Excellent Flame Retardant Properties Research Articles

Study on thermal runaway propagation inhibition of battery module by flame-retardant phase change material combined with aerogel felt

Phase change materials (PCMs) are susceptible to fire and may accelerate heat transfer when thermal runaway propagation (TRP) in lithium-ion battery (LIB) modules, requiring the design and safe use of insulation structures with excellent flame-retardant properties. In this work, the sandwich structure composed of flame-retardant phase change material (FRPCM) combined with aerogel felt (AEGF) is used to study the inhibitory effect on TRP of pouch battery modules (BMs). The structural materials are applied between cells, and the changes of temperature, voltage, mass and other parameters in the TRP process are analyzed by changing the thickness of FRPCMs and AEGFs, and the changes of heat flux of materials were also qualitatively analyzed. The results show that the increase of FRPCM and AEGF thickness can increase the interval time of TRP and reduce the overall thermal risk of the BMs. Compared to Test-1, the increase in TRP time between cells 1 and 2 in Test-2 to Test-5 ranged from 52.7% to 358.7%, and the longest thermal runaway interval reached 844 s. Both the structural materials in Test-6 and Test-7 block the TRP. Combining the thermal conductivity of PCMs and the thermal insulation properties of AEGFs, this work can effectively conduct heat to the environment and block the TRP when applied to BMs, which provides a valuable reference for efficient inhibition and blocking of TRP.

Mechanical, Flame-Retardant and Dielectric Properties of Intumescent Flame Retardant/Glass Fiber-Reinforced Polypropylene through a Novel Dispersed Distribution Mode

The application of continuous glass fiber-reinforced polypropylene thermoplastic composites (GF/PP) is limited due to the inadequate flame retardancy of the polypropylene (PP) matrix. Apart from altering the composition of the flame retardants, the distribution modes of flame retardants also impact material performance. In this study, an alternative approach involving non-uniform distribution is proposed, namely, dispersed distribution, in which non-flame-retardant-content layers (NFRLs) and/or low-flame-retardant-content layers (LFRLs) are dispersed among high-flame-retardant-content layers (HFRLs). The mechanical, flame retardant and dielectric properties of GF/PP with intumescent flame retardant (IFR/GF/PP) are investigated comparatively under uniform, gradient, and dispersed distributions of the flame retardants. The results demonstrate that non-uniform distribution exhibits superior flame retardant performance compared to uniform distribution. Dispersed distribution enables IFR/GF/PP to attain enhanced mechanical properties and reduced dielectric constants while maintaining excellent flame-retardant properties.

Bio-based phytic acid/amino acid complex coating for antimicrobial and flame-retardant cotton fabrics

Here, a novel multifunctional coating containing bio-based phytic acid (PA), L-glutamic acid (L-Glu), and trimesoyl chloride (TMC) is constructed by a simple soaking strategy, giving cotton fabrics excellent flame retardancy, washability, and antibacterial properties. The coating layer on the cotton surface was prepared via the electrostatic and hydrogen bonding between PA and L-Glu, accompanied by the interface polymerization between PA, L-Glu, and TMC. Among them, the limiting oxygen index value of the treated cotton fabrics (C2 and C2-TMC) was as high as 40 %. During the vertical flammability test, both C2 and C2-TMC cotton showed self-extinguished behavior with a short damaged length (≤50 mm). Remarkably, the LOI of C2-TMC sustained a high value (30 %) even after 300 laundering cycles, maintaining its self-extinguishing behavior in the vertical combustion test. Additionally, in the cone calorimetry test, peak heat release rate and total heat release of treated cotton were lower than control cotton. Surprisingly, after 30 or 60 laundering cycles, the C2-TMC cotton exhibited excellent antibacterial activity against Escherichia coli, Staphylococcus aureus, and Candida albicans due to the continuous exposure of PA and L-Glu. Moreover, the coating layer on the cotton surface had little impact on the mechanical properties and feel of the fabric.

Schiff base derivative flame-retardant endowing epoxy resin with toughness, transparency, and high flame retardancy

In this study, a novel phosphorus-containing flame retardant, SMAE, was prepared through a nucleophilic addition of N,N'-bis(salicylidene)ethylenediamine (SAED) and phenyl hypophosphite. SMAE can dissolve well in epoxy resin and provides molecular-level flame retardancy. By using SMAE as a co-curing agent and DDM to cure epoxy resin, EP/SMAE composites with excellent flame retardancy and good mechanical properties were obtained. As the dosage gradually increases, the limited oxygen index (LOI) values continue to rise. At a 5 % dosage, the Limiting Oxygen Index (LOI) value can reach 39.7 % and meet the UL 94 V-0 standard. It is observed that SMAE mainly exerts a blowing-out effect in EP. In addition, the use of SMAE as a co-curing agent can improve the impact strength of EP. The impact strength of 5 % SMAE/EP can reach 14.15 kJ/m2, which is 25 % higher than that of pure EP.

Eco-friendly multifunctional coating for polyester-cotton blended fabrics with superior flame retardancy and antibacterial properties

Since the fire hazards of polyester-cotton blended (PTCO) fabrics and the hidden dangers of bacterial infection concerns caused by the contained cotton fiber, the design of flame retardant and antibacterial PTCO fabrics has received considerable attention. In this work, flame-retardant PTCO fabrics with satisfactory antibacterial properties were fabricated via a convenient and eco-friendly impregnation treatment involving guanidine phosphate (GP) and polyethylenimine (PEI). The prepared PTCO fabrics demonstrated excellent flame retardancy with a high limiting oxygen index value of 30.5 % and self-extinguishing capability, the damaged length was only 34 mm in the vertical flammability test. Furthermore, the peak heat release rate and the total heat release of coated PTCO fabrics were reduced significantly by 49 % and 38 %, respectively, indicating a substantial enhancement in fire safety. According to the analysis of the char residues and volatiles, GP presented great catalytic carbonization property, and PEI assisted the formation of the dense and stable carbon layer. The stable carbon layer effectively restricted mass and oxygen transfer between the PTCO fabrics and the environment. In addition, the introduction of PEI also produced more nonflammable gases to enhance the flame retardancy of the PTCO fabrics. Importantly, the GP/PEI coating barely deteriorate the physical and mechanical properties of the PTCO fabrics. The antibacterial rate of the GP/PEI-coated PTCO fabrics against Escherichia coli and Staphylococcus aureus was 99.99 %, similar to that of GP-coated fabrics, indicating the efficacy antibacterial properties of GP, and the addition of PEI did not compromise the antibacterial properties of GP. This work offers an efficient and simple approach to producing multifunctional PTCO fabrics with excellent flame retardancy and antibacterial properties, which are hopeful to expand the promising application of PTCO fabrics.

Achieving heat storage coatings from ethylene vinyl acetate copolymers and phase change nano-capsules with excellent flame-retardant and thermal comfort performances

The heat-storage coatings from ethylene vinyl acetate (EVA) copolymers were developed by incorporating in-situ synthesized phase change nano-capsules (NEPCMs). The coatings were applied to the interior walls of the building, aimed at enhancing thermal storage and flame-retardant performances. Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD) are utilized to evaluate the chemical composition of the NEPCMs. At the same time, the thermal properties and microstructure of NEPCMs and the coatings are analyzed using differential scanning calorimetry (DSC) and scanning electron microscopy (SEM). The enthalpy of NEPCMs is 158.14 J/g, while that of heat-storage coatings is 56.45 J/g. NEPCMs and heat-storage coatings exhibit excellent thermal storage performance even after 200 heating-cooling cycles, demonstrating the excellent thermal stability of NEPCMs and heat-storage coatings. Furthermore, excellent flame-retardant properties are also provided by the heat-storage coating. In dynamic heat transfer experiments, under the same conditions, the heat-storage coatings were capable of maintaining the chamber in the thermal comfort zone (24–28 °C) for 141 min, while the conventional coatings lasted only 34 min. The results show that incorporating heat-storage coatings can effectively enhance the thermal regulation performance of interior walls and improve the thermal comfort of indoor environments. Therefore, heat-storage coatings hold a high potential for application in energy-saving buildings.

A zinc-embedded multicomponent copolymer customized for polypropylene and its synergistic flame-retardant effect and outstanding mechanical properties

The poor compatibility between the common polar intumescent flame-retardant system (IFR) and the nonpolar polypropylene (PP), as well as the high additive amount, seriously impacts the mechanical properties of the composites. This study introduced collaborative flame-retardant technology to construct block copolymer flame retardants and prepared a zinc-embedded multicomponent copolymer (PM-Zn2+) customized for PP composites. In the PM-Zn2+ system, zinc oxide was embedded into the copolymer composed of piperazine phosphate oligomer and melamine phosphate. PM-Zn2+ exhibited an amorphous structure with extremely low crystallinity and demonstrated specific morphological adaptability. The PM-Zn2+ were well dispersed in the PP matrix and changed their morphology during processing. When applied to PP, excellent flame retardancy and mechanical properties were obtained by using a minimal amount of flame retardants (20 %). PM-2 %Zn2+ gave PP an LOI value of 31.5 %, and achieved a UL94 V-0 rating (1.6 mm thick), exhibiting a lower heat release rate and smoke release. The flame-retardant mechanisms of PM-Zn2+ mainly involved the synergistic and aggregative effects. Transition metal zinc synergistically interacted with polyphosphate groups to create a charring barrier effect and enhance synergistic smoke suppression, leading to a significant reduction in combustion intensity. In comparison to the Mix-Zn/PP composites, the mechanical properties of PM-Zn2+/PP were significantly enhanced due to the specific morphological adaptability and improved compatibility. The elongation at break increased significantly from 15.6 % to 627.9 %, marking a remarkable improvement of 40-fold improvement, while the impact strength rose from 23.7 kJ/m2 to 54.3 kJ/m2, representing a 129 % enhancement. Finally, the zinc-embedded multicomponent block copolymer offers a promising approach to developing high-performance flame-retardant polypropylene materials.

Development of effective coloured flame-retardant finishing for cotton fabric

Coloured flame-retardant (FR) dyes are important for applying cotton textile materials. In this study, we have developed flame-retardant coloured cotton fabric (FR@Coloured cotton fabric) using FR-Vat dye. The flame retardant vat dye (FR-Vat dye) was synthesized by the phosphorus group functionalization on active nitrogen and oxygen sites of vat dye, which was further dyed on cotton fabric called FR@Coloured cotton fabric. The synthesized FR@Coloured cotton fabric showed excellent flame retardancy and sustained for 315 s on continuous flame exposure. In contrast, only dyed cotton fabric entirely burned within 18 s. We observed excellent limiting oxygen index (LOI), i.e., 35 % and vertical flammability (char length) value, i.e., 3 cm, for synthesized FR@Coloured cotton fabric. This excellent flame-retardant property provides it an ideal material for practical application and opens a new window for synthesizing coloured flame-retardant fabrics with other dyes and broadens the flame-retardant area for different applications.

Preparation and Modification of Flexible Polyurethane Foam for Effective Flame Resistance and Sound Absorption

Polyurethane foam as an important sound absorption material is limited by the poor flame resistances in building field, but the modifications of flame resistances tend to have adverse effects on the sound absorption performance. Herein, dibutyltin dilaurate and triethylenediamine are used simultaneously as catalysts, and four new types of flame retardant polyether polyols (FPMPO) are synthesized and combined with modified expanded graphite (PEG) to prepare the flame resistance flexible polyurethane foam (FFPUF) by one-step method. The results show that the combination of the two catalysts can control the cell structure of FFPUF availably for sound absorption. The FPMPO have little negative influence on the cell morphology and the sound absorption performance of FFPUF, but the increase of flame resistances is finite due to the limited amount of FPMPO. In order to improve the flame retardant properties further, the FPMPO and the PEG are combined in the modification. Benefitting by the effective control structure and the modification with composite flame retardant, the FFPUF shows excellent sound absorption and flame retardant properties. The LOI value of FFPUF is 33.4 and the vertical burning level reaches V-0, and the average sound absorption coefficient maintains 0.68 in the 800-6300 Hz range.

Synthesis of CoMn‐LDH@MXene Hybrid Materials as Flame Retardant to Effectively Improve the Fire Safety of Thermoplastic Polyurethane

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

Synergistic effects of organosilicon flame retardant and DOPO-based reactive compatibilizer for high performance PC/PBT composites

PC/PBT alloy is flammable resulting in fire safety hazards in practical applications and the existing flame retardants have a great influence on the mechanical properties, which limits its application range. Therefore, it is an urgent problem to improve the flame retardancy of PC/PBT alloy while taking its mechanical properties into account. Herein, a novel flame retardant and reactive compatibilizer was synthesized by grafting 9,10-dihydro-9-oxa-10-phosphophenanthrene-10-oxide (DOPO) onto ethylene-methyl acrylate-glycidyl methacrylate (EMA-GMA), named as DOPO-EG, to improve the flame retardancy and mechanical properties of PC/PBT alloy simultaneously. Additionally, based on the effective synergistic effect of enhancing the charring and flame retardancy between silicon and phosphorus, the organosilicon flame retardant (RMSi) is introduced and compounded with DOPO-EG to prepare excellent flame retardancy PC/PBT/DOPO-EG/RMSi composites. The results showed that the PC/PBT/DOPO-EG/RMSi composites with 10 wt% DOPO-EG and 8 wt% RMSi (CBE10P10Si8) reached UL-94 V-0 rating and the peak of heat release rate (PHRR) and total heat release rate (THR) of CBE10P10Si8 decreased by 42% and 16% respectively. This is due to the fact that DOPO is cracked into phosphorus radicals to capture and eliminate the active H and OH radicals, inhibiting the chain free radical reaction, and RMSi is enriched on the surface of CBE10P10Si8 to form an inorganic oxygen insulation protective layer during combustion. The impact strength of CBE10P10Si8 increased from 5.8 kJ/m2 to 11.9 kJ/m2. The improvement of impact strength is owing to the existence of DOPO-EG which promotes the formation of the interface layer between PC and PBT phases, resulting in the transfer of stress between the two phases. This work provides a new method for the preparation of PC/PBT alloy with excellent flame retardancy and mechanical properties, and also provides a certain reference value for the research of flame retardancy and toughening modification of polymer composites.

Mechanical and Fire Properties of Flame-Retardant Laminated Bamboo Lumber Glued with Phenol Formaldehyde and Melamine Urea Formaldehyde Adhesives.

This study investigated the effects of different adhesives, phenol formaldehyde (PF) and melamine urea formaldehyde (MUF), on the mechanical and fire properties of flame-retardant laminated bamboo lumber (LBL). The results demonstrated that the flame-retardant treatment using phosphorus-nitrogen-boron compounds endowed the LBL with excellent flame retardancy and smoke suppression properties, even though the bending strength and bond shear strength were slightly reduced. The PF-glued LBL exhibited superior mechanical and shear properties to the MUF-glued ones, primarily due to its higher processing temperature and deeper adhesive penetration. In addition, the MUF-glued flame-retardant LBL displayed better heat release reduction and smoke suppression properties than the PF-glued LBL, which resulted from the synergistic flame retardancy between the melamine element in MUF and the applied flame retardant. The analysis of the influence of adhesive type on the mechanical and fire properties of flame-retardant LBL holds significant importance for the future design and production of high-performance LBL material.

High flame retardant composite phase change materials with triphenyl phosphate for thermal safety system of power battery module

The thermal safety of battery pack has attracted much attention accompany with the growth in electric vehicles (EVs) in recent years. Although various battery thermal management systems (BTMS) are investigated by many research, the thermal runaway propagation (TRP) of battery packs under extremely abused conditions is just at the level of structural design and theoretical model. How to explore an innovative technology to improve the integrated thermal safety including the BTMS and TRP is still a great challenge. In this study, a multifunctional flame-retardant paraffin (PA)/styrene-butadiene-styrene (SBS)/expanded graphite (EG)/methylphenyl silicone resin (MPS)/triphenyl phosphate (TPP) composite phase change material (PSEMT) has successfully prepared. Besides, it has applied in 26650 ternary power battery modules. When the proportion of MPS and TPP is 1:2, the experimental results reveal that PSEMT possesses high thermal stability, and excellent flame-retardant properties owing to synergistic flame-retardant effect with phosphorus and silicon. Further, the cylindrical 26650 battery module with PSEMT exhibits optimum thermal management performance. Even at 2C discharge rate after ten cycles, the maximum operating temperature of battery module can still be maintained below 50 °C, and the maximum temperature difference is controlled within 4.6 °C. Additionally, it displays an excellent thermal runaway suppression through triggering by multiple heat sources. What's more, the battery with PSEMT can suppress the peak temperature and delay the occurrence time of thermal runaway. Therefore, it can be induced that the battery module with PSEMT can effectively avoid heat accumulation and significantly reduce its thermal safety risk. This study offers a new solution with promising prospects from the perspectives of energy storage and EVs, for balancing the temperature inconsistencies in batteries and suppressing thermal runaway in the battery packs.

A novel phosphorus/nitrogen-containing polyacrylonitrile fiber with excellent flame retardancy and mechanical properties

To improve the flame retardancy, smoke suppression and mechanical properties of polyacrylonitrile (PAN) fiber, it was first modified with diethylenetriamine to prepare the aminated PAN fiber (A-PAN). Second, diethyl phosphite (DEP) was grafted onto the A-PAN to fabricate flame retardant PAN fiber (DEP-A-PAN). XPS and FTIR analysis confirmed that phosphorus and nitrogen elements were covalently bonded to the surface of PAN fiber. TGA revealed that the incorporation of DEP promoted char formation of PAN matrix and suppressed the thermal degradation. DEP-A-PAN exhibited a significantly reduced peak heat release rate (pHRR) compared to the control sample. Moreover, the limiting oxygen index (LOI) of DEP-A-PAN was up to 34.3 %, and remained at 26.6 % even after 50 laundering cycles (LCs), demonstrating excellent durable flame retardancy. Interestingly, DEP-A-PAN exhibited improved tensile strength of 2.97 cN/dtex. This work developed a simple and feasible method for preparing mechanical-enhanced flame retardant and smoke suppressive PAN fiber, which could be large-scale preparation.

Sustainable adhesives for ultra-composites from biomass powder

Green adhesives with roborant performance are still a challenge. Here, we prepare a sustainable adhesive directly from biomass-based lignin and furfural in green deep eutectic solvent (DES, ChCl/urea), and then composite materials have been prepared by mixing the as-prepared adhesives with various kinds of biomass powder following a hot-pressing process. The composite material made from bamboo powder shows excellent multifunctional properties. The bending strength reaches 46.06 MPa while the bending modulus even exceeds 10 GPa, and it also has a super high internal bonding strength of 4.54 MPa. The composite also has excellent flame-retardant properties, with a flame-retardant grade of V0. In addition, the LCA-MB has high heat insulation, water resistance, thermal stability, and mildew resistance. In addition, the composite is not only biodegradable but also extremely low-cost, which is much cheaper than most petroleum-based plastics.

Preparation and properties of fiber-reinforced polybenzoxazine composite aerogels based on freeze drying and ambient pressure drying methods

Polybenzoxazine aerogels have gained much attention as a new type of polymeric aerogels in the field of flame resistant materials. Herein, a unique method for the preparation of fiber-reinforced PBa composite aerogels has been reported using polyvinyl alcohol (PVA) and carboxymethyl cellulose (CMC) as dispersion carriers through freeze-drying for surface modified basalt fibers (Z@BF). Bisphenol-A type benzoxazine (Ba) monomer was used as the matrix, which infiltrated into the carrier for dispersed fibers to obtain a PBa composite gel by sol-gel method. Solvent exchange and ambient drying techniques were used to obtain the final composite aerogel samples. Z@BF formed a double-network structure with the aerogel matrix, which resulted in 55.43% increase in compressive strength, a low volumetric shrinkage (27.46%), and density (0.19–0.21 g cm3) of the prepared aerogel. The addition of Z@BF increased the residual carbon content (59.6% at 800 °C) in the aerogel, while reducing the total heat release rate by 36.9% and the peak heat release rate by 60.61%. Besides, the aerogels possessed excellent self-extinguishing property, and the self-extinguishing time was only 1.31 s after flame burning at 1200 ℃ for 10 s. The composite aerogels obtained by this combination of atmospheric pressure drying and freeze-drying techniques not only possessed high mechanical strength and excellent flame retardant properties, but also provided a new idea for the preparation of fiber-reinforced PBa aerogels. This would further expand the potential use of PBa aerogels in flame retardant materials.

Eco-Friendly Flame-Retardant Phase-Change Composite Films Based on Polyphosphazene/Phosphorene Hybrid Foam and Paraffin Wax for Light/Heat-Dual-Actuated Shape Memory.

Multiactuated shape memory materials are a class of promising intelligent materials that have received great interest in the fields of self-healing, anticounterfeiting, biomedical, soft robotic, and smart thermal management applications. To obtain a light/heat-dual-actuated shape memory material for thermal management applications in fire safety, we have designed a type of halogen-free flame-retardant phase-change composite film based on polyaryloxyphosphazene (PDAP)/phosphorene (PR) hybrid foam as a support material and paraffin wax (PW) as a phase-change material (PCM). PDAP was synthesized as a flexible foam matrix through the ring-opening polymerization of hexachlorocyclotriphosphazene, followed by a substitution reaction of aryloxy groups. The porosity of the PDAP foam is improved by introducing PR nanosheets, facilitating a high latent heat capacity of the PDAP-PR/PW composite films for thermal management applications. The PDAP-PR/PW composite films can implement rapid shape recovery within 65 s in the heating process, which is much shorter than that of the corresponding film without PR nanosheets (185 s). Furthermore, the PDAP-PR/PW composite films also exhibit light-actuated shape memory behavior thanks to their good solar-to-thermal energy absorption and conversion contributed by PR nanosheets as a highly effective photothermal material. More importantly, the presence of PR nanosheets imparts an excellent flame-retardant property to the PDAP-PR/PW composite films. The PDAP-PR/PW composite film can be self-extinguished within 2 s after the flame. Through an innovative integration of flexible polyphosphazene foam, PR nanosheets, and solid-liquid PCM to obtain a sensitive actuating response to light and heat, this study offers a new approach for developing multiactuated and eco-friendly flame-retardant shape memory materials to meet the requirement of applications with a requirement of fire safety in soft actuators, thermal therapy, control devices, and so on.

A flame-retardant, hydrophobic and thermo-responsive multi-functional fabric: Application in fire-alarm device and self-powered system

Conventional textiles present high flammability and rapid-fire propagation, posing significant fire hazards in daily life. In this study, nylon and cotton fabrics were endowed with flame retardancy and hydrophobicity, and a low-cost and eco-friendly flame-retardant and hydrophobic fabric-based triboelectric nanogenerator (FHF-TENG) was fabricated through integrated and modular design. This TENG exhibits excellent flame-retardant properties (self-extinguishment and melt-dripping resistance) and high energy harvesting efficiency (with a maximum output power of 173 mW/m2). Furthermore, the FHF-TENG was successfully employed in a fire-alarm system as a self-powered sensor, providing fire-warning signals for evacuees and fire rescue operations. This work advances the development of fire rescue field and showcases innovative application of multifunctional smart textiles in energy harvesting and self-powered sensing.

Balanced Thermal Insulation, Flame-Retardant and Mechanical Properties of PU Foam Constructed via Cost-Effective EG/APP/SA Ternary Synergistic Modification.

To address the challenge of balancing the mechanical, thermal insulation, and flame-retardant properties of building insulation materials, this study presented a facile approach to modify the rigid polyurethane foam composites (RPUFs) via commercial expandable graphite (EG), ammonium polyphosphate (APP), and silica aerogel (SA). The resulting EG/APP/SA/RPUFs exhibited low thermal conductivity close to neat RPUF. However, the compressive strength of the 6EG/2APP/SA/RPUF increased by 49% along with achieving a V-0 flame retardant rating. The residual weight at 700 °C increased from 19.2 wt.% to 30.9 wt.%. Results from cone calorimetry test (CCT) revealed a 9.2% reduction in total heat release (THR) and a 17.5% decrease in total smoke production (TSP). The synergistic flame-retardant mechanism of APP/EG made significant contribution to the excellent flame retardant properties of EG/APP/SA/RPUFs. The addition of SA played a vital role in reducing thermal conductivity and enhancing mechanical performance, effectively compensating for the shortcomings of APP/EG. The cost-effective EG/APP/SA system demonstrates a positive ternary synergistic effect in achieving a balance in RPUFs properties. This study provides a novel strategy aimed at developing affordable building wall insulation material with enhanced safety features.

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.