Excellent Flame Retardant Properties Research Articles

Preparation and Application of a Urea–Formaldehyde-Blended Guanidinium Azole–Phytic Acid–Copper Flame-Retardant Resin Coating

In this study, environmentally friendly flame retardants capable of efficient flame retardancy at low concentrations in wood were developed. Urea-formaldehyde (UF) resin and guanidinium azole (GZ)-phytate (PA)-copper hydroxide (Cu(OH)2) flame-retardant resin coating blends were prepared using urea, formaldehyde, 3,5-diamino-1,2,4-triazole (GZ), phytanic acid (PA), and copper hydroxide (Cu(OH)2). Employing dioctyl phthalate as the plasticizer and tannic acid as the curing agent, a three-stage reaction was performed to obtain the desired UF-GZ/PA/Cu as a bio-based flame retardant. Thermal evaluations demonstrated that UF-GZ/PA/Cu lost 5% of its mass through decomposition at a temperature of 195.5 ± 2.1 °C, with its maximum decomposition rate being observed at 300.6 ± 1.5 °C, and 29.8 ± 2.5 wt.% of dense residual charcoal being obtained at 800 °C. When applied as a flame retardant coating on wood, the prepared UF-GZ/PA/Cu exhibited excellent flame-retardant properties, forming a continuous dense charcoal residual layer, with a limiting oxygen index of 32.0%, and passing the UL-94 V-0 test. In addition, the heat release rate and total heat release rate of the flame retardant were determined to be reduced by 87.7 and 83.66%, respectively. Overall, this study provides a green and effective method for the preparation of flame-retardant wood.

Fabrication of multifunctional cu-coated melamine foam by electroless chemical deposition technique for thermal management, EMI shielding, and antibacterial applications

Melamine foam (MF) inherently possesses excellent flame-retardant properties due to its ability to release nitrogen upon combustion. Its porous and loose structure also contributes to its high flexibility, breathability, and sound absorption capabilities. Incorporating copper nanoparticles (Cu NPs) significantly enhances the material's electrical conductivity, including its electromagnetic shielding effectiveness, thermal conductivity, and antibacterial properties. This, in turn, greatly broadens the material's potential applications. This research investigated the coating of Cu NPs on three-dimensional MF using an electroless chemical deposition technique to fabricate multifunctional materials. The electromagnetic shielding effectiveness (SET) increased to 85 dB as the Cu NPs content rose from 0 to 0.31 g. Similarly, the electrical conductivity increased from 0.19 to 357 S/m. These results indicate that the Cu-coated MF has high EMI shielding and conductivity properties. The strong adhesion of the Cu NPs to the MF surface created a coating with low infrared emissivity, contributing to the material's excellent thermal insulation properties. With a modest supply voltage of around 4 V, the material exhibited promising electrical conductivity, generating additional warmth of up to 74 °C through efficient joule heating. Furthermore, the Cu-coated MF demonstrated 100 % antibacterial activity, making it a promising candidate for a variety of applications.

Melamine-based biomass-containing P/N synergistic flame retardants confer superb flame retardancy and toughness to epoxy resins

Epoxy resin (EPs) coatings for aircraft need to have good flame retardant properties and toughness. On the other hand, to meet the needs of sustainable development, EPs also have high environmental friendliness and low cost requirements. In light of this, a one-pot approach was used to create a bio-based phosphorus‑nitrogen synergistic flame retardant (MDV) employing DOPO, vanillin, and MA as raw materials. The results showed that MDV can give EP superb flame retardancy and toughness. With the addition of 3 wt% MDV, the tensile and flexural strengths of EP composites increased by 13.6 % and 14.5 %, respectively, and the impact strength increased from 13.9 KJ/m2 to 43.1 KJ/m2. The excellent toughness enhancement comes from the fact that the structure of MDV itself can preferentially consume and dissipate energy when counteracting external impacts. In addition, MDV/EP also has excellent flame retardant properties, showing good self-extinguishing capability off fire in tests. Compared with pure EP, the total heat release (THR) and peak heat release rate (PHRR) of 7-MDV/EP composites were reduced by 45.3 % and 64.5 %, respectively. Mechanistic analyzes showed that the segregation of the condensed phase and the gas-phase flame-retardant effect both originated from the P/N synergistic effect, which was the source of the excellent flame-retardant effect of MDV/EP.

Synthesis of a new flame retardant and performance study of flame retardant epoxy resin

This paper aims to study a new halogen-free flame-retardant curing agent, 6,6'-(1,5-bis((4-(4-aminobenzyl)phenyl)amino)pentane-1,5-diyl)bis(dibenzo-oxaphosphinine 6-oxide) (DOPO-DMG). The DOPO-DMG was synthesized using 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO), 4,4-Diaminodiphenyl methane (DDM), and glutaric dialdehyde as raw materials in this paper. The chemical structures of DMG and DOPO-DMG were characterized by 1H NMR and FTIR. The results showed that the DOPO -DMG was successfully prepared. The thermal stability, mechanical and flame properties, as well as the morphology of the char layer in composite materials were investigated separately using TG (Thermogravimetric analysis), tensile and Charpy impact tests, LOI (Limiting Oxygen Index) and UL-94 (UL-94 HB flammability standard), and SEM (scanning electron microscope). When IFR (Intumescent Flame Retardants) was added to the EP, the LOI of the composite material improved. DOPO-DMG exhibited excellent flame-retardant properties and produced no toxic fumes when burned in case of fire. Under optimal conditions, it was found that adding DOPO-DMG with a phosphorus content of 2.01% to the epoxy resin resulted in an LOI of 28.8, UL 94 rating of V-0, tensile strength of 39.1 MPa, impact strength of 5.2 KJ/m2 respectively, and a char yield at 800°C of 25.63%.

Preparation of Phosphorus/Hollow Silica Microsphere Modified Polyacrylonitrile-Based Carbon Fiber Composites and Their Thermal Insulation and Flame Retardant Properties

Since thermal insulation materials with a single function cannot satisfy the increasing requirements for complex usage, the combination of thermal insulation with flame retardancy is desirable in multiple applications. Herein, phosphorous-containing flame retardant modifier (5.0 wt.%, 9.0 wt.%, and 13.0 wt.%) and hollow silica microsphere (130 nm of diameter) were composited with polyacrylonitrile-based carbon nanofibers via electrospinning technique. Electrospun phosphorous/silica/carbon nanofibers (P/HSM/CF) exhibited a uniform and clear fibrous structure (508, 170, and 1550 nm of average fiber diameter) with modified uniform and complete spherical silica. Reduced thermal conductivity (39.9–41.2 mW/m/K) and enhanced limiting oxygen index (29.5–33.5%) were achieved, enabling fire protection grade of fiber membrane from UL-94 V-1 grade to UL-94 V-0 grade efficiently. Moreover, favorable tensile strength (8.64–9.27 MPa) and elongation at break (43.28–48.54%) were obtained, presenting expected applications in structural components. The findings of this work provided a valuable reference for the fabrication of carbon nanofiber-based thermal insulation materials with excellent flame retardant and mechanical properties.

Preparation of phosphorus-nitrogen synergistic flame retardant cellulose composite aerogel from waste cotton/phytic acid/acrylamide

Cellulose aerogel is a green and biodegradable material, but the high flammability of cellulose aerogel hinders its development. In order to expand the application range of cellulose aerogel, it is necessary to improve the flame retardancy of cellulose aerogel. In this paper, cellulose hydrogels were prepared by decolorizing waste cotton fabrics (WCF) and dissolving them in 1-butyl-3-methylimidazole chloride salt ([Bmim]Cl)/DMSO. The cellulose hydrogels were impregnated in aqueous phytic acid (PA)/acrylamide (AM) solution for a period of time and then heated and treated. A cellulose composite aerogel with excellent flame retardant properties was successfully prepared by using in situ polymerization. The results show that the cellulose composite aerogel has a porous structure and good thermal stability, and the residual carbon content in the air at 800 °C is >2.86 %. At the same time, it has excellent flame retardancy, the ultimate oxygen index (LOL) is >40, and the vertical combustion carbon length is <3.5 cm. The thermal insulation performance has also been improved, and the composite aerogel with a height of 1 cm has a temperature difference of 40.2 °C between the upper and lower surfaces on the 80 °C heating table.

Making aerogel films like playing LEGO: A universal fabrication strategy for Kevlar based aerogel films with arbitrarily designed functions

Highly flexible, ultrathin and mechanically robust aerogel films activated by functional nanofillers exhibit tremendous potentials for wide applications. However, it is difficult to design different functionalities in a single aerogel film, as different nanofillers often possess opposing properties. Herein, a LEGO®-inspired fabrication strategy to construct Kevlar-based aerogel film with arbitrarily designed functions is introduced by stacking functionalized aerogel film units as stacking LEGO® bricks. The aerogel film units are reliably connected by precursor dispersion-derived LEGO® embossed nodes, leading to superior mechanical strength. Moreover, owing to the flexibility of the LEGO®-inspired assembly method, targeted functions of the aerogel films can be achieved by designing and purposefully combining various stacks. As demonstrations, optimized joule heating, greatly enhanced electromagnetic wave shielding and excellent flame-retardant properties are realized with stacking of different aerogel film units. The unique fabrication strategy opens up opportunities for the design and fabrication of aerogel film with tunable and tailored properties for wide applications.

Constructing boiling water resistant and flame-retardant wood composites based on enzyme catalyzed synergistic high branching crosslinking strategy

In the realm of sustainable and regenerative environments, the development of a biomass-based laminated composites endowed with boiling water resistance and flame retardant capabilities holds paramount importance. First of all, a novel maleic anhydride-based polyamine (MAN) was designed and synthesized, characterized by its branched structure replete with numerous reactive sites. Subsequently, utilizing sucrose, MAN, and sucrase (I), a novel sucrose-based adhesive (S-I-MAN) was synthesized, capable of fostering a multifaceted chemical network through enzyme-catalyzed air oxidation cross-linking. And the enzyme-catalysed air oxidation reaction can provide a milder and more specific reaction pathway when catalysed by sucrase. Next, the laminated composites prepared from wood and biomass adhesive (S-I-MAN) exhibited excellent flame retardant properties by organic–inorganic surface modification using tannic acid (TA) and sodium perborate (NaBO3). Further research showed that potassium persulfate can effectively initiate the free radical polymerisation of the carbon–carbon double bond in S-I-MAN, increase the strength and stability of S-I-MAN, and make the laminated composites have more excellent mechanical properties. On the one hand this study developed a new organic–inorganic biomass-based composite adhesive. On the other hand, the surface modification of laminated composites with excellent flame retardant properties provided a new “organic-inorganic composite system with flame retardant” idea.

PAM material that instantly gives ordinary fabrics excellent flame retardant and thermal insulation properties for fire rescue

To effectively reduce the damage caused by flame burns or heat transfer to the human body during fire, we used PAM aqueous solution as the matrix, XG as the thickener, HPMC as the water-retaining agent to form the basic material system, and added different functional particles (APP, PTW, HCB) to prepare a fire-proof and heat-insulating PAM flame-retardant material for fire emergency rescue. Ordinary cotton fabrics were impregnated into PAM flame-retardant materials using a simple impregnation process. After the impregnation, the test was performed in a non-dropping state (simulating the thermal protection effect of PAM flame retardant materials directly acting on the outside of the human body at the fire scene). The results show that the PAM flame retardant material prepared by adding 4 wt% HCB has the best comprehensive performance. TPP test shows that spraying PAM flame retardant material on the outside of the fabric can instantly give the fabric a higher thermal protection performance. Under the total heat flux of 84 kW/m2, the thermal performance protection value of the fabric is 2641.8 kW s/m2, and the second-degree burn time can reach 31.45 s. PAM flame retardant material does not damage the fabric. After soaping, the air permeability of the fabric decreases slightly, the moisture permeability and wettability are improved, and the breaking strength is almost unchanged. The CCT test showed that the thermal radiation flux was 50 kW/m2, the PHRR value of PAM flame retardant material was 10.64552 kW/m2, the THR was 6.9 MJ/m2, and the flame retardant performance was excellent. The PAM flame retardant material prepared in this project can be applied to the fire scene and directly sprayed on the outside of the clothing of rescuers and recipients, giving the fabric a better thermal protection effect. It can also be used to extinguish fires in the external environment. This material offers a novel solution for enhancing fire rescuers' and victims' safety protection levels.

A novel phosphorus-containing pyridinium porous organic framework with flame retardancy for enhancing efficiency and safety of solid-state polymer electrolyte

The development of solid-state polymer electrolytes (SPEs) is aimed to obtain electrolyte materials with higher ionic conductivity, better mechanical properties, and greater flame retardancy. Based on the above considerations, a phosphorus-containing cationic porous organic polymer (ZR-POF) is prepared through “one-pot” three-component polymerization and incorporated as a filler to prepare poly(ethylene oxide) (PEO)-based SPEs. By padding ZR-POF into PEO, the ionic conductivity of SPEs is significantly improved, especially the PEO-10 % ZR-POF electrolyte exhibits the highest ionic conductivity at 90 °C (1.26 × 10−3 S cm−1). And due to the nanosheet characteristics of ZR-POF, SPEs exhibit excellent mechanical properties, could form a more stable interface with the metal anode. It is worth noting that the introduction of phosphorus endows SPEs with excellent flame retardant properties, achieving rapid self-extinguishing within 12 s under intense combustion. Therefore, the resultant battery based on PEO-10 % ZR-POF electrolyte exhibits excellent electrochemical performance, with a capacity maintained at 591.8 mAh g−1 and a capacity attenuation rate of 0.027 % over 500 cycles at 1 C.

Zr4+ and Al3+ coordinated cross-linked conductive collagen fibers/solvent-free polyurethane foam with ultra-low reflective electromagnetic shielding properties

In recent years, electromagnetic shielding materials with low reflectance have developed rapidly. However, high material cost, poor bonding fastness, weak mechanical properties and other problems seriously limit its effect in practical use. In this work, flexible conductive collagen fibers (CLF-Zr4+/Al3+-CNTs) were prepared using chromium tanned waste leather as ingredient, carbon nanotubes (CNTs) as conductive filler and transition metal ions as coordination crosslinking agents, and their molecular dynamics were investigated by quantum chemical simulation software. On this basis, a flexible conductive foam with the double layer and double core-clad structure containing carbon nanotubes was constructed using the solvent-free polyurethane (SFPU) chemical foaming technology, and their electromagnetic shielding properties and reflectance were studied. The experiment results showed that when the ratio of CLF-Zr4+/Al3+-CNTs to SFPU polyol is 1:9 and the impregnation times of CNTs are 2, the loading capacity of CNTs in conductive foam is 0.14 mg/cm3, the electrical conductivity is 57.8 S/m, and the thermal conductivity is 0.061 W/(m·K). Meanwhile, when the thickness is 3 cm, the electromagnetic shielding performance is 42.09 dB, and the reflection efficiency is 0.66 %, the lowest reflection efficiency reaches 0.16 % in the experiment. The mechanism of electromagnetic shielding in conductive foams with the double layer and double core-clad structure has been further explored. The experiment results proved that the flexible conductive foam has excellent mechanical properties, stability, heat insulation and flame retardant properties, and has excellent electromagnetic shielding and low reflection characteristics due to its abundant holes, functional group, interface and hierarchical structure.

Bio-derived epoxy thermosets incorporating imine linkages: Towards sustainable and advanced polymer materials

In the search for sustainable and eco-friendly alternatives, Schiff-based epoxy thermosets are emerging as a promising strategy due to the inherent dynamic and reversible nature of their imine functional groups, which enables thermal reprocessability and chemical recyclability. This article explores the synthesis of Schiff-based epoxy thermosets using sustainable approaches. Starting from vanillin or syringaldehyde, the synthesis involves the incorporation of imine linkages into the epoxy network. A new strategy has been employed by self-polymerization without the use of additional curing agents. This approach conducts to novel thermosets with superior material properties that exceed those reported in previous studies. Thermo-mechanical investigations showed that the designed thermosets have high mechanical properties, with storage moduli at room temperature ranging between 1.5–2.2 GPa, and glass transition values between 138 and 249 °C. Thermal analyses allowed to evaluate the Limit Oxygen Index (LOI) which ranged from 33 % to 36 %, demonstrating excellent flame-retardant properties without the addition of supplementary additives. Their reduced density (0.74–1.09 g/cm3) makes them suitable for applications where weight considerations are critical. These results obtained results place the designed Schiff-based materials as promising candidates for a wide range of high-end applications, particularly in industries that prioritize eco-friendly processes and materials.

HNTs Improve Flame Retardant and Thermal Insulation of the PVA/CA Composite Aerogel.

Porous materials are widely used in construction, batteries, electrical appliances, and other fields. In order to meet the demand for flame-retardant and thermal insulation properties of organic porous materials, in this work, poly(vinyl alcohol)/calcium alginate/halloysite nanotube (PVA/CA/HNTs) aerogels with a hierarchical pore structure at micrometer-nanometer scales were prepared through freeze-drying using PVA as the substrate. The cross-linking reactions of PVA with H3BO3 and sodium alginate (SA) with CaCl2 constructed a double cross-linking network structure within the aerogel. And the HNTs were incorporated as reinforcing agents. The experimental results showed that the PVA/CA/HNTs aerogels had excellent flame-retardant and thermal insulation properties, and the heat release rate (HRR) and total heat release (THR) were effectively reduced compared to the PVA/CA aerogel. In addition, PVA/CA/HNTs aerogels had a high limiting oxygen index (LOI 60%) and low thermal conductivity (0.040 W/m·K). While their surface was subjected to a flame (800-1000 °C) for 25 min, the temperatures of the back surface were still lower than 80 °C. The low thermal conductivity of HNTs with hollow nanotube-like structures and the excellent flame-retardant properties of CA contributed to this phenomenon. The presence of HNTs and CA facilitated the formation of a dense carbon layer during combustion, enhancing the flame retardancy for PVA. In addition, the interpenetrating cross-linking network and the unique nanopores of HNTs collectively established a hierarchical pore structure within the gel, effectively impeding substance and heat exchange between the substrate and external environment. As the flame-retardant and thermal insulating material, PVA/CA/HNTs aerogels have a promising development prospect and potential in the fields of construction, transportation, electronics, and electrical appliances.

Phytic acid-induced durable fire-proof and hydrophobic complex coating for versatile cotton fabrics

To address the current development requirements for multifunctional cotton fabrics, a phytic acid-induced flame-retardant hydrophobic coating containing nitrogen (N), phosphorus (P), and silicon (Si) was grafted on the surface of cotton fabrics using a facile step-by-step immersion method. The limiting oxygen index value improved to 31.2 %, decreasing to 26.7 % after 50 laundering cycles, while the fabric remained self-extinguishing effect in the vertical flammability test and showed a water contact angle of 126.1°. Cone calorimetry test showed that the modified fabric could not be ignited at the irradiation heat flux of 35 kW/m2. When the irradiation heat flux was raised to 50 kW/m2, there was a significant decline in the peak heat release rate of the modified cotton fabric, which decreased by 43.2 % to a remarkably low value of 114.0 kW/m2, indicating excellent flame-retardant properties. The analysis of the flame-retardant mechanism uncovered that the modified coating exhibited a significant dual flame-retardant mechanism involving both the gaseous phase and the condensed phase. Additionally, the oil-water separation tests revealed that the separation efficiency of the modified cotton fabrics was as high as 97.1 % and remained around 96 % after 10 cycles, which made them reusable for the clean-up of hazardous chemicals.

Enhanced flame retardancy and thermal insulation of epoxy resins composites incorporated with ammonium polyphosphate and ionic liquids loaded CuO-ZnO hollow spheres

Epoxy resin, as a thermosetting polymer material with good performance, has been limited in application due to its high flammability. In this investigation, porous CuO-ZnO hollow spheres (CZHS) were prepared by a hydrothermal method. By incorporation with ionic liquids loaded CuO-ZnO hollow spheres (CZHS@Ils) and ammonium polyphosphate (APP) into epoxy resin (EP) matrix, a new composite flame retardant material, named as EP/7.5APP/1.5CZHS@ILs, was developed for improvement of their thermal insulation and flame retardancy. The thermal conductivity of EP/7.5APP/1.5CZHS@ILs was measured to be 0.0197 W m −1 K −1, which is lesser than that of APP incorporated epoxy resin (EP/APP), demonstrating good thermal insulation capability. The flame retardancy were assessed using the limiting oxygen index (LOI) test, the Vertical flame testing (UL-94) test, and the cone calorimeter (CC) test. The results obtained from LOI test show that the EP/7.5APP/1.5CZHS@ILs has good flame retardancy with a LOI value of up to 28, better than that of pure EP which has a LOI value of 19.2. Moreover, a V-0 level of the EP/7.5APP/1.5CZHS@ILs was observed from the UL-94 test. The peak heat release rate (PHRR) was reduced to 257.9 kW m−2, which is 74.8 % lower than that of the pure EP. Such results are attributed to the synergy effect of CZHS@ILs and APP which offers the epoxy resin excellent flame retardancy. Taking advantages of the excellent thermal insulation, flame retardancy and better mechanical properties, the as-resulted EP/7.5APP/1.5CZHS@ILs may hold great potential for future thermal insulation and flame-retardant applications of energy saving building.

Synthesis of a phosphorus-containing L-lactic acid-based flame-retardant plasticizer for simultaneously enhancing flexibility and flame retardancy of poly(lactic acid)

This work provides a straightforward strategy for synthesizing efficient bio-based flame-retardant plasticizers, offering promising prospects for flame-retardant flexible materials. Poly(lactic acid) (PLA) has garnered significant attention as an environmentally friendly polymer among numerous biodegradable materials. However, its high flammability and brittleness severely hinder its application in the field of electronics and electrical devices. To address these challenges, a bio-based flame-retardant plasticizer (EPDL) was designed and synthesized using renewable L-lactic acid, which significantly enhances the flexibility and flame retardancy of PLA. Incorporating 40 phr EPDL resulted in PLA achieving UL94 V-0 grade and a limiting oxygen index of 34.3 %, demonstrating excellent flame-retardant properties. Meanwhile, the peak of heat release rate and total heat release of PLA/EPDL blends exhibited a marked reduction by 23.1 % and 34.1 % compared to that of pristine PLA, respectively. The flame-retardant action mode of EPDL is the combination of gas phase and condensed phase action. Additionally, the introduction of 40 phr EPDL significantly enhanced the ductility of PLA, resulting in a substantial rise in the elongation at break of the PLA/EPDL to 181.8 %, which is approximately 52 times higher than neat PLA. Intriguingly, the crystallization performance of PLA was enhanced by the presence of EPDL.

Sustainably sourced and DOPO-derived triols as hardeners for epoxy thermosets: A promising solution to synchronously improve flame retardancy, mechanical strength and toughness

The flammability and brittleness of the diglycidyl ether of bisphenol A (DGEBA)-type epoxy resin greatly restrict its application in electronic appliances and structural materials. However, the synchronous improvement in the flame retardancy, mechanical strength, and toughness of DGEBA-type epoxy thermosets remains a significant challenge. To overcome this challenge, in this study, a sustainably sourced and DOPO-derived triol (DOPO-GL-DCDA) was synthesized from a bio-based material, glycerol 1, 3-diglycerolate diacrylate (GL-DCDA). A series of epoxy thermosets with different phosphorus contents were prepared by introducing DOPO-GL-DCDA into the DGEBA matrix. EP/DOPO-GL-DCDA demonstrated excellent flame retardancy and mechanical properties without compromising transparency. Specifically, EP/DOPO-GL-DCDA-1.0P exhibited a limit oxygen index (LOI) of 34.0 % and a UL-94 V-0 rating, and the total heat release (THR) and peak heat release rate (PHRR) of EP/DOPO-GL-DCDA-1.5P decreased by 36.6 % and 46.8 %, respectively, compared with those of pure EP. In addition, compared with those of pure EP, the tensile strength, impact strength, fracture toughness (KIC), and fracture energy (GIC) of EP/DOPO-GL-DCDA-1.5P increased by 62.8 %, 69.9 %, 62.9 %, and 99.0 %, respectively. Moreover, EP/DOPO-GL-DCDA had better dielectric properties than pure EP. Under the premise of maintaining transparency, this work provided a promising solution to synchronously improve the flame retardancy, mechanical strength, and toughness of epoxy thermosets.

Thermal, mechanical property and flame retardant analysis of bio-based rigid polyurethane foam modified with expandable graphite

As an energy-efficient building material, rigid polyurethane foam (RPUF) has attracted attention. However, there are still great challenges in how to easily prepare RPUF materials with good mechanical properties, flame retardant properties, thermal insulation and other properties. In the current work, expandable graphite (EG)-modified lignin-based polyol (RPUF) was prepared by a one-step method. Thermogravimetric analysis was used to study the pyrolysis of modified foams under nitrogen conditions. It was found that the RPUF-4 with an EG of 10 wt% had the highest the apparent activation energy (E), integral procedural decomposition temperature (IPDT), initial temperature and residue rate. And RPUF-4 also had excellent thermal insulation properties. In addition, RPUF-4 exhibited excellent flame retardancy and smoke suppression properties (peak heat release rate (RHRR), total heat release rate (THR) and Ds were 65.46 %, 23.92 % and 45.94 % lower than those of the unadded RPUF, respectively). At the same time, RPUF-4 also had good mechanical properties and energy absorption properties. These results will lay the foundation for the development and application of RPUF in the field of building insulation.

Enhancing flame retardancy and heat insulation performances of polyamide 66 composite film by adding CNC/Al2O3 nanohybrids

Polyamide 66 (PA66) has garnered significant attention due to its exceptional properties; unfortunately, its flammability is challenging. Adding flame retardants (FRs) is a primary approach to enhance PA66 flame retardancy. This study developed a highly flame-retardant PA66 composite film by adding corn-like functional nanohybrids (CNC/Al2O3). Interestingly, CNC/Al2O3 nanohybrids not only formed hydrogen bond interactions with PA66 but also improved crystallization properties as heterogeneous nucleating agents, resulting in the excellent mechanical properties of PA66 composite film. Remarkably, the incorporation of 3 wt% CNC/Al2O3 nanohybrids into PA66 matrix contributed to increasing the LOI to 28.5 %. The pHRR, THR, and TSR were reduced obviously by 55.7 %, 15.3 %, and 65.2 %, respectively. The excellent flame retardancy of PA66 composite film was attributed to the forming of a compact carbon layer catalyzed by the CNC/Al2O3 nanohybrids. Besides, the homogeneous distribution of CNC/Al2O3 nanohybrids endowed the composite film with excellent heat insulation, and the heat insulation rate was up to 31.9 %. Thus, such PA66 composite films with excellent flame retardancy, heat insulation, and mechanical properties could meet the broader application requirements.

Phosphonitrile based porous organic polymers as effective flame-retardant electrolytes for lithium battery

Developing electrolytes with flame-retardant properties become the critical factor in making high safety lithium batteries. As phosphonitrile-based compounds are a kind of typical flame-retardant materials, herein, taking phosphonitrile-based aldehyde as the basic organic building blocks, two porous organic polymers (POPs) named as PVPH and PVPH-CO2H were successfully fabricated after solvothermal reaction with 1,3-diaminobenzene (MPD) and 5-carboxy-1,3-diaminobenzene (MPD-CO2H), respectively for electrolytes of lithium batteries. Studies revealed that both of the phosphonitrile-based POPs demonstrate good thermal stability and excellent flame-retardant properties, suggesting they are promising flame-retardant electrolytes for the application in battery. Battery performance investigations revealed that both of them, especially PVPH-CO2H, show good performance after assembling them into lithium batteries. This study paves the way to improve battery safety performance by employing the flame-retardant phosphonitrile-based porous polymers as effective electrolytes. Moreover, it also broadens the application of flame-retardant materials in energy storage materials.