Excellent Flame Retardant Properties Research Articles

Sustainable furfuryl alcohol-based flame retardants with regular spherical morphology: Endow polypropylene with excellent flame retardancy, smoke suppression, and mechanical properties

Preparation of polyolefins possessing superior flame retardant and mechanical properties has always been a hot research topic. Herein, a novel high-performance flame retardant was designed and prepared to address the dilemma between flame retardancy and mechanical properties. Through self-stabilized precipitation polymerization of furfuryl alcohol (FA) and maleic anhydride (Ma), followed by successive amination and phosphorylation treatment, bio-based phosphorylated FMa microspheres (P-FMa) were successfully obtained. Benefiting from strong synergistic effect between P-FMa and ammonium polyphosphate (APP), the polypropylene (PP)/APP/P-FMa composites exhibited excellent flame retardant and smoke suppression properties. At a dosage of only 19 wt% APP/P-FMa, the PP/APP/P-FMa reached UL-94 V-0 rating and a limiting oxygen index of 32.2 %, and the peak heat release rate and peak smoke production rate decreased by 76.1 % and 52.6 % compared with neat PP, respectively, due to the formation of denser and firmer char layer. Notably, the tensile strength of PP/APP/P-FMa maintained at a high level of 43.2 MPa. More importantly, the impact strength reached 10.5 kJ/m2, increase by 138.6 % compared to PP/APP, mainly attributed to improved dispersion and compatibility between APP/P-FMa and PP matrix. Owing to its ability to simultaneously improve flame retardant and mechanical properties, P-FMa possesses great potiential as a high-performance flame-retardant filler.

All-natural, thermally conductive, flame-retardant electrical insulating lignocellulose-mica composite film fabricated via in-situ mineralization

Miniaturized, integrated, and functional electronic devices generate a large amount of heat accumulation during operation, which significantly affects the reliability, durability, and safety of electronic devices. In severe cases, it may even lead to fires. Therefore, the development of insulation composite materials with thermal conductivity and flame-retardant properties is particularly important. In this study, we propose an in-situ mineralization strategy to prepare insulation composite materials with thermal conductivity and flame-retardant properties. By dissolving and preparing a gel film, Al3+ and Zn2+ retained inside the lignocellulose are in situ mineralized to form Al(OH)3 and ZnO, and introducing inorganic blocks with high insulation performance (industrial waste mica tailings and synthetic mica). The prepared film has excellent tensile strength (117.4 MPa), low dielectric loss, high dielectric strength (83.8 kV mm−1), high insulation resistance, four times higher thermal conductivity than the unmineralized film, and excellent flame-retardant properties. Meanwhile, the environmental impact of the composite film is much lower than that of petrochemical-based plastic films and can easily degrade under natural conditions within 32 days. It is a composite material that meets the standards of the new electrical insulation field, and the in-situ mineralization strategy can also provide ideas for the preparation of high-performance lignocellulose-based materials.

Effects of Recycled Polyethylene on Natural Rubber Composite Blends Filled with Aluminum Trihydroxide and Polyurethane Waste: Mechanical and Dynamic Mechanical Properties, Flammability.

This research studies natural rubber (NR) composite blends prepared with recycled polyethylene (PE), polyurethane waste (PU), silica (SiO2), and aluminum trihydroxide (ATH) under the proper mixing conditions using an internal mixer and a two-roll mill. The mechanical, impact, dynamic mechanical, and thermal properties, together with flammability, were investigated. NR/PU composites filled with a specific SiO2/ATH concentration resulted in excellent flame-retardant properties without using PE. Adding PE causes poor flammability, while using PU and SiO2 prevents flame extensibility of the composites. In addition, SiO2 and ATH synergistically improved both mechanical and dynamical mechanical properties. This is attributed to the reinforcement of SiO2 particles inside the matrix, whereas the ATH releases water as a flame retardant. The V-0 composites tested with UL-94 showed acceptable heat resistance, strength, and durability, making them suitable for interior and exterior applications in buildings without the lightweight requirement.

Modification with lignin-based N-P flame retardant to improve the flame retardancy and smoke suppression of wood

The development of effective and eco-friendly wood-based functional composites is crucial for maximizing the value of forest resources. In this paper, we propose a novel method for preparing an aqueous-phase flame retardant (MPUC) using carboxymethylation alkali lignin, phytic acid, and melamine-urea-glyoxal resin. This approach aims to manufacture modified wood (MW/MPUC) with exceptional flame-retardant and smoke-suppressing properties. The results from the cone calorimeter test indicate that the modified wood achieved a remarkable reduction of up to 56.8 % in total heat release and an impressive 92.3 % decrease in total smoke production. Furthermore, the limiting oxygen index increased significantly from 23.6 % (natural wood) to 41.5 % (MW/MPUC-2). Notably, all modified wood successfully passed the V-1 test for UL-94 flammability rating. Further, our investigation into the gas-phase products formed during pyrolysis and the condensed-phase system created after combustion has led us to propose potential flame-retardant mechanisms for these flame retardants. Moreover, modified wood had improved mechanical properties and dimensional stability than natural wood. In addition, we extended the application of MPUC-2 flame-retardant to other flammable materials and demonstrated its excellent flame-retardant properties. Thus, the proposed strategy provided a new approach for preparing wood-based flame-retardant composites with lignin-based N-P flame retardants.

A novel and convenient zeolite modification strategy for enhancing the fire resistance of epoxy resin

The preparation process of new environmentally friendly flame retardants to endow epoxy resin (EP) with excellent flame retardancy and mechanical properties remains a challenging task. In this study, a novel Zeolite@DPA-Cu flame retardant was designed and prepared by a simple and environmentally friendly aqueous preparation process using zeolite, copper sulfate and diphenylphosphonic acid as main raw materials. As expected, Zeolite@DPA-Cu significantly improved the flame retardancy and mechanical properties of EP composites. The results showed that the LOI and UL-94 grade of the EP/5 wt% Zeolite@DPA-Cu composite reached 32.4 % and V-0 rating, respectively. The synergistic effect of the physical barrier, free radical capture and catalytic char formation of Zeolite@DPA-Cu significantly improved the flame retardancy of EP. In addition, due to the strong interfacial interaction between Zeolite@DPA-Cu and EP, the tensile strength and elongation at break of the EP were increased to 57.92 MPa and 4.7 %, respectively. Generally, this study proposed a modification strategy that takes into account both flame retardancy and mechanical properties, which is extremely important for the practical application of EP flame retardant materials.

Intrinsic flame-retardant epoxy resin based on phosphorus-containing liquid imidazole compound: Simultaneously improving fire safety, mechanical property and heat resistance

In this work, two phosphorus-containing liquid imidazole compounds with different phosphorus oxidation states (1,1′-(phenylphosphanediyl)bis(1H-imidazole) (DCPPI) with + 1 valence phosphorus, and imidazole-phenylphosphate (PPOAI) with + 3 valence phosphorus) were designed and synthesized. Both of DCPPI and PPOAI were used as curing agents to obtain intrinsic flame-retardant epoxy resin (EP-DCPPI and EP-PPOAI), in which the imidazole group was used as the curing group of EP, and the phosphorus-containing group was directly connected to the EP crosslinking network. On the one hand, the efficient flame-retardant groups containing + 1 or + 3 valence phosphorus were incorporated into the EP system to obtain excellent flame-retardant properties; on the other hand, the introduction of phenylphosphine or phenoxyphosphine groups in the molecular chain of EP greatly enhanced the interaction between molecular chains, adjusted crosslinking density and endowed EP with excellent tensile strength and toughness. Compared with imidazole cured EP (EP-MZ), the peak heat release rate (PHRR) of EP-15DCPPI and EP-15PPOAI decreased by 70 % and 68 %, and the total heat release rate (THR) decreased by 37 % and 36 %, respectively. Meanwhile, EP-15DCPPI passed UL-94 V-0 rating, and the limiting oxygen index (LOI) reached 36.1 %. EP-15PPOAI passed UL-94 V-1 rating and the LOI reached 29.1 %. The flame-retardant mechanism was analyzed and discussed. Compared with EP-MZ, the dynamic and static mechanical properties of EP-15DCPPI and EP-15PPOAI were enhanced simultaneously, and the glass transition temperature (Tg) was obviously increased.

Equol-based epoxy resin as an ideal substitute for the diglycidyl ether of bisphenol A (DGEBA)

The development of high-performance bio-based epoxies with excellent mechanical properties, heat resistance and flame retardant properties is essential to mitigating the resource and environmental burdens caused by the widespread utilization of petroleum-based epoxies. This work focuses on the synthesis of a bifunctional epoxy resin (EEU) with the rigid tetrahydrobenzopyran ring derived from equol. The structure of the EEU epoxy resin was characterized, and using 4,4′ diamino diphenyl sulfone as the curing agent, the rheological properties, curing behavior and comprehensive properties of cured resin were studied. The results demonstrate that EEU-DDS presents the same curing behavior as DGEBA-DDS. The mechanical properties heat resistance and flame retardant properties of EEU-DDS are superior to DGEBA-DDS. The tensile strength, tensile modulus and glass transition temperature reached to 94.0 MPa, 3.62 GPa and 221 °C, respectively, higher than those of DGEBA-DDS (83.2 MPa, 2.81 GPa and 203 °C). EEU-DDS reached the V-1 rating in UL-94 tests with a high limiting oxygen index (LOI) (28 %), and the peak heat release rate and smoke release rate of 631 kW/m2 and 0.155 m2/s were significantly lower than that of DGEBA-DDS. The flame retardant mechanism was proven to be gas-coacervated phase synergistic flame retardant. In addition, the interlamellar shear strength (ILSS), bending strength, and impact strength of carbon fiber reinforced resin matrix composites prepared by EEU-DDS reached 97.9 MPa, 1281 MPa, and 81.3 kJ/m2, respectively, higher than those of DGEBA-DDS. Therefore, equol-based epoxy resin can serve as an ideal alternative to petroleum-based bisphenol A-type epoxy resin, offering superior comprehensive properties.

Melamine Polymerization Promotes Compact Phosphorus/Carbon Composite for High-Performance and Safe Lithium Storage.

Phosphorus is regarded as a promising material for high-performance lithium-ion batteries (LIBs) due to its high theoretical capacity, appropriate lithiation potential, and low lithium-ion diffusion barrier. Phosphorus/carbon composites (PC) are engineered to serve as high-capacity high-rate anodes; the interaction between phosphorus and carbon, long-term capacity retention, and safety problems are important issues that must be well addressed simultaneously. Herein, an in situ polymerization approach to fabricate a poly-melamine-hybridized (pMA) phosphorus/carbon composite (pMA-PC) is employed. The pMA hybridization enhances the density and electrical conductivity of the PC, improves the structural integrity, and facilitates stable electron transfer within the pMA-PC composite. Moreover, the pMA-PC composite exhibits efficient adsorption of lithium polysulfides, enabling stable transport of Li+ ions. Therefore, the pMA-PC anode demonstrates a high specific charging capacity of 1,381mAhg-1 at 10Ag-1, and a great capacity retention of 86.7% at 1Ag-1 over 500 cycles. The synergistic effect of phosphorus and nitrogen further confers excellent flame retardant properties to the pMA-PC anode, including self-extinguishing in 2.5s, and a much lower combustion temperature than PC. The enhanced capacity and safety performance of pMA-PC show potential in future high-capacity and high-rate LIBs.

Integration of N- and P- elements in sodium alginate aerogels for efficient flame retardant and thermal insulating properties

In the field of building energy conservation, the development of biodegradable biomass aerogels with excellent mechanical performance, flame retardancy and thermal insulation properties is of particular importance. Here, a directional freeze-drying method was used for fabricating composite sodium alginate (SA) aerogels containing functionalized ammonium polyphosphate (APP) flame retardant. In particular, APP was coated with melamine (MEL) and phytic acid (PA) by a supramolecular assembly process. Through optimizing the flame retardant addition, the SA-20 AMP sample exhibited excellent flame retardant and thermal insulation properties, with the limiting oxygen index of 38.2 % and the UL-94 rating of V-0. Such aerogels with anisotropic morphology demonstrated a low thermal conductivity of 0.0288 (W/m·K) in the radial direction (perpendicular to the lamellar structure). In addition, as-obtained aerogels displayed remarkable water stability and mechanical properties, indicating significant potential for practical applications.

Interface engineering of multi-component core-shell flame retardant towards enhancing fire safety of thermoplastic polyurethane and mechanism investigation

Polymeric materials usually present substantial hazards to human health and the environment as a consequence of their flammability which leads to the emission of a great deal of heat and toxic fumes. To address this issue, it is imperative to urgently enhance the flame retardancy of polymer materials. This study focuses on the synthesis of a novel gel-silica/polydopamine double-layer microencapsulated cobalt ions (Co2+) modified ammonium polyphosphate (APP-Co@PDA@Si) and its utilization in thermoplastic polyurethane (TPU) composites. The resulting TPU composite, containing 10.0 wt% APP-Co@PDA@Si, exhibited excellent flame-retardant properties, i.e. achieving a limiting oxygen index of 30.0 % and the V-0 grade in the UL-94 test. Furthermore, peak heat release rate, total heat release, peak smoke production rate, and total smoke release of the TPU composite were decreased by 88.51 %, 66.06 %, 61.73 %, and 74.01 %, respectively, in comparison to those of pure TPU. The enhanced fire safety of the TPU composite was attributed to the synergistic effect among Co2+ catalytic carbonization, the free radicals capture effect of APP, and the flame-retardant functions of PDA and silane. This innovative strategy proposed in this work holds great promise for improving the fire-resistance of TPU.

Facile Fabrication of Highly Efficient Chitosan-Based Multifunctional Coating for Cotton Fabrics with Excellent Flame-Retardant and Antibacterial Properties.

Interest in the development of eco-friendly, sustainable, and convenient bio-based coatings to enhance flame retardancy and antibacterial properties in cotton fabrics is growing. In this work, chitosan was protonated at its amino groups using a method with a high atom economy using an equimolar amount of amino trimethylene phosphonic acid (ATMP), resulting in the fabrication of a single-component chitosan-based multifunctional coating (ATMP-CS), thereby avoiding any additional neutralization or purification steps. Cotton fabrics coated with various loads of ATMP-CS were prepared through a padding-drying-curing process. The morphology, thermal stability, mechanical properties, antibacterial properties, flame-retardant behavior, and flame-retardant mechanism of these fabrics were investigated. The coating exhibited excellent film-forming properties, and it imparted a uniform protective layer onto the surfaces of the cotton fabrics. When the load capacity reached 11.5%, the coated fabrics achieved a limiting oxygen index of 29.7% and successfully passed the VFT test. Moreover, the ATMP-CS coating demonstrated antibacterial rates against Escherichia coli and Staphylococcus aureus reaching 95.1% and 99.9%, respectively. This work presents a straightforward and gentle approach to fabricating colorless, environmentally friendly, and highly efficient fabric coatings that have potential applications in promoting the use of bio-based materials.

Eco-friendly multifunctional coating for polyester-cotton blended fabrics with superior flame retardancy and antibacterial properties

Since the fire hazards of polyester-cotton blended (PTCO) fabrics and the hidden dangers of bacterial infection concerns caused by the contained cotton fiber, the design of flame retardant and antibacterial PTCO fabrics has received considerable attention. In this work, flame-retardant PTCO fabrics with satisfactory antibacterial properties were fabricated via a convenient and eco-friendly impregnation treatment involving guanidine phosphate (GP) and polyethylenimine (PEI). The prepared PTCO fabrics demonstrated excellent flame retardancy with a high limiting oxygen index value of 30.5 % and self-extinguishing capability, the damaged length was only 34 mm in the vertical flammability test. Furthermore, the peak heat release rate and the total heat release of coated PTCO fabrics were reduced significantly by 49 % and 38 %, respectively, indicating a substantial enhancement in fire safety. According to the analysis of the char residues and volatiles, GP presented great catalytic carbonization property, and PEI assisted the formation of the dense and stable carbon layer. The stable carbon layer effectively restricted mass and oxygen transfer between the PTCO fabrics and the environment. In addition, the introduction of PEI also produced more nonflammable gases to enhance the flame retardancy of the PTCO fabrics. Importantly, the GP/PEI coating barely deteriorate the physical and mechanical properties of the PTCO fabrics. The antibacterial rate of the GP/PEI-coated PTCO fabrics against Escherichia coli and Staphylococcus aureus was 99.99 %, similar to that of GP-coated fabrics, indicating the efficacy antibacterial properties of GP, and the addition of PEI did not compromise the antibacterial properties of GP. This work offers an efficient and simple approach to producing multifunctional PTCO fabrics with excellent flame retardancy and antibacterial properties, which are hopeful to expand the promising application of PTCO fabrics.

Schiff base derivative flame-retardant endowing epoxy resin with toughness, transparency, and high flame retardancy

In this study, a novel phosphorus-containing flame retardant, SMAE, was prepared through a nucleophilic addition of N,N'-bis(salicylidene)ethylenediamine (SAED) and phenyl hypophosphite. SMAE can dissolve well in epoxy resin and provides molecular-level flame retardancy. By using SMAE as a co-curing agent and DDM to cure epoxy resin, EP/SMAE composites with excellent flame retardancy and good mechanical properties were obtained. As the dosage gradually increases, the limited oxygen index (LOI) values continue to rise. At a 5 % dosage, the Limiting Oxygen Index (LOI) value can reach 39.7 % and meet the UL 94 V-0 standard. It is observed that SMAE mainly exerts a blowing-out effect in EP. In addition, the use of SMAE as a co-curing agent can improve the impact strength of EP. The impact strength of 5 % SMAE/EP can reach 14.15 kJ/m2, which is 25 % higher than that of pure EP.

Study on thermal runaway propagation inhibition of battery module by flame-retardant phase change material combined with aerogel felt

Phase change materials (PCMs) are susceptible to fire and may accelerate heat transfer when thermal runaway propagation (TRP) in lithium-ion battery (LIB) modules, requiring the design and safe use of insulation structures with excellent flame-retardant properties. In this work, the sandwich structure composed of flame-retardant phase change material (FRPCM) combined with aerogel felt (AEGF) is used to study the inhibitory effect on TRP of pouch battery modules (BMs). The structural materials are applied between cells, and the changes of temperature, voltage, mass and other parameters in the TRP process are analyzed by changing the thickness of FRPCMs and AEGFs, and the changes of heat flux of materials were also qualitatively analyzed. The results show that the increase of FRPCM and AEGF thickness can increase the interval time of TRP and reduce the overall thermal risk of the BMs. Compared to Test-1, the increase in TRP time between cells 1 and 2 in Test-2 to Test-5 ranged from 52.7% to 358.7%, and the longest thermal runaway interval reached 844 s. Both the structural materials in Test-6 and Test-7 block the TRP. Combining the thermal conductivity of PCMs and the thermal insulation properties of AEGFs, this work can effectively conduct heat to the environment and block the TRP when applied to BMs, which provides a valuable reference for efficient inhibition and blocking of TRP.

Mechanical, Flame-Retardant and Dielectric Properties of Intumescent Flame Retardant/Glass Fiber-Reinforced Polypropylene through a Novel Dispersed Distribution Mode.

The application of continuous glass fiber-reinforced polypropylene thermoplastic composites (GF/PP) is limited due to the inadequate flame retardancy of the polypropylene (PP) matrix. Apart from altering the composition of the flame retardants, the distribution modes of flame retardants also impact material performance. In this study, an alternative approach involving non-uniform distribution is proposed, namely, dispersed distribution, in which non-flame-retardant-content layers (NFRLs) and/or low-flame-retardant-content layers (LFRLs) are dispersed among high-flame-retardant-content layers (HFRLs). The mechanical, flame retardant and dielectric properties of GF/PP with intumescent flame retardant (IFR/GF/PP) are investigated comparatively under uniform, gradient, and dispersed distributions of the flame retardants. The results demonstrate that non-uniform distribution exhibits superior flame retardant performance compared to uniform distribution. Dispersed distribution enables IFR/GF/PP to attain enhanced mechanical properties and reduced dielectric constants while maintaining excellent flame-retardant properties.

Bio-based phytic acid/amino acid complex coating for antimicrobial and flame-retardant cotton fabrics

Here, a novel multifunctional coating containing bio-based phytic acid (PA), L-glutamic acid (L-Glu), and trimesoyl chloride (TMC) is constructed by a simple soaking strategy, giving cotton fabrics excellent flame retardancy, washability, and antibacterial properties. The coating layer on the cotton surface was prepared via the electrostatic and hydrogen bonding between PA and L-Glu, accompanied by the interface polymerization between PA, L-Glu, and TMC. Among them, the limiting oxygen index value of the treated cotton fabrics (C2 and C2-TMC) was as high as 40 %. During the vertical flammability test, both C2 and C2-TMC cotton showed self-extinguished behavior with a short damaged length (≤50 mm). Remarkably, the LOI of C2-TMC sustained a high value (30 %) even after 300 laundering cycles, maintaining its self-extinguishing behavior in the vertical combustion test. Additionally, in the cone calorimetry test, peak heat release rate and total heat release of treated cotton were lower than control cotton. Surprisingly, after 30 or 60 laundering cycles, the C2-TMC cotton exhibited excellent antibacterial activity against Escherichia coli, Staphylococcus aureus, and Candida albicans due to the continuous exposure of PA and L-Glu. Moreover, the coating layer on the cotton surface had little impact on the mechanical properties and feel of the fabric.

Inventorization and ecological risk assessment of tetrabromobisphenol A and hexabromocyclododecane in sediments from Guangdong coastal area of South China Sea

Brominated flame retardants (BFRs) exhibit excellent flame retardant properties and are widely used in various industries. Among the common BFRs, tetrabromobisphenol A (TBBPA) and hexabromocyclododecane (HBCDs) pose substantial ecological and human health risks due to their extensive application and long-range transport. This study established 131 sample collection sites along the coast of the South China Sea (SCS) in Guangdong Province to assess the concentration, distribution, inventory, and ecological risk of TBBPA and HBCDs in surface sediments. The concentrations of TBBPA in SCS sediments ranged from < limit of detection (LOD) to 80 μg/kg dry weight (dw), and those of HBCDs from < LOD to 18 μg/kg dw. The diastereoisomers of HBCDs (α-, β-, and γ-HBCD) in the sediment samples accounted for 36 %, 13 %, and 51 %, respectively. Human activities, particularly those associated with nearby electronic waste disassembly and textile and garment industries, considerably influenced the dispersion of TBBPA and HBCDs. The inventories of TBBPA and HBCDs in Guangdong Province's SCS were estimated to be 3.2 × 105 kg and 7.2 × 104 kg, respectively. The average risk quotient values ranged from <0.01 to 0.016, indicating a low to negligible environmental risk. This study provides deeper insights into the distribution and scientific significance of HBCDs and TBBPA in SCS sediment samples, elucidates the current state of BFR contamination, and offers recommendations for future research on environmental safety and human health in the region.

Achieving heat storage coatings from ethylene vinyl acetate copolymers and phase change nano-capsules with excellent flame-retardant and thermal comfort performances

The heat-storage coatings from ethylene vinyl acetate (EVA) copolymers were developed by incorporating in-situ synthesized phase change nano-capsules (NEPCMs). The coatings were applied to the interior walls of the building, aimed at enhancing thermal storage and flame-retardant performances. Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD) are utilized to evaluate the chemical composition of the NEPCMs. At the same time, the thermal properties and microstructure of NEPCMs and the coatings are analyzed using differential scanning calorimetry (DSC) and scanning electron microscopy (SEM). The enthalpy of NEPCMs is 158.14 J/g, while that of heat-storage coatings is 56.45 J/g. NEPCMs and heat-storage coatings exhibit excellent thermal storage performance even after 200 heating-cooling cycles, demonstrating the excellent thermal stability of NEPCMs and heat-storage coatings. Furthermore, excellent flame-retardant properties are also provided by the heat-storage coating. In dynamic heat transfer experiments, under the same conditions, the heat-storage coatings were capable of maintaining the chamber in the thermal comfort zone (24–28 °C) for 141 min, while the conventional coatings lasted only 34 min. The results show that incorporating heat-storage coatings can effectively enhance the thermal regulation performance of interior walls and improve the thermal comfort of indoor environments. Therefore, heat-storage coatings hold a high potential for application in energy-saving buildings.

A P/N/S containing flame retardant for epoxy resins with excellent optical, mechanical and flame retardant properties

A highly efficient flame retardant TFD was synthesized based on 2-thenaldehyde, furfurylamine and DOPO. When 4 % of TFD is incorporated into EP, EP/TFD-4 exhibits 38.9 % of LOI value and UL-94 V-0 rating. In cone calorimeter test, the peak of heat release rate, total heat release, total smoke production are dropped by 20 %, 9 % and 65 % respectively, and the char residue is increased by 67 % as compared with the pure EP. The P/N/S elements in TFD play important roles both in gas phase and condensed phase. The decomposition of 2-thenaldehyde and furfurylamine moieties produces NH3, H2S, H2O, etc., which partly leak and dilute flammable gases, but majorly participate into structural reorganization in the char layer. The degradation of DOPO group releases phosphorus-containing free radicals and phosphate-like compounds. The former quenches the chain combustion reaction, and the later promotes the formation of a stable carbon layer as a barrier effect. Benefited from the good compatability between TFD and EP, and the fine balance between the increased rigidity and the declined cross-linking density, the EP/TFDs exhibit the strikingly similar transmittance to pure EP in the range of 200–800 nm, and the improved mechanical performance in tensile, flexural, and impact tests.

A zinc-embedded multicomponent copolymer customized for polypropylene and its synergistic flame-retardant effect and outstanding mechanical properties

The poor compatibility between the common polar intumescent flame-retardant system (IFR) and the nonpolar polypropylene (PP), as well as the high additive amount, seriously impacts the mechanical properties of the composites. This study introduced collaborative flame-retardant technology to construct block copolymer flame retardants and prepared a zinc-embedded multicomponent copolymer (PM-Zn2+) customized for PP composites. In the PM-Zn2+ system, zinc oxide was embedded into the copolymer composed of piperazine phosphate oligomer and melamine phosphate. PM-Zn2+ exhibited an amorphous structure with extremely low crystallinity and demonstrated specific morphological adaptability. The PM-Zn2+ were well dispersed in the PP matrix and changed their morphology during processing. When applied to PP, excellent flame retardancy and mechanical properties were obtained by using a minimal amount of flame retardants (20 %). PM-2 %Zn2+ gave PP an LOI value of 31.5 %, and achieved a UL94 V-0 rating (1.6 mm thick), exhibiting a lower heat release rate and smoke release. The flame-retardant mechanisms of PM-Zn2+ mainly involved the synergistic and aggregative effects. Transition metal zinc synergistically interacted with polyphosphate groups to create a charring barrier effect and enhance synergistic smoke suppression, leading to a significant reduction in combustion intensity. In comparison to the Mix-Zn/PP composites, the mechanical properties of PM-Zn2+/PP were significantly enhanced due to the specific morphological adaptability and improved compatibility. The elongation at break increased significantly from 15.6 % to 627.9 %, marking a remarkable improvement of 40-fold improvement, while the impact strength rose from 23.7 kJ/m2 to 54.3 kJ/m2, representing a 129 % enhancement. Finally, the zinc-embedded multicomponent block copolymer offers a promising approach to developing high-performance flame-retardant polypropylene materials.