Good Flame Retardancy Research Articles

Thermal stability and combustion properties of polyurethane foam modified with manganese phytate and expandable graphite

Manganese phytate (MnPa) was prepared and synergistically combined with expandable graphite (EG) flame retardant modified polyurethane foam (PUF). Utilizing thermogravimetric (TG), pyrolysis kinetic analysis, CONE analysis, smoke toxicity analysis, limiting oxygen index (LOI), and UL-94 horizontal combustion test procedures, the thermal stability and combustion parameters of the modified PUFs were examined. The flame retardancy and smoke suppression of the modified PUFs were analyzed based on the heat release rate (HRR), total heat release (THR), smoke production rate (SPR), and total smoke release (TSR). The results showed that MEPUF3 had the highest thermal decomposition rate temperature, initial thermogravimetric temperature, and activation energy (E). It was shown that MEPUF3 had the lowest HRR of 17.68 kW/m2, the lowest THR of 1.15 MJ/m2, the lowest SPR of 0.0046 m2/s, the lowest TSR of 19.58 m2/m2, the lowest Ds of 32.1, the highest transmittance of 57.7%, and the highest LOI of 23.0%. The present study showed that MEPUF3 possessed good thermal stability and flame retardant properties, which provided useful references for subsequent phytate and EG-modified PUFs.

Multifunctional Anisotropic Aerogels for Intelligent Electromagnetic Wave Absorption

AbstractThe rapidly developing modern society has higher requirements for intelligent electromagnetic wave absorbing (EMA) materials than ever before. Herein, lightweight, multifunctional metal‐free carbon‐based aerogels (RCPs) with a longitudinal honeycomb porous framework and a transverse neatly layered structure are obtained by heat‐treating graphene oxide/oxidized carbon nanotubes/hexachlorocyclotriphosphazene complex to simultaneously achieve the tunable EMA, flame retardancy, and thermal insulation. The anisotropic structure ensures the tunable properties of the carbon aerogels along with tilt angles according to environmental needs. The honeycomb porous structure effectively promotes multiple reflections and scatterings of electromagnetic waves compared with the layered structure, maximizing the penetration inside the material and thus a high EMA performance. The optimized R10C2P‐4 exhibits a minimum reflection loss in the longitudinal direction of−61.5 dB, while the value is as low as −22.4 dB in the transverse direction. Furthermore, the porous structure adequately inhibits the spread of heat, accompanied by the phosphorus species induced by hexachlorocyclotriphosphazene pyrolysis, endowing a good flame retardancy and thermal insulation with a low thermal conductivity of 20.6 mW m−1 K−1 in the longitudinal direction, rather than the transverse direction. This work provides an ingenious insight into the design of multifunctional EMA materials, adapting flexibly to various application requirements.

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.

Recycling the sediment of cotton spinning effluent for rigid polyurethane foams

Sediment from the effluent of cotton spinning industry was valorized as the renewable bio-based polyols substitute for the rigid polyurethane (RPUFs), targeting to generate the economic and environmental benefits. Before reaction with the isocyanate, the sediment was functionalized by hydroxymethylation, in order to increase the density of the active hydroxyl groups for higher reactivity. The structural characterization results of the functionalized sediment indicated the material exhibited narrow molecular weight distribution, high hydroxyl groups content, and highly aromatic skeleton, which can be qualified as the renewable polyols for the RPUFs. In the crosslinking process, the effect of the polyols substitute rate of the sediments on the physio-chemical properties and the thermo-resistant performances of the resulting RPUFs was investigated. Specifically, in the group with 30 wt% of polyols substitution, the received foam exhibited comprehensive superiorities in compressive strength (0.58 MPa), apparent density (58 kg m−3), and thermo-conductivity (0.032 W m−1 K−1). Attractively, the RPUFs also exhibited good flame retardancy. The burning time can be extended by 30 % compared to the control group that without the sediment's substitution. Moreover, the RPUF also possessed good degradability, allowing for harmless recycling. The current work provided a potential route for the valorization of the hazardous waste effluent from the cotton spinning industry.

Key Process Control for Synthesizing High-Performance Inherently Flame-Retardant Long-Chain Bio-Based Polyamide.

Long-chain bio-based polyamide has shown promising development prospects due to its excellent properties and green renewable characteristics; however, synthesizing inherently flame-retardant long-chain bio-based polyamide remains a big challenge due to the lack of effective knowledge of the key polymerization process. Herein, intrinsicly flame-retardant long-chain bio-based polyamide 512 (PA512) was synthesized in the presence of a reactive flame retardant with high thermal stability and good water solubility. The reaction conditions and existing problems in each stage of the copolymerization system have been clarified and optimized. By utilizing a two-step pre-polymerization approach, a series of intrinsicly flame-retardant PA512 (FRPA512) with large molecular weight, high phosphorus element content and good mechanical properties were obtained. More importantly, the prepared FRPA512 with 5wt% flame retardant loading exhibited good flame retardancy, showing a limiting oxygen index (LOI) of 28.1% and a vertical burning rating of V-0. This study provides a feasible solution to the common problem in the synthesis of flame-retardant polyamides, while also offering new insights for future modification of polyamide copolymerization.

Rigid polyurethane foam with durable hydrophobicity and flame retardancy endowed by novel functional surfactants

Traditional rigid polyurethane foam (RPUF) with flame retardancy might be easily damaged in some moist condition due to its hydrophobicity, which would lead to unsafety. Therefore, novel surfactants with both hydrophobic fluorinated group and flame-retardant phosphorus group were synthesized. With lower surface tension and more hydrogen bonds formed in polyurethane, the mixed surfactants, which were used in the preparation of RPUF, have not only obviously improved the size uniformity and integrity of cells but also enhanced its hydrophobicity, compressive strength and thermal insulating performance. Besides, effective ‘protection’ could be constructed on the surface of RPUF by prepared surfactants, when ammonium polyphosphate (APP) and expandable graphite (EG) were introduced to provide good flame retardancy. As a result, with just 2.8 wt% content of those functional surfactants, hydrophobic and flame-retardant RPUF with water contact angle of 126 °, limiting oxygen index of 25 %, compressive strength of 1.3 MPa and thermal conductivity of 27 mW/mK, were finally obtained, which is ahead of other flame-retardant RPUF reported before. It’s worth noting that, this hydrophobic and flame-retardant RPUF exhibits more stable and durable properties when soaking in HCl solution (2 mol/L), NaOH solution (2 mol/L), NaCl saturated solution and various solvents (THF and EtOH), or under strong fiction for 100 times and high and low temperature cycling test for 20 times. This would provide a novel and effective strategy to endow RPUF with enhanced and durable flame retardancy, hydrophobicity, compressive strength and thermal insulating performance even under extreme conditions.

Superior filaments-based fabric with thermal-mechanical-electrical coupling properties for remote temperature alarm

The safeguarding fabrics featuring good thermal insulation, flame retardancy, and force dissipation simultaneously remain challenging due to the current filaments with limited properties. Herein, a novel and flame-retardant filament (F-filament) is developed by hot-extruding the mixture of shear stiffening gel/thermoplastic polyurethane (SSG/TPU) and microencapsulated ammonium polyphosphate (MHAPP), which is conducive to knitting protective fabrics. The conductive F-filament (cF-filament) is further prepared by incorporating with MXene. The F-filament-based fabrics present better anti-impact properties than commercial fabrics and can dissipate 6.32 kN impacting force to 1.89 kN. The patterned knitted fabric also facilitates heat exchange, reducing the contact temperature of the body surface to approximately 37 °C when exposed to an 80 °C heat source, effectively avoiding thermal damage through its porous structure. Moreover, the F-filament-based fabrics are intact even after 19 s of continuous burning. Notably, the cF-filament is demonstrated for use as a sensor for real-time multimodal monitoring, such as detecting external mechanical loadings and temperature stimuli. The cF-filament sensor can be integrated into the F-filament-based knitted fabrics, which accurately realizes environmental monitoring and explores the best-escaping route through a remote temperature alarm system.

Highly robust, processable and multi-functional PDMS/graphene composite aerogel constructed by “soft-hard” interface engineering strategy

Graphene aerogel (GA) has attracted wide attention for its potential applications in various fields. However, the graphene nanosheets in the GA framework often exhibit insufficient adhesion and interfacial contact due to weak interactions, resulting in fragile cell walls and poor structural stability. Here, inspired by the principle of “soft-hard” compounding, a class of GA with extraordinary structural stability and mechanical property was prepared based on the in-situ bonding interfacial engineering between different phases in Pickering emulsion. Through interfacial engineering, the fatal compounding drawback between fusing oily polymer soft chains and water-soluble hard graphene oxide (GO) nanosheets is resolved, which enables polydimethylsiloxane (PDMS) chains to in-situ adhere onto GO nanosheets, eventually resulting in compelling structural-stable PDMS/GO aerogel (PGOA) backbone. Later, PDMS/GA (PGA) can be easily obtained by simple reduction of PGOA. The obtained PGA achieves excellent structural stability, 97.5 % elasticity, 1.7 MPa compressive capacity, and unprecedented isotropic characteristics. The assembled flexible sensor based on PGA has a high sensitivity of 17.08 kPa−1. Additionally, PGA has low thermal conductivity (0.0245–0.0301 W/(m ∙ K)) and good flame retardancy (∼1000 °C). Because of these excellent properties, PGA has a wide range of potential applications in areas such as flexible sensing, thermal protection, and fire detection.

Waterborne novolac epoxy‐based thermal resistant and fire‐retardant thermal insulation coatings

AbstractWaterborne novolac epoxy based thermal resistant and fire‐retardant thermal insulation coatings were developed in this work. Novolac (phenolic) epoxy emulsion (PEE) was prepared by the phase inversion method based on formulation optimization by orthogonal array testing. The prepared emulsions have similar particle size, viscosity, and stability to commercial bisphenol a glycidyl ether epoxy emulsion (PZ). DSC results showed that the varnish film based on PEE had a higher glass transition temperature and initial thermal decomposition temperature compared with PZ cured by the same curing agent. Waterborne thermal insulation coating with PEE and PZ as binders and hollow glass microspheres (HGMs) as thermal insulation fillers were studied. The results indicated that the thermal conductivity of the coating decreased with an increase in HGMs content. Specifically, the thermal conductivity of the PEE coating containing 20 wt% HGMs is as low as 0.093 W/(m·K). It reduces the exterior temperature of the hot tank from approximately 200 °C to approximately 106 °C. Furthermore, the HGMs/PEE waterborne thermal insulation coating exhibits good thermal stability and flame retardance.

Polymerized lignin based carbon nanofiber for high-performance energy generator and storage

It is a challenge to develop simple and efficient methods to optimize the lignin structure for preparing high-performance lignin-based carbon nanofibers (CFs). Herein, a novel and effective strategy for preparing high-performance lignin-based CFs is designed. Lignin samples with different chemical structures are prepared by polymerization modification and fractionation. This strategy completely gets over the dependence on petroleum-based polymers in the electrospinning process, and makes the lignin-based CFs show good performance in energy storage, temperature sensor, and moisture power generators. The specific capacitance and energy density of lignin-based supercapacitors reach 357.2 F/g and 31.5 Wh/kg, respectively. The CFs exhibit good flame retardancy and thermal sensitivity (about 1 s). In addition, moisture power generators assembled with CFs exhibit great potential. The output voltage of moisture power generators has a linear relationship with the number of devices. With the increase of series equipment, the output voltage of 5 series connected moisture power generators reaches 4.7 V. This work provides a new approach to prepare high-performance lignin-based CFs, which has a good application prospect in the fields of energy storage, sensor and power generation.

Hydrogen bond self-assembly strategy to preparation Zeolite@BM for enhancing the fire retardancy of EP

The inflammability of EP limits its wide application, and it is important to enhance its fire safety with appropriate flame retardants. In this study, a novel Zeolite@BM flame retardant was constructed based on the self-assembly of boric acid and melamine on the surface of zeolite. Synthetic Zeolite@BM incorporated into EP to strengthen its flame retardance. The incorporation of 10 wt% Zeolite@BM dramatically raised the flame retardation of EP. The LOI of EP climbed from 24.7 % to 27.4 %, reaching the V-0 level. Moreover, the PHRR, THR and TSP dropped significantly by 55.01 %, 29.14 % and 49.96 %, respectively. Zeolite@BM promotes char formation, minimizing thermolytic products emissions and significantly raising the fire retardance of EP. Therefore, Zeolite@BM endows EP with good flame retardancy, low smoke emission and heat release, providing a practicable and efficient strategy for using EP under high flame retardancy requirements.

A novel conjugated microporous polymer nano hollow sphere containing N, P and Si flame retardant elements with both thermal insulation and flame retardant properties

It is particularly important to develop new materials with both thermal insulation and flame retardant properties for addressing the severe issues caused by fire accidents. Herein, a kind of conjugated microporous polymer nanospheres with hollow structure (HCMPNS) was synthesized by Sonogashira-Hagihara cross-coupling reaction using SiO2 nanospheres as hard template and 1,3,5-triacetylenebenzene, as alkynyl monomer. Then, HCMPNS was chemically graft-modified with azidotrimethylsilane (TMSA) by "click" chemistry (HCMPNS-FRSi), and the HCMPNS-FRSi obtained from the reaction was introduced into flammable epoxy resin (EP) to obtain EP based composites, i.e. EP-Ⅰ and EP-Ⅱ. The thermal conductivities were found to be 0.0341 W m−1 K−1 and 0.0268 W m−1 K−1 for EP-Ⅰ and EP-Ⅱ, respectively, showing excellent thermal insulation performance. The total heat release (THR), the total smoke production (TSP) and the peak CO2 produced (CO2P) of EP-Ⅰ were reduced by 18.0 %, 8.0 %, 14.3 % compared with pure EP as measured by cone calorimetry (CC), respectively, indicating a certain extent flame retardant effect. In order to further improve its flame retardant properties, phosphoric acid containing the flame retardant phosphorus element was added to HCMPNS-FRSi (HCMPNS-FRSi-P), followed by the introduction of the resulting HCMPNS-FRSi-P into EP matrix to form EP based composites with Si and P dual incorporation (EP-III and EP-IV), with the thermal conductivities of 0.0470 W m−1 K−1 and 0.0855 W m−1 K−1, respectively. Through the cone calorimetry (CC) of EP-III, EP-IV, total heat release (THR) were reduced by 17.0 %, 23.8 %, total smoke production (TSP) were reduced by 6.2 %, 7.2 %, respectively. The peak heat release rate (HRR) and the peak CO2 produced (CO2P) of EP-Ⅳ were reduced by 16 % and 25 %, respectively, compared with pure EP. It has good thermal insulation and flame retardant effect. Therefore, HCMPNS-FRSi-P, as a new type of flame retardant material, has great potential in the fields of electronics, construction, transportation and so on.

Solid polymer electrolytes with dual salts enhance lithium-metal interfacial stability for long cycle performance of lithium batteries

Solid-state lithium metal batteries (LMBs) are considered to be the ideal energy storage system for achieving higher energy density and high safety. However, poor physical contact at the interface between the solid-state electrolyte and lithium metal, as well as the growth of dendrites make the cycling stability of LMBs challenging. Therefore, we developed a multifunctional ionic liquid-based polymer electrolyte including montmorillonite (MMT) and double salts (NaFSI and LiTFSI). The self-concentration effect of MMT lithium ions, combined with the electrostatic shielding effect of the double salts, resulted in homogeneous ion deposition, reducing dendritic lithium generation and improving lithium battery performance, with lithium batteries achieving a stable cycling rate of 1000 cycles at 1 C. Moreover, Due to the integrated assembly of the battery assembly process using light curing, the physical interface between the positive electrode-electrolyte-negative electrode achieves good contact and wettability. NaFSI achieves the enhancement of solid electrolyte interface (SEI) by introducing NaF/LiF to SEI of lithium metal, and the optimization of ion deposition pattern at the interface can be achieved by electrostatic shielding effect. Ultimately, stable ion transport at the solid-solid interface for lithium metal solid-state batteries can be realized. Notably, the ionic liquid-based polymer electrolyte with high ionic conductivity (1.2 × 10−3 S cm−1) and high oxidative stability (5.2 V vs. Li/Li+) at room temperature. In addition, the good flame retardant properties of the electrolytes indicate that dual-salt polymer electrolytes are an effective strategy for achieving high safety and long cycle stability of LMBs.

Study on preparation and performance of bagasse/sodium carboxymethyl cellulose gel for inhibiting coal spontaneous combustion

In order to effectively prevent and control coal spontaneous combustion and improve the safety of coal mining, bagasse carboxymethy cellulose (BCC) prepared from bagasse (BS) and sodium carboxymethyl cellulose (CMC) were used as the substrates. A gel (BCC-CMC) for inhibiting coal spontaneous combustion was prepared using a chemical crosslinking method involving zirconium citrate crosslinking and glucono-delta-lactone (GDL) modification. X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy were utilized to characterize both the crystal and molecular structure of bagasse and its derived bagasse carboxymethyl cellulose. The results indicated that new carboxymethyl groups were introduced into bagasse during the treatment, facilitating the successful extraction and preparation of sodium carboxymethyl cellulose. The results of viscosity and bonding tests demonstrated that the concentration and dosage of CMC had the most significant influence on the gel viscosity, which remained higher and more stable at room temperature. The coal bonded by the gel coal mixture can effectively seal surface cracks, with a bonding degree of up to 70.72 %. TG-DTG, temperature-programmed oxidation experiment and FTIR analyses revealed that, compared to raw coal, coal samples treated with gel exhibited improved stability, fewer active groups, and fewer oxygen-containing functional groups, effectively inhibiting coal’s low temperature oxidation and reducing the risk of spontaneous combustion. The gel is environmentally friendly, cost-effective, and exhibits good flame retardant properties. This study is of great significance for preventing and controlling coal spontaneous combustion, effectively ensuring the safe production of coal resources and the safety of mine workers, achieving the green sustainable development of the mine.

Aminated lignin and phytic acid-assisted polyacrylic acid hydrogel sensors with enhanced mechanical properties and strong adhesion

Excellent comprehensive performance of hydrogels can be achieved by synergistically combining multiple interaction mechanisms. In this study, a series of hydrogels with rapid gelation and excellent adhesive, mechanical, self-healing, and conductive properties, driven by covalent bonds and multiple reversible interactions, were constructed by mixing acrylic acid (AA), aminated alkaline lignin (AAL), phytic acid (PA), and Fe3+. The rigid skeletons of polyacrylic acid (PAA) and AAL, as well as the metal coordination bonds formed between them and Fe3+, enhance the mechanical properties of the samples. The samples exhibit excellent tensile strength and compressive strength, reaching 73.7 kPa and 4.6 MPa (under a compressive strain of 80 %), respectively, with a tensile strain of 1142 % under the same condition. Adding PA enhances the compliance and adhesion (148.2 kPa for porcine skin) of the gel and endowed it with good flame retardancy. Additionally, the sample maintained its good mechanical properties and conductivity even after five cutting-healing cycles. Good durability, robust adhesion, and high electrical conductivity of the sample render it a promising strain sensor for electronic devices. This work provides a design strategy for preparing hydrogels with superior adhesion and good comprehensive performance.

Single overall ‘H-shaped’ multifunctional compound achieves fire safety, durability, enhanced strength, and smoke suppression of cotton fabrics

Challenges currently faced by phosphorus-based flame retardants for cotton fabrics include reduced fabric strength after treatment, high smoke release during combustion, formaldehyde release from commercial phosphorus-based flame retardants and poor flame retardant durability after treatment. In the present work, a P/N/B synergistic flame retardant TBST is synthesized using phosphoric acid, cyanuric acid, boric acid, pentaerythritol, etc. The phosphorus‑nitrogen‑boron atomic ratio is 2:3:1, and it is successfully prepared on cotton fabric to prepare TBST/Cotton. When the weight gain rate is 29.8 %, the LOI value is 41.6 ± 0.3 %, indicating that TBST/Cotton has excellent flame retardant performance. At the same time, in the vertical flame test, the length of residual carbon is 5.6 cm. In addition, the THR and HRR are reduced by 58.4 % and 91.9 % respectively compared to Cotton, indicating that TBST/Cotton has excellent combustion performance. In addition, compared to the residual carbon content of Cotton at 710 °C, the residual carbon content of TBST/Cotton in nitrogen increased by 27.79 %. For a 30 % increase in weight, the increase in longitudinal mechanical strength is 23.1 %. Inferred the decomposition mechanism and flame retardant mechanism of TBST/Cotton. TBST/Cotton has the advantages of good flame retardant durability and enhanced mechanical properties, and the reinforcement mechanism of TBST has been speculated.

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.

Room-temperature self-healing polyurethane with superior mechanical properties based on supramolecular structure for flame retardant application

Self-healing polymers, with their ability to extend service life and conserve resources, have garnered significant attention across various fields due to their immense potential applications. However, most repairable polymers typically require high temperatures for repair, and their relatively weak mechanical properties limit their practical use. Moreover, the flammability of polymers not only poses safety hazards during use but also fails to meet specific requirements for flame retardancy in certain fields. Addressing these issues, this study successfully designed a reactive self-extinguishing room-temperature self-healing polyurethane (PU) by introducing hyperbranched catechol (DBPA) onto the PU main chain. The prepared self-healing PU elastomer (DPU) exhibited high tensile strength (∼51.2 MPa), outstanding toughness (∼119.0 MJ/m3), recyclability, and good flame retardancy. Through intermolecular and intramolecular multilevel hydrogen bonding, the prepared DPU0.6 achieved room-temperature self-healing with an efficiency of approximately 71.2 %. The results showed that the addition of trace amounts of DBPA (0.6 wt%) significantly enhanced the flame retardancy and thermal stability of DPU. Compared to DPU0, the heat release rate (HRR) of DPU0.6 decreased by approximately 13 %, the total heat release (THR) reduced by 18 %, and the time to ignition (TTI) was extended by 7 s (reduced by ∼ 21 %). This study not only provides insights into the synthesis and design of novel self-healing PU but also further expands the application scope of self-healing PU.

Construction of a β-cyclodextrin-based colloid containing silicon, phosphorus and nitrogen components: Toward enhancing flame retardancy of flax fabrics

Natural cellulose fabrics, as one of the combustibles prone to causing indoor fires, are modified with flame retardants encouraged by the fire protection industry. Herein, a bio-based colloid named ASDPC was prepared by 3-aminopropyltriethoxysilane, diethylenetriaminepentakis(methylphosphonic acid) and β-cyclodextrin, and used to enhance the flame retardancy of flax fabrics via the pad-dry-cure method. The treated flax fabrics named ASDPC-FF showed good flame retardancy with a damaged length of only 6.4 cm in the vertical burning test and a limiting oxygen index value of up to 33.8 %. Meanwhile, ASDPC-FF exhibited thermal stability and combustion behavior distinct from untreated flax fabrics. Thermogravimetric analysis presented that the char residue produced by ASDPC-FF at 800 °C was as high as 36.2 %. Cone calorimetry test indicated that the peak heat release rate and total heat release of ASDPC-FF decreased by approximately 89.0 % and 35.7 %, respectively. Furthermore, compared to untreated flax fabrics, condensed-phase and gas-phase studies found that ASDPC-FF turned into expanded char and produced fewer gaseous volatiles containing C-H, CO and C-O-C at high temperatures. More importantly, ASDPC-FF remained self-extinguishing after 25 laundering cycles with flame retardancy surpassing untreated flax fabrics. In summary, this work provides a novel route for expanding the manufacture of flame-retardant flax fabrics.

Preparation and flame retardant properties of new mining fireproof gel

Coal spontaneous combustion (CSC) brings great danger to mine safety. Although traditional colloidal fire-fighting materials can reside at high fire source points, their permeability and fluidity are poor, and such materials focus on their water absorption, but pay less attention to water retention and resistance, which makes their fire-fighting effect not good. This paper proposed a new type of mining fire prevention colloid material (CPS-α), which had good solid water gel formation, viscosity, fluidity, and blocking properties to compensate for traditional colloids' shortcomings. According to the single-factor experiment, polymeric polyacrylamide (PAM) as the base material, sodium carboxymethyl cellulose (CMC) as the coagulant, modified starch (SS) as the flame retardant and reduced ascorbic acid were determined. After gel treatment, compared with raw coal, the critical temperature point of spontaneous combustion of coal was increased by about 28 °C, the time to reach the critical temperature point was delayed by 190s, and the characteristic temperature points were significantly increased; the overlap area of coal and water increases by about 20 % after adding gel, and the change slope of the diffusion coefficient of water decreases, which indicated that CPS-α had good flame retardant effect.