Preparation method of carbon nanotube surface-loaded alkali metal silsesquioxane particle nanocomposite flame retardant

Abstract

This invention relates to the field of nanocomposite flame retardants, and more particularly to a method for preparing a nanocomposite flame retardant of carbon nanotubes loaded with alkali metal silsesquioxane particles. The method involves adding an organic solvent and carbon nanotubes to a reaction vessel, followed by ultrasonication and mechanical stirring. Alkali metal silsesquioxane powder is then added to the reaction vessel, resulting in a grayish-black mixture. The mixture is filtered, and the resulting filter cake is dried to obtain the nanocomposite flame retardant of carbon nanotubes loaded with alkali metal silsesquioxane particles. The product prepared by this invention retains a one-dimensional nanotube morphology and exhibits good structural thermal stability. While maintaining the one-dimensional nanotube microstructure, the prepared nanotubes have a rough surface, effectively preventing aggregation between multiple nanotubes. This method results in a nanocomposite flame retardant that combines the excellent properties of both carbon nanotubes and silsesquioxane.

Description

Technical Field

[0001] This invention relates to the field of nanocomposite flame retardants, and more particularly to a method for preparing a nanocomposite flame retardant of carbon nanotubes loaded with alkali metal silicon silsesquioxane particles. Background Technology

[0002] Polyhedral oligomeric silsesquioxanes (POSS) are commonly used, highly efficient silicon-based organic-inorganic hybrid nanoscale flame retardants. POSS molecules possess a precise cage-like nanostructure composed of Si-O-Si, with molecular particle sizes ranging from 1 to 3 nanometers. Introducing POSS into a polymer matrix, the rigid Si-O-Si framework facilitates the formation of a high-quality char layer during polymer combustion, while the side-chain organic groups improve the compatibility between POSS and the polymer matrix. Introducing alkali metal elements into POSS can achieve superior smoke suppression effects and is currently a hot research topic in the field of organic-inorganic hybrid materials science.

[0003] Carbon nanotubes, as a common carbon nanomaterial, are often used as flame-retardant nanofillers in polymer-based composites due to their high thermal stability and excellent mechanical properties. The effectiveness of carbon nanotubes mainly stems from the protective char layer formed during combustion, which effectively reduces heat release during the composite material's combustion process. However, carbon nanotubes are susceptible to entanglement caused by their elongated tubular structure and van der Waals forces between different nanotubes, causing them to tend to aggregate, thus offering limited improvement to the flame-retardant properties of the prepared composite material.

[0004] Loading POSS nanoparticles onto the surface of one-dimensional carbon nanotubes can form "barriers," effectively preventing the aggregation of multiple elongated tubular structures. Therefore, loading POSS nanoparticles onto the surface of one-dimensional carbon nanotubes can effectively inhibit the aggregation of different nanotubes while also preventing the aggregation of individual POSS molecules. However, existing research on carbon nanotube and POSS particle nanocomposite systems is limited. Summary of the Invention

[0005] This invention aims to provide a method for preparing a carbon nanotube surface-loaded alkali metal silsesquioxane particle nanocomposite flame retardant (CNT-POSS(Li)). This invention uses two alkaline alkali metal silsesquioxanes (Li-Ph-POSS and Na-Ph-POSS) and commercially available carbon nanotubes with carboxyl groups on their surface as raw materials, and successfully prepares the carbon nanotube surface-loaded alkali metal silsesquioxane particle nanocomposite flame retardant through electrostatic interactions.

[0006] This invention is achieved through the following technical solution: a method for preparing a carbon nanotube surface-loaded alkali metal silicon silsesquioxane particle nanocomposite flame retardant, comprising the following steps:

[0007] Organic solvent and carbon nanotubes were added to a reaction vessel. The water bath temperature was controlled at 40-60 ºC, the ultrasonic power was 50-100 W, and the mixture was mechanically stirred for 0.5-1 h. Then, alkali metal silsesquioxane powder was added to the reaction vessel, and the reaction time was 4-12 h to obtain a gray-black mixture. The mixture was filtered, and the resulting filter cake was dried to obtain a carbon nanotube-supported alkali metal silsesquioxane particle nanocomposite flame retardant.

[0008] As a further improvement to the technical solution of the present invention, the mass ratio of the carbon nanotubes to the alkali metal silsesquioxane powder is (0.5~1):(1.2~3.6).

[0009] As a further improvement to the technical solution of the present invention, the organic solvent is one or more of methanol, ethanol, isopropanol, acetone, butanone, tetrahydrofuran, dichloromethane, chloroform, and dimethyl sulfoxide.

[0010] As a further improvement to the technical solution of the present invention, the mass-to-volume ratio of the carbon nanotubes to the organic solvent is 1~3:150~500, specifically (1~3) g:(150~500) mL. The mass-to-volume ratio of the alkali metal silsesquioxane powder to the organic solvent is 2~9:100~400, specifically (2~9) g:(100~400) mL.

[0011] As a further improvement to the technical solution of the present invention, the carbon nanotubes are carboxylated single-walled carbon nanotubes or multi-walled carbon nanotubes.

[0012] As a further improvement to the technical solution of the present invention, the alkali metal silsesquioxane is a lithium salt of heptaphenylsilsesquioxane or a sodium salt of heptaphenylsilsesquioxane.

[0013] The method for preparing carbon nanotube surface-loaded alkali metal silicon silsesquioxane particle nanocomposite flame retardant provided by the present invention has the following advantages compared with the prior art:

[0014] The organic solvent selected in this invention is recyclable, thus reducing costs. The reaction process is simple to operate, under relatively mild conditions, and exhibits good reproducibility, resulting in high yield and a short synthesis cycle. The prepared product retains a one-dimensional nanotube morphology and possesses good structural thermal stability. While maintaining the one-dimensional nanotube microstructure, the surface of the prepared nanotubes is roughened, effectively preventing aggregation between multiple nanotubes. This invention is a nanocomposite flame retardant that combines the excellent properties of both carbon nanotubes and metallic silicon silsesquioxane. This invention will provide a new strategy for the diversified preparation of highly efficient nanoscale composite flame retardants. Attached Figure Description

[0015] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with the invention and, together with the description, serve to explain the principles of the invention.

[0016] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0017] Figure 1 The structural formula of the reaction raw material is heptaphenylsilsesquioxane lithium salt.

[0018] Figure 2 The structural formula of sodium salt of heptaphenylsilsesquioxane, a reactant.

[0019] Figure 3 A schematic diagram of the microstructure of carbon nanotubes loaded with alkali metal silicon silsesquioxane particles as a nanocomposite flame retardant (CNT-POSS(Li)).

[0020] Figure 4 The images show the FT-IR spectra of the carboxylated multi-walled carbon nanotubes (MWCNTs-COOH), Li-Ph-POSS, and the prepared nanocomposite (CNT-POSS(Li)) used in Example 1.

[0021] Figure 5 The XRD patterns are of the carboxylated multi-walled carbon nanotubes (MWCNTs-COOH), Li-Ph-POSS, and the prepared nanocomposite (CNT-POSS(Li)) used in Example 1.

[0022] Figure 6 The TG spectra (in nitrogen atmosphere) of the raw materials carboxylated multi-walled carbon nanotubes (MWCNTs-COOH), Li-Ph-POSS, and the prepared nanocomposite (CNT-POSS(Li)) in Example 1 are shown.

[0023] Figure 7 The image shows a scanning electron microscope (SEM) image and corresponding elemental surface scans of the nanocomposite (CNT-POSS(Li)) prepared in Example 1. Detailed Implementation

[0024] To better understand the above-mentioned objectives, features, and advantages of the present invention, the solutions of the present invention will be further described below. It should be noted that, unless otherwise specified, the embodiments of the present invention and the features thereof can be combined with each other.

[0025] Many specific details are set forth in the following description in order to provide a full understanding of the invention, but the invention may also be practiced in other ways different from those described herein; obviously, the embodiments in the specification are only some embodiments of the invention, and not all embodiments.

[0026] This invention provides a specific embodiment of a method for preparing a carbon nanotube surface-loaded alkali metal silicon silsesquioxane particle nanocomposite flame retardant, comprising the following steps:

[0027] Organic solvent and carbon nanotubes were added to a reaction vessel. The water bath temperature was controlled at 40-60 ºC, the ultrasonic power was 50-100 W, and the mixture was mechanically stirred for 0.5-1 h. Then, alkali metal silsesquioxane powder was added to the reaction vessel, and the reaction time was 4-12 h to obtain a gray-black mixture. The mixture was filtered, and the resulting filter cake was dried to obtain a carbon nanotube-supported alkali metal silsesquioxane particle nanocomposite flame retardant.

[0028] In one embodiment of the present invention, the mass ratio of the carbon nanotubes to the alkali metal silsesquioxane powder is (0.5~1):(1.2~3.6).

[0029] In another embodiment of the present invention, the organic solvent is one or more of methanol, ethanol, isopropanol, acetone, butanone, tetrahydrofuran, dichloromethane, chloroform, and dimethyl sulfoxide.

[0030] In this invention, the organic solvent can also be added to the reaction vessel in steps, specifically: a portion of the organic solvent is added when adding carbon nanotubes, and a portion of the organic solvent is added when adding alkali metal silsesquioxane powder.

[0031] In one embodiment of the present invention, the mass-to-volume ratio of the carbon nanotubes to the organic solvent is 1~3:150~500, specifically (1~3) g:(150~500) mL. The mass-to-volume ratio of the alkali metal silsesquioxane powder to the organic solvent is 2~9:100~400, specifically (2~9) g:(100~400) mL.

[0032] In another embodiment of the present invention, the carbon nanotubes are carboxylated single-walled carbon nanotubes or multi-walled carbon nanotubes.

[0033] In one embodiment of the present invention, the alkali metal silsesquioxane is a lithium salt of heptaphenylsilsesquioxane or a sodium salt of heptaphenylsilsesquioxane. See the specific structural formula. Figure 1 and Figure 2 .

[0034] The specific embodiments of the present invention will be described in detail below. Example 1

[0035] A method for preparing a carbon nanotube surface-loaded alkali metal silicon silsesquioxane particle nanocomposite flame retardant includes the following steps:

[0036] 3 g of carboxylated multi-walled carbon nanotubes (MWCNTs-COOH) were weighed and added to a three-necked round-bottom flask. 300 mL of anhydrous ethanol was added as a solvent. The flask was then capped and ultrasonically heated to 45 °C. During heating, 9 g of Li-Ph-POSS and 100 mL of anhydrous ethanol were weighed and added to a beaker. A magnetic stir bar was placed in the beaker, and the mixture was stirred on a magnetic stirrer at 300 r / min for 30 min. After stirring for 30 min, the mixture of Li-Ph-POSS and anhydrous ethanol was poured into the three-necked round-bottom flask containing the carboxylated multi-walled carbon nanotubes, and the reaction continued for 6 h. After the reaction was complete, the product was filtered, and then dried in an oven at 60 °C for 12 h. The product was then weighed and packaged. The yield was 10.98 g, with a yield of 91.5%.

[0037] Figure 4 The FT-IR spectra of carboxylated multi-walled carbon nanotubes (MWCNTs-COOH), Li-Ph-POSS, and the prepared nanocomposite (CNT-POSS(Li)) are shown. The characteristic peaks of the carboxyl group are 3650-3110 cm⁻¹, and the peaks are 3100-2980 cm⁻¹. -1 The multiplet at 1638 cm⁻¹ is the absorption peak of the CH stretching vibration on the benzene ring. -1 The absorption peak is the C=O stretching vibration peak, 1200~900 cm⁻¹. -1 These are absorption peaks associated with C-Si, Si-O-Si, and Si-O-Li bond vibrations.

[0038] Figure 5 The XRD patterns of carboxylated multi-walled carbon nanotubes (MWCNTs-COOH), Li-Ph-POSS, and the prepared nanocomposite (CNT-POSS(Li)) show several weak diffraction peaks at 26.1°, which are attributed to the (002) crystal plane of hexagonal graphite in the carbon nanotubes. This indicates that Li-Ph-POSS covers the surface of the carbon nanotubes, leading to a decrease in the intensity of its diffraction peaks. When the diffraction angle is less than 20°, several sharp and strong diffraction peaks appear in the XRD pattern of Li-Ph-POSS, while the position and intensity of the corresponding diffraction peaks in CNT-POSS(Li) are not affected, further proving that Li-Ph-POSS covers the surface of the carbon nanotubes.

[0039] Figure 6TG spectra (nitrogen atmosphere, heating rate 10 ºC / min) of carboxylated multi-walled carbon nanotubes (MWCNTs-COOH), Li-Ph-POSS, and the prepared nanocomposite (CNT-POSS(Li)) are shown. The TG images show the properties of CNT-POSS(Li). T 95% The carbon residue at 344 ºC and 800 ºC is 69.7 wt%, indicating that it meets the processing requirements of general polymers and has high thermal stability.

[0040] Figure 7 The scanning electron microscope (SEM) images and corresponding elemental surface scans of the prepared nanocomposite (CNT-POSS(Li)) show that CNT-POSS(Li) exhibits a nanotube morphology and that silicon is uniformly distributed on the nanotubes, proving that Li-Ph-POSS nanoparticles were successfully coated on the surface of MWCNTs-COOH. Example 2

[0041] A method for preparing a carbon nanotube surface-loaded alkali metal silicon silsesquioxane particle nanocomposite flame retardant includes the following steps:

[0042] 1 g of carboxylated single-walled carbon nanotubes (SWCNTs-COOH) was weighed and added to a three-necked round-bottom flask. 200 mL of anhydrous acetone was added as a solvent. The flask was then capped and ultrasonically heated to 40 °C. During heating, 3 g of Na-Ph-POSS and 50 mL of anhydrous acetone were weighed and added to a beaker. A magnetic stir bar was placed in the beaker, and the mixture was stirred on a magnetic stirrer at 200 r / min for 15 min. After stirring for 15 min, the mixture of Li-Ph-POSS and anhydrous acetone was poured into the three-necked round-bottom flask containing the carboxylated single-walled carbon nanotubes, and the reaction continued for 4 h. After the reaction was complete, the product was filtered, and then dried in an oven at 70 °C for 16 h. The product was then weighed and packaged. The yield was 3.57 g, with a yield of 89.3%. Example 3

[0043] A method for preparing a carbon nanotube surface-loaded alkali metal silicon silsesquioxane particle nanocomposite flame retardant includes the following steps:

[0044] 1 g of carboxylated multi-walled carbon nanotubes (MWCNTs-COOH) was weighed and added to a three-necked round-bottom flask. 100 ml of chloroform was added as a solvent. The flask was then capped and ultrasonically heated to 40 °C. During heating, 3 g of Li-Ph-POSS and 60 mL of chloroform were weighed and added to a beaker. A magnetic stir bar was placed in the beaker, and the mixture was stirred on a magnetic stirrer at 400 r / min for 20 min. After stirring for 20 min, the mixture of Li-Ph-POSS and chloroform was poured into the three-necked round-bottom flask containing the carboxylated multi-walled carbon nanotubes, and the reaction continued for 4 h. After the reaction was complete, the product was filtered, and then dried in an oven at 60 °C for 12 h. The product was then weighed and packaged. The yield was 3.82 g, with a yield of 95.5%. Example 4

[0045] A method for preparing a carbon nanotube surface-loaded alkali metal silicon silsesquioxane particle nanocomposite flame retardant includes the following steps:

[0046] 3 g of carboxylated single-walled carbon nanotubes (MWCNTs-COOH) were weighed and added to a three-necked round-bottom flask. 200 mL of anhydrous isopropanol was added as a solvent. The flask was then capped and ultrasonically heated to 50 °C. During heating, 6 g of Na-Ph-POSS and 100 mL of anhydrous isopropanol were weighed and added to a beaker. A magnetic stir bar was placed in the beaker, and the mixture was stirred on a magnetic stirrer at 300 r / min for 20 min. After stirring for 6 min, the mixture of Na-Ph-POSS and anhydrous isopropanol was poured into the three-necked round-bottom flask containing the carboxylated single-walled carbon nanotubes, and the reaction continued for 6 h. After the reaction was complete, the product was filtered, and then dried in an oven at 80 °C for 15 h. The product was then weighed and packaged. The yield was 7.3 g, with a yield of 81.1%.

[0047] The above description is merely a specific embodiment of the present invention, enabling those skilled in the art to understand or implement the present invention. Although detailed descriptions have been provided 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 or all of the technical features therein; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments, and they should all be covered within the protection scope of the claims.

Claims

1. A method for preparing a carbon nanotube surface-loaded alkali metal silicon silsesquioxane particle nanocomposite flame retardant, characterized in that, The steps include: Organic solvent and carbon nanotubes were added to a reaction vessel. The water bath temperature was controlled at 40-60 ºC, the ultrasonic power was 50-100 W, and the mixture was mechanically stirred for 0.5-1 h. Then, alkali metal silsesquioxane powder was added to the reaction vessel, and the reaction time was 4-12 h to obtain a gray-black mixture. The mixture was filtered, and the resulting filter cake was dried to obtain a carbon nanotube-supported alkali metal silsesquioxane particle nanocomposite flame retardant.

2. The method for preparing a carbon nanotube surface-loaded alkali metal silicon silsesquioxane particle nanocomposite flame retardant according to claim 1, characterized in that, The mass ratio of the carbon nanotubes to the alkali metal silsesquioxane powder is (0.5~1):(1.2~3.6).

3. The method for preparing a carbon nanotube surface-loaded alkali metal silicon silsesquioxane particle nanocomposite flame retardant according to claim 1, characterized in that, The organic solvent is one or more of methanol, ethanol, isopropanol, acetone, butanone, tetrahydrofuran, dichloromethane, chloroform, and dimethyl sulfoxide.

4. The preparation method of a carbon nanotube surface-loaded alkali metal silicon silsesquioxane particle nanocomposite flame retardant according to claim 1, characterized in that, The mass-to-volume ratio of the carbon nanotubes to the organic solvent is 1~3:150~500, and the mass-to-volume ratio of the alkali metal silsesquioxane powder to the organic solvent is 2~9:100~400.

5. The method for preparing a carbon nanotube surface-loaded alkali metal silicon silsesquioxane particle nanocomposite flame retardant according to claim 1, characterized in that, The carbon nanotubes are carboxylated single-walled carbon nanotubes or multi-walled carbon nanotubes.

6. The method for preparing a carbon nanotube surface-loaded alkali metal silicon silsesquioxane particle nanocomposite flame retardant according to claim 1, characterized in that, The alkali metal silsesquioxane is a lithium salt of heptaphenylsilsesquioxane or a sodium salt of heptaphenylsilsesquioxane.

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