Traditional Flame Retardants Research Articles

Eco‐Friendly Self‐Adaptive Catalytic Strategy for Plastics Lifecycles: Achieving Green Preparation, Superior Flame Retardancy, and Self‐Driven Sustainability

AbstractSemi‐rigid polyurethane foams (SPUF) with high deformation resistance and strength are indispensable for cushioning applications. However, for high fire risk and cascaded pollutant effects, overused multifarious additives and foam wastes exacerbate global environmental concerns. One option to address this issue is to develop eco‐friendly multifunctional flame retardants that participate in the material lifecycles of preparation, safe service, waste management, and sustainable recycling. Herein, a novel self‐adaptive catalytic strategy is reported that exploits the temperature and agent structure‐responsive catalytic ability of eco‐friendly sodium propionate (SP), reconciling the often‐conflicting properties of fabrication and recycling while effectively mitigating combustion risks and additive pollution. The adaptive catalytic function of SP impressively involves all aspects of foam life cycles: 1) catalyzing foaming without complex/hazardous catalysts; 2) providing superior flame‐retardant efficiency with a high limiting oxygen index of 25.5% without relying on traditional flame retardants; 3) promoting in situ network fragmentation and reorganization into strong adhesives (5.8 MPa); and 4) further recycling of the newly formed adhesives in a self‐driven sustainable manner. A novel green strategy is presented that addresses fire hazards, plastic pollution, and the unsustainability of recycling, minimizing the ecological risks of foam, which will positively impact future sustainable material design involving diverse additives.

Novel Aryl Phosphate for Improving Fire Safety and Mechanical Properties of Epoxy Resins.

Epoxy resins (EPs) are highly flammable, and traditional flame retardant modifications often lead to a significant reduction in their mechanical performance, limiting their applications in aerospace and electrical and electronic fields. In this study, a novel flame retardant, bis(4-(((diphenylphosphoryl)oxy)methyl)phenyl)phenyl phosphate (DMP), was successfully prepared and introduced into the EP matrix. When the addition of DMP was 9 wt%, the EP/9 wt% DMP thermosets passed the UL-94 V-0 rating, and their LOI was increased from 24.5% of EP to 35.0%. With the introduction of DMP, the phosphoric acid compounds from the decomposition of DMP promoted the dehydration and charring of the EP matrix, and the compact, dense char layer effectively exerted the shielding effect in the condensed phase. Meanwhile, the produced phosphorus-containing radicals played a quenching effect in the gas phase. As a result, the peak heat release rate (PHRR) and total heat release (THR) of EP/9 wt% DMP were reduced by 68.9% and 18.1% compared to pure EP. In addition, the polyaromatic structure of DMP had good compatibility with the EP matrix, and the tensile strength, flexural strength and impact strength of EP/9 wt% DMP were enhanced by 116.38%, 17.84% and 59.11% in comparison with that of pure EP. This study is valuable for expanding the application of flame-retardant EP/DMP thermosets in emerging fields.

A novel macromolecular flame retardant based on sulfonyl diphenol monomer for simultaneous fire safety, transparency and high performance of thin-walled polycarbonate

In order to further advance the development of transparency, fire safety, and high-performance thin-walled polycarbonate (PC), it is essential to avoid the negative impact of traditional flame retardants on the overall performance of PC. In this work, a new copolymer polycarbonate (ASPC) containing sulfonyl diphenol monomer was synthesized by interfacial polycondensation, and it was used as a flame retardant for PC. Due to the fact that the compounds containing sulfonic acid groups produced by the decomposition of ASPC in a high temperature environment promote the crosslinking and rearrangement of PC, the PC can generate a denser char layer during combustion, thus effectively preventing the exchange of heat and gas inside and outside the matrix. To addition of 20 wt% ASPC can make PC with a thickness of 1.5 mm to pass the UL 94 V-0 rating and LOI increased to 33.5 %. The peak of heat release rate (PHRR) and smoke produce rate (PSPR) of PC/ASPC-20 was decreased by 32.4 % and 38.4 %, respectively. More importantly, the addition of ASPC can delay the speed of flame spread, provide people with more escape time and reduce the fire hazard. Furthermore, the ASPC is good compatibility with PC due to the structural similarity between ASPC and PC. Therefore, PC/ASPC maintains the comparable transparency and tensile properties of PC. The transmittance of PC/ASPC-20 is 87.7 %, and the elongation at break is 32.5 % higher than that of PC. This work provides a new solution for the preparation of flame-retardant modification of transparent and thin-walled PC, and expands the application scope of PC composites.

Influence of Additives on Flame-Retardant, Thermal, and Mechanical Properties of a Sulfur–Triglyceride Polymer Composite

Plastics and composites for consumer goods often require flame retardants (FRs) to mitigate flammability risks. Finding FRs that are effective in new sustainable materials is important for bringing them to the market. This study evaluated various FRs in SunBG90 (a composite made from triglycerides and sulfur)—a high sulfur-content material (HSM) promising for use in Li–S batteries, where flame resistance is critical. SunBG90 was blended with FRs from several classes (inorganic, phosphorus-based, brominated, and nitrogen-containing) to assess compliance with UL94 Burning Test standards. Inorganic FRs showed poor flame retardancy and lower mechanical strength, while organic additives significantly improved fire resistance. The addition of 20 wt. % tetrabromobisphenol A enabled SunBG90 to achieve the highest flame retardancy rating (94V-0), while also enhancing wear resistance (52 IW, ASTM C1353) and bonding strength (26 psi, ASTM C482). Selected organic FRs also enhance compressive strength compared to the FR-free SunBG90. This research highlights the potential of HSMs with traditional FRs to meet stringent fire safety standards while preserving or enhancing the mechanical integrity of HSM composites.

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.

Exploiting Waste towards More Sustainable Flame-Retardant Solutions for Polymers: A Review.

The development of sustainable flame retardants is gaining momentum due to their enhanced safety attributes and environmental compatibility. One effective strategy is to use waste materials as a primary source of chemical components, which can help mitigate environmental issues associated with traditional flame retardants. This paper reviews recent research in flame retardancy for waste flame retardants, categorizing them based on waste types like industrial, food, and plant waste. The paper focuses on recent advancements in this area, focusing on their impact on the thermal stability, flame retardancy, smoke suppression, and mechanical properties of polymeric materials. The study also provides a summary of functionalization methodologies used and key factors involved in modifying polymer systems. Finally, their major challenges and prospects for the future are identified.

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

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

Preparation of flame retardant and thermal insulation polystyrene foams via high internal phase emulsion template

AbstractExpanded polystyrene foam (EPSF), valued for its excellent insulation properties, faces a significant flammability challenge due to its cellular structure. Traditional flame retardant methods such as physical blending and layer‐by‐layer assembly have poor applicability to EPSF. Therefore, it is necessary to find other more effective methods for synthesizing flame‐retardant EPSF. The high internal phase emulsion (HIPE) template is one of the simplest and most commonly used methods for synthesizing porous materials, which have features such as adjustable pore structures and high porosity. In this work, ammonium polyphosphate (APP)/starch was added to the dispersed phase of the HIPE to prepare the flame‐retardant EPSF by one‐pot method. The morphology, thermal stability and flame retardancy of the foams were investigated. When the addition of APP/starch (the weight ratio is 1:1) reached 30 wt.%, the peak heat release rate (PHRR), total heat release (THR), and total smoke release (TSR) of the composite foam decreased by 74.7%, 65.9%, and 24.7%, respectively, compared to the pure PS foam. Meanwhile, its limiting oxygen index (LOI) value reached 25.8%, and the UL‐94 rating reached V‐1 level, indicating significant improvement in flame retardancy. This study provides an effective strategy for synthesizing flame‐retardant porous materials.

Bioinspired phosphorus-free and halogen-free biomass coatings for durable flame retardant modification of regenerated cellulose fibers

Inspired by mussel adhesion and intrinsic flame retardant alginate fibers, a biomass flame retardant (PPCA) containing adhesive catechol and sodium carboxylate structure (-COO−Na+) based on biomass amino acids and protocatechualdehyde was designed to prepare flame retardant Lyocell fibers (Lyocell@PPCA@Na). Furthermore, through the substitution and chelation of metal ions by PPCA in the cellulose molecular chain, flame retardant Lyocell fibers chelating copper and iron ions (Lyocell@PPCA@Cu, Lyocell@PPCA@Fe) were prepared. Compared with the original sample, the peak heat release rate (PHRR) and total heat release (THR) for modified Lyocell fibers were significantly reduced. In addition, the modified sample exhibited a certain flame retardant durability. TG-FTIR analysis showed that the release of flammable gaseous substances was inhibited. The introduction of Schiff bases and aromatic structures in PPCA, as well as the decomposition of carboxylic metal salts were beneficial for the formation of char residue containing metal carbonates and metal oxides to play the condensed phase flame retardant effect. This work develops a new idea for the preparation of eco-friendly flame retardant Lyocell fibers without the traditional flame retardant elements such as P, Cl, and Br.

Preparation of flame retardant and anti-dripping PET fabric based on sodium copper chlorophyllin dyeing, UV grafting and phosphorylation

The traditional flame retardant polyester fiber containing phosphorus has serious melt droplet phenomenon, and its flame retardancy will be greatly decreased after dyeing, which seriously restricts its wide application. To address the issue, PET fibers were dyed by sodium copper chlorophyllin (SCC) at high temperature to prepare dyed PET fibers (DPET) with dyeing and anti-dripping properties. To further improve the flame retardancy of DPET, N-hydroxymethylacrylamide (NMA) was UV-grafted to DPET (DPET-g-NMA), which was then chemically modified by diammonium hydrogen phosphate (DAP) through high-temperature esterification reaction to obtain flame retardant PET fibers (FR-PET). The results showed that the char-forming ability of FR-PET was higher than that of DPET, and the melt droplet was effectively suppressed. In addition, the heat release rate (HRR), the peak of heat release rate (PHRR), and the total smoke production (TSP) of FR-PET were all significantly reduced, showing good flame retardancy. This work developed a simple and green strategy to improve the flame retardancy and anti-dripping performance of PET fiber without subsequent dyeing, showing great application prospects.

Comprehensive analysis of the impact of emerging flame retardants on prostate cancer progression: The potential molecular mechanisms and immune infiltration landscape

Emerging flame retardants have been used to replace traditional flame retardants, but their potential impact on cancer, especially prostate cancer, is not well understood. Our study aimed to explore the link between flame retardants and prostate cancer, and identify potential carcinogenic mechanisms among populations exposed to emerging flame retardants. We screened flame retardant interacting genes differentially expressed in prostate cancer patients and identified hub genes by protein-protein interaction (PPI) analysis based on the STRING database. Univariate and multivariate Cox regression analyses were performed to construct risk models and identify flame retardant-related prognostic genes. We calculated the proportion of immune cell infiltration to explore the potential mechanism of the prognostic gene, and verified the target cell population of the prognostic gene in the single-cell transcriptome dataset. Our study revealed a significant link between emerging flame retardants and prostate cancer. We constructed a risk model with good predictive ability for prostate cancer prognosis using TCGA dataset, and identified six flame retardant-related prognostic genes validated in the GSE70769 dataset. We found that the expression of M2 macrophages was up-regulated in patients with high expression of prognostic genes, and the single-cell dataset confirmed the expression of prognostic genes in macrophages. Our study confirms the link between emerging flame retardants and prostate cancer, and highlights the role of immune-related pathways in the high-risk population exposed to these flame retardants.

Fabrication of a cinnamaldehyde-based bi-DOPO flame retardant with excellent glass transition temperature, fire safety and mechanical properties for epoxy resins

Manufacturing fire-resistant, tough, and durable epoxy resin (EP) is a challenging task. Traditional flame retardants derived from 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) tend to aggregate and plasticize, causing a decline in glass transition temperature (Tg) and mechanical properties of EP. To overcome this issue, a bulky aromatic DOPO-based derivative called PPCANT was synthesized successfully using biomass-derived cinnamaldehyde (CA). The steric hindrance and intermolecular interactions (π-π stacking) of PPCANT's mitigated Tg deterioration and significantly improved mechanical properties. Incorporating 5 wt% PPCANT into the EP (EP/PPCANT-5) achieved a limiting oxygen index (LOI) of 32.6% and UL-94 V-0 rating, reducing both total heat release and smoke production. Moreover, PPCANT endowed the EP with exceptional char-forming ability. Analysis of the flame retardant mechanism indicated that the PPCANT structure imparted an ideal flame quenching mechanism, characterized by the instantaneous extinction of flames caused by the blowout of PO·/PO2 radicals, and a dilution effect of free radicals from non-flammable gases. In addition, the incorporation of nitro and amino groups in PPCANT facilitates the formation of hydrogen bonds with the hydroxyl groups generated in the ring-opened EP, leading to a significant decrease in the hydrophilicity of EP. These findings highlight PPCANT as a promising flame retardant that simultaneously enhances flame retardancy, mechanical strength, and hydrophobicity in EP materials.

A P/N synergistic flame retardant containing flexible nitrile group for enhancing the mechanical properties and fire safety of epoxy resins

AbstractTo further enhance the fire safety of epoxy resins, a phosphorus–nitrogen synergistic flame retardant (DPVHD) with a flexible chain segment and a nitrile group was synthesized. In addition to the traditional flame retardant elements P and N, the flame retardancy of the epoxy composites is further enhanced by the cross‐linking effect of the nitrile groups introduced to form an interpenetrating network with the epoxy matrix. The results showed that the sample with 10 wt% DPVHD‐10/EP had a LOI of 32.3% and passed the UL‐94 V‐0 rating, with PHRR and THR reduced by 15.4% and 47%, respectively, compared to pure EP. It is worth noting that the introduction of flexible chain segments improves the flexural properties of the epoxy resin matrix. Compared with pure epoxy, the flexural properties of epoxy‐cured compounds with DPVHD addition show a rising trend with the increase of flame‐retardant additive. And the rise of DPVHD‐10/EP reaches 33.6%, which greatly reduces the negative effect of flame‐retardant additives on the mechanical properties of the epoxy resin matrix. This work therefore provides new ideas for exploiting the advantages of phosphorus‐nitrogen synergy and nitrile‐based cross‐linking for flame retardancy in epoxy resins.

The thermoplastic polyurethane coated-LZH nanohybrids as a strategy for epoxy resin flame retardancy

Over traditional flame retardants, the hybrid material technology of flame retardant combines separate constituents into an entirety, demonstrating the benefit of the simultaneous development in polymer flame retardant. Zinc-layered hydroxide, borate, and thermoplastic polyurethane were used to create LZH/B/TU, a new organic-inorganic composite flame retardant. The structure of LZH, LZH/B, and LZH/B/TU was studied after synthesis with analysis spectroscopy. The borate ion was effectively intercalated into the interlayer space of the LZH, according to the XRD and FTIR studies. Using EDS analysis, the chemical makeup of the materials was assessed. The morphology of the synthesized product was identified using FESEM. The dynamic mechanical thermal (DMT) properties of the optimum sample were evaluated with DMTA analysis. The fire risk of epoxy resin was considerably reduced by using a small amount of LZH/B/TU. According to the flammability test and plate temperature experiment, LZH/B/TU with 1% w/w led to the creation of the char layer’s capacity to insulate heat with strong thermal resistance, resulting in dramatically reduced fire hazards.

Recent Advances and Outlook in 2D Nanomaterial-Based Flame-Retardant PLA Materials.

Poly (lactic acid) or polylactide (PLA) has gained widespread use in many industries and has become a commodity polymer. Its potential as a perfect replacement for petrochemically made plastics has been constrained by its extreme flammability and propensity to flow in a fire. Traditional flame-retardants (FRs), such as organo-halogen chemicals, can be added to PLA without significantly affecting the material's mechanical properties. However, the restricted usage of these substances causes them to bioaccumulate and endanger plants and animals. Research on PLA flame-retardants has mostly concentrated on organic and inorganic substances for the past few years. Meanwhile, there has been a significant increase in renewed interest in creating environmentally acceptable flame-retardants for PLA to maintain the integrity of the polymer, which is the current trend. This article reviews recent advancements in novel FRs for PLA. The emphasis is on two-dimensional (2D) nanosystems and the composites made from them that have been used to develop PLA nanocomposite (NCP) systems that are flame retarding. The association between FR loadings and efficiency for different FR-PLA systems is also briefly discussed in the paper, as well as their influence on processing and other material attributes. It is unmistakably established from the literature that adding 2D nanoparticles to PLA matrix systems reduces their flammability by forming an intumescent char/carbonized surface layer. This creates a barrier effect that successfully blocks the filtration of volatiles and oxygen, heat and mass transfer, and the release of combustible gases produced during combustion.

Study on the inhibition of lubricating oil in conjunction with a flame retardant on the flammability of propane

As the key part of the refrigeration systems, heat pump systems, and Organic Rankine Cycle (ORC) systems, most working fluids with low global warming potential (GWP) are flammable. This paper proposed a novel method called indirect inhibition to mitigate their flammability to enhance the applicability of low-GWP working fluids. Firstly, the effect of lubricants oil, indirect flame retardants (IFR), and mixtures of the two on the flammability of propane were investigated. The experimental results showed that lubricating oil promoted the combustion of propane to a certain extent. The introduction of indirect flame retardant (CP-52) weakened the combustion intensity of propane. The lubricating oil, in conjunction with a flame retardant, could inhibit the combustion of propane. Secondly, the effects of the indirect flame retardant and mineral oil on the flammability of propane were theoretically analyzed using density functional theory (DFT). The theoretical calculation results showed that the ability of IFR to capture reactive free radicals was comparable to that of traditional flame retardants. The research results are of great significance for improving the safety of the cycle system and reducing the risk of accidents.

An interlayer flame retardant method to effectively fire retardant and reinforce CF/EP composites by nanofiber film intercalation

As an advanced material with wide application, carbon fiber reinforced epoxy resin matrix composites (CF/EP) are flammable, but the traditional flame retardant methods negatively affect its molding process, heat resistance, mechanical properties, and how to solve this problem has been a challenge. This paper adopts a novel flame retardant method of inserting nanofiber films of flame retardant into the interlayer of the composite laminate to achieve fire resistance, higher strength, and toughness of the composite. In this work, pentaerythritol phosphate (PEPA) nanofiber films with phenoxy resin (PKHH) as a carrier was prepared by electrospinning and placed between the layers of CF/EP laminates. The results show that a dense charring layer with isolation and protection functions can be formed between the layers of the CF/EP intercalated by the nanofiber films during combustion. Accordingly, the nanofiber film containing 50 wt% PEPA with the thickness of only 30 μm increased the LOI value of CF/EP from 27.8% to 34.7%, while reducing the THR and pSD by 14% and 27.2% respectively. What’s more, due to the Ex-situ toughening effect of the nanofibers, the flexural strength, interlaminar shear strength, and compression strength after the impact of the modified CF/EP were increased by a maximum of 11.2%, 11.3%, and 12.2% compared to unmodified CF/EP. This work proves the feasibility of interlayer flame retardant fiber reinforced resin composites, and provides a new method to prepare high-performance flame-retardant composites.

Synergetic Effect of α-ZrP Nanosheets and Nitrogen-Based Flame Retardants on Thermoplastic Polyurethane

A supramolecular self-assembly method was used to prepare melamine cyanurate/α-ZrP nanosheets (MCA@α-ZrP) as a novel hybrid flame retardant for thermoplastic polyurethane (TPU). Microstructure characterization showed a uniform dispersion with strong interfacial strength of the MCA@α-ZrP hybrid within the TPU matrix, leading to simultaneous enhancements in both mechanical and fire-safety properties. The TPU/MCA@α-ZrP nanocomposite exhibited 43.1 and 47.0% increments in tensile strength and fracture energy, respectively. Thanks to the platelike structure of α-ZrP coupled with the dilution effect of MCA (releasing nonflammable gases), the hybrid MCA@α-ZrP reduced the peak heat release rate of TPU by 49.7% in comparison with 15.8 and 35.4% for TPU/MCA and TPU/ α-ZrP composites, respectively. The fire performance index of TPU is significantly promoted by 90% upon adding the MCA@α-ZrP hybrid. Additionally, LOI and UL-94 tests showed high flame-retarding characteristics for the MCA@α-ZrP hybrid. For example, LOI increased from 20.0% for neat TPU to 25.5% for the MCA@α-ZrP hybrid system, and it was rated V-1 from the UL-94 test. Furthermore, the smoke production and pyrolysis products were significantly suppressed by adding the MCA@α-ZrP hybrid into TPU. Interfacial hydrogen bonding, the dilution effect of MCA, forming a "labyrinth" layer, and catalytic action of α-ZrP nanosheets synergistically improved both the mechanical performance and flame retardancy of TPU nanocomposites. This work provides a new example of integrating traditional flame retardants with functional nanosheets to develop polymeric nanocomposites with high mechanical and fire-safety properties.

A facile strategy to construct multifunctional microencapsulated urea ammonium polyphosphate for epoxy resins towards satisfied fire safety, thermal stability and compatibility

AbstractEnhancing the fire safety of epoxy resin (EP) concomitant with less mechanical performance degradation is still a challenge for traditional flame retardants. Hence, polypyrrole (PPy) was used as a film material to fabricate microencapsulated urea ammonium polyphosphate (UAPP) for simultaneously improving the fire safety, thermal stability and compatibility of epoxy composites. The obtained polypyrrole‐coated urea ammonium polyphosphate (PPy‐UAPP) at a load of 10 wt% endows the EP with a UL94 V‐0 rating and a limiting oxygen index (LOI) value of 32.3%, while 10 wt% ammonium polyphosphate (APP) only endows EP with a LOI of 28.5%. Furthermore, the peak heat release rate (PHRR) and peak smoke production rate (PSPR) of EP containing 10 wt% PPy‐UAPP are decreased by 12.3% and 21.4% compared to EP containing 10 wt% APP. The decreased fire hazard of EP/PPy‐UAPP is attributed to the reduction of hazardous gases including CO2 and CO and the generation of more incombustible gases including H2O and NH3 to reduce the combustion intensity. Meanwhile, the good compatibility between EP matrix and PPy‐UAPP endows the resulting EP composites with a superior balance between fire safety and mechanical properties.

Caffeic acid decorated ammonium polyphosphate-based flame retardant for fire safety and anti-aging of wood plastic composites

Wood plastic composites (WPCs) are facing fire hazard and aging when they are used as building materials. In current work, ammonium polyphosphate-based flame retardant decorated with caffeic acid (MAPP-CA) was prepared by the two-step reaction of ammonium polyphosphate (APP), ethylenediamine, and caffeic acid. The chemical structure of MAPP-CA was characterized by different measurements. When the loading amount of MAPP-CA was 25 wt% in WPC, WPC/MAPP-CA25 sample passed the UL-94 V-0 rating and limited oxygen index (LOI) value reached 26.5%. Compared with WPC, WPC/MAPP-CA25 showed significantly lower heat release and smoke release. Besides, MAPP-CA improved the anti-aging property of WPC. According to oxidation induction time (OIT) result of WPC, WPC/APP25 and WPC/MAPP-CA25. The OIT of WPC/MAPP-CA25 is much longer than that of WPC (17.8 min) and WPC/APP25 (36.8 min), about 7.4 and 3.6 times of the latter two, respectively. Further, the retention ratios of mechanical properties showed that the retention in flexural strength and notched impact strength for WPC/MAPP-CA25 is superior to that of WPC/APP25 and WPC after aging at 120 ℃. Flame-retardant and anti-aging mechanisms of MAPP-CA were investigated in detail. This work opens a new route for upgrading traditional flame retardant.