke and toxic gases, yet their preparation has been seldom reported. Herein, ammonium polyphosphate (APP) was decorated by organophosphorus triazole (D-ATA) with Fe (III) as the medium through the interfacial coordination strategy for the construction of the hybrid (APP@FeDT), which was expected to address the issues related to the combustibility, harmful smoke and toxic gases of epoxy resin (EP). APP@FeDT showed better compatibility in EP than APP owing to the enhanced roughness and organophosphorus-based triazolyl. Compared to pristine EP, EP with 6 wt% APP@FeDT achieved the UL-94 V-0 rating and the LOI of 29.6 %, and its PHRR, THR and TSP were reduced by 81.4 %, 64.1 % and 66.5 %, respectively. Generally, this work provides a feasible strategy for the preparation of phosphorus-based hybrid flame retardant and reveals its potential application in high fire safety polymers.

The fabrication of organic-inorganic hybrid structure towards high mechanical property and improved flame retardancy

In order to design UPR composites with high mechanical property and improved flame retardancy, an organic-inorganic hybrid flame retardant (DA-Si-HNT) was fabricated by grafting silane coupling agent (KH560) and the phosphorus-nitrogen containing structure (DOPA-A, the production of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide and adenine) on the surface of halloysite nanotube (HNTs). The UPR/DA-Si-HNT15 composites exhibited significant improvements in tensile strength, tensile modulus, and flexural strength, with respective increases of 65.6 %, 140.6 %, and 80.2 % compared to neat UPR. These enhancements can be attributed to the enhanced compatibility and interfacial force between the flame retardants and the polymer matrix. Meanwhile, it passed the UL-94 V-0 rating at a limiting oxygen index (LOI) value of 34.5 %. The peak of heat release rate (PHRR) and total heat release (THR) decreased by 49.5 % and 43.5 % comparing to that of UPR, indicating a sharp decline in the heat hazard. Moreover, an obvious catalytic carbonization effect in the condensed phase accompanied with moderate gas-phase effect jointly improved flame retardancy of the UPR/DA-Si-HNT15 composites.

Self-assembled lignin-based flame retardant hybrids carrying Cu2+ for poly(lactic acid) composites with improved fire safety and mechanical properties

To enhance the flame retardancy and mechanical performance of PLA, a polyelectrolyte complex predicated on lignin was obtained by electrostatic mutual adsorption of ammonium polyphosphate (APP), polyethyleneimine (PEI), and copper ions as raw materials. The FT-IR spectra and EDX analysis confirmed the successful synthesis of a lignin-based flame retardant hybrid (APL-Cu2+) containing copper, phosphorus, and nitrogen elements. The combustion test results showed that the peak heat release rate and total heat release of the PLA composite containing 12 wt% APL-Cu2+ were decreased by 15.1 % and 18.2 %, respectively, as compared to those of pure PLA. The char residue morphology observation revealed that the addition of APL-Cu2+ could promote the formation of a highly dense and stable graphitized char layer, while TG-MS detected the emission of refractory gases such as ammonia gas, carbon dioxide, and water during combustion. The strong hydrogen bonding between APL-Cu2+ and the PLA matrix kept the composite maintaining good strength and toughness. The tensile strength and impact strength of PLA/6APL-Cu2+ increased by 4.73 % and 65.71 %, respectively, due to its high crystallinity and good interfacial compatibility. This work provides a feasible method to develop biobased flame retardant hybrids for PLA composites with better fire safety and improved mechanical properties.

Advancing building fire safety through heat resistant and flame retardant hybrid silicone sealant

Rapid urbanization and population growth have led to a significant transformation in the urban landscape, characterized by the proliferation of high-rise buildings. However, this urban development has brought about new challenges, particularly in terms of fire safety. The escalating risk of disasters, especially fires, underscores the critical importance of implementing effective fire safety measures across all building types, necessitating legislative reforms. Despite their crucial role in ensuring structural integrity, sealants have often been overlooked in building safety standards, resulting in a lack of comprehensive regulations. The research addresses these challenges by focusing on the development of fire-resistant silicone sealants designed to enhance the fire resistance of building materials. These sealants were formulated independently, incorporating three fire retardants and four heat-resistant agents. While metal oxide flame retardants generally exhibited excellent performance, excessive mixing led to surface deformation and reduced workability. Optimal combinations of flame retardants and heat-resistant agents were identified, with the FR2 specimen demonstrating promising fire resistance performance. Full-scale fire performance tests conducted on FR2 revealed a maximum temperature difference of 40.6 °C between heated and unheated surfaces over a 2-h period, indicating high thermal insulation performance. These findings validate the efficacy of the proposed method and offer significant enhancements to building safety, thereby mitigating fire damage in urban environments.

Fully bio-based intumescent flame retardant hybrid: A green strategy towards reducing fire hazard and improving degradation of polylactic acid

Polylactic acid (PLA) is a promising renewable polymer material with excellent biodegradability and good mechanical properties. However, the easy flammability and slow natural degradation limited its further applications, especially in high-security fields. In this work, a fully bio-based intumescent flame-retardant system was designed to reduce the fire hazard of PLA. Firstly, arginine (Arg) and phytic acid (PA) were combined through electrostatic ionic interaction, followed by the introduction of starch as a carbon source, namely APS. The UL-94 grade of PLA/APS composites reached V-0 grade by adding 3 wt% of APS and exhibited excellent anti-dripping performance. With APS addition increasing to 7 wt%, LOI value increased to 26 % and total heat release decreased from 58.4 (neat PLA) to 51.1 MJ/m2. Moreover, the addition of APS increased its crystallinity up to 83.5 % and maintained the mechanical strength of pristine PLA. Noteworthy, APS accelerated the degradation rate of PLA under submerged conditions. Compared with pristine PLA, PLA/APS showed more apparent destructive network morphology and higher mass and Mn loss, suggesting effective degradation promotion. This work provides a full biomass modification strategy to construct renewable plastic with both good flame retardancy and high degradation efficiency.

Construction of an organic iron phosphate/graphite carbon nitride hybrid system for improved fire safety of epoxy resin

Enhancing the fire safety of epoxy resin (EP) is crucial due to its widespread but inherent flammability, necessitating the integration of additive flame retardants (FRs) that are effective in small quantities and exhibit efficient flame retardancy. This study constructed a novel, efficient FR by synthesizing organic iron phosphate (ATMP-Fe) and loading it on graphitic carbon nitride (g-C3N4). The resulting hybrid flame retardant (ATMP-Fe/g-C3N4) was added to EP in minimal amount to bolster its flame retardancy and safety features. Incorporating a mere 3 wt% of ATMP-Fe/g-C3N4 into EP significantly improved its flame retardancy and thermal stability. This was evidenced by an increase in the limiting oxygen index from 25.5% for EP to 30.1%, achieving a V-1 rating in the UL-94 test, and producing a 22.0 wt% char residue. Moreover, there was a substantial reduction in peak heat release rate, total heat release, and total smoke production by 36.3%, 27.5%, and 39.3%, respectively. The reduction in pyrolysis products, along with the formation of a dense and stable char layer facilitated by the synergistic effects of phosphorus and iron elements, significantly improved the fire safety of EP. Additionally, the enhanced hydrophobicity, mechanical properties, and electrical conductivity of the EP/3ATMP-Fe/g-C3N4 composite suggested potential for wider application of EP in various fields.

Construction of a hybrid flame retardant based on mesoporous silica for enhancing fire safety, smoke suppression, and mechanical properties of epoxy resins

AbstractIn order to improve the fire safety of epoxy resins (EPs), the SBA‐15 based hybrid flame retardant (SNAZD) was synthesized via an organic–inorganic hybridization strategy of mesoporous silica SBA‐15. Relying on electrostatic interaction, the zinc amino‐tris‐(methylenephosphonate) (Zn‐ATMP) was successfully introduced into the pore channels of SBA‐15. Then, 9,10‐dihydro‐9‐oxa‐10‐phosphaphenanthrene‐10‐oxide (DOPO) was successfully loaded into the pores of SBA‐15 under vacuum. The results show that the EP composites with the 5%SNAZD sample (sample EP‐5%SNAZD) showed a LOI value of 30.9% and achieved the vertical burning V‐0 rating. In comparison to EP, the peak heat release rate, peak smoke production rate, and production rate of CO of EP‐3%SNAZD were reduced by 32.2%, 31.9%, and 20.0%, respectively. This is due to the presence of Si, P, N, and Zn elements in the SNAZD, which promoted the generation of a high yield of dense char residue and inhibited the release of toxic gasses. And the impact strength and flexural strength of EP‐1%SNAZD were increased by 19.5% and 15.6%, respectively, and the E' of EP‐5%SNAZD increased by 49.1% when compared with the neat EP. This work provides a general strategy for the design of mesoporous hybrid flame retardant and creates additional opportunities for applications of EP.

Bio-derived polyphosphazene modified halloysite nanotubes as eco-friendly flame retardants to significantly reduce smoke release and enhance the fire safety of epoxy resin

At present, designing efficient bio-based flame retardants for epoxy resin (EP) and exploring low-toxicity and sustainable flame retardant strategies is still a great challenge. In this work, a novel bio-based hybrid flame retardant was successfully prepared by constructing a resveratrol-based cyclic cross-linked polyphosphazene (PPZ) shell on the surface of halloysite nanotube (HNT). The enhancement effects of HNT@PPZ on the fire safety of EP composites were investigated by thermal degradation, simulated fire performance (cone calorimeter test), gas-phase product analysis, and condensed-phase char residue analysis. Compared to pure EP, he total heat release (THR), total smoke production (TSP) and the average yield of carbon monoxide (Av-COY) of EP/3HNT@PPZ were reduced by 47.8 %, 46.5 % and 48.8 % respectively. Furthermore, the EP composites containing HNT@PPZ had a stable flame retardancy even after 6 months of natural aging. It was found the barrier effect of HNT@PPZ in condensed phase was further strengthened by the formation of new product aluminum phosphate, which formed a multiple protective char layer. Additionally, PPZ shell improved compatibility and dispersion of HNT in EP matrix, the mechanical properties of the composite with HNT@PPZ were improved significantly. This work proposed a feasible solution for the preparation of highly efficient bio-based flame retardants with excellent heat reduction and smoke toxicity reduction ability, which could be expected to broaden the application of biomass resources in the development of highly efficient flame retardants.

Dimensional change of red phosphorus into nanosheets by metal–organic frameworks with enhanced dispersion in flame retardant polyurea composites

Red phosphorus (RP) is a promising polymeric flame retardant due to its abundance of flame-retardant elements. Unfortunately, the irregular size of RP leads to poor dispersion in polymer matrices, which greatly limits its wide application in flame-retardant polymer materials. Here, RP is transformed into a two-dimensional (2D) lamellar structure by a simple green method, while ZIF-67 nanoparticles are grown in situ and uniformly embedded in them. The 2D porous RP@ZIF (2D RP@ZIF) composites exhibit excellent flame-retardant properties and mechanical properties in polyurea (PUA) matrix. The peak heat release rate, total heat release, the peak of smoke production rate and total smoke production of PUA composites added with 5 wt% 2D RP@ZIF decreased by 48.0 %, 54.2 %, 20.4 % and 22.2 %, respectively. Due to its well compatibility, the elongation at break and tensile strength of PUA composites were 308.02 % and 9.21 N in the mechanical test, respectively. Compared with previous work, this is the first time that a 2D RP hybrid flame retardant has been prepared by metal organic framework and applied to flame retardant PUA.

Multi-element hybrid flame retardants balance flame retardancy and mechanical performance of epoxy coatings

A phosphorus‑silicon‑boron ternary hybrid flame retardant (BSiP) was synthesized using 9,10-dihydro-9-oxa-10-phosphaphenantrene-10-oxide, p-phthalaldehyde, (3-aminopropyl) triethoxysilane and boric acid. The BSiP was applied to modify the performance of epoxy (EP) coatings. A phosphorus‑boron binary hybrid flame retardant BP was incorporated into this system to balance the performance of EP coatings. Using BSiP and BP alone requires 3 wt% and 6 wt% for EP coating, respectively, to achieve the vertical burning UL-94 V0 rating, while 4 wt% BSiP/BP (1/1) is enough for EP coating to achieve the same UL-94 rating. In addition, the impact strength of EP/BSiP/BP is 11.8 KJ/m2, which is 131 % and 103 % more than that of EP and EP/BSiP, respectively. The BSiP and BP work in both the gas phase and the condensed phase, and they have a good synergistic effect on flame retardancy of EP. The blend of BSiP and BP increases the free volume of EP and thus toughens EP coatings. The hybridization of multi-element covalent bonds and physical blending effectively balance the flame retardancy and impact strength of EP coatings.

A novel P/N/Si/Zn-containing hybrid flame retardant for enhancing flame retardancy and smoke suppression of epoxy resins.

Currently, additively efficient flame retardants are being developed to enhance the smoke suppression, flame retardancy, and thermal properties of composite materials. To this end, the current study designed and prepared a novel P/N/Si/Zn-containing organic-inorganic hybrid denoted as APHZ. Its inorganic part was 2-methylimidazole zinc salt (ZIF-8), which improved its smoke suppression and catalytic carbonization. The organic part (P/N/Si-containing compound) promoted its flame retardancy and interfacial compatibility between APHZ and epoxy resin (EP). The test results revealed that EP/APHZ-3 composites achieved a V-0 rating and a notable LOI value of 30.7% when introducing 3 wt% APHZ into the EP matrix. Cone calorimetry tests (CCT) further demonstrated that the average heat release rate (av-HRR), total smoke production (TSP), and CO production (COP) of EP/APHZ-3 were reduced by 23.3%, 14.0%, and 21.1%, respectively. Meanwhile, the char residual was increased by 60.6%, as compared to pure EP. Furthermore, the flame-retardant mechanism of EP/APHZ composites was investigated by the XPS, TG-FTIR, and Raman spectroscopy techniques. The observed synergistic effect of the imidazole skeleton ZIF-8 and P/N/Si-containing compound in APHZ facilitated the generation of a dense multi-element char layer, with the condensed phase flame-retardant mechanism playing a dominant role. These findings contribute to developing and designing high-performance flame-retardant EP.

Design of Novel Types of Phosphorus-Containing Flame-Retardant Hybrid Solid Electrolytes with Enhanced Ionic Conductivities

Hybrid polymer/inorganic solid electrolytes have been considered one of the promising routes toward improved safety and higher energy density compared to today’s liquid electrolytes. Herein, flame-retardant phosphorus-containing random copolymers, namely poly(oligo(ethylene glycol) methyl ether methacrylate)-co-(dimethyl(methacryloyloxy)methyl phosphonate) (P(xPEGMA-co-yMAPC1)), were synthesized with different ratio of monomer compositions and further used as the polymer matrix. By mixing P(xPEGMA-co-yMAPC1) with lithium perchlorate (LiClO4) and acetonitrile (ACN), the solid polymer electrolytes were obtained after vacuum evaporation of ACN. Among the P(xPEGMA-co-yMAPC1) copolymer electrolytes, the P(9PEGMA-co-1MAPC1) with 10wt% LiClO4 presented an ionic conductivity of 1.0×10-4 S cm-1 at 60℃ and 3.1×10-5 S cm-1 at 30℃ and showed good flame-retardant performance compared to pure PPEGMA. The increase in MAPC1 content upgraded the flame-retardant performances but enhanced the glass transition temperature (Tg) of the copolymers, leading to a decrease in ionic conductivity. To further enhance the ionic conductivity of the copolymer electrolytes, hybrid polymer/inorganic solid electrolytes are synthesized by adding Li1.3Al0.3Ti1.7(PO4)3 (LATP) and SiO2 inorganic fillers, respectively. P(9PEGMA-co-1MAPC1) with 10wt% LATP exhibits a higher ionic conductivity of 1.4×10-4 S cm-1 at 60℃, while P(9PEGMA-co-1MAPC1) with SiO2 fillers show a lower ionic conductivity of 8.5×10-5 S cm-1 at 60. Finally, the cycling performances of hybrid solid electrolytes containing LiFePO4|P(9PEGMA-co-1MAPC1) + LiClO4 + LATP/SiO2|Li batteries were tested. The capacity reaches 164.2 mAh g−1 at 0.05 C, and the capacity retention reaches 90% after 200 cycles at 0.1 C. Figure 1

A graphene@Cu-MOF hybrid synthesized by mechanical ball milling method and its flame retardancy and smoke suppression effect on EP

The traditional method of preparing graphene will cause serious environmental pollution, and the combustion of polymer materials will seriously harm people's health. In this paper, a Cu-MOF-coated graphene composite flame retardant (G@Cu-MOF) rich in flame retardant elements such as B and N was synthesized through green mechanical ball milling method. Flame retardants reduce the threat to the environment and people's lives and property. After adding 6 wt% G@Cu-MOF, the peak heat release rate, total heat release rate, CO production and CO2 production of epoxy resin (EP) composite samples decreased by 55, 14, 59, and 55%, respectively. This type of Cu-MOF releases incombustible gases such as boron trifluoride (BF3) and ammonia (NH3) during combustion, diluting the concentration of combustible gases and producing copper borate in the condensed phase. Cu2+ is reduced to Cu, and boron compounds are converted into boron oxides. The thermal conductivity of graphene can reduce the temperature of the matrix, and has good flame retardancy. It synergistically acts with Cu-MOF to promote the formation of high-quality residual char, and can significantly inhibit the heat and smoke release of EP. It plays a role in flame retardancy and protecting the substrate from fire. This study provides a new approach for preparing graphene hybrid flame retardants through mechanical ball milling, in order to improve the flame retardancy of EP and suppress the release of smoke and toxic gases.

Novel organic-inorganic hybrid towards enhancement of flame retardancy, suppression of volatile organic compounds and toxic smokes for asphalt

The enhancement of flame retardancy, the suppression of volatile organic compounds (VOCs) and carcinogenic smokes at elevated temperature are urgent for the widely application of asphalt. In present work, an organic-inorganic hybrid flame retardant (ATH@SA@Fe3+) was designed via simple two-step reactions, including in-situ growth of sodium alginate (SA) on the surface of alumina trihydrate (ATH) and a crosslinking of iron ion (Fe3+) on ATH@SA. The three-dimensional network crosslinking structure of ATH@SA@Fe3+ effectively hindered and retarded the thermal decomposition progress of asphalt, producing fewer hydrocarbon derivatives, reducing VOCs constituents and their release amounts. For the Asphalt/10ATH@SA@Fe3+ composites, the total heat release (THR), the total smoke production (TSP) and the peak smoke production rate (pSPR) was reduced by 28.2%, 35.2% and 28.0% respectively, indicating a high flame-retarding and smoke suppression efficiency via the formation of expanded, impact and continuous carbon layer. Meanwhile, the network crosslinking structure could arrest the molecular motion and lead to the thermal stability, elasticity rutting resistance enhancement of asphalt materials. In perspective, the research results provided a scientific basis for the management of flame-retardant materials for asphalt pavement and the formulation of emission reduction strategies.

Zinc Hydroxystannate/Carbon Nanotube Hybrids as Flame Retardant and Smoke Suppressant for Epoxy Resins.

Novel hybrid flame retardants containing zinc hydroxystannate and carbon nanotubes (ZHS-CNTs) were synthesized using the coprecipitation method, and the structure and morphology of ZHS-CNTs were investigate using an X-ray powder diffractometer (XRD), scanning electron microscope (SEM), transmission electron microscopy (TEM) and thermogravimetric analyzer (TGA). Then, the ZHS, CNTs and ZHS-CNTs were incorporated into EP, respectively, and the flame-retardant and smoke inhibition performance of the composites were compared and studied. Among the three composites, the EP/ZHS-CNT composites have the highest improvements on the fire resistance and smoke inhibition properties. With only 2.0 wt.% ZHS-CNT hybrids, the pHRR of EP/ZHS-CNT composite materials is reduced by 34.2% compared with EP. Moreover, the release of toxic gases including CO, CO2 and SPR from the composites was also effectively inhibited. The mechanisms of flame retardant and smoke inhibition were investigated and the improved properties were generally ascribed to the synergistic flame-retardant effects between ZHS and CNTs, the catalyzing effect of ZHS and the stable network structure of CNTs.

Synthesis of organic–inorganic hybrid flame retardant and its use in polyurethane composite fiber membrane

AbstractIn this article, we presented an inventive organic–inorganic hybrid flame retardant, MPKG, by the strategic reaction of phytic acid (PA) with melamine (MA), γ‐aminopropyl triethoxysilane (KH550) and graphene oxide (GO). Subsequently, an MPKG/PU fiber membrane was fabricated through electrospinning, wherein MPKG was seamlessly incorporated into the PU spinning solution. The morphology and chemical structures of the flame retardants were characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and x‐ray photoelectron spectroscopy (XPS). The flame retardancy and resilience to soaping of the fiber membranes were assessed via the limiting oxygen index (LOI), thermogravimetric analysis (TGA), and microscale combustion calorimetry (MCC). Impressively, the results demonstrate a significant 38.8% reduction in total heat release (THR) for the MPKG/PU fiber membrane in comparison to pure PU fiber membrane. Moreover, the incorporation of MPKG leads to an increase in LOI from 18.8% to 21.5% for the PU fiber membrane, accompanied by a notable enhancement in char yield at 800°C from 13.5% to 28.5%. These results underscore the augmentative impact of MPKG on the flame retardancy of PU fiber membrane. Remarkably, the MPKG/PU fiber membrane exhibits robust soaping resistance, with the LOI maintaining a level above 20% post‐soaping.