Flame Retardant Research Articles

Strategic insights of imparting flame retardancy into nano-cellulosic materials: A review

Nanocellulose (NC) is a biomaterial with prospective use as a futuristic material. NC-based materials have several diverse uses, and their demand is growing every year. However, because of their highly flammable nature, the use of NC in harsh settings is greatly restricted. Hence, it is crucial to minimize the risk of fire caused by NC-based materials to maintain a superior level of performance. To diminish the inherent flammability of these substances, flame-retardant elements are often added as additives to produce flame-retardant nanocomposites. Hence, in this review, we have provided a comprehensive summary of the characteristics of NC and the principles and categorization of flame retardants. Subsequently, we have discussed the methods used for the synthesis and characterization of NC-based flame-retardant materials. It also delves into the historical progressions in these materials, intending to enhance the ability to resist flames. The article investigates the fire resistance properties of several materials based on NC, including aerogels, coatings, films, and textiles. The objective of this review is to provide a comprehensive analysis of the future directions and advancements in multi-functional flame-retardant NC materials, with a focus on their potential applications in harsh situations.

Improving flame retardancy of microfiber synthetic leather by decorating with phosphorus/boron hybrid polysiloxanes

Microfiber synthetic leather (MSL) as a fiber reinforced composite has famous application. However, its highly flammability as well as melt-dripping need to be solved. Currently, enhancing the flame retardancy of MSL is still challenging. In this study, we developed a phosphorus/boron hybrid polysiloxane coating on MSL by co-depositing phosphorus-based polysiloxane (PDPTES) and boric acid (BA), creating a multi-element synergistic flame-retardant system. By decorating with phosphorus/boron hybrid polysiloxanes, the modified MSLs with PDPTES and PDPTES-BA achieved a limited oxygen index (LOI) of 27.0 % and 28.8 %, achieving self-extinguishing ability with short damage length and no melt-dripping in vertical flammability test (VFT). Both PDPTES and PDPTES-BA well-maintained the good thermal stability of MSL and char residues at high temperature was obviously increased. The incorporation of BA could enhance the char-forming ability of PDPTES modified MSL. The peak heat release rate (PHRR) and total heat release (THR) of MSL-PDPTES-BA was 20 % and 25 %, respectively. This multi-elemental flame retardant system owned both condensed and gaseous phase action by strengthening the carbonization effects, reducing the release of combustible volatiles and releasing silicon/phosphorus/boron-containing fragments. Additionally, the modification of PDPTES and PDPTES-BA has little effect on the air permeability of MSL. Thus, this work provides a suitable strategy for developing microfiber synthetic leather with good flame-retardant performance.

Optimization Design of Flame-Retardant Rigid Polyurethane Foam Modified by Piperazine pyrophosphate/ Zinc Tailings/ Sodium Ligninsulfonate based on Orthogonal experiment

The flammability of rigid polyurethane foams (RPUF) is a significant concern for application. This study introduces a novel flame-retardant RPUF modified by piperazine pyrophosphate (PAPP), zinc tailings (ZTs), and sodium lignosulfonate (LS). The result of cone calorimeter test reveals that the peak heat release rate (p-HRR) and total heat release (THR) of the RPUF doped with 18wt.% PAPP, 10wt.% ZTs and 2.5wt.% LS decreases by 49.4% and 58.3% respectively. The Fire Resistance Index (FRI) achieved a value of 10.17, and vertical combustion tests indicated V-0 rating, signifying improved flame retardancy. Furthermore, the TG/DTG analysis shows that the decomposition activation energy (Eα) increased from 132.85kJ·mol-1 to 222.12kJ·mol-1 in the main stage of decomposition (249~342 ℃), representing enhanced thermal stability. Subsequently, the orthogonal experiments and regression analysis reveal that LS has the most significant impact on p-HRR, followed by ZTs. The combination of ZTs and LS exerts the most significant synergistic influence on p-HRR, whereas the combination of PAPP and LS has the most insignificant impact. The introduction of LS provides carbon and gas source, and improve the dispersion of PAPP and ZTs in the whole system. The optimal experimental ratio of modified RPUF is obtained through regression optimization. Consequently, the flame-retardant RPUF represents a sustainable bio-based composite material that effectively utilizes industrial and biowaste resources.

Liquid phosphorus-based bis-imidazole compounds as latent curing agents for enhancing thermal, mechanical, and flame-retardant performances of single-component epoxy resins

The escalating need for advanced, fire-resistant, single-component epoxy resin (EP) is fueled by its practicality and economic benefits, highlighting the necessity for the development of multifunctional flame-retardant latent curing agents. Herein, two liquid phosphorus-containing bis-imidazole compounds, PPDM and DPCMI, were synthesized as latent curing agents for EP, demonstrating multiple effects in improving latency, thermal stability, mechanical properties, and fire safety. EP/PPDM and EP/DPCMI showcased superior storage stability and rapid curing at moderate temperatures, with EP/PPDM standing out for its long shelf life of 7 d and being gelled within 18 min at 100°C. The resulting thermosets presented increased glass transition temperatures (189.5 and 178.9°C), due to the enhanced crosslinking densities. The presence of bis-imidazole groups in PPDM and DPCMI enabled EPs to form denser crosslinked networks, leading to improved mechanical strength and toughness. The limiting oxygen index (LOI) values of EP/PPDM and EP/DPCMI reached 29.5% and 29.0%, respectively. Compared to the control EP, EP/PPDM and EP/DPCMI showed 23.1% and 18.8% reductions in total heat release and 22.0% and 23.11% decreases in total smoke production. These results confirm the enhanced flame retardancy and smoke suppression of EP/PPDM and EP/DPCMI because of introducing phosphorus-containing groups. Even though the curing time was halved to 2.5 hours, EP/PPDM systems maintained satisfactory overall performances. Therefore, this work offers a scalable strategy for the fabrication of single-component EP systems combining rapid curing, satisfactory flame retardancy, and enhanced thermal stability and mechanical properties, aligning with the needs of industrial applications.

Sustainable calcium gluconate-based coatings for lyocell fabrics with superior flame retardancy, antibacteria and wearing properties

Sustainability and high performance of flame retardants for lyocell fabrics were still difficult to balance. Here, the full bio-based coatings (PACG) for lyocell fabrics with superior efficient flame-retardant, antibacterial and wearing properties were prepared by phytic acid (PA) and calcium gluconate (CG) in the water solvent. The fire safety of PACG/Lyocell fabrics was remarkably enhanced with an increase in limiting oxygen index (LOI) to 28.7 % when the weight gain was only 4.8 wt%. Meanwhile, PACG/Lyocell fabrics do well work on the heat and smoke release inhibition deriving from the satisfactory synergistic effect of PACG between fast formation of dense residuals and a large release noncombustible gas. Additionally, the existence of calcium ion in the PACG endowed the Lyocell fabrics with excellent antibacterial activity, where the antibacterial properties of Staphylococcus aureus (S. aureus) reached to 99.99 %. Moreover, after 100 dry friction cycles, PACG/Lyocell fabrics still maintained superior flame retardancy and antibacterial properties. More interestingly, unlike other treatment, this efficient and mild treatment method did not deteriorate the whiteness, moisture regain, and wearing properties of lyocell fabrics, which offered a simple and eco-friendly way to obtain the flame-retardant and antibacterial lyocell fabrics with well wearing properties.

Effect of expandable graphite content on the physical, thermal and mechanical properties of novolac matrix composites: Halogen-free flame-retardant polymer composites

Flame-retardant properties are particularly important for materials used in high-temperature applications. This study focuses on novolac matrix composites reinforced with expandable graphite (EG) particles, produced through a hot pressing process using powders prepared by mechanical milling. The research examines the particle size of both the matrix and the reinforcing particles used in composite production. Additionally, the morphology of the powders, the microstructural properties of the composites, and the fracture surfaces after tensile testing were analyzed using scanning electron microscopy (SEM). Phase analysis of the samples was performed using X-ray diffraction (XRD). Hardness and tensile tests were conducted to evaluate the mechanical properties. The effect of EG particles on the thermal stability of the composites was assessed using thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and thermal conductivity tests. Furthermore, flammability was evaluated by determining the Limit Oxygen Index (LOI) values. The experimental results identified the optimum reinforcement ratio as 20 wt% EG. TGA results showed residue values of approximately 37.39 % for pure novolac and 57.87 % for novolac matrix composites reinforced with 20 wt% EG. The highest thermal conductivity (0.72 W/mK) and LOI values (40.64 %) were achieved with 20 wt% EG reinforcement, resulting in an LOI value approximately 1.25 times greater than that of the pure novolac sample (32.45 %). Additionally, tensile strength increased by approximately 2.7 times compared to the pure novolac sample. This research highlights the potential of the novolac/EG composites for advanced high-temperature applications where enhanced flame retardancy and structural integrity are essential.

Advanced multifunctional fabrics enabled by bioinspired coatings

The demand for textiles with functional properties has been increasing over the past few decades, driven by both civilian and military applications. In this study, we present a method to impart flame retardant (FR) and insect repellent (IR) properties to nylon-cotton blends. Flame retardancy was achieved by covalently attaching phytic acid, a bio-derived material, to the hydroxyl groups of cotton in nyco fabrics. Subsequently, these FR-treated nyco fabrics were coated with an acylate-based monomer along with permethrin to confer insect-repellent properties. FTIR-ATR spectroscopy confirmed the presence of weight of phytic acid on nyco fabric and the weight gain from this was 6 % with respect to initial fabric weight. The multifunctional fabrics exhibited a 200 % increase in char formation upon thermal degradation compared to untreated nyco. Moreover, the multifunctional fabrics demonstrated self-extinguishing properties with a char length of <15 cm, whereas untreated fabrics burned completely. In cone calorimeter experiments, FR-treated fabrics showed a reduction of over 25 % in total heat release compared to untreated controls. The addition of FR facilitates char formation and the release of non-flammable gases such as water vapor (H2O), carbon dioxide (CO2), and ammonia (NH3), suggesting a condensed phase mechanism of FR action as evident from TGA-FTIR evolved gas analysis. The insect repellent properties (IR) were evaluated using a tube test method as described by the World Health Organization, revealing a knockdown rate exceeding 98 % for fabrics treated with insect repellent.

Effect of filler loading on the frictional, thermal and mechanical properties of ABS/boron nitride (h-BN) nanocomposites

The effect of hexagonal boron nitride (h-BN) nanoparticles in acrylonitrile butadiene styrene (ABS) polymer matrix is investigated. ABS/h-BN nanocomposites were prepared with h-BN content ranging from 0.5 to 5 wt% and their frictional, thermal and mechanical properties were evaluated. XRD analysis showed that the 'd' spacing in h-BN stacks increased in the ABS nanocomposite due to the interpenetration of ABS polymer chains. The tensile properties and thermal stability of ABS matrix showed better improvement with 0.5 wt% addition of h-BN nanoparticles. The tensile fracture mechanism in ABS/h-BN nanocomposites was predicted using tensile fracture surface analysis. Coats-Redfern approach was applied to support the thermal stability analysis results. Significant enhancement (28 %) in frictional property of ABS was observed in the nanocomposite with h-BN. Wettability and flame retardancy of the ABS/h-BN nanocomposites were also investigated.

Gene biomarkers in estuarine oysters indicate pollution profiles of metals, brominated flame retardants, and poly- and perfluoroalkyl substances in and near the Laizhou Bay

The Laizhou Bay (LZB) is of ecological and fishery importance. The discharge of effluents containing numerous pollutants into the LZB via rivers poses significant risks to ecosystem and human health. Estuarine biomonitoring is therefore crucial for assessing the contribution of rivers to coastal pollution and their impacts on species. Estuarine oyster Crassostrea gigas is a preferable bioindicator to pollution conditions. This study measured accumulation of contaminants and expression levels of gene biomarkers in the LZB and Northern Shandong Peninsula (NSP) oysters. The LZB oysters accumulated higher levels of brominated flame retardants (BFRs) and poly- and perfluoroalkyl substances (PFAS), while NSP oysters exhibited greater accumulation of heavy metals. Decabromodiphenyl ethane was the dominant BFR, while perfluorooctanoic acid and perfluoro-2-methoxyacetic acid were the dominant PFASs in oysters. The expression of gene biomarkers effectively distinguished the LZB and NSP oysters, with CYP2 subfamilies expression correlating with BFRs and PFASs and metallothionein expression indicating heavy metals. The reproductive endocrine and neuroendocrine-immune systems in oysters might be the targets of BFRs and heavy metal pollution, respectively. The negative correlation between contaminant accumulation and gene expression might be explained by adaptive evolution, emphasizing the need to consider genetic diversity in ecological risk assessments.

Development and performance evaluation of composite flame retardant based on the thermodynamic properties of asphalt components

Development and performance evaluation of composite flame retardant based on the thermodynamic properties of asphalt components

Determination of brominated flame retardants in electrical and electronic equipment by micro-sample pretreatment technique combined with ion chromatography

A method for the determination of brominated flame retardants was established by micro sample pretreatment technology combined with ion chromatography. Using a sealed glass capillary as a micro reactor, the brominated flame retardants were debrominated by pyrolysis at 300 ℃ and absorbed by absorbing liquid, followed by ion chromatography determination. To improve the debromination efficiency, important factors including pyrolysis time and absorbing liquid were investigated. The linearity of the method was satisfactory over a Br− concentration of 0.05∼100 mg/L and the determination coefficient was greater than 0.999. The limit of detection and limit of quantitation of bromide ion were 1.50 μg/L and 5.00 μg/L, respectively. The potential of the established method was assessed by applying it to the determination of total bromine in actual electrical and electronic equipment. The average recoveries (97.1–104.2 %) and the precision (3.1–7.5 %) were achieved by real samples spiked with three levels. This proposed method, with simple operation and low cost, could be a good supplementary for the oxygen bomb combustion-ion chromatography method for the determination of brominated flame retardants in electrical and electronic products.

A Bio-Based Polybenzoxazine Derived from Diphenolic Acid with Intrinsic Flame Retardancy, High Glass Transition Temperature and Dielectric Properties.

A bio-based benzoxazine monomer, diphenolic methyl ester hexafluoro diamino benzoxazine (DPME-HFBz), was successfully synthesized from diphenolic acid (DPA), and the chemical structure was successfully verified. The curing kinetics were studied via non-isothermal differential scanning calorimetry (DSC). The activation energies of DPME-HFBz were calculated by Kissinger and Ozawa methods to be 136.15 and 139.92 kJ/mol, respectively, and the reaction order was calculated to be first order. Owing to the large number of hydrogen bonds after polymerization, poly(DPME-HFBz) presented an ultra-high glass transition temperature of 312 °C and a high initial decomposition temperature (350 °C under air and 345 °C under nitrogen). Because of the excellent charring ability (50.2% residue under nitrogen), the LOI value of poly(DPME-HFBz) was as high as 38%. Poly(DPME-HFBz) also exhibited a very low heat release capacity (HRC) of 90 J/(g·K). In addition, poly(DPME-HFBz) had a dielectric constant (Dk) of 1.88 at 1.5 MHz, which was much lower than the Dk of the reported low-dielectric polymers. This work provides an efficient and sustainable strategy for the synthesis of benzoxazine thermosetting materials with excellent comprehensive properties.

Study on the mechanical properties of layered gradient structure PBT-based flame retardant composite materials

Abstract To enhance the flame retardancy of Polybutylene Terephthalate (PBT) based composite materials and overcome the decrease in mechanical properties due to the high content of nano-antimony trioxide (nano-Sb2O3), this study initially applies a composite modification method to treat the surface of nano-Sb2O3. Subsequently, composite materials with a gradient distribution of nano-Sb2O3 are prepared through lamination hot-pressing technology, and their mechanical and flame retardant properties are investigated. The results show that the modifiers CTAB and KH560 are successfully grafted onto the surface of nano-Sb2O3, altering its surface properties. Through lamination hot-pressing technology, a gradient distribution from the surface to the core is achieved. Compared to the homogeneous distribution P666, G828 exhibits a 6% increase in Limiting Oxygen Index (LOI), improving the flame retardancy of the composite material. As nano-Sb2O3 enriches on the composite material's surface, the amount of char residue increases. The tensile strength, bending strength, and impact strength of G828 composite material increase by 19.7%, 37.1%, and 103%, respectively, compared to the homogeneous composite material P666, proving the significant effect of G828's gradient distribution in enhancing the mechanical properties of the composite material.&amp;#xD;

Strengthen Water O−H Bond in Electrolytes for Enhanced Reversibility and Safety in Aqueous Aluminum Ion Batteries

AbstractAqueous aluminum‐ion batteries present a promising prospect for large‐scale energy storage applications, owing to the abundance, inherent safety, and the high theoretical capacity of aluminum. However, their voltage output and energy density are significantly hindered by challenges such as complex hydrogen evolution and uncontrollable solvation reactions. In this work, we demonstrate that water decomposition is restrain by increasing the electron density of water protons and increasing the dissociation energy of H2O through robust dipole interactions with highly polar dimethylformamide (DMF) molecules. Moreover, the incorporation of dimethyl methylphosphonate (DMMP) flame retardant effectively addresses the flammability risk arising from a substantial presence of organic additives The in‐depth study with experimental and theoretical simulations reveals that the water‐poor solvation structure with reduced water activity is achieved, which can (i) effectively mitigate undesired solvated H2O‐mediated side reactions on the Al anode; (ii) boost the de‐solvation kinetics of Al3+ while preventing cathode structural distortion; (iii) reduce the flammability of hybrid electrolytes. As a proof of concept, the Al//AlxMnO2 full cell employing a hybrid electrolyte demonstrate enhanced stability (deliver 335 mAh g−1 while retaining 71 % capacity for 400 cycles) compared to those with pure electrolyte.

Interlayer-Functionalized Graphene with Phosphorus–Silicon-Containing Elements for Improving Thermal Stability and Flame Retardance of Polyacrylonitrile

Highly-effective non-halogenated flame retardants have received widespread attention because they are environmentally friendly, with low toxicity and low smoke density. In this work, interlayer-functionalized graphene (fRGO) containing silicon and phosphorus elements was synthesized via hydrolytic condensation with 3-(methacryloyloxy)propyltrimethoxysilane and addition reaction with 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide. Interlayer spacing and oxygen-containing groups of reduced graphene oxide (RGO) were regulated by controlling the hydrazine hydrate dosage. Then, phosphorus–silicon-containing organic molecules were inserted into RGO interlayers; this was verified by FTIR, XPS, TEM, etc. The fRGO was added to a polyacrylonitrile (PAN) matrix using a solution blending method to prepare polyacrylonitrile (PAN) composites. The fRGO addition caused the significant decrease in cyclization heat and the considerable increase in char residues, indicating improved thermal stability. Importantly, PAN composites exhibited outstanding flame-retardant properties, with the peak heat release rate reduced by 45%, which is ascribed to the dense graphitic carbon layers induced by phosphorus–silicon-containing organics and the 2D barrier effect of RGO layers to prevent the heat and mass transfer.

All-Polymer Composite Film with Outstanding Mechanical, Thermal Conductive, and EMI Shielding Performances.

Robust polymer-based composites with high thermal conductivity (TC) and electromagnetic interference shielding effectiveness (EMI SE) hold great promise for applications in rapidly developing electronics. Traditional composites containing inorganic fillers often suffer from increases in processing difficulty, density, and significant deterioration in mechanical properties. Herein, we report for the first time a flexible multilayered all-polymer composite of poly(p-phenyl-2,6-phenylene bisoxazole) (PBO) and poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS), featuring excellent mechanical strength of 203.9 MPa, in-plane TC of 21.9 W/mK, EMI shielding effectiveness (SE) of 44.2 dB, high-temperature stability, and flame retardancy. The excellent TC, mechanical strength, and flame retardancy of PBO, the remarkable EMI shielding performance of PEDOT:PSS, and the π-π stacking interactions between adjacent layers contribute to the comprehensive properties, which outperform most of the traditional composites of polymers and inorganic fillers reported so far. This full-polymer design may pioneer a new strategy for the preparation of robust and lightweight multifunctional composites.

Biobased Hyperbranched Flame Retardant for Epoxy Resin Modification: Simultaneously Improved Flame Retardancy, Toughness, and Smoke Toxicity Suppression

Biobased Hyperbranched Flame Retardant for Epoxy Resin Modification: Simultaneously Improved Flame Retardancy, Toughness, and Smoke Toxicity Suppression

Enhancing the flame retardancy, thermal stability, and superhydrophobicity of paper through Na₂O·nSiO₂ and polydimethylsiloxane modification

Enhancing the flame retardancy, thermal stability, and superhydrophobicity of paper through Na₂O·nSiO₂ and polydimethylsiloxane modification

Tertiary nitrogen carbonization and imine cross‐linking facilitated solid‐phase flame retardant for anti‐dripping PA6 fiber

AbstractA developing society requires polycaprolactam (PA6) fibers with flame retardant. Currently, the additive flame retardants commonly used in PA6 fibers cannot solve the molten droplet problem. In this work, (1E,1′ E)‐N,N′‐(6‐phenyl‐1,3,5‐triazine‐2,4‐diyl)bis(1‐(4‐methoxyphenyl) methanimine) (NBM) with triazine ring structure was synthesized. The triazine ring structure was used to expand into carbon and benzoguanimine structure to produce irreversible chemical crosslinking in NBM, thereby achieving anti‐dripping and flame retardant of PA6 fiber. LOI of PA6/NBM8 reaches 30.0 vol.%, UL‐94 reaches V‐0 when the NBM addition amount is 8 wt.%, meanwhile, the residual carbon content is 235.7% higher than that of PA6. The mechanical strength can still reach to 3.22 cN/dTex. From structural design to synthesis, the effects of NBM addition on the flame retardants, rheology, thermal stability and residual carbon morphology of PA6/NBMx were analyzed in detail in this work. It is hoped that in the future work, the structural characteristics and performance requirements can be matched to provide reference for conception and synthesis of flame retardants oriented to other polymers.

A facile and sustainable preparation of effective biomass macromolecular flame retardants for epoxy resins with improved flame retardation, smoke suppression, and mechanical performance

AbstractThe preparation of biomass flame retardants with efficient flame‐retardant properties is conducive to the realization of sustainable development and is of great practical significance. In this work, a green and sustainable biomass flame retardant PATAPEI was prepared by using phytic acid (PA), tannic acid (TA), and polyethyleneimine (PEI) as reactants via a one‐step method to develop biomass flame retardants that can synchronize enhanced flame retardation, smoke suppression, and mechanical performance of epoxy resin (EP). The EP with only a 3% PATAPEI (EP/3PTP) has a LOI value of 28.5% with a UL‐94 V‐0 classification. The peak heat release rate (PHRR), total heat release (THR), and total smoke release (TSR) of EP/3PTP were decreased by 29.72%, 25.80%, and 21.16%, respectively, in comparison with the ones of pure EP. Additionally, the tensile and impact strengths of EP/3PTP are higher than the ones of pure EP. PATAPEI on heating decomposes to produce phosphorus‐containing acids and biphenyltriol‐containing compounds, which promote to form a good char layer with the aromatic structures during the combustion of EP/3PTP. Therefore, PATAPEI has prospects of wide application in the development of sustainable biomass flame retardant EP.