Total Heat Release Research Articles

Phosphonitrile hybrid metal-polyphenol network: An effective strategy for developing functional PVA composites with flame retardancy, antibacterial and UV resistance

The white pollution caused by non-degradable plastics poses a serious threat to human society and the environment, thus developing biodegradable material is urgent. In this work, a novel phosphonitrile hybrid metal-polyphenol network was constructed and used for the preparation of flame retardant, UV resistant and antibacterial multifunctional polyvinyl alcohol composite (PVA@HCPD-Ag). The limiting oxygen index (LOI) value of PVA@HCPD-Ag was improved to 33.5%, while the peak heat release rate (PHRR) and total heat release (THR) decreased by 35.62% and 47.76%. Besides, the ultraviolet protection factor (UPF) value of PVA@HCPD-Ag was significantly improved from 4.63 of the original PVA to 482.79, while the tensile strength was increased by 10.23%. Furthermore, the inhibition efficacy of PVA@HCPD-Ag for E. coli and S. aureus was up to 98.12% and 99.99%. This work explored the synergistic flame retardant effect of in-situ reduced Ag0 and phosphonitrile crosslinked polyphenol network and proposed an advanced strategy for developing high value-added functionalized PVA materials.

Fabrication of superior flame-retardant phosphorylated chitosan biobased porous composites reinforced by superhydrophobic silicone interpenetrating crosslinking networks

Chitosan-based porous materials have potential to develop into a new generation of high performance sustainable thermal insulation materials. In this study, hydrophobic and enhanced phosphorylated porous materials (PCSM) were constructed by the in-situ crosslinking of methytrimethoxylsilane (MTMS), and modified SiO2 nanoparticles (H-SiO2) were further incorporated into the crosslinking networks to fabricate superhydrophobic and reinforced PCSM-H-SiO2 porous composites. The morphology of PCSM-H-SiO2 porous materials exhibited special micro-nanoscale “pearl string-like” rough and interpenetrating pore wall structure, which endowed them superhydrophobicity and self-cleaning ability. The water contact angles (WCAs) of PCSM-H-SiO2 porous composites achieved up to 150o, and the compressive and specific moduli of PCSM2-H-SiO2–2 porous composite significantly increased to 11.0 MPa and 89.6 m2·s−2, 5.39 and 1.74 times higher than those of PCS porous material, respectively. The limited oxygen index (LOI) values of PCSM2-H-SiO2–2 porous composite were above 80 %. The cone calorimeter test result demonstrated the peak heat release rate and total heat release rate values of PCSM-H-SiO2–2 porous composite were lower than those of PCS porous material. The ultra-high flame-retardant PCSM-H-SiO2–2 porous composite with superhydrophobicity and excellent compressive property is a promising biodegradable thermal-insulation material as replacement of petroleum-based material.

Magnetic, self-heating and superhydrophobic sponge decorated with BN and CoFe2O4 for high-efficient cleanup of crude oil spills using facile co-precipitation strategy

Accidents involving petrochemical spills have repeatedly threatened the security of the eco-environment. The leaked crude oil exhibits poor fluidity, low adsorption efficiency, and urgent issues such as potential fire risks that require immediate attention. Herein, a multifunctional superhydrophobic sponge Si@CFO@BN@PU was prepared by a simple co-precipitation strategy based on BN and CoFe2O4. The results demonstrate that Si@CFO@BN@PU exhibits excellent superhydrophobic properties, with a water contact angle of 162° and a slide angle of less than 10°, and oil adsorption capacity ranging from 32.3 to 68.4 g/g. Furthermore, the modified sponge also possesses certain magnetic properties, allowing Si@CFO@BN@PU to be moved on the water surface via an external magnetic field and effectively adsorb floating oil. Meanwhile, the modified sponge exhibits excellent photothermal properties. The whole sponge can be heated up to 80 °C in just 60 s under simulated sunlight conditions, effectively reducing the adsorption time of viscous oil by 90 %. Moreover, the cone calorimeter test results demonstrate excellent fire safety of Si@CFO@BN@PU even after adsorption of petroleum. The peak heat release rate (pHRR), total heat release (TSR), maximum CO release rate, and maximum CO2 release rate have decreased by 37.8 %, 23.3 %, 45.4 %, and 34.1 %, respectively. Therefore, Si@CFO@BN@PU is an effective, safe and sustainable new adsorbent material with a wide range of applications in treating petrochemical spills.

Mechanical properties, microstructure and life-cycle assessment of eco-friendly cementitious materials containing circulating fluidized bed fly ash and ground granulated blast furnace slag

To reduce CO2 emission from the cement industry and solve environmental issues caused by the accumulation of circulating fluidized bed fly ash (CFA), this study aimed to prepare eco-friendly cementitious materials using CFA and ground granulated blast furnace slag (GGBS) as supplemental cementitious materials. The hydration properties, reaction kinetics, microstructure and life-cycle assessment of blended cements were investigated. The results showed that the compressive strengths of the blended cement samples containing 10 % CFA and 20 % GGBS increased by 7.3 % and 5 % at 7d and 28d, respectively, compared to the pure cement paste. The hydration process was characterized using isothermal calorimetry and analyzed by the Krstulovic-Dabic (K-D) model. The blended cement paste with the best compressive strength exhibited the highest total hydration heat release throughout the hydration process, with extended reaction times. The synergistic effect of CFA and GGBS promoted the formation of C-(A)-S-H gel, consuming more portlandite and leading to a decrease in the most probable pore size and an increase in gel pore volume in the pore structure. From the perspective of cost, economy, and environment, the normalized strength cost, energy consumption efficiency index, and CO2 intensity index can be reduced by 16.1 %, 27.1 %, and 33.3 % respectively. This work contributes to a better understanding of the synergistic mechanism in the CFA-GGBS blended cement system, and serves as a significant reference for the development of economical and eco-friendly cementitious materials.

Improved thermal stability and flame retardancy of soybean oil-based polyol rigid polyurethane foams modified with magnesium borate hydroxide and ammonium polyphosphate

The concept of sustainable development has led to a growing research interest in bio-based flame-retardant polyurethane foams. These foams offer environmentally friendly, sustainable, and flame-retardant raw materials for the construction, automotive, and furniture industries. The 15 wt% soybean oil-based polyol rigid polyurethane foams (RPUF-S3A20B system) were modified with 20 wt% ammonium polyphosphate (APP) and homemade magnesium borate hydroxide (MgBO2(OH)). Thermogravimetric analysis, pyrolysis kinetic analysis, limiting oxygen index (LOI) test, cone calorimetry (CONE), morphological analysis, and smoke density (Ds) were employed to investigate the impact of MgBO2(OH) on the thermal stability and flame-retardant properties of the RPUF-S3A20B system. The results indicated that RPUF-S3A20B12.5 with 12.5 wt% MgBO2(OH) had better thermal stability and higher activation energy. In addition, its LOI was increased by 3.1% compared to RPUF-S3A20 without MgBO2(OH). The peak heat release rate (PHRR) and total heat release rate (THR) of RPUF-S3A20B12.5 at a radiant flux of 25 kW/m2 were reduced by 45.8% and 35.0% compared with RPUF-S3A20. RPUF-S3A20B12.5 demonstrated the lowest smoke density (17.4 and 17.5) and highest light transmission (73.9% and 73.7%) in both flameless and flame conditions, indicating superior flame-retardant and smoke-suppression properties. These findings offered valuable insights for further research on synergistic flame-retardant systems in bio-based polyurethane foams.

Flame retardant and smoke suppression properties of 9,10‐dihydro‐9‐oxa‐10‐phosphaphenanthrene 10‐oxide derivative/zinc molybdate sepiolite modified acrylate emulsion

AbstractAcrylate emulsion is widely used in various industrial fields and is an important polymer emulsion. However, the high flammability limits its application. Besides, acrylate emulsion generally releases a large amount of smoke during combustion. To improve the fire resistance and smoke suppression properties of acrylate emulsions, methyl methacrylate‐butyl acrylate copolymer P(MMA‐BA)/DOPO‐based polymerizable monomer (HEPO)/zinc molybdate sepiolite (Mo‐Sep) composite emulsion was prepared by emulsion polymerization, and the effect of Mo‐Sep content on the flame‐retardant performance, thermal stability, and smoke suppression performance of the composite emulsion was studied. Through microcalorimeter and smoke density meter tests, it was found that the heat release rate (HRR) of the composite emulsion, added with 30% HEPO/3% Mo‐Sep, was reduced by 63.3%, and the peak heat release rate (PHRR) was reduced by 72.1%. The total heat release (THR) is reduced by 49.0%, while the peak‐specific optical density is reduced by 48.0%. It shows that the composite emulsion has excellent flame‐retardant and smoke suppression properties compared to pure MAA‐BA emulsion. In addition, scanning electron microscope (SEM) images show that the addition of Mo‐Sep increases the density of carbon residue. This composite emulsion may have potential application scenarios in the field of flame‐retardant coatings.

Effect of partial replacement of antimony trioxide with zinc borate and stannic oxide on the flame retardancy of flexible PVC films

AbstractReplacing antimony trioxide (Sb2O3) with an environmentally friendly alternative is of great scientific and commercial value for studying the flame retardant properties of flexible PVC (fPVC) films in automotive interior materials. This study develops flame retardant fPVC films with reduced Sb2O3 content by introducing stannic oxide (SnO2) and zinc borate (ZB). The results indicate that the fPVC film with ZB partially replacing Sb2O3 exhibits superior flame retardancy and smoke suppression compared to the product containing SnO2. The peak heat release rate (PHRR), total heat release (THR), and total smoke release (TSR) of 2ZB/2Sb2O3 fPVC film are reduced by 32.1%, 27.5%, and 22.1%, respectively, compared to that of 4Sb2O3 contained fPVC film. The increase in flame retardancy is attributed to the presence of ZB, which compensates for the deficiency of char formation ability of Sb2O3 in the condensed phase. The PHRR and THR of 2SnO2/2Sb2O3 fPVC film decrease by 27% and 12.5%, respectively, compared to that of 4Sb2O3 fPVC film, while the TSR increases by 16.5%. This study develops a straightforward approach to creating a flame retardant fPVC film that is suitable for the latest industrial application in automotive interior materials.

Fabrication of green montmorillonite modified bio-based rigid polyurethane foam with improved flame retardancy and enhanced mechanical properties

A low-carbon and sustainable green rigid polyurethane foam was prepared by compounding montmorillonite (MMT) with homemade barium phytate (BAPA). The flame retardancy, thermal stability and mechanical properties of the modified RPUFs investigated using the limiting oxygen index (LOI) method, cone calorimetry (CONE) and thermogravimetry. The results showed that the BAPA/MMT2 composite containing 2 wt% MMT had the highest LOI (25.1 %), and its peak heat release rate (PHRR) and total heat release (THR) were reduced by 14.33 % and 34.68 %, respectively, compared with that of the BAPA/MMT0 material without added MMT. In addition, the smoke production rate (SPR) and total smoke release (TSR) were reduced by 20.54 % and 30.77 %, respectively. BAPA/MMT2 had good flame retardancy and smoke suppression effect. The mechanical properties of BAPA/MMT2 with 2 wt% MMT were improved. The flame retardant mechanism confirmed that BAPA and MMT synergistically improved the quality of the carbon layer. At the same time, phosphorus-containing compounds (PO·), CO2 and water vapor were produced, which diluted the combustible gas in the gas phase and inhibit the flames spread. The current results provided a new strategy for the preparation of high-performance RPUFs.

Synthesis of graphene oxide/layered double hydroxides hybrids via co-precipitation and their polypropylene composites

A series of hybrid particles consisting of graphene oxide and magnesium–aluminium-layered double hydroxides (GO/Mg–Al-LDHs) were prepared by the co-precipitation method and then modified by allyltrimethoxysilane (ATMS). X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectra, Raman spectra and field emission scanning electron microscope (FESEM) micrograph results showed the modified GO/Mg–Al-LDHs were synthesised with a smaller particle size and better dispersion. The polypropylene (PP) composites were prepared via the reactive extrusion method, and the effects of GO content in hybrids on the mechanical properties, processability, thermal stability, flame retardation, melting and crystallisation behaviour of composites were investigated in detail. The comprehensive properties of composites containing GO/Mg–Al-LDHs were excellent compared to those of Mg–Al-LDHs under the same filler concentration. Compared with pure PP, 20 wt-% of GO/Mg–Al-LDHs-2.5 increased the limiting oxygen index (LOI) value of composites from 16.4% to 28.8% with a V-0 level of U-94 testing and decreased the heat release rate (HRR) and total heat release (THR) values from 1206.4 kW/m2 and 133.9 MJ/m2 to 146.9 kW/m2 and 69.6 MJ/m2. Meanwhile, the tensile, impact strength and elongation at break were 36.2 MPa, 3.0 kJ/m2 and 68.6%, respectively. This work provided an effective strategy for enhancing the dispersion and comprehensive properties of GO/LDHs-based composites.

Innovative multifunctional nanocomposite coated aluminum alloy for improved mechanical, flame retardant, and corrosion resistance in automobile industries

ABSTRACT Nanocomposites with impermeable two-dimensional materials show promise for metal corrosion protection. A coating matrix incorporating (3-aminopropyl)trimethoxysilane (AMS) functionalized molybdenum nitride (Mo2N) enhances the barrier effect due to its chemical and thermal stability. Further improvement is achieved by adding functionalized Mo2N into graphitic carbon nitride (GCN) within a polyurethane (PU) matrix, enhancing corrosion protection and fire retardancy. Electrochemical techniques evaluated the efficacy of aluminium coated with PU and varying concentrations of functionalized Mo2N/GCN. The resulting PU composite exhibited superior flame retardant capabilities, reducing peak heat release rate (pHRR), total heat release (THR), and total smoke production (TSP) compared to pure PU. Electrochemical impedance spectroscopy (EIS) showed enhanced coating resistance (5.55 × 101 1 Ω.cm2) even after 500 hours of exposure. Additionally, the composite displayed exceptional water repellency with a water contact angle (WCA) of 156° and commendable mechanical properties, including an adhesive strength of 19.2 MPa within the PU substrate. This multifunctional PU composite, incorporating functionalized Mo2N/GCN, presents a promising option for automotive coatings, offering corrosion protection, flame retardancy, water repellency, and mechanical robustness, thus enhancing durability and performance in harsh conditions.

Synthesis of novel reactive flame retardant to improve fire resistance and mechanical properties in epoxy resin

A novel reactive flame-retardant (FR), phosphorus-modified tetraethylenepentamine (TEPA-m-MVP), was prepared via aza-Michael addition process, using dimethyl vinylphosphonate (MVP). TEPA-m-MVP was successfully covalently introduced into the structure of the epoxy system, into the epoxy resin matrix synthesised from tetraethylenepentamine (TEPA) and diglycidyl ether bisphenol A (DGEBA) reaction, leading to the development of a flame-retardant epoxy resin (FR-EP). The curing behaviour, mechanical properties, thermal stability and flame-retardant behaviour of FR-EP samples were investigated and compared to the behaviour of the neat epoxy resin (EP). FR-EPs showed an increase in glass transition temperature (Tg), from 120 to 147 °C upon integrating TEPA-m-MVP into the epoxy resin structure, while the value of the E modulus remained unaffected. Furthermore, FR-EP-2%P sample with the optimal P content, approximately 2 wt%, displayed excellent flame-retardant properties. In comparison to EP, total heat release (THR) and peak heat release rate (pHRR) for FR-EP-2%P decreased from 22.6 to 15.3 kJ.g−1 and from 1557 to 572 kW.m−2, respectively. In addition, an interesting impact of the crosslinking density of FR-EP samples on the fire behaviour was observed. This work presents a new strategy for the simultaneous modification of the flame retardancy and mechanical properties of epoxy systems.

A Comparison Between Conventional and MILD Combustion Processes of Turbulent Stratified Mixtures

ABSTRACT The relative enhancements of volume-integrated burning rate and flame surface area under turbulence and heat release rate contributions due to different combustion and flame propagation modes have been compared between conventional and Moderate or Intense Low Oxygen Dilution (MILD) combustion of stratified mixtures (for a global mean equivalence ratio of 0.8) for the first time using three-dimensional Direct Numerical Simulation (DNS) data. The burning rate enhancement under turbulence is found to be comparable to the enhancement of flame surface area for the conventional stratified flames considered here, whereas the burning rate enhancement is found to be considerably greater than flame area augmentation in the MILD cases analyzed here. It has been found that almost all the heat release rate arises due to the lean-premixed mode of combustion for the conventional stratified flame cases considered here. In contrast, the lean premixed mode of combustion accounts for about 50% of the total heat release rate for the MILD cases where rich-premixed and non-premixed modes of combustion contribute significantly to the overall heat release rate. Under the conditions analyzed here, more than 75% of heat release rate arises from the propagation-dominated regions for both MILD combustion and stratified flame cases, but the trend is stronger in the conventional stratified mixture combustion. More than 80% of heat release rate in the globally lean conventional stratified flame cases considered here originates from back-supported flame propagation, whereas both front and back-supported flame propagation modes have comparable contributions to heat release in the MILD combustion cases. The non-premixed mode of combustion has been found to play a more important role in the MILD combustion cases than in the case of conventional stratified flames. This implies that the closures, which work reasonably well for MILD combustion of homogeneous mixtures, may not be sufficient for modeling of MILD combustion of stratified/inhomogeneous mixtures.

Fabrication of nickel phytate modified bio-based polyol rigid polyurethane foam with enhanced compression-resistant and improved flame-retardant

A bio-based flame retardant nickel phytate (PA-Ni) was synthesized and combined with soybean oil-based polyol (SO) to create a green rigid polyurethane foam (RPUF) with enhanced compressive strength, good thermal stability and flame retardant. The results showed that the RPUF-SO2/Ni3 with 3 wt% PA-Ni had the highest initial and termination temperature, maximum thermal decomposition rate temperature and carbon residue, and better thermal stability. Its limiting oxygen index was increased by 2.6% compared with RPUF-SO2 without PA-Ni added, and the peak heat release rate (PHRR) and total heat release rate (THR) were reduced by 14.92% and 19.92%, respectively. In addition, RPUF-SO2/Ni3 had the lowest Ds under the conditions of flame (18.90) and flameless (22.41), and had the best smoke suppression effect. And the compressive strength of RPUF-SO/Ni3 was significantly enhanced by the addition of PA-Ni. The results show that the improvement of flame retardancy of RPUF is mainly the result of the combined effect of gas-phase and condensed-phase flame retardancy, among which the flame retardancy of RPUF-SO/Ni3 was the best. The current findings offer a practical way to produce green and low-carbon RPUF as well as promising prospects for the material's safe application.

Flame-retardant performance of a novel lignin-based rigid polyurethane foam prepared from pulping black liquor

To improve the flame retardancy of rigid polyurethane foam (RPUF), black liquor lignin-based rigid polyurethane foam (LRPUF) was prepared in this work through a one-step foaming method using lignin and inorganic salt in black liquor lignin as the structural modifier and the additive flame retardant, respectively. Effect of the addition of carbon dioxide treated black liquor lignin (CBL) on the structure and flame retardancy of LRPUF, as well as the flame flame-retardant mechanism of LRPUF, were investigated. The limiting oxygen index (LOI) test and cone calorimetric tests showed that compared to the RPUF, the LOI of LRPUF with 40 wt% CBL increased from 18.9 % to 21.3 %, and the peak heat release rate, total heat release, and total smoke production decreased by 19.5 %, 25.3 %, and 20.5 %, respectively, indicating that the addition of CBL improved the flame retardancy of LRPUF. The flame-retardant mechanism was investigated by analyzing the structure and components of the char residue. We found that a dense protective layer, consisted of char residue and a considerable amount of sodium sesquicarbonate on the surface of the char residue, was formed after combustion. This study provided a novel strategy for the resource utilization of black liquor lignin.

Thermal and Combustion Properties of Biomass-Based Flame-Retardant Polyurethane Foams Containing P and N.

Biomass has been widely used due to its environmental friendliness, sustainability, and low toxicity. In this study, aminophosphorylated cellulose (PNC), a biomass flame retardant containing phosphorus and nitrogen, was synthesized by esterification from cellulose and introduced into polyurethane to prepare flame-retardant rigid polyurethane foam. The combustion properties of the PU and PU/PNC composites were studied using the limiting oxygen index (LOI), UL-94, and cone calorimeter (CCT) methods. The thermal degradation behavior of the PU and PU/PNC composites was analyzed by thermogravimetric analysis (TGA) and thermogravimetric infrared spectroscopy (TG-IR). The char layer after combustion was characterized using SEM, Raman, and XPS. The experimental results showed that the introduction of PNC significantly improved the flame-retardant effect and safety of PU/PNC composites. Adding 15 wt% PNC to PU resulted in a vertical burning grade of V-0 and a limiting oxygen index of 23.5%. Compared to the pure sample, the residual char content of PU/PNC15 in a nitrogen atmosphere increased by 181%, and the total heat release (THR) decreased by 56.3%. A Raman analysis of the char layer after CCT combustion revealed that the ID/IG ratio of PU/PNC15 decreased from 4.11 to 3.61, indicating that the flame retardant could increase the stability of the char layer. The TG-IR results showed that PNC diluted the concentration of O2 and combustible gases by releasing inert gases such as CO2. These findings suggest that the developed PU/PNC composites have significant potential for real-world applications, particularly in industries requiring enhanced fire safety, such as construction, transportation, and electronics. The use of PNC provides an eco-friendly alternative to traditional flame retardants. This research paves the way for the development of safer, more sustainable, and environmentally friendly fire-resistant materials for a wide range of applications.

Catalyst-Free synthesis of sulfonamide-functionalized Poly(phosphonate)s and Poly(phosphate)s using Bis(aziridine)s

We present an efficient step-growth polymerization method for synthesizing sulfonamide-functionalized poly(phosphonate)s and poly(phosphate)s. The polymerization process involves treating bis(aziridine) with organophosphorus acid in toluene, without the need for any catalyst, yielding the desired polymers in high yields. Six different types of organophosphorus acids and inorganic phosphoric acid were found to be suitable for this method. Thermal analysis of the resulting poly(phosphonate)s and poly(phosphate)s revealed a decomposition temperature (Td,5%) of up to 330 °C at 5 % weight loss, while differential scanning calorimetry (DSC) analysis showed glass transition temperatures (Tg) ranging from 54 to 98 °C. Microscale combustion calorimetry (MCC) analysis demonstrated that the cross-linked poly(phosphate) derived from inorganic phosphoric acid exhibited the lowest peak heat release rate (HRR) and total heat release (THR) compared to the linear ones. These findings are expected to provide a straightforward approach for synthesizing novel phosphorus-containing polymers.

Porous liquids assisted in-situ generated Co-LDH@MOF heterostructure with abundant defects for flame retardant and mechanical enhancement in polyurea composites

Preventing aggregation and inducing homogeneous dispersion of flame retardant nanofillers is critical to enhance the fire safety and mechanical properties of nanocomposites. Although chemical modifications are commonly used to improve the filler’s compatibility with the polymer chain, such methods are often cumbersome and limited. Herein, porous liquids (PLs) with flame retardant function were constructed in which porous defect-Co-LDH@ZIF-67 (d-LDH@ZIF) heterostructure particles were converted into liquid materials by electrostatic interaction with a large-volume solvent. This is also the first report of PLs in the field of flame retardant. Specifically, the d-LDH@ZIF heterostructure was designed by defect engineering and in situ growth strategy to compensate for the low catalytic activity and specific surface area of Co-LDH, and to serve as a rigid porous framework for PLs. Numerous cobalt/oxygen vacancies and lattice defects in the d-LDH@ZIF heterostructure have also been proven to confer higher flame retardancy relative to Co-LDH. d-LDH@ZIF porous liquids (PLs-d-L@Z) presents favorable liquid characteristics and achieves a monodisperse state in the polyurea matrix. The limiting oxygen index of polyurea composites blended with 20 wt% PLs-d-L@Z (3 wt% d-LDH@ZIF content) can be increased to 24.2 % and pass the V-0 rating in the UL-94 test. Moreover, the peak of heat release rate, total heat release, and total smoke production are reduced by around 40.4, 27.0, and 39.9 %, respectively, compared to neat polyurea. Emphatically, the PLs-modified polyurea composites exhibit significantly improved mechanical and impact resistance properties, as well as favorable chemical resistance. This strategy of liquefying solid flame retardant fillers will open an avenue to the design of functional nanomaterials for fire safety and other potential applications.

Synthesis and Polymerization of the Bio‐Benzoxazine Derived from Resveratrol and Thiophenemethylamine and Properties of its Polymer

AbstractResveratrol and 2‐thiophenemethylamine have been employed in the synthesis of a novel tri‐functional benzoxazine (RES‐th) to develop the bio‐benzoxazine monomer. The chemical structure of the synthesized monomer is confirmed by various characterization technics. The polymerization behavior is monitored by in situ Fourier transform infrared spectroscopy (FTIR) and differential scanning calorimetry (DSC). The in situ FTIR results reveal distinct reaction mechanisms for the three oxazine rings presented in RES‐th, with both ether and phenolic Mannich bridge structures observed in the products. The activation energy values of RES‐th are calculated to be 119.05, 120.97, and 119.44 kJ mol−1 by Kissinger, Ozawa, and Starink methods, respectively, which are all based on the heat flow curves at various heating temperatures. The thermal stability and flame retardancy of the resulting polybenzoxazine (poly(RES‐th)) are investigated by thermogravimetric analysis (TGA) and microscale combustion calorimeter (MCC). The values of Td5 and Td10 of polybenzoxazine are found to be 356 °C and 399 °C, respectively, with a char yield of 66.3% at 800 °C. The prepared polybenzoxazine also demonstrates nonflammability characteristics with the values of heat release capacity (HRC) and total heat release rate (THR) of 18.65 J (g K)−1 and 2.69 kJ g−1, respectively. These findings suggest that the thermoset, poly(RES‐th), is a promising candidate for fire‐resistant applications.

Polydopamine-primed FeCo-LDH endowed epoxy resin with enhanced flame retardancy and mechanical properties

The integration of layered double metal hydroxides (LDH) into epoxy resin (EP) for flame retardancy is in line with the principles of environmentally friendly and sustainable development. In this study, polydopamine (PDA)-primed intercalated LDH containing iron and cobalt ions (LDH-DBS@PDA) was prepared, and its chemical composition, structure and morphology were thoroughly characterized. Due to the synergistic flame-retardant properties exhibited by LDH and PDA, as well as the catalytic charring properties of iron and cobalt ions in both condensed and gaseous phases, EP composite with 5 wt% LDH-DBS@PDA achieved a UL-94 V-0 rating with a limiting oxygen index of 30.7 %. Moreover, EP/LDH-DBS@PDA exhibited a significant decrease in total heat release by 48 % and smoke release by 52 %, demonstrating remarkable fire safety performance. Additionally, the existence of LDH-DBS@PDA improved impact strength, tensile strength, and glass transition temperature due to strong interactions between PDA and EP matrix. This work presents a promising strategy for developing highly efficiency flame retardants with excellent compatibility for polymeric materials.

Smoke Suppression Properties of Fe2O3 on Intumescent Fire-Retardant Coatings of Styrene–Acrylic Emulsion

The intumescent flame-retardant coatings were prepared using ammonium polyphosphate (APP), pentaerythritol (PER), melamine (MEL), styrene–acrylic emulsion, and iron oxide yellow (FeOOH) as the base material. A cone calorimeter (CCT), smoke density meter (SDA), and scanning electron microscope (SEM) were employed to investigate the smoke suppression and flame retardancy of FeOOH in intumescent fire-retardant coatings. The thermal degradation performance of intumescent fireproofing coatings with varying FeOOH content was investigated through thermogravimetric analysis (TGA). The structure of the carbon slag in the CCT test was analyzed using a scanning electron microscope (SEM). The results of the cone calorimeter (CCT) experiments demonstrated that FeOOH significantly reduced the heat release rate (HRR), total heat release rate (THR), smoke production rate (SPR), and total smoke release rate (TSR) of the coating, while simultaneously increasing the carbon residue rate of the coating. The smoke density analysis (SDA) results demonstrate that adding FeOOH can effectively reduce smoke generation, regardless of whether a pilot flame is used. TGA results demonstrate that FeOOH can enhance the weight of coke residue at elevated temperatures. SEM results indicate that incorporating FeOOH resulted in a more compact coke residue. According to these findings, among all the samples, those containing 2 wt% FeOOH showed low levels of HRR, THR, SPR, and TSR and high levels of SOD, which proves that FeOOH can be used as a smoke inhibitor in flame-retardant coatings.