Flame-retardant flexible epoxy resin / HMN-MXene composite material with fire early warning function as well as preparation method and application thereof

Abstract

The invention discloses a flame-retardant flexible epoxy resin / HMN-MXene composite material with a fire early warning function as well as a preparation method and application of the flame-retardant flexible epoxy resin / HMN-MXene composite material. Carrying out nucleophilic substitution on chlorine elements in hexachlorotripolyphosphazene molecules by using melamine and ammonia water in sequence to synthesize HMN; the preparation method comprises the following steps: carrying out surface modification on hydroxylated titanium carbide by using HMN to prepare HMN-MXene, adding the HMN-MXene into an epoxy resin precursor 1, 4-butanediol glycidyl ether and triethylene tetramine mixed solution by using a solution blending method, and carrying out rapid molding at room temperature. The EP / HMN-MXene composite material prepared after thermocuring treatment is formed by uniformly dispersing surface-wrinkled HMN-MXene nanosheets in an epoxy resin matrix, and has the advantages of low glass transition temperature, excellent flexibility and flame retardant property, and fire safety early warning function. Wide application prospects are realized in the fields of flame-retardant polymers, thermal safety monitoring and early warning, flexible sensing and the like.

Description

Technical Field

[0001] The present invention relates to the technical field of the synthesis of phosphorus-nitrogen compounds and the preparation and application of surface-modified inorganic layered compounds in polymer composites, and specifically relates to a flame-retardant flexible epoxy resin / HMN-MXene composite material with a fire warning function, a preparation method thereof, and an application thereof. Background Art

[0002] Epoxy resin (EP) has a wide range of applications in the fields of construction, coatings, and aviation. However, the inherent flammability and high heat release characteristics of EP can lead to serious fire risks; moreover, the preparation process of EP is complex, and the cumbersome steps not only prolong the material preparation time but also increase the production cost. In addition, the toughness of EP resin after thermal curing is poor, which limits its application in the fields such as flexible sensing. Developing a flexible EP composite material with a simple forming process and excellent flame retardancy is crucial for expanding the application fields of EP.

[0003] In recent years, the research on EP / MXene nanocomposites has become one of the hotspots of domestic and international attention. Due to the unique physical barrier effect and catalytic performance of MXene, it has a wide range of applications in improving the flame retardancy of EP. However, MXene cannot effectively improve the flexibility of EP, nor can it promote the rapid forming of EP precursors at room temperature to simplify the process flow. Therefore, it is of great significance to develop a multifunctional new filler based on surface-modified MXene to simplify the preparation process of EP and improve its flexibility and flame retardancy.

[0004] In view of this, the present invention first attempts to synthesize a water-soluble multi-amino phosphorus-nitrogen compound (HMN), and uses it to perform surface modification on hydroxylated MXene (MXene-OH) to obtain an HMN-modified MXene composite (HMN-MXene); then, HMN-MXene is used as a nano-filler and added to the EP resin precursor, while simplifying the EP forming process, endowing the EP / HMN-MXene composite material with excellent comprehensive properties, and being able to be applied to the fields of flame-retardant polymers, thermal safety monitoring and early warning, and flexible sensing. Summary of the Invention

[0005] To overcome the above-mentioned defects existing in the prior art, the present invention proposes a preparation idea of a water-soluble polyamino phosphazene compound (HMN), an HMN-modified titanium carbide (HMN-MXene) composite, and an EP / HMN-MXene composite material. The prepared HMN has high reactivity, and HMN-MXene can promote the rapid molding at room temperature of the mixed solution of the EP precursor 1,4-butanediol diglycidyl ether (BDGE) and triethylenetetramine (TETA). The EP / HMN-MXene composite material after thermal curing is composed of surface-creased HMN-MXene nanosheets uniformly dispersed in an epoxy resin matrix, and has a low glass transition temperature, excellent flexibility and flame retardancy, as well as a fire safety warning function, and has broad application prospects in the fields of flame-retardant polymers, thermal safety monitoring and warning, flexible sensing, etc.

[0006] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0007] A flame-retardant flexible epoxy resin / HMN-MXene composite material with a fire warning function is composed of surface-creased HMN-MXene nanosheets uniformly dispersed in an epoxy resin matrix, and has a low glass transition temperature, excellent flexibility and flame retardancy, as well as a thermal safety monitoring and warning function.

[0008] The preparation method is: adding the HMN-MXene composite as a nano filler into an epoxy resin precursor solution, stirring evenly and then rapidly molding at room temperature, and obtaining a flame-retardant flexible epoxy resin / HMN-MXene composite material with a fire warning function after thermal curing.

[0009] As a preferred technical solution of the present invention, the HMN-MXene composite is first synthesized by nucleophilic substitution of the chlorine element in the hexachlorocyclotriphosphazene molecule with melamine and ammonia water in sequence to obtain a water-soluble polyamino phosphazene compound (HMN), and then its surface is modified with hydroxylated titanium carbide (MXene-OH) to obtain it.

[0010] As a preferred technical solution of the present invention, an appropriate amount of the epoxy resin precursor 1,4-butanediol diglycidyl ether (BDGE) and triethylenetetramine (TETA) are taken, added to the HMN-MXene aqueous dispersion, stirred evenly in an ice-water bath, and then transferred to a mold and naturally molded at room temperature; after the molded sample is thermally cured, the EP / HMN-MXene composite material is obtained.

[0011] More preferably in the preparation method: the mass ratio of TETA to BDGE is 1:(3 - 5), and the mass ratio of (BDGE + TETA) to HMN-MXene is 1:(0.01 - 0.06); the forming temperature of the sample in the oven is 15 - 30°C, and the forming time is 15 - 50 min; the thermal curing temperature of the sample is 100 - 120°C, and the curing time is 10 - 14 h.

[0012] In the present invention, melamine and ammonia water are successively used to carry out nucleophilic substitution on the chlorine element in the hexachlorocyclotriphosphazene molecule to synthesize HMN, and then HMN is used to modify the surface of hydroxylated titanium carbide (MXene-OH) to prepare (HMN-MXene). Finally, the solution blending method is adopted to add it to the mixed solution of the EP precursor 1,4-butanediol diglycidyl ether (BDGE) and triethylenetetramine (TETA). The obtained mixed solution can be rapidly formed at room temperature; after thermal curing treatment, the prepared EP / HMN-MXene composite material is composed of surface wrinkled HMN-MXene nanosheets uniformly dispersed in the epoxy resin matrix, has a low glass transition temperature, excellent flexibility and flame retardant properties, and a fire safety warning function, and has broad application prospects in the fields of flame retardant polymers, thermal safety monitoring and warning, flexible sensing, etc.

[0013] Compared with the prior art, the beneficial effects of the present invention are shown in:

[0014] (1), By means of organic synthesis, the present invention successfully prepares a water-soluble phosphazene compound HMN with multi-amino characteristics.

[0015] (2), Modifying MXene with HMN can promote the subsequent rapid completion of the forming process of epoxy resin (EP) at room temperature, simplifying the forming process of epoxy resin.

[0016] (3), The epoxy resin / HMN-MXene composite material prepared by the present invention has multifunctionality, expanding the application fields of epoxy resin. Description of the Drawings

[0017] Figure 1 is the nuclear magnetic phosphorus spectrum of HCCP.

[0018] Figure 2 is the nuclear magnetic phosphorus spectrum of HMN prepared in Example 1.

[0019] Figure 3 is the infrared spectrum of HCCP and HMN prepared in Example 1.

[0020] Figure 4 is the mass spectrum of HMN prepared in Example 1.

[0021] Figure 5It is the thermogravimetric spectrogram of the HMN-MXene composites prepared in Examples 2, 3, and 4.

[0022] Figure 6 It is the scanning electron microscope photograph of MXene.

[0023] Figure 7 It is the scanning electron microscope photograph of the HMN-MXene composite prepared in Example 3.

[0024] Figure 8 It is the XRD spectrogram of MXene and the HMN-MXene composite prepared in Example 3.

[0025] Figure 9 It is the digital photograph of the pure EP prepared in Example 5 and the EP / HMN-MXene composites prepared in Examples 6, 7, and 8.

[0026] Figure 10 It is the dynamic thermomechanical curve of the EP / HMN-MXene composite prepared in Example 7.

[0027] Figure 11 It is the relative resistance change curve of the EP / HMN-MXene composites prepared in Examples 6, 7, and 8 under flame attack. Detailed implementation mode

[0028] The present invention will be further described in detail below in conjunction with examples and drawings.

[0029] Example 1

[0030] The synthesis method of water-soluble polyamino phosphazene compound (HMN) includes the following steps:

[0031] (1) Synthesis of melamine-modified hexachlorocyclotriphosphazene intermediate (HM): Dissolve 1 g of MA in 100 mL of deionized water at 70 °C. Under nitrogen protection, add 2.41 g of triethylamine (TEA) and stir for 15 min; dissolve 1.38 g of HCCP in 30 mL of acetonitrile solution, and dropwise add it to the above three-necked flask. React at 70 °C for 18 h, where the mass ratio of MA, TEA, and HCCP is 1:2.41:1.38. After the reaction, centrifuge to remove the triethylamine hydrochloride generated by the reaction. The centrifuge speed is 9500 rpm, and the centrifugation time is 5 min; place the centrifuged supernatant in an ice-water bath to precipitate the unreacted MA, and separate it by vacuum filtration; perform rotary evaporation on the filtrate at a temperature of 70 °C for 2 h; dry the obtained product in a vacuum oven at 60 °C for 24 h to obtain the product melamine-modified hexachlorocyclotriphosphazene intermediate (HM).

[0032] (2) Synthesis of water-soluble polyamino phosphazene (HMN): Weigh 2 g of HM and dissolve it in 100 mL of deionized water. Maintain the temperature at 1 °C. Under nitrogen protection, add 1.97 g of TEA and stir for 15 min. Dropwise add 0.5 mL of ammonia water and stir for 18 h. The mass ratio of HM, TEA, and ammonia water is 1:0.985:0.23. After the reaction, centrifuge to remove triethylamine hydrochloride produced by the reaction. The centrifuge speed is 9500 rpm, and the centrifugation time is 5 min. Rotavaporize the supernatant at 70 °C for 2 h. Dry the obtained product in a vacuum oven at 60 °C for 24 h to obtain the product water-soluble polyamino phosphazene (HMN).

[0033] Figure 1 and Figure 2 are the phosphorus NMR spectra ( 31 P NMR) of HCCP and HMN prepared in Example 1 respectively. Figure 3 is the infrared spectrum of HCCP and HMN prepared in Example 1. Figure 4 is the mass spectrum of HMN prepared in Example 1. From Figure 1 and Figure 2 , only a single peak can be seen, indicating that the chemical environments of the three phosphorus atoms in HCCP and HMN are the same. Compared with HCCP, the chemical shift of the phosphorus element in HMN moves towards the high field direction, indicating that the group connected to the phosphorus element has changed from an electron-withdrawing chlorine atom to an electron-donating nitrogen atom. From Figure 3 , it can be seen that HCCP has a stretching vibration absorption peak belonging to the P-Cl bond at 605 cm -1 , while there is no corresponding absorption peak in HMN, indicating that the chlorine atoms on HCCP have been completely replaced. At the same time, a bending vibration absorption peak of N-H appears at 1545 cm -1 , and a stretching vibration absorption peak of N-H appears in the range of 3100 - 3500 cm -1 , indicating the presence of amino groups in the molecule. The peak at 1689 cm -1 belongs to the stretching vibration absorption peak of C=N, and the peak at 1398 cm -1 belongs to the stretching vibration absorption peak of C-N, indicating the presence of a triazine structure in the molecule. Figure 4 The mass-to-charge ratio value of the theoretical molecular ion peak of HMN in

[0034] Example 2

[0035] Synthesis method of HMN-modified MXene, including the following steps:

[0036] (1) Add 100 mL of MXene aqueous dispersion with a concentration of 4 mg / mL to 200 mL of sodium hydroxide aqueous solution with a concentration of 1 mol / L, stir and react at 25 °C for 3 h, repeatedly centrifuge and wash until the pH value of the supernatant is neutral, the centrifugation speed is 9500 rpm, and the centrifugation time is 5 min; ultrasonically disperse the centrifuged precipitate in 100 mL of deionized water to obtain a hydroxylated MXene (MXene-OH) aqueous dispersion with a concentration of 4 mg / mL.

[0037] (2) Under nitrogen protection, add 10 mL of HMN aqueous dispersion with a concentration of 2 mg / mL (prepared by the method in step of Example 1 and dispersed in water, the same below) to 100 mL of MXene-OH aqueous dispersion with a concentration of 4 mg / mL, and react at 70 °C for 3 h to obtain an HMN-MXene composite aqueous dispersion with a concentration of 3.82 mg / mL, where the mass ratio of MXene to HMN is 1:0.05;

[0038] Example 3

[0039] Synthesis method of HMN-modified MXene, comprising the following steps:

[0040] (1) Add 100 mL of MXene aqueous dispersion with a concentration of 4 mg / mL to 200 mL of sodium hydroxide aqueous solution with a concentration of 1 mol / L, stir and react at 25 °C for 3 h, repeatedly centrifuge and wash until the pH value of the supernatant is neutral, the centrifugation speed is 9500 rpm, and the centrifugation time is 5 min; ultrasonically disperse the centrifuged precipitate in 100 mL of deionized water to obtain a hydroxylated MXene (MXene-OH) aqueous dispersion with a concentration of 4 mg / mL.

[0041] (2) Under nitrogen protection, add 20 mL of HMN aqueous dispersion with a concentration of 2 mg / mL to 100 mL of MXene-OH aqueous dispersion with a concentration of 4 mg / mL, and react at 70 °C for 3 h to obtain an HMN-MXene composite aqueous dispersion with a concentration of 3.67 mg / mL, where the mass ratio of MXene to HMN is 1:0.1;

[0042] Example 4

[0043] Synthesis method of HMN-modified MXene, comprising the following steps:

[0044] (1) Add 100 mL of MXene aqueous dispersion with a concentration of 4 mg / mL to 200 mL of sodium hydroxide aqueous solution with a concentration of 1 mol / L, stir and react at 25 °C for 3 h, and repeatedly centrifuge and wash until the pH value of the supernatant is neutral. The centrifugation speed is 9500 rpm and the centrifugation time is 5 min; ultrasonically disperse the centrifuged precipitate in 100 mL of deionized water to obtain a hydroxylated MXene (MXene-OH) aqueous dispersion with a concentration of 4 mg / mL.

[0045] (2) Under nitrogen protection, add 40 mL of HMN aqueous dispersion with a concentration of 2 mg / mL to 100 mL of MXene-OH aqueous dispersion with a concentration of 4 mg / mL, and react at 70 °C for 3 h to obtain an HMN-MXene composite aqueous dispersion with a concentration of 3.43 mg / mL, where the mass ratio of MXene to HMN is 1:0.2.

[0046] Figure 5 is the thermogravimetric spectrum of the HMN-MXene composites prepared in Examples 2, 3, and 4. HMN-MXene exhibits excellent char-forming performance. The char residue amounts of Examples 2, 3, and 4 at 750 °C are 95.4%, 96.9%, and 90.7% respectively, all higher than their theoretical char residue amounts of 94.0%, 90.2%, and 84.2%.

[0047] Figure 6 、 7 are the scanning electron microscope photos of MXene and the HMN-MXene composite prepared in Example 3 respectively. It can be seen from the figure that the surface of MXene is smooth and the interlayer spacing is small; while the surface of HMN-MXene is wrinkled and the interlayer spacing is significantly enlarged. Figure 8 is the XRD spectrum of MXene and the HMN-MXene composite prepared in Example 3. The disappearance of the (002) characteristic peak (2θ = 6.7°) of MXene in the HMN-MXene composite indicates an increase in the interlayer spacing of MXene, presenting a delaminated state, which is consistent with the scanning electron microscope results.

[0048] Example 5

[0049] The preparation of pure epoxy resin (EP) includes the following steps:

[0050] Use a pipette to measure 2.4 mL of BDGE and 0.6 mL of TETA respectively, stir in an ice-water bath for 30 min at a speed of 400 rpm, then transfer the mixture to a polytetrafluoroethylene mold and place it in an oven at 25 °C. The sample is molded after 45 min; take out the molded sample and cure it at 110 °C for 12 h, and the obtained product is epoxy resin (EP).

[0051] Example 6

[0052] For comparison, the preparation of the EP / HMN-MXene composite material comprises the following steps:

[0053] Using a pipette, 0.84 mL of BDGE and 0.21 mL of TETA were respectively measured and added to 1.95 mL of an HMN-MXene aqueous dispersion with a concentration of 5.12 mg / mL (the HMN-MXene aqueous dispersion prepared in Example 3 was vacuum filtered and then redispersed in deionized water, the same hereinafter). The mixture was stirred in an ice-water bath for 30 min at a rotation speed of 400 rpm. Subsequently, the mixture was transferred to a polytetrafluoroethylene mold and placed in an oven at 25 °C. The sample was formed after 20 min. After the formed sample was taken out, it was cured at 110 °C for 12 h. The obtained product was the EP / HMN-MXene composite material, where the mass ratio of EP to HMN-MXene was 1:0.01.

[0054] Example 7

[0055] For comparison, the preparation of the EP / HMN-MXene composite material comprises the following steps:

[0056] Using a pipette, 0.84 mL of BDGE and 0.21 mL of TETA were respectively measured and added to 5.25 mL of an HMN-MXene aqueous dispersion with a concentration of 5.12 mg / mL. The mixture was stirred in an ice-water bath for 30 min at a rotation speed of 400 rpm. Subsequently, the mixture was transferred to a polytetrafluoroethylene mold and placed in an oven at 25 °C. The sample was formed after 20 min. After the formed sample was taken out, it was cured at 110 °C for 12 h. The obtained product was the EP / HMN-MXene composite material, where the mass ratio of EP to HMN-MXene was 1:0.027.

[0057] Example 8

[0058] For comparison, the preparation of the EP / HMN-MXene composite material comprises the following steps:

[0059] Using a pipette, 0.84 mL of BDGE and 0.21 mL of TETA were respectively measured and added to 10.80 mL of an HMN-MXene aqueous dispersion with a concentration of 5.12 mg / mL. The mixture was stirred in an ice-water bath for 30 min at a rotation speed of 400 rpm. Subsequently, the mixture was transferred to a polytetrafluoroethylene mold and placed in an oven at 25 °C. The sample was formed after 20 min. After the formed sample was taken out, it was cured at 110 °C for 12 h. The obtained product was the EP / HMN-MXene composite material, where the mass ratio of EP to HMN-MXene was 1:0.055.

[0060] Figure 9 Digital photos of the pure EP prepared in Example 5 and the EP / HMN-MXene composites prepared in Examples 6, 7, and 8. Cracks appeared and fragmentation occurred in the pure EP prepared in Example 5 after thermal curing, while the morphologies of the EP / HMN-MXene composites prepared in Examples 6, 7, and 8 were intact. Figure 10 Dynamic thermomechanical curve of the EP / HMN-MXene composite prepared in Example 7. As shown in the figure, the glass transition temperature of the EP / HMN-MXene composite is 44.9 °C, which is significantly lower than that of the pure EP. This indicates that the addition of HMN-MXene reduces the crosslinking degree of EP and significantly increases the flexibility of the EP / HMN-MXene composite. Figure 11 Relative resistance change curves of the EP / HMN-MXene composites prepared in Examples 6, 7, and 8 under flame attack. As shown in the figure, the EP / HMN-MXene composites all exhibit a negative temperature effect, and the resistance drops sharply at the moment they come into contact with the flame. This indicates that the material is highly sensitive to flame and can be applied to fire warning. In addition, its excellent flame retardant performance provides the possibility of continuously sending out fire warning signals.

[0061] The above content is only an example and illustration of the concept of the present invention. Those skilled in the art of this technology can make various modifications or supplements to the described specific embodiments or use similar methods for substitution, as long as they do not deviate from the concept of the invention or exceed the scope defined by this claim book, they should fall within the protection scope of the present invention.

Claims

1. A flame-retardant flexible epoxy resin / HMN-MXene composite material with fire warning function, characterized in that: It is composed of wrinkled HMN-MXene nanosheets uniformly dispersed in an epoxy resin matrix, and has a low glass transition temperature, excellent flexibility and flame retardant properties, as well as thermal safety monitoring and early warning functions.

2. The method for preparing the epoxy resin / HMN-MXene composite material according to claim 1, characterized in that: The HMN-MXene composite was added as a nanofiller to the epoxy resin precursor solution, stirred evenly and then quickly molded at room temperature. After thermal curing, a flame-retardant flexible epoxy resin / HMN-MXene composite material with fire warning function was obtained.

3. The preparation method according to claim 2, characterized in that: The HMN-MXene composite is first prepared by sequentially using melamine and ammonia to perform nucleophilic substitution of the chlorine element in the hexachlorotriphosphazene molecule to synthesize a water-soluble polyaminophosphorus nitrogen compound (HMN), which is then used to perform surface modification on hydroxylated titanium carbide (MXene-OH).

4. The preparation method according to claim 2, characterized in that: Take appropriate amounts of epoxy resin precursors 1,4-butanediol glycidyl ether (BDGE) and triethylenetetramine (TETA), add them to the HMN-MXene aqueous dispersion, stir evenly in an ice water bath, then transfer them to a mold and naturally form them at room temperature; after thermal curing the molded sample, an epoxy resin / HMN-MXene composite material is obtained.

5. The preparation method according to claim 4, characterized in that: The mass ratio of TETA to BDGE is 1:(3~5), and the mass ratio of (BDGE+TETA) to HMN-MXene is 1:(0.01~0.06).

6. The preparation method according to claim 4, characterized in that: The temperature of the sample naturally formed at room temperature is 15 to 30°C, and the forming time is 15 to 50 minutes.

7. The preparation method according to claim 4, characterized in that: The thermal curing temperature of the sample is 100-120°C, and the curing time is 10-14h.

8. Application of the flexible flame-retardant epoxy resin / HMN-MXene composite material with fire warning function as claimed in claim 1 in the fields of flame-retardant polymers, thermal safety monitoring and warning, and flexible sensing.

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