A manganese phytate grafted modified MXene / carbon microsphere flame retardant and its preparation method

Abstract

The present invention discloses a manganese phytate grafted modified MXene / carbon microsphere flame retardant and a preparation method thereof. By using the silane coupling agent APTES as a surface modifier, manganese phytate is used to graft-modify MXene, and hydrothermal carbon microspheres are electrostatically self-assembled on the surface, the manganese phytate grafted modified MXene / carbon microsphere flame retardant is successfully prepared. The flame retardant and smoke suppression performance of the MXene / carbon microsphere is significantly improved, and the hydrophobicity and compatibility with the PLA matrix are also improved. At the same time, the charring performance of the composite material is greatly improved, and its flame retardant performance is greatly enhanced.

Description

Technical Field

[0001] The present invention belongs to the technical field of flame retardancy, and specifically relates to a manganese phytate-grafted modified MXene / carbon microsphere flame retardant and a preparation method thereof. Background Art

[0002] MXene was first discovered in 2011 by Professor Yury Gogotsi and Professor Michel Barsoum of Drexel University. Due to its excellent conductivity, hydrophilicity, and outstanding mechanical properties, it quickly became a research hotspot in academia. As a two-dimensional layered nanomaterial, MXene has good thermal stability, a unique layered structure, excellent catalytic activity, and adjustable surface functional groups. Its unique two-dimensional structure and high specific surface area enable it to act as a physical barrier layer to effectively block heat transfer and delay the thermal decomposition of the matrix. This physical barrier can form a protective layer on the surface of the material, reducing the transfer of heat and oxygen, thereby reducing the combustion rate of the material. Moreover, the transition metal compounds such as TiO2 produced by the combustion of MXene have good catalytic activity, which can promote the carbonization of the polymer matrix, help form a stable carbon layer during the combustion process, reduce the release of combustible gases, and play an excellent role in catalytic carbonization and smoke suppression. In addition, the rich functional groups on the surface of MXene make it easier to modify, enhance its dispersibility and compatibility in composite materials, and thus improve the flame retardant effect. However, Ti3C2T x It also exhibits some inherent defects. For example, as a single flame retardant, its flame retardant efficiency is low. Moreover, MXene, like other layered nanomaterials, is easy to stack and aggregate. Its dispersibility and interfacial compatibility with the PLA matrix are poor, which affects the mechanical properties and flame retardant properties of the composite material. This seriously hinders its application in the flame retardant field. Summary of the Invention

[0003] In order to solve the problems existing in the prior art, the purpose of the present invention is to provide a manganese phytate grafted modified MXene / carbon microsphere flame retardant and a preparation method thereof. By using the silane coupling agent APTES as a surface modifier, using manganese phytate to graft modify MXene and electrostatically self-assemble hydrothermal carbon microspheres on the surface, a manganese phytate grafted modified MXene / carbon microsphere flame retardant was successfully prepared. It not only significantly improves the flame retardant and smoke suppression performance, but also improves the hydrophobicity and its compatibility with the PLA matrix. At the same time, the charring performance of the composite material is greatly improved, which greatly enhances its flame retardant properties.

[0004] In order to achieve the above object, the present invention adopts the following technical solutions:

[0005] A method for preparing a manganese phytate-grafted modified MXene / carbon microsphere flame retardant comprises the following steps:

[0006] (1) Chitosan powder is dissolved in acetic acid solution, subjected to hydrothermal reaction, solid-liquid separation, and ground into powder to obtain carbon microspheres (CMSs);

[0007] (2) Ultrasonic dispersion of MXene in deionized water to obtain a MXene dispersion; APTES (3-aminopropyltriethoxysilane) is added to the MXene dispersion, stirred and mixed thoroughly, and silanized MXene is obtained after solid-liquid separation;

[0008] (3) The silanized MXene was ultrasonically dispersed in deionized water. After ultrasonic treatment in an ice bath, PA (phytic acid) and manganese acetate were added in sequence and stirred thoroughly to obtain phytic acid manganese grafted modified MXene, which was recorded as MXene-PAMn.

[0009] (4) CMSs and MXene-PAMn were ultrasonically dispersed in deionized water to obtain a mixed slurry, which was fully stirred and reacted under a nitrogen atmosphere. The solid sample obtained after solid-liquid separation was calcined to obtain phytic acid manganese grafted modified MXene / carbon microsphere flame retardant, which was recorded as MXene-PAMn / CMSs.

[0010] Those skilled in the art are aware that MXene, as a two-dimensional layered nanomaterial, has a unique layered structure and high specific surface area, enabling it to act as a physical barrier, effectively blocking heat transfer and delaying thermal decomposition of the matrix. Furthermore, the transition metal compounds in MXene possess excellent catalytic activity, contributing to excellent catalytic carbonization and smoke suppression. However, like other layered nanomaterials, MXene is prone to stacking and aggregation, resulting in poor dispersibility and interfacial compatibility with the PLA matrix, which affects the mechanical and flame retardant properties of the composite material.

[0011] In view of this, the present invention uses silane coupling agent (3-aminopropyl) triethoxysilane (APTES) as a surface modifier, PA and CMSs as flame retardant synergists, and the silanol groups in APTES undergo condensation reaction with the hydroxyl groups on the surface of MXene to form Ti-O-Si bonds. Then, phytic acid molecules are grafted onto the surface of MXene nanosheets through the silane coupling method to chelate Mn 2+, a bio-based organic / inorganic hybrid MXene-based flame retardant containing N / P was prepared, in which the physical barrier effect of the evenly dispersed flame retardant and the nitrogen-phosphorus synergistic flame retardant system promoted the cross-linking of the carbon layer, and the synergistic catalytic carbonization of the transition metal elements Ti and Mn formed dense and stable char to block heat and oxygen transfer, reduce smoke release, and significantly improve the flame retardant and smoke suppression properties; phytic acid releases phosphorus-containing free radicals PO· when thermally decomposed, which interrupts the combustion chain reaction by capturing HO· and H· in the air, thereby reducing the combustion rate; PA grafting and silane coupling to introduce long carbon chains significantly improve the hydrophobicity of the flame retardant, reduce the agglomeration and stacking phenomenon of the flame retardant in the PLA matrix, and improve the dispersibility of the flame retardant in the PLA matrix.

[0012] Preferably, in step (1), the temperature of the hydrothermal reaction is 160-200° C., and the time is 8-24 h.

[0013] Preferably, in step (2), the concentration of the MXene dispersion is 0.2-0.5 g:100 ml.

[0014] Preferably, in step (2), the mass volume ratio of MXene and APTES is 1 g:30-50 ml.

[0015] Preferably, in step (3), the amount of silanized MXene, PA and manganese acetate is 1 g: 1-3 ml: 0.3-0.6 g.

[0016] Preferably, in step (4), the mass ratio of CMSs to MXene-PAMn is 2:1.

[0017] Preferably, in step (4), the calcination temperature is 150-200° C. and the calcination time is 0.5-2 h.

[0018] The present invention also provides a manganese phytate grafted modified MXene / carbon microsphere flame retardant prepared by the above preparation method.

[0019] The advantages of the present invention are:

[0020] (1) The present invention successfully prepared a phytic acid-grafted MXene / carbon microsphere flame retardant by using silane coupling agent APTES as a surface modifier, grafting MXene with manganese phytate, and electrostatically self-assembling hydrothermal carbon microspheres on the surface. The physical barrier effect of the uniformly dispersed flame retardant and the nitrogen-phosphorus synergistic flame retardant system promote the cross-linking of the carbon layer and the synergistic catalytic carbonization effect of the transition metal elements Ti and Mn form dense and stable coke to block heat and oxygen transfer, thereby reducing smoke release. In addition, phytic acid releases phosphorus-containing free radicals PO· when thermally cracked, which interrupt the combustion chain reaction by capturing HO· and H· in the air, thereby reducing the combustion rate.

[0021] (2) The present invention introduces long carbon chains through PA grafting and silane coupling, giving the flame retardant a rough surface and a larger interlayer spacing without destroying the special layered structure, significantly improving the hydrophobicity of the flame retardant, reducing the agglomeration and stacking phenomenon of the flame retardant in the PLA matrix, and improving the dispersibility of the flame retardant in the PLA matrix.

[0022] In summary, the present invention successfully prepared a manganese phytate-grafted MXene / carbon microsphere flame retardant by using the silane coupling agent APTES as a surface modifier, grafting MXene with manganese phytate, and loading hydrothermal carbon microspheres on the surface. This not only significantly improved the flame retardant and smoke suppression performance, but also improved the hydrophobicity and compatibility with the PLA matrix. At the same time, the charring performance of the composite material was greatly improved, greatly enhancing its flame retardant properties. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 1 is the XRD pattern of MXene, MXene / CMSs prepared in Comparative Example 1, and MXene-PAMn / CMSs prepared in Example 1;

[0024] like Figure 1 As shown in the XRD patterns of MXene, characteristic diffraction peaks can be observed at 2θ = 8.9° (002), 16.3° (004), 27.4° (008), and 34.1° (110). The peaks are sharp and strong and correspond to the standard version of titanium aluminum carbide card (JCPDS52-0875). In addition to the peaks at (002), (004), (008), and (110), the XRD patterns of MXene / CMSs and MXene-PAMn / CMSs also have a characteristic peak at 2θ = 21.8° corresponding to the graphite plane in the carbon microspheres. Compared with MXene / CMSs, the (002) position in the XRD pattern of MXene-PAMn / CMSs shifts to a smaller angle, with 2θ=5.7° reduced to 5.4°, and the interplanar spacing calculated by the Bragg equation 2dsinθ=nλ increases from d(002)=0.78nm to 0.82nm, indicating that the interlayer spacing of MXene-PAMn / CMSs nanosheets after grafting phytic acid is further increased on the basis of MXene / CMSs.

[0025] Figure 2 FT-IR images of MXene, MXene / CMSs prepared in Comparative Example 1, and MXene-PAMn / CMSs prepared in Example 1;

[0026] like Figure 2 As shown in the infrared spectrum of MXene, the -1The broad vibration peak at 2921cm corresponds to the stretching vibration of the hydroxyl group (ν-OH) on the MXene surface. -1 、1630cm -1 and 1440cm -1 The characteristic absorption peaks at 655 cm correspond to the stretching vibrations of CH, -CH and C=O bonds, respectively. -1 The characteristic peak at 1154 cm corresponds to the stretching vibration of the Ti-O bond. Compared with the FT-IR spectrum of MXene, the infrared spectrum of MXene / CMSs not only has the above characteristic peaks of MXene, but also can observe the peak at 1154 cm -1 In addition, by analyzing the infrared spectrum of MXene-PAMn / CMSs, it can be seen that the stretching vibration peak of the CN bond in CMSs is at 3400~3500cm -1 The broad vibration peak at 1113 cm is attributed to the stretching vibration of the hydroxyl group in MXene-PAMn / CMSs. In addition to the characteristic absorption peaks of MXene and CMSs, such as CH, C=O, CN and Ti-O bonds, the infrared spectrum of MXene-PAMn / CMSs also has a new characteristic peak at 1113 cm -1 、1097cm -1 and 760cm -1 The characteristic absorption peaks at the 300 nm and 300 nm correspond to the P=O, PO, and P-OH groups in the PA molecular structure, confirming the presence of phytic acid. Combined with XRD analysis, infrared spectroscopy further confirmed the preparation of the N / P-containing organic / inorganic hybrid flame retardant MXene-PAMn / CMSs via grafting modification.

[0027] Figure 3 These are SEM and TEM images of MXene, MXene / CMSs prepared in Comparative Example 1, and MXene-PAMn / CMSs prepared in Example 1;

[0028] like Figure 3As shown in the SEM image (A) and TEM image (F) of MXene, a typical two-dimensional layered nanosheet structure is observed, along with surface ripples and wrinkles, indicating that the nanosheets are stacked and agglomerated. The SEM image (B) of MXene-PAMn shows that the nanosheet surface is covered with evenly distributed nanoparticles, resulting from the grafting of PAMn onto the surface of the silanized MXene. The modified MXene-PAMn retains its two-dimensional layered structure. For MXene-PAMn / CMSs, SEM images (C and D) and TEM images (G, H, and I) show evenly distributed nanoparticles and spherical structures on the nanosheet surface, corresponding to the PAMn and CMSs components in the system, respectively. Compared to the relatively smooth surface of MXene, the surfaces of MXene-PAMn and MXene-PAMn / CMSs become significantly rougher due to the phytic acid grafting and CMSs loading, resulting in an increased specific surface area. This enhances the interfacial interaction between the flame retardant and the matrix material, thereby promoting dispersion and compatibility. EDS mapping results (E) of MXene-PAMn / CMSs reveal the presence of elements such as C, N, O, Ti, P, and Mn. P and Mn further confirm the grafting of PAMn onto the MXene, while N originates from the surface-loaded chitosan carbon microspheres. This analysis suggests that grafting and silanization impart a roughened surface and increased interlayer spacing to the flame retardant without disrupting its unique layered structure, facilitating its dispersion in PLA. The successful modification of MXene with PA and CMSs creates a multi-component N / P synergistic flame-retardant system, introducing the transition metals Ti and Mn.

[0029] Figure 4 TG (A) and DTG (B) graphs of MXene, MXene / CMSs prepared in Comparative Example 1, and MXene-PAMn / CMSs prepared in Example 1;

[0030] like Figure 4 As shown, the TG curve of MXene shows that there are three thermal weight loss stages between 30℃ and 800℃: the first thermal weight loss stage is before 120℃, and this process is mainly the removal of physically adsorbed water on the MXene surface. The second thermal weight loss stage occurs between 160℃ and 300℃, and this process mainly involves the thermal decomposition of functional groups on the MXene surface, such as the decomposition of hydroxyl groups. The third stage of the thermal weight loss process is between 600℃ and 800℃, which is attributed to the oxidation of Ti to form TiO2, and the transformation of layered MXene into anatase form. The total thermal weight loss of MXene is 13.8%, and the initial decomposition temperature (T 5％) is 163.1℃. The thermal decomposition process of MXene / CMSs and MXene-PAMn / CMSs is similar to that of MXene, but the decomposition temperature has increased to varying degrees, indicating that the thermal stability has been enhanced. For MXene-PAMn / CMSs, the first thermal weight loss stage also occurs before 120℃, and the second thermal weight loss peak is around 581.5℃. During this stage, the decomposition and carbonization of MXene mainly occurred. The thermal weight loss of MXene-PAMn / CMSs is only 5.8%, which is 8% and 10.2% lower than that of MXene (13.8%) and MXene / CMSs (16%), respectively. 5％ It is 590.5℃, which is 423.9℃ higher than that of MXene, and the thermal weight loss curve becomes smoother, indicating that the introduction of grafted phytic acid can enhance the heat resistance of the flame retardant. The significantly improved thermal stability and residual rate are mainly due to the synergistic effect of nitrogen and phosphorus after PAMn grafting and the catalytic carbonization of manganese elements. Therefore, at high temperatures, MXene-PAMn / CMSs can better play a physical barrier role, protect the further thermal decomposition of the bottom PLA matrix to inhibit combustion, and enable it to better play a flame retardant effect.

[0031] Figure 5 : is the water contact angle diagram of MXene, MXene / CMSs prepared in Comparative Example 1, and MXene-PAMn / CMSs prepared in Example 1;

[0032] like Figure 5 As shown in the figure, generally speaking, the lower the WCA value of a material, the stronger its hydrophilicity, and the higher the WCA value, the stronger its hydrophobicity. The water contact angle of MXene is 7.8°, while the water contact angle of MXene / CMSs increases to 49.5°. The extremely low water contact angle of MXene indicates that MXene is a material with extremely poor hydrophobicity. However, the water contact angle of the MXene / CMSs flame retardant increases significantly, indicating that its hydrophobicity has been significantly improved. This is because the uniform loading of CMSs on the surface expands the contact area of ​​MXene / CMSs nanosheets, which is conducive to the dispersion and compatibility of the flame retardant. It is worth noting that the water contact angle of the MXene-PAMn / CMSs flame retardant further increases to 54.4°. This is not only due to the increased specific surface area, but also largely due to the replacement of surface hydrophilic groups (such as -OH) by phytic acid grafting and silanization of MXene with long hydrophobic carbon chains. The improvement of the hydrophobicity of the MXene-PAMn / CMSs flame retardant after grafting modification is beneficial to improving the dispersion and compatibility between the nanosheets and the matrix during the melt processing of the composite material, thereby enhancing the mechanical properties of the PLA composite material and the density and quality of the carbon layer generated after combustion, thereby significantly improving the flame retardant properties of PLA.

[0033] Figure 6The cross-sectional SEM images of pure PLA and PLA / MXene and PLA / MXene-PAMn / CMSs composites prepared by melt blending of MXene and MXene-PAMn / CMSs, respectively;

[0034] like Figure 6 As shown in the figure, the microstructures of the liquid nitrogen brittle fracture sections of pure PLA, PLA / MXene and PLA / MXene-PAMn / CMSs composites are compared. The fracture section of pure PLA is relatively smooth with a small amount of cracks, which is the stress result during liquid nitrogen brittle fracture. By observing the micromorphology of the fracture section of PLA / MXene composite material through SEM, it can be seen that the cross section is uneven and due to the agglomeration between layered MXene nanosheets, the flame retardant filler is scattered and disorderly accumulated in the PLA matrix, presenting an irregular block structure of varying sizes, indicating poor dispersion. Furthermore, the interface between the MXene and PLA matrix is ​​distinct, with MXene nanosheets unevenly embedded within the PLA, creating pores and defects in the composite. This indicates poor interfacial compatibility between MXene and PLA, which is bound to negatively impact mechanical and flame retardancy. SEM images of fractured cross-sections of the PLA / MXene-PAMn / CMSs composites reveal spherical structures resembling those of CMSs and layered structures of MXene nanosheets. Flame retardant stacking and agglomeration are reduced, with very blurred edges. The interface between the flame retardant additive and the matrix is ​​virtually invisible, appearing to be fused together. PA grafting of MXene / CMSs reduces nanosheet stacking and agglomeration, promoting compatibility and dispersibility of the MXene-PAMn / CMSs flame retardant with PLA, consistent with WCA analysis. Furthermore, these improved dispersibility and compatibility enhance the mechanical properties of melt-processed PLA / MXene-PAMn / CMSs composites, as well as the uniformity, density, and quality of the char layer formed upon combustion, thereby improving flame retardancy.

[0035] Figure 7 These are digital photos and SEM images of carbon residues after CCT testing of pure PLA and PLA / MXene and PLA / MXene-PAMn / CMSs composites prepared by melt blending of MXene and MXene-PAMn / CMSs, respectively.

[0036] like Figure 7As shown in the figure, the digital photo of the residual carbon shows that there is almost no residual coke after the combustion of PLA; while the residual carbon after the combustion of PLA / MXene composite material is very loose, with low density and carbon yield, and there are honeycomb holes on the surface of the carbon layer and white matter appears on the surface, indicating that MXene is oxidized to anatase in the air during combustion, and the loose carbon layer cannot show ideal flame retardancy and smoke suppression efficiency; the carbon layer of PLA / MXene-PAMn / CMSs composite material is denser, and the thickness and carbonization rate are also significantly improved. The SEM image shows that the char residue after combustion of pure PLA is very thin and cannot play a physical barrier role during the combustion process; the SEM image of the char residue after combustion of PLA / MXene composite material shows the anatase structure after oxidation of MXene, and the scattered and disordered accumulation forms a carbon layer. This is because the extremely poor dispersion and compatibility of MXene in the PLA matrix makes the carbon layer unevenly distributed and not dense. This carbon layer also cannot play a good physical barrier role and cannot effectively suppress the release of heat and toxic smoke; the SEM image of the char residue of PLA / MXene-PAMn / CMSs composite material shows that its carbon layer structure is continuous and evenly distributed. The synergistic catalytic carbonization of titanium and manganese causes the transition metal oxide and the carbon layer to be tightly stacked to form a stable and dense barrier. The dense carbon layer formed by the composite material during combustion blocks heat exchange and oxygen, blocks the escape of combustion smoke, and inhibits further combustion of the PLA matrix, significantly improving the flame retardant and smoke suppression properties of the PLA composite material. DETAILED DESCRIPTION

[0037] The present invention will be further described below with reference to the embodiments.

[0038] MXene is obtained by etching Ti3AlC2:

[0039] First, using a plastic spatula, 1g of Ti3AlC2 powder was slowly added to a plastic beaker containing 20mL of 50% pure HF solution and magnetically stirred at room temperature for 24 hours. The resulting solution was then centrifuged multiple times at 5000rpm until the pH of the suspension reached >6. The resulting solid was added to a certain amount of deionized water and sonicated for 20 minutes, then washed with deionized water and filtered. Finally, the filtered solid was dried at 80°C for 8 hours, ground to obtain MXene powder, and sealed for storage.

[0040] Example 1

[0041] (1) MXene was grafted and modified using phytic acid (PA) and silane coupling agent 3-aminopropyltriethoxysilane (APTES): 1 g of the prepared MXene was weighed and dissolved in 300 mL of deionized water. The mixture was ultrasonicated in an ice bath for 30 min to make it uniformly dispersed. Then, 40 mL of 1% APTES solution was added dropwise. After magnetic stirring for 1 h, the mixture was centrifuged, washed, and dried to obtain the silanized MXene. Then, 1 g of silanized MXene sample was ultrasonically dispersed in 300 mL of deionized water. After ultrasonic treatment in an ice bath for 30 min, 2 mL of 70% PA solution was accurately measured with a pipette and added to 50 mL of deionized water. The diluted PA solution was slowly added dropwise to the reaction system. Then, 0.5 g of manganese acetate was weighed and dissolved in 50 mL of deionized water to form a solution, which was added dropwise to the above reaction system. After magnetic stirring for 30 min, the reaction was completed, filtered and washed with a filter membrane to remove the remaining reactants, and vacuum dried at 80 ° C for 12 h to obtain phytic acid manganese grafted modified MXene, recorded as MXene-PAMn.

[0042] (2) Weigh 2 g of CMSs and 1 g of MXene-PAMn and disperse them in 50 mL of deionized water. Ultrasonicate to make them uniformly dispersed. Then transfer the liquid to a three-necked flask and place it in a constant temperature magnetic stirrer. React for 1.5 h under a nitrogen atmosphere. Filter, wash, and dry the slurry after the reaction. In the second step, place the sample in a quartz boat and calcine it at 180 ° C for 1 h in a tube furnace under a nitrogen atmosphere. After the reaction is cooled to room temperature, the obtained product is washed with 0.1 M HCl and deionized water, filtered and dried to obtain a phytic acid manganese grafted modified MXene / carbon microsphere flame retardant, which is recorded as MXene-PAMn / CMSs.

[0043] Comparative Example 1

[0044] 2g of CMSs and 1g of MXene were weighed and dispersed in 50mL of deionized water, and ultrasonically dispersed to achieve uniform dispersion. The liquid was then transferred to a three-necked flask and placed in a constant-temperature magnetic stirrer. The reaction was carried out under a nitrogen atmosphere for 1.5 hours. The slurry after the reaction was filtered, washed, and dried. In the second step, the sample was placed in a quartz boat and calcined at 180°C in a tube furnace under a nitrogen atmosphere for 1 hour. After the reaction cooled to room temperature, the obtained product was washed with 0.1M HCl and deionized water, filtered and dried to obtain a chitosan carbon microsphere-modified MXene flame retardant, recorded as MXene / CMSs.

[0045] Performance testing:

[0046] By melt blending, MXene (D1), MXene / CMSs (D2) and MXene-PAMn / CMSs (S1) flame retardants were melt-blended with PLA to prepare PLA composite materials with a flame retardant mass fraction of 5 wt%. The flame retardant and mechanical properties of the composite materials were tested, and the results are shown in Table 1.

[0047] Table 1 Flame retardant and mechanical properties test results of different PLA composites

[0048]

[0049] As shown in Table 1, the tensile strength and elongation at break of pure PLA are 52.7 MPa and 5.4%, respectively, demonstrating good elasticity and toughness. With the addition of flame retardants, the tensile strength and elongation at break of the composite material decrease to varying degrees. When 5 wt% MXene is added, the tensile strength and elongation at break of the PLA / MXene composite material decrease significantly, reaching 48.8 MPa and 1.7%, respectively. However, when 5 wt% MXene-PAMn / CMSs is added, the mechanical properties significantly improve, reaching a tensile strength and elongation of 50.7 MPa and 2.9%, respectively.

[0050] Pure PLA is extremely flammable and exhibits droplet formation in combustion experiments, with an LOI value of only 19.2. When 5 wt% MXene is added, the LOI value is 20.9%, which only passes the UL-94V-2 rating. However, when 5 wt% MXene-PAMn / CMSs is added, the LOI directly increases to 27.5%, achieving the UL-94V-0 rating and exhibiting excellent flame retardant properties.

[0051] The pHRR (peak heat release rate) of pure PLA is 446.4 kW·m -2 , which makes it extremely easy to burn in the air. After adding different flame retardants, the pHRR of PLA / MXene decreased to 358.4kW·m -2 , while the pHRR of PLA / MXene-PAMn / CMSs composite material further decreased to 310.2kW·m -2 The THR (total heat release) of pure PLA is 74.9 MJ·m -2 The THR of PLA / MXene is 68.4 MJ·m -2 , while that of PLA / MXene-PAMn / CMSs composite material was reduced to 61.6 MJ·m -2 It can be seen that MXene-PAMn / CMSs can significantly improve the flame retardant properties of PLA.

[0052] The toxic smoke released by polymers during combustion is the main cause of most deaths in fires, so studying the smoke suppression properties of polymers is of great significance. Pure PLA releases a large amount of smoke during combustion, and its TSP (total smoke production) is 24.64m 2 When 5 wt% MXene was added, the TSP of the PLA / MXene composite material dropped to 19.08 m 2 After adding MXene-PAMn / CMSs flame retardant to PLA, the TSP of PLA / MXene-PAMn / CMSs composite material dropped to 15.43m 2 , the smoke release during the combustion process has been significantly controlled and its smoke suppression performance has been significantly improved.

Claims

1. A method for preparing a manganese phytate-grafted modified MXene / carbon microsphere flame retardant, characterized in that: The following steps are involved: (1) Chitosan powder is dissolved in acetic acid solution, subjected to hydrothermal reaction, solid-liquid separation, and ground into powder to obtain carbon microspheres (CMSs); (2) ultrasonically dispersing MXene in deionized water to obtain a MXene dispersion; adding 3-aminopropyltriethoxysilane to the MXene dispersion, stirring and mixing thoroughly, and obtaining silanized MXene after solid-liquid separation; (3) The silanized MXene was ultrasonically dispersed in deionized water. After ultrasonic treatment in an ice bath, phytic acid and manganese acetate were added in sequence and stirred thoroughly to obtain phytic acid-manganese-grafted modified MXene, which was recorded as MXene-PAMn. (4) CMSs and MXene-PAMn were ultrasonically dispersed in deionized water to obtain a mixed slurry, which was fully stirred and reacted under a nitrogen atmosphere. The solid sample obtained after solid-liquid separation was calcined to obtain phytic acid manganese grafted modified MXene / carbon microsphere flame retardant, which was recorded as MXene-PAMn / CMSs.

2. The preparation method according to claim 1, characterized in that In step (1), the temperature of the hydrothermal reaction is 160-200° C., and the time is 8-24 hours.

3. The preparation method according to claim 1, characterized in that In step (2), the concentration of the MXene dispersion is 0.2-0.5 g:100 ml.

4. The preparation method according to claim 1, characterized in that In step (2), the mass volume ratio of MXene and 3-aminopropyltriethoxysilane is 1 g:30-50 ml.

5. The preparation method according to claim 1, characterized in that In step (3), the amount of silanized MXene, phytic acid, and manganese acetate is 1 g: 1-3 ml: 0.3-0.6 g.

6. The preparation method according to claim 1, characterized in that In step (4), the mass ratio of CMSs and MXene-PAMn is 2:

1.

7. The preparation method according to claim 1, characterized in that In step (4), the calcination temperature is 150-200° C. and the calcination time is 0.5-2 h.

8. A manganese phytate-grafted MXene / carbon microsphere flame retardant prepared by the preparation method according to any one of claims 1 to 7.

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