Fire Safety Properties Research Articles

Ensuring fire safety: compliance tests for the use of polystyrene foam in facades systems

Ensuring fire safety is the most important thing in the construction industry, especially when it comes to facade materials. The inherent flammability of polystyrene foam poses significant safety concerns, especially when integrated into facade systems. Therefore, the main focus is on meeting the strict flammability requirements set for construction products, which are assessed by applying rigorous test procedures. This study focuses on the fire resistance testing of a facade system using EPS 70 with graphite additives. The system has been evaluated according to the strict DIN 4102-20 standards. Tests were conducted under real-world conditions to gain insight into the performance of the EPS 70 in real-world fire scenarios. Temperature measurements were taken at various points in the facade system, including at least 3.5 meters above the combustion chamber. The results showed that the temperature does not exceed 500 °C, so it is possible to quantify the thermal properties of the material and the ability to prevent the vertical spread of fire. After the tests, detailed post-test inspections were carried out to evaluate the internal flame propagation after removing the top layer of plaster. The study confirms that polystyrene foam EPS 70 with graphite additives meets the fire safety requirements of DIN 4102-20, which suggests that it can be used more widely in building facades to improve fire safety in residential and commercial buildings. The study highlights the importance of adhering to installation standards, emphasizing the need for accurate installation practices. It also encourages the development of new composite materials with similar or improved fire safety properties, laying the foundation for further innovations in fire-resistant materials

High fire-safety epoxy thermosets with a macromolecular phosphorus-nitrogen containing flame retardant at a low loading

In this article, a macromolecular phosphorus-nitrogen containing flame retardant defined as PDPSB was incorporated into epoxy resins (EP). The fire safety, flame-retardant mechanism and mechanical properties of EP/PDPSB thermosets were systematically investigated. The EP-5 sheets containing 5 wt% PDPSB passed V-0 level in the vertical burning tests (UL-94) with a high limiting oxygen index (LOI) value of 30.9%. The results of cone calorimeter tests (CCT) revealed that both the emission of heat and smoke for EP/PDPSB thermosets was substantially suppressed. Compared to pure EP, the values for peak of heat release rate (PHRR), total heat release (THR) and total smoke production (TSP) of EP-5 were dropped by 19.4%, 31.5% and 33.0%, respectively. Remarkably, the char residue mass of EP-5 was enhanced by 87.7%. The maximum smoke density (Ds, max) was slashed by 18.9%. Furthermore, the tensile, flexural and charpy impact strength of EP-5 were maintained to 97.3%, 95.1% and 86.9%, respectively. The investigation of flame-retardant mechanism demonstrated PDPSB exerted flame retardant effect both in condensed and gaseous phase by the scanning electron microscopy and energy dispersive X-ray spectroscopy (SEM-EDX), X-ray photoelectron spectra (XPS), laser Raman spectra (LRS) and thermogravimetric-Fourier transform infrared spectroscopy (TG-FTIR). As PDPSB was a one-component multifunctional additive renowned for its exceptional efficiency, it was anticipated to facilitate the advancement of high-performance epoxy thermosets via researching on EP/PDPSB thermosets.

Efficient fabrication of paper nanocomposites for superior flame retardancy and strengthening properties

Innovative and cost-effective paper sheets with superior fire safety and reinforcement properties have been developed. The paper sheets were fabricated via valorization of agricultural waste to paper and then coated with nanoparticles. Paper attained from rice straw was used to create the sheets. Afterward, bentonite sheets were incorporated in these sheets, and finally, PbO nanoparticles were coated on prepared paper nanocomposites. The mass ratio of bentonite sheets was altered. The flammability and mechanical properties of the developed paper nanocomposites were studied. The flame retardancy of developed paper nanocomposite was significantly improved achieving LOI value of 24% compared to 20% for bentonite and PbO nanoparticle-free sample. Additionally, the tensile strength was improved recording 44% enhancement compared to unmodified sample. Furthermore, the flame retardancy mechanism was proposed and studied.

Cyclodextrin-based host-guest hierarchical fire retardants: Synthesis and novel strategy to endow polylactic acid fire retardancy and UV resistance

β-Cyclodextrin (β-CD) with a cage-like supramolecular structure possesses the hydrophobic internal ring and external hydroxyl groups, which are beneficial for intramolecular interactions known as “host-guest” chemistry. This study presents a β-CD-based three-functions-in-one and host-guest fire retardant (βCD-MOF@Schiff base), which incorporates self-crosslinking Schiff base into its cavity and modification of its surface by metal-organic framework (MOF). With the presence of 5 wt% of βCD-MOF@Schiff base, the LOI value of PLA composites increased to 29 % and showed 15 %, 17 % and 62 % reductions in peak heat release rate (pHRR), total heat release (THR), and the yield of hazard gas carbon monoxide, respectively. The mode action of FR on fire retardation of PLA showed that the FR promoted the char formation with higher thermal stability and graphitization, and modified the decomposition path of PLA. Additionally, the PLA composites exhibited enhanced UV resistance in the UVA and UVB areas with improved UV absorbance and the UPF values improving and doubling. This work develops a new approach to preparing biodegradable FR, which simultaneously endows fire safety and anti-UV properties for PLA.

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.

Ionic-physical–chemical triple cross-linked all-biomass-based aerogel for thermal insulation applications

Aerogels, as a unique porous material, are expected to be used as insulation materials to solve the global environmental and energy crisis. Using chitosan, citric acid, pectin and phytic acid as raw materials, an all-biomass-based aerogel with high modulus was prepared by the triple strategy of ionic, physical and chemical cross-linking through directional freezing technique. Based on this three-dimensional network, the aerogel exhibited excellent compressive modulus (24.89 ± 1.76 MPa) over a wide temperature range and thermal insulation properties. In the presence of chitosan, citric acid and phytic acid, the aerogel obtained excellent fire safety (LOI value up to 31.2%) and antibacterial properties (antibacterial activity against Staphylococcus aureus and Escherichia coli reached 81.98% and 67.43%). In addition, the modified aerogel exhibited excellent hydrophobicity (hydrophobic angle of 146°) and oil–water separation properties. More importantly, the aerogel exhibited a biodegradation rate of up to 40.31% for 35 days due to its all-biomass nature. This work provides a green and sustainable strategy for the production of highly environmentally friendly thermal insulation materials with high strength, flame retardant, antibacterial and hydrophobic properties.

Phosphononitrile based bismaleimide electronic packaging substrate with both fire safety and dielectric properties: Assisting 5G communication

Due to the high polarizability of traditional flame retardants, it is difficult to meet the excellent dielectric properties and flame retardancy required for electronic packaging materials. Therefore, we have designed a novel linear polyphosphazene that can balance the dielectric properties and flame retardancy of bismaleimide (BMI) composites. Here, fluorinated aromatic ring structure with the large freedom volume is connected to the main chain of polydichlorophosphazene (PDCP) as a side group, resulting in multifunctional fluorinated linear polyphosphazene (PBTFP). Attributed to the excellent P/N/F combination flame retardant strategy, extremely low polarizability, and large molecular free volume, PBTFP simultaneously improves the dielectric properties and flame retardancy of the BMI composites, including UL-94 rating of V0, and a dielectric constant (Dk) as low as 2.69. In addition, as an elastomer, PBTFP exhibits positive effects on improving the hydrophobicity and toughness of BMI. Therefore, through a simple affinity substitution reaction, we prepared a multifunctional fluorinated linear polyphosphazene modified BMI based electronic packaging substrate material that can be applied to 5G high-frequency communication.

Non-covalently functionalized black phosphorene to efficient flame retardant EVA with improved mechanical properties

The development of flame-retardant polymer materials play a vital role in reducing fire hazards and protecting both lives and property. Black phosphorus (BP) is an extremely promising flame retardant since its synergistic flame retardancy with different modifiers. Nevertheless, the issue of unven dispersion within the polymer matrix has severely restricted its practical applications. Herein, BP nanosheets functionalized with ionic liquid (IL-BP) were prepared and then compounding with EVA to improve the mechanical and the flame-retardant properties of EVA matrix. The results demonstrated enhanced compatibility of IL-BP nanosheets within the EVA matrix, leading to the 1.5 %IL-BP/EVA composite displayed a 25 % and 9.6 % increase in tensile strength and elongation at break, respectively. Remarkably, the flammability test results demonstrated that the 1.5 %IL-BP/EVA sample featured a significant decrease of 18.1 % and 21.5 % in total heat release (THR) and peak heat release rate (PHRR), respectively. Meanwhile, the composite also achieved a V-0 rating in UL-94 test and demonstrated superior resistance to melt dripping. The flame-retardant mechanisms of IL-BP/EVA composites in both gas phase and condensed phase were studied. This work provides a promising strategy to design synergetic flame retardants that simultaneously enhanced the fire safety and mechanical properties of EVA.

Arone-containing cyclomatrix-type polyphosphazene hybrid microspheres for epoxy resin: Enhancing fire safety and mechanical properties

Arone-containing cyclomatrix-type polyphosphazene hybrid microspheres (PZK) were synthesized to enhance both the fire safety and mechanical performance of epoxy resin (EP). The chemical structure and micro-morphology of PZK were characterized using Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), transmission electron microscopy, and X-ray photoelectron spectroscopy. Subsequently, PZK was employed in fabricating EP thermosets. Thermal properties of the PZK modified EP thermosets were comprehensively assessed through thermalgravimetric analysis (TGA) and dynamic mechanical analysis. The results indicate that PZK endowed EP with enhanced char yield and storage modulus, attributed to its exceptional thermal stability and distinctive microsphere structure. Additionally, with only a 1.5% loading of PZK, EP achieved a UL-94 V-1 rating during vertical flame testing, accompanied by an increased limiting oxygen index of 28.3%. Additional analysis with a cone calorimeter demonstrated that the addition of PZK markedly reduced the peak heat release rate, total heat release, fire growth rate, and total smoke production of EP, indicating notable efficacy in suppressing heat and smoke release. Char residue and pyrolysis products were analyzed using SEM, TG-FTIR, and pyrolysis gas chromatography-mass spectrometry, revealing that PZK effectively inhibits the release of combustible gases from EP during thermal decomposition. The expected generation of Ph—O• radicals from arone units in PZK suggested a gaseous free radical trapping mechanism. The phosphazene framework played a crucial role in forming condensed-phase char due to its exceptional thermal stability. Consequently, PZK exhibited a typical biphasic flame-retardant mechanism for EP. Notably, the study observed that the introduction of PZK simultaneously enhances the tensile strength, flexural strength, and modulus of EP, with a particularly significant improvement observed in impact strength. This research expands the scope of investigation into the preparation and flame-retardant application of cyclomatrix-type polyphosphazene hybrid microspheres in polymers.

Bismuth oxyiodide nanorods towards improvements in fire safety and mechanical properties of natural rubber

Fire safety represents an enduring challenge in the realm of polymer-based nanocomposites, significantly limiting their application. The utilization of bismuth oxyiodide in flame retardant applications offers advantages such as increased surface area for improved interaction with combustible materials, the formation of a uniform flame retardant layer at the interface, and enhanced thermal stability. Hence, this work explored a facile strategy to synthesize bismuth oxyiodide nanorods by hydrothermal method combined with ball milling in anticipation of constructing an efficient flame retardant system. The bismuth oxyiodide nanorods dispersed relatively uniformly in the natural rubber matrix and endowed natural rubber nanocomposites with enhanced mechanical properties and fire-safety. The resultant natural rubber nanocomposite containing 5 wt% of bismuth oxyiodide showed a 36 % improvement in the tensile strength and a 39 % increase in the tear strength compared to those of the neat natural rubber. Cone calorimeter tests revealed that the introduction of 5 wt% bismuth oxyiodide to natural rubber matrix remarkably reduced the peak of heat release rate and peak smoke production release by 22 % and 25 %, respectively. A rational flame retardant mode of action for bismuth oxyiodide nanorods was proposed based on the analysis of pyrolysis fragments and char residues. Hence, this work provides a green and feasible method to prepare bismuth oxyiodide nanorods for flame retardant natural rubber products.

Life cycle assessment of mycelium-based composite materials

Mycelium-based composites (MBCs) show promising acoustic and thermal insulation, fire safety, and mechanical strength properties and are suitable for multiple applications in the construction, packing or furniture industry. A life cycle assessment confirmed climate change and fossil energy demand benefits in a laboratory scale production modelled for Germany. MBC are associated with 0.3668 kg CO2e / kg MBC (EN 15804 + A2). The electricity required to run MBC production and hemp cultivation, if used as a substrate, contribute significantly to the environmental impact categories considered. Compared to conventional insulation materials, environmental advantages of MBC can be confirmed. Particularly, MBC has a better climate change impact than extruded polystyrene, quadcore sandwich panel, foam concrete and rockwool. However, since the end-of-life is not assessed, the wood-fiber and straw panels perform better regarding climate change. Moreover, MBC has lower fossil energy demand than all conventional insulation materials. Land-use and water demand are higher than for conventional materials.

A rare‐earth‐based nano‐flame retardant with 2D MXene for improving fire safety and mechanical property of thermoplastic polyurethane composites

AbstractA kind of rare earth flame retardant, two‐dimensional lamellar compounds (MXene) loading with cerium phosphate nanorod, MXene@CePO4 (CMX) was prepared by hydrothermal and electrostatic adsorption methods. It was then applied in thermoplastic polyurethane (TPU). With the 3 wt% addition of CMX improving the mass rate of residual char from 4.42 wt% to 11.33 wt% compared to pristine TPU, there were reductions of 53.8%, 12.3%, and 24.7% in peak heat release rate (pHRR), total heat release (THR), and smoke density maximum (Ds max), respectively. Moreover, the TPU/CMX composites were shown to have superior mechanical properties compared with pristine TPU. For TPU/CMX‐3.0, there was a visible improvement in tensile strength (TS) and elongation at break (EB) of 12.5% and 54.1% respectively, compared to pure TPU. The analysis of the flame retardancy mechanism of TPU/CMX shows that CMX plays an effective role in quenching free radicals in the gas phase and promotes char formation of TPU in the condense phase. Therefore, this paper offers a new solution for designing multifunctional rare earth flame retardants that are applied in TPU, thereby extending its application in industries and daily life.

Three-in-one novel flame retardant through grafting organophosphorus onto Fe-MOF functionalized Mg(OH)2 for improving fire safety and mechanical properties of PBS composites

As one typically sustainable polymer material, poly(butylene succinate) (PBS) is highly necessary to improve its flame retardancy and simultaneously maintain satisfied mechanical performances. In this study, “three-in-one” novel flame retardant was synthesized through grafting organophosphorus onto Fe-MOF functionalized Mg(OH)2 (labeled as MH@Fe-MOF-P), then it was introduced into PBS matrix to investigate its effect on flame retardancy and mechanical properties. The results indicated that PBS/20MH@Fe-MOF-P exhibited excellent flame retardancy, including that the LOI was 29.6%, the UL-94 rating reached to V0, and the peak of heat release rate (PHRR) decreased by 82.1%. The flame retardant mechanism was ascribed to the synergistic effect of Mg(OH)2, Fe-MOF and organophosphorus on delaying the decomposition and catalyzing the carbonization of PBS. Meanwhile, PBS/20MH@Fe-MOF-P presented better mechanical performances than PBS/20MH and PBS/20MH@Fe-MOF composites, resulting from the special structure of MH@Fe-MOF-P to achieve good dispersion of fillers and strong polymer-filler interface adhesion. This work provides a novel strategy to modify Mg(OH)2 with high flame retardant efficiency, and also broadens the practical applications of PBS materials with balanced comprehensive performances.

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.

The influence of well-dispersed mesoporous hydroxystannate ferrate anchored magnesium hydroxide hybrids on enhancing interfacial compatibility and fire safety of EVA/EPDM composites

In this work, an innovative methodology for enhancing the fire safety of EVA/EPDM (EE) composites by employing an in-situ encapsulation technique to integrate magnesium hydroxide (MH) within the mesoporous hydroxystannate ferrate (mHSF) framework via ion-driven self-assembly. Comprehensive characterization involving X-ray diffraction, scanning electron microscopy, and transmission electron microscopy was employed to investigate the structure, elemental composition, and morphology of the resulting hybrids. In comparison to EE/MH composites, the MH@mHSF hybrids exhibited favorable dispersion within the EE matrix, demonstrating minimal aggregation. Upon incorporation of MH@mHSF hybrids, a significant reduction in peak heat release rate and total heat release (73.5 and 50%) compared with pristine EE, and an achievement in limiting oxygen index value of 32.5% from 19% for pristine EE was achieved. Notably, when contrasted with the findings of EE/MH/mHSF, the EE/MH@mHSF composite showcased superior tensile strength and enhanced fire safety properties. This improvement can be ascribed to the catalytic charring behavior and adsorption effects facilitated by well-dispersed MH@mHSF hybrids within the polymer matrix. Thermogravimetric analysis/infrared spectrometry (TG-IR) corroborated a substantial reduction in organic volatiles and the suppression of carbon monoxide emissions upon integration of MH@mHSF hybrids, underscoring the alleviation of fire hazards. The observed synergy of the catalytic and adsorption effects of mesoporous HSF, combined with the flame-retardant characteristics of MH, plays a pivotal role in the suppression of smoke generation.

Designing of layered double hydroxide, metal oxides, and borate‐reinforced thermoplastic polyurethanes composites

AbstractThermoplastic polyurethanes (TPUs) are widely used in automotive, medical, and marine applications due to their excellent properties such as high tensile strength, flexibility, and durability. However, the presence of isocyanate groups in TPUs increases their flammability and produces toxic gases during combustion, limiting their application. Here, the study aims to modify TPUs to improve their flame‐retardant behavior. Various fillers such as metal oxides, Layer double hydroxides (LDH), and borates were synthesized and added into the TPU matrix by using extrusion and compression molding. At a 10% loading of Zinc‐Magnesium oxides, a limiting oxygen index (LOI) of 25% was achieved, along with no dripping and complete burning cessation within 20 s. Magnesium aluminium LDH exhibited maximum flame retardancy at a 5% loading, with an LOI of 25%, burning cessation within 23 s without dripping, and a V1 rating. Overall, this research aims to develop TPU composites with improved fire safety properties by incorporating various additives. The synthesized additives showed potential for enhancing the mechanical, thermal, and flame‐retardant properties of TPU.

Synthesis of FePP@MoS2@Ni‐MOF composites for improving thermal and flame retardant safety properties of polyurea

AbstractPolyurea (PUA) is widely used as a coating in construction, tunnels, bridges, and other fields because of its excellent performance. However, its combustion emits toxic gases and smoke, hindering escape and posing potential fatality risks. Enhancing the flame retardancy of PUA is crucial for safety and expanding its applications. The synthesis of two‐dimensional FePP nanosheets was reported in this paper, employing the solvothermal method, followed by the sequential growth of MoS2 and Ni‐MOF to establish a multilayer composite structure. The elemental composition and morphology of the synthesized FePP@MoS2@Ni‐MOF flame retardants were characterized and analyzed. The flame retardant properties of polyurea composites with varying amounts of FePP@MoS2@Ni‐MOF were investigated using Cone calorimeter tests. The results showed that the prepared flame retardant had good thermal stability and significantly improved fire safety properties. The PUA/FePP@MoS2@Ni‐MOF 3.0 composite exhibited notable improvements compared to pure PUA. Specifically, the peak heat release rate, total heat release rate and peak smoke production rate were reduced by 39.76%, 29.33% and 17.86%, respectively, while total smoke production and total CO production (COP) were reduced by 21.30% and 54.47%. This study provides new insights and experimental basis for the technological development of novel flame retardant coating materials.

Combination effect of ADP‐intercalated kaolinite and ammonium polyphosphate on simultaneously enhancing the flame retardancy and smoke suppression of epoxy resins

AbstractIn this article, ammonium dihydrogen phosphate (ADP) was successfully intercalated into kaolinite (Kaol) to prepare a novel synergist named ADP‐intercalated kaolinite (K‐ADP). The chemical structure of K‐ADP was thoroughly characterized using various analytical methods, and then K‐ADP was combined with ammonium polyphosphate (APP) to enhance the fire safety of epoxy resins (EPs). The flammability results indicate that the combination of K‐ADP and APP exerts super positive effects on reducing the heat release and smoke emission of EPs than the mixture of Kaol and APP. Especially, the EP/8 wt% APP/2 wt% K‐ADP has a super LOI value of 33.2% and reaches a UL94 V‐0 rating accompanying with a 29.1% reduction in total heat release (THR) and a 72.7% reduction in total smoke production (TSP) compared to pure EP. The morphology and component analyses show that the combination of K‐ADP and APP facilitates the formation of more phosphorus‐rich crosslinking and aromatic structures in the condensed phase to enhance the compactness and intumescence of char layer, which effectively segregates heat, combustible compounds and smoke particles. Thermogravimetric analysis shows that the combination of K‐ADP and APP exerts super char‐forming ability in EPs, and the residual weight of EP/8 wt% APP/2 wt% K‐ADP at 800°C increases from 7.8% of pure EP to 19.7%. Mechanical test shows that the addition of K‐ADP displays the less adverse effect on the mechanical properties of EP composites compared to Kaol due to the better compatibility of K‐ADP and epoxy matrix with DSC analysis support.Highlights A novel ammonium dihydrogen phosphate‐intercalated kaolinite (K‐ADP) was synthesized. APP/K‐ADP system exerts super positive effect on reducing fire hazards of EPs. APP/K‐ADP system takes effect in both gas phase and condensed phase. APP/K‐ADP has a satisfying balance between fire safety and mechanical properties in EPs.

Organic copper phosphate-decorated layered double hydroxide to enhance the flame retardancy and smoke suppression of epoxy resin

It is essential to endow epoxy resin (EP) with high fire safety and mechanical properties due to its extensive application. In light of the flame-retardant efficiency and facile agglomeration of layered double hydroxide within polymers, surfactant-intercalated LDH decorated with organic copper phosphate (LDH@ATMP-Cu) was developed via electrostatic assembly. The EP composites containing 3 wt% resultant LDH@ATMP-Cu exhibited comparable tensile strength and slightly enhanced glass transition temperature compared to EP. Moreover, EP/LDH@ATMP-Cu achieved a V-0 rating in UL-94 test, an LOI value of 27.5 %, and sharply reduction of peak heat release rate by 57 % and total smoke production by 31 % in cone calorimeter test. Additionally, the flame-retardant mechanism was investigated by analyzing the char residue and pyrolysis gases. The high-efficiency flame retardancy was involved in the flame inhibition of gaseous water release, as well as the barrier effect of the refractory metal oxide from LDH and the high-quality char residue resulting from the catalytic charring effect of ATMP-Cu in condensed phase. Therefore, simultaneously enlarging the interlayer spacing and enhancing surface functionalization is a highly effective approach to improve the flame-retardant efficiency of LDH for polymers.

Facile construction strategy for intrinsically fire-safe and thermal-insulating bio-based chitosan aerogel

Bio-based aerogels have become a research hotspot in the emerging fields because of their remarkable biocompatibility, degradability and light weight, but their low strength and flammability limits their further application. In this study, chitosan (CS) containing flame retardant element was selected as the matrix, and a lightweight, flame retardant and thermal insulating CS aerogel was successfully prepared by the ion exchange between methylphosphonic acid (MPA) and acetic acid (HAc), and directional freeze-drying technology. The compressive strength and elastic modulus of CS@MPA aerogel were 15.2% and 8.5% higher than that of CS@HAc aerogel due to the 3D cross-linking structure between MPA and CS. Compared with CS@HAc aerogel, CA@MPA1.1 aerogel demonstrated excellent thermal insulating properties, and its thermal conductivity (25.46 mW/mK) was significantly lower than that of air (26.7 mW/mK). The introduction of MPA promoted the degradation and charring of CA@MPA aerogel, and the formation of high quality char layer efficiently exerted the barrier effect. Meanwhile, the phosphorus oxygen radicals and inert gases from the decomposition of CS@MPA aerogels effectively decreased the combustion intensity in gas phase. Therefore, the PHRR and THR of CS@MPA1.1 aerogels were decreased by 91.7% and 69.5% compared to CS@HAc aerogels. In summary, CS@MPA aerogel not only conforms to the current concept of sustainable development, but also possessed excellent thermal insulation, mechanical, and fire safety properties. It is expected to replace the traditional petrochemical-based materials, and shows broad application prospects in the fields of building insulation and energy storage.