ABSTRACT To enhance the flame retardancy of epoxy resin (EP), aluminum diethyl phosphinate (ADP) was surface‐modified using phenyl trimethoxysilane (PTMS). The modified ADP (PTMS@ADP) was then used as a main flame retardant, in combination with melamine polyphosphate (MPP) as a synergistic acid source and triazine carbonization agent (CFA) as a carbon source, to fabricate an intumescent flame retardant system (PTMS@ADP/MPP/CFA), hereafter referred to as IFR system. This system was incorporated into EP materials to investigate the flame retardancy of the resulting composites. The synergistic flame‐retardant effects among PTMS@ADP, MPP, and CFA were analyzed using scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and char residue analysis. The results show that the carbon residue rate of PTMS@ADP after modification is increased to 37.4 wt %, which is 63.3% higher than that of ADP, showing higher thermal stability at high temperature. Under a constant total loading of 15 wt %, the optimal ratio of PTMS@ADP:MPP:CFA was found to be 3:2:1, achieving the highest LOI value of 33.5%, with all samples meeting the V‐0 rating. Additionally, the char yield at 600°C increased by 89.6% compared with pure EP. Cone calorimetry tests revealed that the average heat release rate and total smoke production were reduced by 40.7% and 29.7%, respectively, indicating that the IFR system significantly improved both the flame retardancy and smoke suppression of the EP composites. The mechanical properties of the EP composite were significantly reduced when ADP was added alone. In contrast, the mechanical properties of the composite were improved upon the addition of PTMS@ADP or PTMS@ADP/MCA/CFA, although they remained lower than those of pure EP. Based on the comprehensive test results of flame retardancy and mechanical properties, the PTMS@ADP/MCA/CFA composite is suitable for applications requiring high flame retardancy with relatively lower demands on mechanical performance.

This study introduces a time-dependent solvothermal synthesis of hydrogen-bonded melamine cyanurate and melamine diborate at 180 °C, offering precise control over their framework compositions and structures through reaction time. The selective formation of melamine diborate and melamine cyanurate is achieved using the same set of precursors with cyanuric acid generated in situ from melamine hydrolysis. The phase composition varies with the reaction time, as confirmed by Fourier transformed infrared (FTIR) and X-ray photoelectron spectroscopy (XPS), which reveal the structural progression of these frameworks. Our synthesis method allows melamine cyanurate to nucleate or grow on melamine diborate crystals adopting a more crystalline rod-like morphology with clearer texture. Density functional theory (DFT) enhances the understanding of their electronic structures, highlighting core-level binding energy shifts (N 1s and B 1s) and the chemical activity of lone pair electrons, with the mixture of π and σ bonds playing a key role in determining the bandgaps. This proposed synthesis method enables precise tuning of hydrogen-bonded framework compositions providing valuable insights for material synthesis and structural design.

ABSTRACT The deterioration of traditional flame‐retardant silicone rubber under accelerated thermal and radiation aging limits its use as an electrical material for safety equipment in nuclear power plants (NPPs). To address this issue, this study developed a silane coupling agent, a novel phosphorus‐containing polysilazane, and silicone resin, and prepared surface‐modified melamine cyanurate (MCAM‐x) to improve its compatibility with silicone rubber and the flame‐retardant effect. The introduction of MCAM‐x not only enhanced the mechanical properties of silicone rubber but also visibly improved its electrical insulating properties. Moreover, the MCA‐modified silicone rubber composites also exhibit excellent thermal stability, with low thermal decomposition rates and high residual carbon layers at elevated temperatures, helping to maintain the structural integrity of the material. In terms of flame retardancy, the modified silicone rubber shows excellent flame retardancy, with an increase in the limiting oxygen index (LOI) test and a V‐0 rating in the UL‐94 vertical flame test. After thermal aging and irradiation aging tests, the MCA‐modified silicone rubber shows excellent aging resistance, which ensures the stability of the material's physical and chemical properties during long‐term use, especially under extreme conditions. This provides a new solution for flame retardant modification of silicone rubber in high‐end application fields such as NPPs.

Simultaneous enhancement of fire retardancy and ceramifiable properties in polyolefin-based composites using melamine cyanurate and layered tri-metallic hydroxide

Assessing the solubility, chemical stability and ecotoxicology of an emerging non-halogenated flame retardant, melamine cyanurate, against a prevalent halogenated congener, tetrabromophthalic anhydride.

ABSTRACTAs urbanization progresses, electrical cables are increasingly installed underground, making them vulnerable to rodent damage, which can lead to short circuits, power outages, signal interruptions, and fires. To address the irritation caused by traditional chemical rodent repellents, this study introduces a novel, environmentally friendly solution. By encapsulating Dihydro capsaicin (DHCP) with β‐cyclodextrin (β‐CD) and modifying melamine cyanurate (MCA), we developed an efficient rodent repellent, β‐CD/DHCP@MCA, which significantly reduces DHCP's irritant effects during processing. This compound was combined with ammonium polyphosphate (APP) and dipentaerythritol (DPER) to create an intumescent flame‐retardant rodent repellent, applied to polypropylene (PP) materials. Experimental results demonstrate that PP materials containing this composite additive exhibit excellent flame‐retardant and rodent‐repellent properties, with an increased oxygen index of 30.9%. Rodent tests indicate that the material provides a significant non‐lethal deterrent effect on rats. This study offers an effective approach to mitigating DHCP's irritant effects and presents new insights for developing efficient flame‐retardant rodent repellents in polymer materials.

To enhance the flame retardancy of epoxy resin (EP), microcapsules (SiO 2 @APP) were prepared by encapsulating ammonium polyphosphate (APP) with silicon dioxide (SiO 2 ). Subsequently, a ternary intumescent flame retardant (IFR) system of SiO 2 @APP/MCA/CaG was formulated, using SiO 2 @APP as the primary flame retardant and acid source, melamine cyanurate (MCA) as the gas source, and calcium gluconate (CaG) as the carbon source. It was then employed for the flame retardant modification of EP. The thermal stability, flame retardancy, and mechanical properties of the EP composites were investigated through thermogravimetric analysis (TG), limiting oxygen index (LOI), UL-94 vertical burning test, cone calorimeter (CONE), scanning electron microscopy (SEM), and universal material testing machine. The results indicate that the SiO 2 @APP/MCA/CaG composite flame retardant can enhance the thermal stability and carbon residue rate of EP materials. When the mass ratio of SiO 2 @APP/MCA/CaG is 4:1:1, the residual carbon rate of EP composites at 600°C is 34.8%, and it gets the highest LOI value of 40.5%, and pass a UL-94 rating of V-0. Furthermore, compared to pure EP, the total heat release (THR) and total smoke production (TSP) are reduced by 68.8% and 66.7%, respectively. SEM testing reveals that the SiO 2 @APP/MCA/CaG flame retardant system can enhance the graphitization degree of the char residue in EP materials, resulting in a more compact structure. Furthermore, mechanical testing demonstrates that the addition of SiO 2 @APP/MCA/CaG composite flame retardant reduces the tensile strength of EP, yet it exhibits better tensile performance compared to EP composites with APP flame retardant alone. Based on the comprehensive test results of flame retardancy and mechanical properties, the SiO 2 @APP/MCA/CaG/EP composite is suitable for applications that require high flame retardancy but have relatively low demands on mechanical properties.

Comparative study on fire properties and HCL capture of PVC- melamine cyanurate composite through experiment and DFT calculation

Self-assembly of triazolyl-based cyclomatrix polyphosphazene and melamine cyanurate for flame-retardant, smoke-suppressing, and mechanically robust epoxy resin

ABSTRACTHalogen‐free flame‐retardant nylon was prepared by melting a mixture of nylon 11 (PA11), melamine cyanurate (MCA) and aluminum diethylphosphonate (AlPi) in a twin‐screw extruder. The addition amount and ratio of the synergistic formula would affect the synergistic flame‐retardant effect and degradation process of the composites. In the cone calorimetric test, when the flame‐retardant content was 35%, the total heat release (THR) of the halogen‐free flame‐retardant formula decreased by 24% to 52% compared with pure PA11. The most noteworthy finding is that the ignition time (TTI) of the flame‐retardant formula with MCA (334 s) is significantly longer than that of the pure PA11 (131 s) and AlPi (140 s) flame‐retardant formulas, and the effect of the compound formula can be better than that of the MCA single‐component formula, up to 404 s. Upon analyzing the structure and composition of the gas products and char residue of each formula, we discerned that MCA and AlPi played different roles in promoting the formation of carbon residues within the condensed phase. Based on all the test results, it was concluded that the mechanism of the nitrogen flame‐retardant MCA involves delaying the decomposition of composites and promoting the formation of an expanded carbon layer by generating refractory gas.

The halogen-free flame retardant (HFFR) thermoplastic elastomers (TPEs) composites filled with aluminum diethylphosphinate (ADP) had been prepared using the melting compounding method by a twin-screw extruder. The flame retardancy, smoke release performance, thermal stability, mechanical properties and microscopic morphology of carbonaceous char of TPE/ADP composites had been investigated by cone calorimeter, NBS smoke density chamber, limiting oxygen index (LOI), UL-94 (vertical flame) test, thermogravimetric analysis (TGA), scanning electron microscopy (SEM) and ultimate tensile. The study results indicated that the flame retardancy and char forming characteristics of TPE/ADP composites had been dramatically improved. The more significant expansion of flame retardant TPE/ADP composites during combustion was found with the addition of synergistic flame retardants Zinc Borate (ZB) or melamine cyanurate (MCA). Among the synergistic agents of organic montmorillonite (OMMT), ZB, and MCA, ZB exhibited the best assisted carbonization performance regardless of high or low heat flux, and formed a multi-level twisted carbonaceous char structure. Meanwhile, due to the addition of synergistic flame retardant ZB, not only the flame retardancy was improved, but also the smoke release was significantly inhibited. The tensile performance test showed the ultimate tensile strength and elongation at break of TPE composites maintained a relatively high level, and which can meet the application requirements of cable sheath materials.

Flame-retardant effects of NH2-MIL-53(Al) in combination with phosphorus-containing and nitrogen-containing flame retardants on polypropylene

Synthesis of nitrogen and phosphorus-doped chitosan derivatives for enhanced flame retardancy, smoke suppression, and mechanical properties in epoxy resin composites.

Abstract This study investigates the innovative use of intumescent flame retardants (IFRs), specifically ammonium polyphosphate (APP), dipentaerythritol (DPER), and melamine cyanurate (MC), to enhance the flame retardancy and thermal stability of poly(ethylene‐ co ‐vinyl acetate)/high‐density polyethylene (EVA/HDPE) blends. The blends were prepared through a melt mixing process, followed by compression molding, allowing for a thorough integration of the IFRs into the polymer matrix. Comprehensive characterization techniques, including limiting oxygen index (LOI) measurements, UL‐94 vertical combustion tests, and cone calorimeter tests, were employed to evaluate the flame retardant performance of the blends. The findings reveal that the incorporation of IFRs significantly improves the flame retardant properties of the EVA/HDPE blends, achieving LOI values of 30.0% and UL‐94 ratings of V‐0 at higher IFR concentrations. This work contributes to the field by demonstrating the effectiveness of IFRs in forming a protective char layer that enhances thermal stability and reduces heat release during combustion. The study not only provides insights into the optimal formulation of EVA/HDPE blends for improved fire safety but also paves the way for the development of advanced materials suitable for applications in wire and cable insulation, where enhanced flame resistance is paramount. Highlights Intumescent flame retardants (IFRs) were incorporated to improve flame retardancy. The effect of IFRs content was investigated. EVA/HDPE/IFRs blends exhibited high thermal stability and flame retardancy.

In order to mitigate the release of toxic phosphine from aluminum hypophosphite in twin-screw processing, montmorillonite–melamine cyanurate was prepared by three methods: (1) mechanical intercalation, (2) water intercalation and (3) in situ intercalation. The sheet spacing of montmorillonite was increased from 1.140 nm to 1.141 nm, 1.208 nm and 1.217 nm for these three methods, respectively, and scanning electron microscope (SEM) and transmission electron microscopy (TEM) proved that melamine cyanurate was successfully inserted into the montmorillonite sheets. The montmorillonite–melamine cyanurate from in situ intercalation can best inhibit the release of PH3 from aluminum hypophosphite, and the peaks of phosphine, mean values of phosphine and integral of phosphine were reduced by 81.9%, 72.1% and 72.2%, respectively. The mode of action of montmorillonite–melamine cyanuric inhibition of the emission of phosphine from aluminum hypophosphite can be attributed to the physical absorption of montmorillonite and the chemical bonding of melamine cyanurate. In addition, in situ intercalation can slightly improve flame retardancy, attributed to incomplete exfoliation of montmorillonite sheets.

This work describes the use of silica particles obtained by sol-gel method as a templat for deposition of supramolecular complexes of melamine cyanurate. To obtain SiO2@melamine-cyanurate (SiO2@MCA) material, the method of covalent modification of silica surface by melamine molecules (SiO2-mel) was applied and the method of its further functionalization by hydrogen-bonded organic framework of melamine-cyanurate (HOF, MCA) was proposed. One of the promising directions of using SiO2@melamine-cyanurate is obtaining SiO2@g-C3N4 material on its basis. Control of the amount of applied melamine-cyanurate allows to potentially obtain g-C3N4 layers of different thicknesses on the silica surface.

In silico analysis of the melamine structural analogues interaction with calcium-sensing receptor: A potential for nephrotoxicity

MoS2@Fe3O4 prepared by γ-ray in situ reduction for enhancing the fire safety and mechanical properties of EVA/MCA composites

Abstract To enhance the flame‐retardant characteristics of ceramifiable polyethylene (PE) composites, a composite flame retardant comprising ammonium polyphosphate (APP) and melamine cyanurate (MCA) was integrated. This addition markedly bolstered their flame‐retardant attributes. A meticulous exploration was conducted to ascertain the impacts of APP and MCA on the ceramifiable PE composites' visible morphology, mechanical robustness, and dimensional constancy, and to study the phase transition and microstructure deformation during sintering. Findings underscored that the amalgamation of APP/MCA markedly enhanced the flame resistance of these ceramifiable composites, registering a limiting oxygen index of 25.6% and achieving the vertical burning test (UL‐94) rating of V‐0. The collaborative flame‐retardant action of APP/MCA significantly enhanced the flame resistance of the PE composites while effectively mitigating the composite's propensity to drip. Upon detailed phase analysis, a eutectic reaction was observed between APP and wollastonite fiber, culminating in the genesis of a novel crystalline phase, calcium pyrophosphate (Ca2P2O7). When subjected to elevated temperatures, glass–ceramics manifest with both crystalline and vitreous phases. The proportion of the vitreous phase plays a pivotal role in influencing the ceramic's overall performance.

The growing requirements regarding the safety of using polymers and their composites are related to the emergence of more effective, sustainable, and hazardous-limited fire retardants (FRs). Significant amounts of FRs are usually required to effectively affect a polymer's burning behavior, while the knowledge of their recycling potential is still insufficient. At the same time, concerns are related not only to the reduced effectiveness of flame retardancy but also, above all, to the potential deterioration of mechanical properties caused by the degradation of temperature-affected additives under processing conditions. This study describes the impact of the four-time reprocessing of bio-based polyamide 11 (PA11) modified with an intumescent flame-retardant (IFR) system composed of ammonium polyphosphate (APP), melamine cyanurate (MC), and pentaerythritol (PER) and its composites containing additional short basalt fibers (BFs). Composites manufactured via twin-screw extrusion were subjected to four reprocessing cycles using injection molding. A comprehensive analysis of their structural, mechanical, and fire behavior changes in each cycle was conducted. The obtained results confirmed the safety of using the proposed fire-retarded polyamide and its composites while reprocessing under the recommended process parameters without the risk of significant changes in the structure. The partial increase in flammability of reprocessed PA-based materials caused mainly by polymer degradation has been described.