Carbon quantum dots, flame retardant biomass composite film, preparation method and application thereof

Abstract

The present invention relates to the technical field of flame retardant materials, and specifically discloses a carbon quantum dot, a flame retardant biomass composite film, a preparation method and an application. The present invention uses urea and its derivatives as hydrogen bond donors, aminoglycerol-type substances as hydrogen bond acceptors, and then coordinates and combines with aluminate to obtain a precursor with good chemical stability; the precursor is used as a raw material to prepare carbon quantum dots through solvent thermal reaction. The flame retardant film formed by the carbon quantum dots, lignin and cellulose is used to modify the polymer substrate, which effectively solves the problems of poor compatibility and bonding between lignin, cellulose and the polymer substrate, and the synergistic effect between the carbon quantum dots and lignin and cellulose significantly improves the flame retardant effect of the biomass composite film. At the same time, it also effectively suppresses the smoke production when the polymer substrate burns, which is conducive to expanding the application field of polymer materials and has broad application prospects in the flame retardant field.

Description

Technical Field

[0001] The present invention relates to the technical field of flame retardant materials, and in particular to carbon quantum dots, a flame retardant biomass composite film and a preparation method thereof. Background Art

[0002] Polymer-based films are widely used in many fields due to their excellent flexibility, mechanical properties, and barrier properties. Among them, biomass films represented by cellulose and lignin, as environmentally friendly polymer materials, have broad application prospects in many fields such as food packaging, electronic devices, and agriculture due to their many advantages such as renewability, biodegradability, and good biocompatibility. In the field of food packaging, they can effectively block oxygen and water vapor, extending the shelf life of food; in electronic devices, they can be used as flexible substrate materials to meet the development trend of lighter, thinner, and more flexible electronic products. However, biomass films have a significant drawback of their own—flammability. This characteristic greatly limits their application in some scenarios with high fire protection requirements, such as architectural decoration, aerospace, and automotive interiors. Once a fire occurs, biomass films are easily ignited, quickly spreading the fire and posing a serious safety hazard.

[0003] As a new type of carbon nanomaterial, carbon quantum dots have attracted much attention in the field of materials science in recent years. Carbon quantum dots are usually composed of carbon elements, are at the nanometer level in size, and have unique optical, electrical and chemical properties. Carbon quantum dots can undergo a series of complex physical and chemical changes during heating, such as decomposing to produce non-flammable gases, diluting the surrounding oxygen concentration, and forming a dense carbon layer on themselves to isolate heat transfer and oxygen diffusion, thereby playing a flame retardant role. However, the research on the application of carbon quantum dots in polymer-based flame retardant films is still immature, and due to their small size and high surface energy, carbon quantum dots are very easy to agglomerate in the film, which will lead to huge differences in the local flame retardant properties of the film, greatly reducing the fireproof reliability of the entire film. At present, traditional carbon quantum dots have poor flame retardant properties, and it is often difficult to make the film reach the optimal flame retardant state. Therefore, it is necessary to provide a new type of carbon quantum dots that can significantly improve the flame retardant properties of the film, so as to expand the application range of biomass films in fields with high fire protection requirements. Summary of the Invention

[0004] In view of the problems in the prior art of carbon quantum dots being applied to high molecular polymer-based films, such as poor flame retardancy, the present invention provides a carbon quantum dot, a flame retardant biomass composite film and a preparation method.

[0005] In order to solve the above technical problems, the technical solution provided by the present invention is:

[0006] A carbon quantum dot, wherein the preparation method of the carbon quantum dot comprises the following steps:

[0007] S1, subjecting urea and its derivatives, aminoglycerol compounds and aluminate to a hydrothermal reaction to obtain a precursor solution;

[0008] S2, uniformly mixing the precursor solution and the alcohol solvent, performing a solvothermal reaction, and performing solid-liquid separation to obtain a carbon quantum dot solution.

[0009] Compared with the prior art, the carbon quantum dots provided by the present invention use urea and its derivatives as hydrogen bond donors, aminoglycerol substances as hydrogen bond acceptors, and then coordinate with aluminate to obtain a precursor with good chemical stability; the carbon quantum dots prepared by solvent thermal reaction using the precursor as raw material. The surface of the carbon quantum dots prepared by the above method is modified with rich functional groups, such as amino, hydroxyl and other functional groups. These functional groups can not only improve the compatibility and binding force between the carbon quantum dots and the substrate material, but also participate in the reaction during the combustion process, play a role in capturing free radicals and promoting the formation of carbon layers, thereby enhancing the flame retardant effect; at the same time, the surface of the prepared carbon quantum dots has modified aluminate groups. During the combustion process, the aluminum element can form stable substances such as aluminum oxide, which produces a synergistic flame retardant effect with the carbon quantum dots, further improving the flame retardant properties of the material. At the same time, the carbon quantum dots provided by the present invention can promote the rapid formation of a stable carbon layer on the surface of the material, prevent heat and oxygen from being transferred to the interior of the material, inhibit further combustion of the material, and reduce the generation of smoke. In addition, the preparation method of the carbon quantum dots is simple and easy, the preparation process is green and environmentally friendly, suitable for large-scale production and application, and has broad application prospects.

[0010] Furthermore, the urea and its derivatives include at least one of urea, isobutylene diurea or uric acid.

[0011] Furthermore, the aminoglycerol compound includes one or both of 3-amino-1,2-propylene glycol and 3-dimethylamino-1,2-propylene glycol.

[0012] Furthermore, the aluminate includes at least one of cobalt aluminate, calcium aluminate or sodium aluminate.

[0013] The carbon quantum dots prepared using the above-mentioned preferred urea and its derivatives, aminoglycerol compounds and aluminates as raw materials have a large specific surface area and a small particle size, which is conducive to better dispersion in flame retardant materials and is not easy to agglomerate, thereby helping to fully exert the flame retardant effect of the carbon quantum dots and avoid problems such as poor local flame retardant effect caused by agglomeration; at the same time, amino, hydroxyl and carboxyl groups can also be modified on the surface of the carbon quantum dots to improve the compatibility and bonding strength of the carbon quantum dots with various substrates, and can also participate in the reaction during the combustion process, promote the formation of the carbon layer, and improve the flame retardant effect.

[0014] Furthermore, the molar ratio of the urea and its derivatives, the aminoglycerol compound and the aluminate is 1:1:0.05 to 1:5:1.

[0015] Furthermore, in S1, the temperature of the hydrothermal reaction is 60° C. to 130° C., and the time of the hydrothermal reaction is 0.5 h to 3 h.

[0016] Furthermore, in S2, the volume ratio of the precursor solution to the alcohol solvent is 1:30 to 1:40.

[0017] Furthermore, in S2, the solvent thermal reaction time is 180° C. to 230° C., and the reaction time is 10 h to 18 h.

[0018] Furthermore, in S2, the alcohol solvent is anhydrous ethanol.

[0019] In a second aspect, the present invention further provides a flame retardant biomass composite film comprising the aforementioned carbon quantum dots, lignin and cellulose.

[0020] Films made from a combination of lignin and cellulose have a rich intramolecular and intermolecular hydrogen bond network structure, which gives the film excellent strength and toughness. However, lignin and cellulose have high crystallinity, strong polarity, and large surface energy. When added as flame retardants to polymer systems, their compatibility with the substrate is poor, resulting in a significant impact on flame retardancy. The present invention uses nanoscale carbon quantum dots to modify lignin and cellulose films, increasing the contact area between lignin and cellulose and the polymer substrate, enhancing their affinity and improving their compatibility, helping to maximize the flame retardant effect of the flame retardant material.

[0021] There is a synergistic effect between lignin, cellulose, and carbon quantum dots. Both lignin and cellulose undergo carbonization during combustion, forming a char layer. Carbon quantum dots can promote the carbonization process of these two substances, making the char layer denser and more stable. The char layer has excellent heat and oxygen insulation properties, effectively preventing heat and oxygen from transferring into the interior of the film, inhibiting further combustion, and thus significantly improving the film's flame retardant properties. At the same time, both lignin and cellulose are rich in functional groups such as hydroxyl groups, which can interact with the functional groups on the surface of carbon quantum dots to form a stable composite structure, allowing the three to be evenly dispersed in the film, exerting a synergistic effect, avoiding phase separation, and improving the stability of the film's flame retardant properties.

[0022] Furthermore, the lignin is one or both of alkaline lignin and sodium lignin sulfonate; and the cellulose is at least one of carboxymethyl cellulose, cellulose acetate or microcrystalline cellulose.

[0023] In a third aspect, the present invention further provides a method for preparing a flame retardant biomass composite film, comprising the following steps:

[0024] The carbon quantum dots, lignin and cellulose are uniformly mixed and reacted at 40° C. to 100° C. for 0.5 h to 2 h to obtain a flame retardant film solution;

[0025] The flame retardant film solution is dried to obtain a flame retardant biomass composite film.

[0026] The method for preparing a flame-retardant biomass composite film provided by the present invention comprises the following steps: reacting carbon quantum dots, lignin and cellulose at a specific temperature, causing the amino groups of the carbon quantum dots to react with the hydroxyl groups of the cellulose, and grafting the carbon quantum dots onto a film of cellulose and lignin, thereby improving the dispersion uniformity of the carbon quantum dots in the film, and greatly increasing the affinity of the cellulose and lignin grafted with the carbon quantum dots to a high molecular polymer substrate, thereby significantly improving the flame retardancy of the high molecular polymer substrate.

[0027] In a fourth aspect, the present invention further provides a high molecular polymer-based flame retardant material, comprising a high molecular polymer substrate and the flame retardant biomass composite film.

[0028] In a fifth aspect, the present invention further provides a method for preparing a polymer-based flame retardant material, comprising the following steps:

[0029] The flame retardant film solution and the curing agent are mixed evenly, coated on a high molecular polymer substrate, and dried to obtain a high molecular polymer-based flame retardant material.

[0030] The cellulose flame-retardant film provided by the present invention can significantly improve the thermal stability of polymer substrates. In the event of a fire, it decomposes to form a stable, dense, and uniform carbonized product that covers the substrate surface, isolating heat, oxygen, and other volatile gases and inhibiting the spread of fire. This biomass flame-retardant film can significantly improve the flame retardancy of polymer substrates, expanding the application areas of polymers.

[0031] Furthermore, the curing agent is m-phenylenediamine; and the mass ratio of the curing agent to the flame retardant film solution is 1:10 to 1:40.

[0032] Furthermore, the mass ratio of the flame retardant film solution to the high molecular polymer substrate is 1:20 to 1:100.

[0033] The present invention uses a flame-retardant film formed by carbon quantum dots, lignin and cellulose to modify the high-molecular polymer material, effectively solving the problems of poor compatibility and bonding between lignin, cellulose and polymer materials. The synergistic effect between carbon quantum dots, lignin and cellulose significantly improves the flame-retardant effect of the biomass composite film. At the same time, it also effectively suppresses the smoke production during combustion of the high-molecular polymer substrate, which is beneficial to expanding the application field of the high-molecular polymer material. The raw materials are widely available, the preparation process is simple, and it is suitable for large-scale production and application, and has broad application prospects in the flame retardant field. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 This is a transmission electron microscopy image of carbon quantum dots prepared in Example 2 of the present invention;

[0035] Figure 2 This is a scanning electron microscope image of the flame-retardant biomass composite film prepared in Example 2 of the present invention;

[0036] Figure 3 This is a Fourier infrared spectrum of the flame retardant biomass composite film prepared in Example 2 of the present invention.

[0037] Figure 4 This is a comparison chart of the relationship between heat release rate and time of the original epoxy resin and the flame retardant epoxy resin in Example 2 of the present invention;

[0038] Figure 5 This is a comparison chart of the total heat release versus time for the original epoxy resin and the flame-retardant epoxy resin in Example 2 of the present invention. DETAILED DESCRIPTION

[0039] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0040] In order to better illustrate the present invention, further examples are given below.

[0041] Example 1

[0042] An embodiment of the present invention provides a carbon quantum dot comprising uric acid, 3-amino-1,2-propanediol, and calcium aluminate in a molar ratio of 1:5:1. The preparation of the carbon quantum dot comprises the following steps:

[0043] 0.1 mol of uric acid, 0.5 mol of 3-amino-1,2-propylene glycol and 0.1 mol of calcium aluminate were mixed uniformly, heated to 120°C, and stirred at constant temperature for 2 hours to obtain a precursor solution;

[0044] 2 mL of the above precursor solution was added to 70 mL of anhydrous ethanol, heated to 200° C. for reaction for 14 h, centrifuged and filtered through a 0.22 μm filter membrane to obtain a carbon quantum dot solution.

[0045] The method for preparing a flame retardant biomass composite film using the above carbon quantum dot solution comprises the following steps:

[0046] 30 g of the carbon quantum dot solution prepared above, 0.2 g of alkaline lignin and 0.8 g of cellulose acetate were added to a three-necked flask, heated to 45° C. and ultrasonically reacted for 2 h to obtain a flame retardant film solution. The flame retardant film solution was dried to obtain a flame retardant biomass composite film.

[0047] The method for preparing a flame retardant epoxy resin using the flame retardant biomass composite film comprises the following steps:

[0048] 20 g of the flame retardant film solution prepared above and 0.7 g of m-phenylenediamine were mixed evenly, coated on 500 g of epoxy resin, and dried to obtain a flame retardant epoxy resin.

[0049] The flame-retardant epoxy resin prepared in this example was tested using an oxygen index meter, revealing a limiting oxygen index of 31.1%, meeting the flame retardancy requirement. A vertical combustion tester also confirmed a UL-94 V-0 rating, significantly improving the flame retardancy of the original epoxy resin, which was rated UL-94 V-2.

[0050] The residual carbon rate was measured by thermogravimetric analysis and was 21%. The initial decomposition temperature (T 5％ ) is 391℃, the maximum decomposition temperature (T max ) is 421℃.

[0051] The total heat release was determined to be 80 MJ / m by cone calorimetry. 2 The maximum heat release rate peak is 550kW / m 2 The total smoke volume is 16m 2 / kg. Compared with the original epoxy resin, the total heat release (120MJ / m 2 ) decreased by 33.3%, and the maximum heat release rate peak (1102kW / m 2 ) decreased by 50.1%, the total smoke volume (24m 2 / kg) decreased by 33.3%.

[0052] Example 2

[0053] An embodiment of the present invention provides a carbon quantum dot comprising urea, 3-amino-1,2-propylene glycol, and cobalt aluminate in a molar ratio of 1:3:0.5. The preparation of the carbon quantum dot comprises the following steps:

[0054] 0.1 mol of urea, 0.3 mol of 3-amino-1,2-propylene glycol, and 0.05 mol of cobalt aluminate were mixed uniformly, heated to 100°C, and stirred at constant temperature for 2 hours to obtain a precursor solution;

[0055] 2 mL of the above precursor solution was added to 80 mL of anhydrous ethanol, heated to 210° C. for reaction for 16 h, centrifuged and filtered through a 0.22 μm filter membrane to obtain a carbon quantum dot solution.

[0056] The transmission electron microscopy images of the carbon quantum dots prepared in this example are as follows: Figure 1 As shown in the figure, it can be seen that the carbon quantum dots are spherical in shape, have relatively uniform particle size, an average particle size of 2 nm, and are evenly distributed.

[0057] The method for preparing a flame retardant biomass composite film using the above carbon quantum dot solution comprises the following steps:

[0058] 30 g of the carbon quantum dot solution prepared above, 0.2 g of alkaline lignin and 0.8 g of cellulose acetate were added to a three-necked flask, heated to 75° C. and ultrasonically reacted for 30 min to obtain a flame retardant film solution. The flame retardant film solution was dried to obtain a flame retardant biomass composite film.

[0059] The scanning electron microscope image of the flame retardant biomass composite film prepared in this example is as follows: Figure 2 As shown in the figure, it can be seen that the carbon quantum dots are successfully loaded onto the film. The infrared spectrum of the flame retardant biomass composite film is shown in Figure 3 As shown, 3425cm -1 The absorption peak at 2906 cm is attributed to the characteristic peak of -OH vibration. -1 The peak at 1637 cm is attributed to the CH bond. -1 The absorption peak at 1460 cm belongs to the amide group. -1 The absorption peak at 1095cm is attributed to CNC stretching vibration. -1 The absorption peak is the CO bond, which shows that the addition of carbon quantum dots in the film makes the surface of the film have rich functional groups.

[0060] The method for preparing a flame retardant epoxy resin using the flame retardant biomass composite film comprises the following steps:

[0061] 20 g of the flame retardant film solution prepared above and 2 g of m-phenylenediamine were mixed evenly, coated on 2000 g of epoxy resin, and dried to obtain a flame retardant epoxy resin.

[0062] The flame retardant epoxy resin prepared in this embodiment was passed through an oxygen index meter, and its limiting oxygen index was measured to be 33.1%, which met the flame retardant requirements. The combustion performance level was measured by a vertical combustion tester and reached UL-94V-0. Compared with the fire rating of the original epoxy resin of UL-94V-2, it has been significantly improved. The residual carbon rate was measured by a thermogravimetric analyzer, and the initial decomposition temperature (T 5％ ) is 418℃, the maximum decomposition temperature (T max ) is 452℃.

[0063] The actual combustion conditions of the flame retardant epoxy resin prepared in this example were measured by cone calorimetry. Figure 4 and Figure 5The following are the comparison diagrams of the total heat release and heat release rate of the original epoxy resin and the flame retardant epoxy resin with time. Figure 4 It can be seen that the total heat release of the original epoxy resin is 120MJ / m 2 The maximum heat release rate peak is 1102kW / m 2 kW / m 2 The total smoke volume is 24m 2 / kg. The total heat release of flame retardant epoxy resin is 75MJ / m 2 The maximum heat release rate peak is 414kW / m 2 The total smoke volume is 13m 2 Compared with the original epoxy resin, the flame retardant performance of the flame retardant epoxy resin was significantly improved, with the total heat release reduced by 37.5%, the peak value of the maximum heat release rate reduced by 62.4%, and the total smoke production reduced by 45.8%.

[0064] Example 3

[0065] An embodiment of the present invention provides a carbon quantum dot comprising isobutylene diurea, 3-dimethylamino-1,2-propylene glycol, and cobalt aluminate in a molar ratio of 1:2:0.3. The preparation of the carbon quantum dot comprises the following steps:

[0066] 0.1 mol of isobutylene diurea, 0.2 mol of 3-dimethylamino-1,2-propylene glycol and 0.03 mol of cobalt aluminate were mixed evenly, heated to 130°C, and stirred at constant temperature for 1 hour to obtain a precursor solution;

[0067] 2 mL of the above precursor solution was added to 75 mL of anhydrous ethanol, heated to 220° C. for reaction for 15 h, centrifuged and filtered through a 0.22 μm filter membrane to obtain a carbon quantum dot solution.

[0068] The method for preparing a flame retardant biomass composite film using the above carbon quantum dot solution comprises the following steps:

[0069] 30 g of the carbon quantum dot solution prepared above, 0.2 g of alkaline lignin and 0.8 g of cellulose acetate were added to a three-necked flask, heated to 100° C. and ultrasonically reacted for 30 min to obtain a flame retardant film solution. The flame retardant film solution was dried to obtain a flame retardant biomass composite film.

[0070] The method for preparing a flame retardant epoxy resin using the flame retardant biomass composite film comprises the following steps:

[0071] 20 g of the flame retardant film solution prepared above and 1.8 g of m-phenylenediamine were mixed evenly, coated on 1600 g of epoxy resin, and dried to obtain a flame retardant epoxy resin.

[0072] The flame-retardant epoxy resin prepared in this example was tested on an oxygen index meter, and its limiting oxygen index was 30%, meeting the flame retardancy requirement. Its combustion performance rating, measured using a vertical combustion tester, reached UL-94 V-0. This represents a significant improvement over the UL-94 V-2 fire rating of the original epoxy resin.

[0073] The residual carbon rate was measured by thermogravimetric analysis and was 29%. The initial decomposition temperature (T 5％ ) is 389℃, the maximum decomposition temperature (T max ) is 425°C. The total heat release was measured by cone calorimetry and was 84 MJ / m 2 The maximum heat release rate peak is 469kW / m 2 The total smoke volume is 18m 2 / kg. Compared with the original epoxy resin, the total heat release (120MJ / m 2 ) decreased by 30%, and the maximum heat release rate peak (1102kW / m 2 ) decreased by 57.4%, the total smoke volume (24m 2 / kg) decreased by 25%.

[0074] Example 4

[0075] An embodiment of the present invention provides a carbon quantum dot comprising urea, 3-amino-1,2-propylene glycol, and calcium aluminate in a molar ratio of 1:5:0.8. The preparation thereof specifically comprises the following steps:

[0076] 0.1 mol of urea, 0.5 mol of 3-amino-1,2-propylene glycol and 0.08 mol of calcium aluminate were mixed uniformly, heated to 110°C, and stirred at constant temperature for 3 hours to obtain a precursor solution;

[0077] 2 mL of the above precursor solution was added to 70 mL of anhydrous ethanol, heated to 180° C. for reaction for 18 h, centrifuged and filtered through a 0.22 μm filter membrane to obtain a carbon quantum dot solution.

[0078] The method for preparing a flame retardant biomass composite film using the above carbon quantum dot solution comprises the following steps:

[0079] 30 g of the carbon quantum dot solution prepared above, 0.2 g of alkaline lignin and 0.8 g of cellulose acetate were added to a three-necked flask, heated to 60° C. and ultrasonically dispersed for 50 min to obtain a flame retardant film solution. The flame retardant film solution was dried to obtain a flame retardant biomass composite film.

[0080] The method for preparing a flame retardant epoxy resin using the flame retardant biomass composite film comprises the following steps:

[0081] 20 g of the flame retardant film solution prepared above and 1.2 g of m-phenylenediamine were mixed evenly, coated on 800 g of epoxy resin, and dried to obtain a flame retardant epoxy resin.

[0082] The flame-retardant epoxy resin prepared in this example was tested on an oxygen index meter, and its limiting oxygen index was 33%, meeting the flame retardancy requirement. The flame retardancy rating, measured on a vertical combustion tester, reached UL-94 V-0. This represents a significant improvement over the UL-94 V-2 fire rating of the original epoxy resin.

[0083] The residual carbon rate was measured by thermogravimetric analyzer to be 31.9%, and the initial decomposition temperature (T 5％ ) is 388℃, the maximum decomposition temperature (T max ) is 426 ° C. The total heat release was measured by cone calorimetry and was 68 MJ / m 2 The maximum heat release rate peak is 390kW / m 2 The total smoke volume is 17m 2 / kg. Compared with the original epoxy resin, the total heat release (120MJ / m 2 ) decreased by 43.3%, and the maximum heat release rate peak (1102kW / m 2 ) decreased by 64.6%, the total smoke volume (24m 2 / kg) decreased by 29.2%.

[0084] Example 5

[0085] An embodiment of the present invention provides a carbon quantum dot comprising uric acid, 3-amino-1,2-propylene glycol, and sodium aluminate in a molar ratio of 1:1:0.05, wherein the preparation thereof specifically comprises the following steps:

[0086] 0.1 mol of uric acid, 0.1 mol of 3-amino-1,2-propylene glycol, and 0.005 mol of sodium aluminate were mixed uniformly, heated to 80°C, and stirred at constant temperature for 3 hours to obtain a precursor solution;

[0087] 2 mL of the above precursor solution was added to 60 mL of anhydrous ethanol, heated to 230° C. for reaction for 10 h, centrifuged and filtered through a 0.22 μm filter membrane to obtain a carbon quantum dot solution.

[0088] The method for preparing a flame retardant biomass composite film using the above carbon quantum dot solution comprises the following steps:

[0089] 30 g of the carbon quantum dot solution prepared above, 0.2 g of alkaline lignin and 0.8 g of cellulose acetate were added to a three-necked flask, heated to 85° C. and ultrasonically dispersed for 40 min to obtain a flame retardant film solution. The flame retardant film solution was dried to obtain a flame retardant biomass composite film.

[0090] The method for preparing a flame retardant epoxy resin using the flame retardant biomass composite film comprises the following steps:

[0091] 20 g of the flame retardant film solution prepared above and 1.5 g of m-phenylenediamine were mixed evenly, coated on 900 g of epoxy resin, and dried to obtain a flame retardant epoxy resin.

[0092] The flame-retardant epoxy resin prepared in this example was tested on an oxygen index meter, and its limiting oxygen index was 32%, meeting the flame retardancy requirement. The flame retardancy rating, measured on a vertical combustion tester, reached UL-94 V-0. This represents a significant improvement over the UL-94 V-2 fire rating of the original epoxy resin.

[0093] The residual carbon rate was 25% and the initial decomposition temperature (T 5％ ) is 391℃, the maximum decomposition temperature (T max ) is 427 ° C. The total heat release was measured by cone calorimetry and was 79 MJ / m 2 The maximum heat release rate peak is 453kW / m 2 , the total smoke volume is 15m 2 / kg. Compared with the original epoxy resin, the total heat release (120MJ / m 2 ) decreased by 34.2%, and the peak value of the maximum heat release rate (1102kW / m 2 ) decreased by 58.9%, the total smoke volume (24m 2 / kg) decreased by 37.5%.

[0094] Comparative Example 1

[0095] This comparative example provides a carbon quantum dot, the preparation method of which is different from that of Example 2 only in that the sodium aluminate in the precursor for preparing the carbon quantum dots in Example 2 is replaced with an equal amount of aluminum titanate, and the rest is exactly the same and will not be repeated here.

[0096] The method for preparing a flame retardant biomass composite film using the above carbon quantum dot solution comprises the following steps:

[0097] 30 g of the carbon quantum dot solution prepared above, 0.2 g of alkaline lignin and 0.8 g of cellulose acetate were added to a three-necked flask, heated to 75 ° C and ultrasonically dispersed for 30 min to obtain a flame retardant film solution. The flame retardant film solution was dried, but no film could be formed. Even if the ultrasonic mixing time or drying time was extended, a film could not be formed.

[0098] Comparative Example 2

[0099] This comparative example provides a carbon quantum dot, the preparation method of which is different from that of Example 2 only in that the urea in the precursor for preparing the carbon quantum dots in Example 2 is replaced with an equal amount of ammonium bicarbonate, and the rest is exactly the same and will not be repeated here.

[0100] The method for preparing a flame retardant biomass composite film using the above carbon quantum dot solution comprises the following steps:

[0101] 30 g of the carbon quantum dot solution prepared above, 0.2 g of alkaline lignin and 0.8 g of cellulose acetate were added to a three-necked flask, heated to 75° C. and ultrasonically dispersed for 30 min to obtain a flame retardant film solution. The flame retardant film solution was dried to obtain a flame retardant biomass composite film.

[0102] The method for preparing a flame retardant epoxy resin using the flame retardant biomass composite film comprises the following steps:

[0103] 20 mL of the flame retardant film solution prepared above and 0.1 g of m-phenylenediamine were mixed evenly, coated on 4 g of epoxy resin, and dried to obtain a flame retardant epoxy resin.

[0104] The flame retardant epoxy resin prepared in this comparative example was tested by an oxygen index tester, and its limiting oxygen index was 28%, which met the flame retardancy requirement. The combustion performance grade of the flame retardant epoxy resin tested by a vertical combustion tester reached UL-94V-1.

[0105] The residual carbon rate was measured by thermogravimetric analyzer to be 16%, and the initial decomposition temperature (T 5％ ) is 379℃, the maximum decomposition temperature (T max ) is 412 ° C. The total heat release was measured by cone calorimetry and was 110 MJ / m 2 The maximum heat release rate peak is 653kW / m 2 The total smoke volume is 22m 2 / kg. Compared with the original epoxy resin, the fire rating is UL-94V-2, which has been improved to a certain extent. However, due to the large amount of dripping during the combustion process, it cannot meet the flame retardant performance requirements. In addition, in the flame retardant performance test, the total heat release and the peak value of the maximum heat release rate have been improved, but the total smoke volume (24m 2 / kg) was only reduced by 8.3%, and the smoke suppression effect was far worse than that of Examples 1-5.

[0106] Comparative Example 3

[0107] This comparative example provides a carbon quantum dot, the preparation method of which is different from that of Example 2 only in that 3-dimethylamino-1,2-propanediol in the precursor for preparing the carbon quantum dots in Example 2 is replaced with an equal amount of 1,3-butanediol. The rest is exactly the same and will not be repeated here.

[0108] The method for preparing a flame retardant biomass composite film using the above carbon quantum dot solution comprises the following steps:

[0109] 30 g of the carbon quantum dot solution prepared above, 0.2 g of alkaline lignin and 0.8 g of cellulose acetate were added to a three-necked flask, heated to 75° C. and ultrasonically dispersed for 30 min to obtain a flame retardant film solution. The flame retardant film solution was dried to obtain a flame retardant biomass composite film.

[0110] The method for preparing a flame retardant epoxy resin using the flame retardant biomass composite film comprises the following steps:

[0111] 20 mL of the flame retardant film solution prepared above and 0.1 g of m-phenylenediamine were mixed evenly, coated on 4 g of epoxy resin, and dried to obtain a flame retardant epoxy resin.

[0112] The flame retardant epoxy resin prepared in this example was tested by an oxygen index meter, and its limiting oxygen index was 26%, which did not meet the flame retardancy requirement. The combustion performance grade of the flame retardant epoxy resin was tested by a vertical combustion tester, and reached UL-94V-1 grade.

[0113] The residual carbon rate was measured by thermogravimetric analyzer to be 21%, and the initial decomposition temperature (T 5％ ) is 383℃, the maximum decomposition temperature (T max ) is 427 ° C. The total heat release was measured by cone calorimetry and was 105 MJ / m 2 The maximum heat release rate peak is 816kW / m 2 , the total smoke volume is 20m 2 / kg.

[0114] In summary, the carbon quantum dots provided by the present invention have a simple preparation method and a wide range of raw material sources. The flame-retardant biomass composite film prepared using the carbon quantum dots, lignin and cellulose has excellent flame retardant properties, can significantly improve the flame retardant properties of polymer materials, and expand the application of polymer materials in occasions with high fire protection requirements, and has high practical value.

[0115] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions or improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A carbon quantum dot, characterized in that The preparation method of the carbon quantum dots comprises the following steps: S1, subjecting urea and its derivatives, aminoglycerol compounds, and aluminate to a solvothermal reaction to obtain a precursor solution; the urea and its derivatives include at least one of urea, isobutylene diurea, or uric acid; the aminoglycerol compounds include one or both of 3-amino-1,2-propylene glycol and 3-dimethylamino-1,2-propylene glycol; the aluminate includes at least one of cobalt aluminate, calcium aluminate, or sodium aluminate; in S1, the solvothermal reaction temperature is 60° C. to 130° C., and the solvothermal reaction time is 0.5 h to 3 h; S2, mixing the precursor solution and alcohol solvent evenly, performing a solvothermal reaction, and performing solid-liquid separation to obtain a carbon quantum dot solution; in S2, the alcohol solvent is anhydrous ethanol; the temperature of the solvothermal reaction is 180°C~230°C, and the reaction time is 10h~18h.

2. The carbon quantum dots according to claim 1, wherein The molar ratio of the urea and its derivatives, the aminoglycerol compound and the aluminate is 1:1:0.05 to 1:5:

1.

3. The carbon quantum dots according to claim 1, wherein In S2, the volume ratio of the precursor solution to the alcohol solvent is 1:30 to 1:

40.

4. A flame retardant biomass composite film, characterized in that: The preparation method comprises the following steps: uniformly mixing the carbon quantum dots according to any one of claims 1 to 3, alkaline lignin and cellulose acetate, and reacting at 40° C. to 100° C. for 0.5 h to 2 h to obtain a flame retardant film solution; The flame retardant film solution is dried to obtain a flame retardant biomass composite film.

5. A method for preparing a flame retardant biomass composite film, characterized in that: The steps include: The carbon quantum dots according to any one of claims 1 to 3, alkaline lignin and cellulose acetate are uniformly mixed and reacted at 40° C. to 100° C. for 0.5 h to 2 h to obtain a flame retardant film solution; The flame retardant film solution is dried to obtain a flame retardant biomass composite film.

6. A polymer-based flame retardant material, characterized in that: The invention comprises a high molecular polymer substrate and the flame retardant biomass composite film according to claim 4.

7. A method for preparing a polymer-based flame retardant material, characterized in that: The steps include: The flame retardant film solution and the curing agent described in claim 5 are mixed evenly, coated on a high molecular polymer substrate, and dried to obtain a high molecular polymer-based flame retardant material.

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