A method for preparing a black phosphorus-based bio-based flame retardant hybrid flame retardant
By using ionic crosslinking and mechanochemical recombination techniques, quercetin and chitosan were deeply hybridized with black phosphorus nanosheets, solving the compatibility and stability issues of chitosan and black phosphorus in polymer materials, and achieving high-efficiency flame retardancy and improved thermal stability.
Patent Information
- Application Number
- CN202610434703.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-04-03
- Publication Date
- 2026-05-26
AI Technical Summary
In existing technologies, chitosan has low flame retardant efficiency, insufficient thermal stability, and poor interfacial compatibility with polymer matrices. Black phosphorus nanosheets are easily oxidized and degraded and have poor interfacial compatibility, which limits their application under high standard flame retardant requirements.
Quercetin and chitosan were self-assembled into bio-based flame retardant units by sodium tripolyphosphate ion crosslinking. These units were then mechanically and chemically recombined with black phosphorus nanosheets through a high-energy ball milling process to form a stable black phosphorus-based bio-hybrid flame retardant. The deep hybridization of the two components was achieved by utilizing strong hydrogen bonds and van der Waals forces.
It significantly improves the flame retardant properties and thermal stability of polymer composites at low addition levels, forms a dense char layer and captures active free radicals in the combustion chain, achieving efficient flame retardancy and performance enhancement.
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Abstract
Description
Technical Field
[0001] This invention belongs to the field of bio-based nano-hybrid flame retardant technology, specifically relating to a method for preparing a black phosphorus / quercetin-chitosan hybrid flame retardant using ionic crosslinking and mechanochemical recombination technology. Background Technology
[0002] When polymers encounter a heat source, they undergo violent pyrolysis and oxidation. Essentially, this process involves the breaking of molecular chains due to heat, releasing low-molecular-weight flammable volatiles and reactive free radicals. When these gases mix with oxygen in the air and are ignited, a free radical chain reaction mediated by H· and OH· is triggered. The enormous heat released by this reaction, in turn, accelerates the degradation of the matrix, forming a feedback loop of continuous combustion. Therefore, the core of flame retardancy lies in interfering with or breaking this "degradation-gasification-combustion" cycle. Currently, the industrial sector commonly uses intumescent flame retardants (IFRs) to slow down this process.
[0003] Driven by the trends of environmental protection and non-toxicity, bio-based macromolecules have become a core force in developing next-generation high-performance flame retardants. Chitosan, a widely sourced natural amino polysaccharide, is widely used in biomedicine and environmental adsorption fields due to its excellent antibacterial properties and ease of functionalization. Structurally, chitosan is rich in hydroxyl and amino groups, which can promote the formation of an expanded char layer when heated and exert a flame-retardant effect by releasing non-flammable gases to dilute oxygen and flammable gas concentrations. However, pristine chitosan suffers from low flame-retardant efficiency, insufficient thermal stability, and poor interfacial compatibility with polymer matrices, limiting its application under high-standard flame-retardant requirements. Meanwhile, quercetin, as a typical flavonoid polyphenol, occupies an important position in the life sciences field due to its excellent free radical scavenging ability. Its unique aromatic structure and abundant phenolic hydroxyl groups endow it with excellent char-forming potential, making it an ideal building block for synthesizing bio-based flame retardants and enhancing the heat resistance of polymers. Nevertheless, using quercetin alone often fails to effectively inhibit flame spread, resulting in limited improvement in flame-retardant performance. Therefore, combining the char-forming ability of quercetin with the inherent expansion properties of chitosan to construct a synergistic flame-retardant system is expected to significantly improve the fire safety and mechanical toughness of materials.
[0004] As an emerging two-dimensional nanomaterial, black phosphorus (BP) exhibits a significant physical barrier effect in the flame retardant field due to its unique layered structure and large specific surface area. Physically, black phosphorus effectively slows down the penetration of heat and oxygen, promotes char formation, and reduces the release of combustible volatiles. Chemically, the phosphorus free radicals released during its decomposition can effectively capture active free radicals in the flame, thereby interrupting the combustion reaction. Although black phosphorus can significantly improve flame retardant efficiency even at low addition levels, its susceptibility to oxidation and degradation in air, along with poor interfacial compatibility with polymer matrices, greatly limits its industrial application.
[0005] Therefore, it is urgent to deeply integrate the advantages of bio-based components and nanomaterials through molecular design: on the one hand, to improve the thermal stability and char quality of bio-based units through cross-linking assembly; on the other hand, to enhance the antioxidant properties and interfacial compatibility of black phosphorus through mechanochemical recombination. By constructing a multi-dimensional synergistic mechanism, the aim is to achieve efficient flame retardancy and performance enhancement of materials with low addition amounts. Summary of the Invention
[0006] This invention provides a method for preparing a black phosphorus-based bio-based flame retardant unit hybrid flame retardant. First, sodium tripolyphosphate is used as an ionic crosslinking agent to mediate the self-assembly of quercetin and chitosan to form stable bio-based flame retardant units (CQ) through electrostatic attraction and hydrogen bonding. Subsequently, the flame retardant units are mechanically and chemically recombined with black phosphorus nanosheets (BP) through a high-energy ball milling process. The deep hybridization of the two is achieved by utilizing intermolecular hydrogen bonds and van der Waals forces to construct a structurally stable hybrid flame retardant (CQBP). This flame retardant fully utilizes the catalytic char formation ability of the CQ units and the physical barrier effect of the black phosphorus nanosheets, and can significantly enhance the flame retardant performance and thermal stability of polymer composites even at low addition levels.
[0007] The technical solution of this invention is as follows: A method for preparing a black phosphorus-based bio-based flame retardant hybrid flame retardant includes the following steps: (1) Ionic crosslinking: Add 10-13 mL of quercetin ethanol suspension to 100-150 mL of chitosan solution, then add 10-15 mL of sodium tripolyphosphate solution, and react at room temperature for 5-8 h to obtain a mixture; (2) Purification and drying: Centrifuge the mixture obtained in step (1), wash the precipitate with deionized water, and freeze-dry it under vacuum to obtain yellow powdered flame retardant unit CQ; (3) Ball milling: The CQ obtained in step (2) is mixed with black phosphorus nanosheets (BP) and recombined by high-energy ball milling process to obtain black phosphorus-based bio-based flame retardant unit hybrid flame retardant CQBP.
[0008] Step (1) The chitosan solution is obtained by dissolving 0.7-1.0g of chitosan in 100-150mL of 1% acetic acid solution and mixing well.
[0009] Step (1) The concentration of quercetin in the ethanol suspension is 50-80 mg / 10-13 mL.
[0010] Step (1) The mass ratio of chitosan to quercetin is 15-18:1.
[0011] In step (1), the concentration of the sodium tripolyphosphate solution is 0.03-0.04 g / mL.
[0012] Step (2) Centrifugation is performed at 10000-12000 rpm for 4-5 minutes.
[0013] In step (3), the mass ratio of CQ to black phosphorus nanosheets (BP) in the ball milling mixture is 1-5:1.
[0014] Step (3) The high-energy ball milling process specifically involves ball milling at a speed of 350 rpm for 3-5 hours.
[0015] The beneficial effects of this invention are: This invention precisely mediates the self-assembly of quercetin and chitosan into a structurally stable bio-based flame retardant unit CQ through the ionic cross-linking of sodium tripolyphosphate in an aqueous system. Furthermore, it utilizes the mechanical force generated by ball milling to induce molecular-level recombination between CQ and black phosphorus nanosheets (BP), and solves the problem of easy oxidation and aggregation of black phosphorus through strong hydrogen bonds and van der Waals forces, thereby achieving uniform dispersion of the hybrid flame retardant in the polymer matrix.
[0016] This invention constructs a multidimensional flame-retardant synergistic mechanism for polymer materials: on the one hand, quercetin and chitosan in the CQ unit play a synergistic role in char formation and expansion in the condensed phase, forming a dense and heat-insulating char layer, while the two-dimensional physical barrier effect of BP nanosheets significantly improves the integrity of the char layer, effectively blocking heat transfer and the overflow of combustible gases; on the other hand, the phosphorus-containing free radicals released by BP nanosheets at high temperatures can enter the gas phase to capture active free radicals in the combustion chain, achieving dual protection of "condensed phase shielding - gas phase quenching".
[0017] This invention overcomes technical challenges such as limited thermal stability of bio-based materials, poor interfacial compatibility of black phosphorus nanosheets, and difficulties in processing and dispersion through interface design involving ionic crosslinking and mechanochemical recombination, thereby endowing polymer materials with excellent expansion flame retardant properties and thermal stability. Attached Figure Description
[0018] Figure 1 Raman diagrams of the flame retardant CQBP prepared in Example 1 and the raw material BP; Figure 2XRD patterns of flame retardant CQBP prepared in Example 1 and raw material BP; Figure 3 The image shows the XRD patterns of the flame retardant CQBP prepared in Example 1 and the raw material BP. Detailed Implementation
[0019] The present invention will be further described below with reference to specific embodiments.
[0020] All raw materials used in the examples can be purchased from the market or prepared using conventional methods that have been disclosed.
[0021] Example 1 A method for preparing a black phosphorus-based bio-based flame retardant hybrid flame retardant includes the following steps: (1) Ionic crosslinking: Dissolve 0.7g of chitosan in 100mL of 1% acetic acid solution, stir to dissolve, add 10mL of ethanol suspension containing 50mg of quercetin, then add 10mL of aqueous solution containing 0.3g of sodium tripolyphosphate, stir at room temperature for 5h to obtain a mixture; (2) Purification and drying: The obtained mixture was centrifuged at 10,000 rpm for 5 min. The precipitate was washed with deionized water and then freeze-dried under vacuum to obtain yellow powder flame retardant unit CQ-1. (3) Ball milling: The CQ-1 obtained in step (2) is mixed with black phosphorus (BP) at a mass ratio of 1:1 and ball milled at a speed of 350 rpm for 4 hours to obtain hybrid flame retardant CQBP-1.
[0022] Example 2 A method for preparing a black phosphorus-based bio-based flame retardant hybrid flame retardant includes the following steps: (1) Ionic crosslinking: Dissolve 0.8g of chitosan in 115mL of 1% acetic acid solution, stir to dissolve, add 11mL of ethanol suspension containing 60mg of quercetin, then add 12mL of aqueous solution containing 0.36g of sodium tripolyphosphate, stir at room temperature for 6h to obtain a mixture; (2) Purification and drying: The obtained mixture was centrifuged at 10,000 rpm for 5 min, washed and freeze-dried to obtain flame retardant unit CQ-2; (3) Ball milling: The CQ-2 obtained in step (2) is mixed with BP at a mass ratio of 2:1 and ball milled at a speed of 350 rpm for 3 hours to obtain hybrid flame retardant CQBP-2.
[0023] Example 3 A method for preparing a black phosphorus-based bio-based flame retardant hybrid flame retardant includes the following steps: (1) Ionic crosslinking: Dissolve 0.9g of chitosan in 125mL of 1% acetic acid solution, stir to dissolve, add 12mL of ethanol suspension containing 70mg of quercetin, then add 10mL of aqueous solution containing 0.4g of sodium tripolyphosphate, stir at room temperature for 7h to obtain a mixture; (2) Purification and drying: The obtained mixture was centrifuged at 10,000 rpm for 5 min, washed and freeze-dried to obtain flame retardant unit CQ-3; (3) Ball milling: The CQ-3 obtained in step (2) is mixed with BP at a mass ratio of 3:1 and ball milled at 350 rpm for 5 hours to obtain hybrid flame retardant CQBP-3.
[0024] Example 4 A method for preparing a black phosphorus-based bio-based flame retardant hybrid flame retardant includes the following steps: (1) Ionic crosslinking: Dissolve 0.95g chitosan in 140mL of 1% acetic acid solution, stir to dissolve, add 12.5mL of ethanol suspension containing 75mg quercetin, then add 14mL of aqueous solution containing 0.45g sodium tripolyphosphate, stir at room temperature for 7.5h to obtain a mixture; (2) Purification and drying: The obtained mixture was centrifuged at 11,000 rpm for 4.5 min, washed and freeze-dried to obtain flame retardant unit CQ-4; (3) Ball milling: The CQ-4 obtained in step (2) is mixed with BP at a mass ratio of 4:1 and ball milled at 350 rpm for 4 hours to obtain hybrid flame retardant CQBP-4.
[0025] Example 5 A method for preparing a black phosphorus-based bio-based flame retardant hybrid flame retardant includes the following steps: (1) Ionic crosslinking: Dissolve 1.0 g of chitosan in 150 mL of 1% acetic acid solution, stir to dissolve, add 13 mL of ethanol suspension containing 80 mg of quercetin, then add 15 mL of aqueous solution containing 0.5 g of sodium tripolyphosphate, stir at room temperature for 8 h to obtain a mixture; (2) Purification and drying: The obtained mixture was centrifuged at 12000 rpm for 4 min, washed and freeze-dried to obtain flame retardant unit CQ-5; (3) Ball milling: The CQ-5 obtained in step (2) is mixed with BP at a mass ratio of 5:1 and ball milled at a speed of 350 rpm for 5 hours to obtain hybrid flame retardant CQBP-5.
[0026] The hybrid product CQBP-1 prepared in Example 1 and the original black phosphorus nanosheet (BP) powder were subjected to X-ray diffraction (XRD) and Raman spectroscopy analysis, respectively. By comparing the diffraction patterns and scattering peak position changes of the two, the influence of the hybridization process on the black phosphorus crystal structure and the interaction between the components were investigated. CQBP-1 and BP prepared in Example 1 were mixed with TPU (thermoplastic polyurethane) at a ratio of 0.5% by mass. After mixing at 170°C for 20 minutes, hot pressing at 170°C for 15 minutes, and cold pressing at 25°C for 2 minutes, the products CQBP-1 / TPU and BP / TPU were obtained. UL-94 vertical burning test and limiting oxygen index analysis were performed.
[0027] Figure 1 Raman spectral characterization analysis of BP and CQBP-1 showed that CQBP-1 and the original BP were in the same range at 360.01 cm⁻¹. -1 433.89cm -1 and 460.34cm -1 The surrounding area all showed clear A g 1 B 2g and A g 2 The vibrational characteristic peaks demonstrate that the flame retardant CQBP-1 fully retains the core lattice vibrational characteristics of black phosphorus. Further comparison shows that, compared to pure BP, the three characteristic peaks of CQBP-1 exhibit a blue shift towards higher wavenumbers. This shift confirms the strong interfacial interaction or chemical bonding effect between the flame retardant component CQ and the black phosphorus matrix. This tight integration of the microstructure is beneficial to improving the chemical stability and dispersibility of the flame retardant in the polymer matrix.
[0028] Figure 2 The XRD patterns of BP and flame retardant CQBP-1 are shown. The diffraction peak positions of CQBP-1 are highly consistent with those of the original BP and the standard card. Sharp and high-intensity diffraction peaks are observed at typical angles of 2θ such as 16.9°, 26.5°, 34.2°, and 35.1°, corresponding to the (020), (021), (040), and (041) crystal planes of black phosphorus, respectively. This indicates that CQBP-1 successfully maintained the original orthorhombic layered structure and extremely high crystallinity of black phosphorus during the composite modification process. At the same time, no obvious impurity phase diffraction peaks were detected in the CQBP-1 spectrum, and its diffraction background was stable, fully demonstrating that the flame retardant has good phase purity. Its regular crystal structure provides a material basis for the formation of a dense char layer during the subsequent flame retardant process.
[0029] pass Figure 3Comparative analysis of the limiting oxygen index (LOI) and UL-94 vertical flammability rating of BP / TPU and CQBP / TPU composites revealed that the BP / TPU composite with only the original BP added had an LOI value of only 21.8% and a vertical flammability rating of only V-1, exhibiting low flame retardant efficiency. In contrast, the CQBP / TPU composite with the CQBP flame retardant prepared in this invention showed a significantly increased LOI value of 29.4%, a substantial 34.9% improvement compared to BP / TPU, and successfully achieved the highest vertical flammability rating of V-0. This significant improvement in flame retardant performance directly demonstrates that the CQBP flame retardant has superior flame retardant efficiency in the TPU matrix, not only more effectively inhibiting matrix combustion but also significantly improving the intrinsic flame retardancy of the material, thereby providing the polymer matrix with a higher level of safety protection.
[0030] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the technical solutions of the embodiments of the present invention.
Claims
1. A method for preparing a black phosphorus-based bio-based flame retardant hybrid flame retardant, characterized in that, Includes the following steps: (1) Ionic crosslinking: Add 10-13 mL of quercetin ethanol suspension to 100-150 mL of chitosan solution, then add 10-15 mL of sodium tripolyphosphate solution, and react at room temperature for 5-8 h to obtain a mixture; (2) Purification and drying: Centrifuge the mixture obtained in step (1), wash the precipitate with deionized water, and freeze-dry it under vacuum to obtain yellow powdered flame retardant unit CQ; (3) Ball milling: The CQ obtained in step (2) is mixed with BP and recombined by high-energy ball milling process to obtain black phosphorus-based bio-based flame retardant unit hybrid flame retardant.
2. The preparation method of the black phosphorus-based bio-based flame retardant hybrid flame retardant according to claim 1, characterized in that, Step (1) The chitosan solution is obtained by dissolving 0.7-1.0g of chitosan in 100-150mL of 1% acetic acid solution and mixing well.
3. The preparation method of the black phosphorus-based bio-based flame retardant hybrid flame retardant according to claim 1, characterized in that, Step (1) The concentration of quercetin in the ethanol suspension is 50-80 mg / 10-13 mL.
4. The preparation method of the black phosphorus-based bio-based flame retardant hybrid flame retardant according to claim 1, characterized in that, Step (1) The mass ratio of chitosan to quercetin is 15-18:
1.
5. The preparation method of the black phosphorus-based bio-based flame retardant hybrid flame retardant according to claim 1, characterized in that, The concentration of sodium tripolyphosphate solution in step (1) is 0.03-0.04 g / mL.
6. The preparation method of the black phosphorus-based bio-based flame retardant hybrid flame retardant according to claim 1, characterized in that, Step (2) Centrifugation is performed at 10000-12000 rpm for 4-5 minutes.
7. The preparation method of the black phosphorus-based bio-based flame retardant hybrid flame retardant according to claim 1, characterized in that, In step (3), the mixing mass ratio of CQ to BP is 1-5:
1.
8. The preparation method of the black phosphorus-based bio-based flame retardant hybrid flame retardant according to claim 1, characterized in that, Step (3) The high-energy ball milling process specifically involves ball milling at a speed of 350 rpm for 3-5 hours.