Polyvinylidene fluoride-based composite material and preparation method and application thereof

Abstract

The present disclosure provides a polyvinylidene fluoride-based composite material and a preparation method and application thereof, and belongs to the technical field of composite materials. The preparation method comprises the following steps: mixing graphene oxide and dimethyl phthalate to perform a modification reaction, so as to obtain a DMP@GO dispersion liquid; performing solid-liquid separation and drying treatment on the DMP@GO dispersion liquid in sequence, so as to obtain a DMP@GO solid product; and using the DMP@GO solid product and polyvinylidene fluoride as raw materials to prepare a polyvinylidene fluoride-based composite material. The polyvinylidene fluoride-based composite material prepared by the present disclosure has a significantly reduced gas permeation coefficient, excellent gas barrier performance, and excellent mechanical properties, and can be well applied to the inner lining layer of a flexible pipe for marine use.

Description

TECHNICAL FIELD

[0001] The present disclosure belongs to the technical field of composite materials, and particularly relates to a polyvinyl fluoride-based composite material and a preparation method and application thereof. BACKGROUND

[0002] With the deep development of oil and gas resources, the environment for offshore oil and gas exploitation is gradually deteriorating. The high-temperature and high-pressure conveying environment poses a challenge to the mechanical and heat resistance performance of the inner liner material of the flexible pipe for offshore use. Since high temperature and high pressure can accelerate the penetration of acidic gas in the oil and gas medium into the inner liner, the acidic gas that has penetrated into the annulus will corrode the metal functional layer, endangering the safety of the pipeline, which puts higher requirements on the barrier performance of the inner liner material of the flexible riser. Therefore, it is very important to develop a new flexible riser inner liner material with high barrier property, heat resistance and excellent mechanical property.

[0003] Polyvinyl fluoride (PVDF) is a semi-crystalline polymer with good processability. The density is relatively large, and the specific gravity can reach 1.7. The PVDF for pipeline use has good heat resistance and excellent mechanical strength, the melting point can reach 160℃, the Young's modulus can reach 1000~1300 MPa, and the yield strength is more than 40 MPa. The stable C-F bond makes PVDF have extremely high intramolecular binding force, which makes it have excellent corrosion resistance and thermal stability. The long-term working temperature of PVDF can reach 130℃. Due to the high crystallinity and strong intramolecular force of PVDF, the material has high density, so it has a certain barrier property to acidic gases such as CO2 and H2S. However, when applied to the inner liner material of the flexible pipe for offshore use, the gas permeation coefficient is still relatively large, which cannot meet the application of the inner liner of the flexible pipe for offshore use well. SUMMARY

[0004] The present disclosure aims to at least solve one of the technical problems existing in the prior art, and provide a polyvinyl fluoride-based composite material and a preparation method and application thereof.

[0005] In one aspect of the present disclosure, a preparation method of a polyvinyl fluoride-based composite material is provided, and the preparation method comprises:

[0006] The graphene oxide and dimethyl phthalate are mixed for a modification reaction to obtain a DMP@GO dispersion liquid;

[0007] The DMP@GO dispersion liquid is sequentially subjected to solid-liquid separation and drying treatment to obtain a DMP@GO solid product;

[0008] The DMP@GO solid product and polyvinyl fluoride are used as raw materials to prepare a polyvinyl fluoride-based composite material.

[0009] Optionally, the mass ratio of the graphene oxide and dimethyl phthalate is 1: (2~10).

[0010] Optionally, the modification reaction is carried out under the condition of ultrasonic, at room temperature, for 8-12 hours.

[0011] Optionally, the drying treatment is carried out at 60-70℃ for 12-24 hours.

[0012] Optionally, the polyvinyl fluoride-based composite material is prepared from the DMP@GO solid product and polyvinyl fluoride, comprising:

[0013] The DMP@GO solid product is dispersed in an organic solvent and subjected to ultrasonic treatment to obtain an ultrasonic treatment solution;

[0014] The ultrasonic treatment solution and first polyvinyl fluoride are mixed to obtain a mixed solution, and the mixed solution is subjected to alcohol precipitation and drying in sequence to obtain a polyvinyl fluoride composite master batch;

[0015] The polyvinyl fluoride composite master batch and second polyvinyl fluoride are melt blended to obtain a polyvinyl fluoride-based composite material.

[0016] Optionally, the mass ratio of the first polyvinyl fluoride to the second polyvinyl fluoride is 1:(4-9).

[0017] The DMP@GO solid product and the organic solvent are used in a ratio of (0.2-0.5) g:100 mL.

[0018] Optionally, the polyvinyl fluoride composite master batch and second polyvinyl fluoride are melt blended at a temperature of 180-200℃, a screw rotation speed of 50-100 r / min, and for 6-10 min.

[0019] Optionally, the mass percentage content of the DMP@GO solid product in the polyvinyl fluoride-based composite material is 0.2-0.9%.

[0020] In another aspect of the present disclosure, a polyvinyl fluoride-based composite material is provided, which is prepared by the preparation method described above.

[0021] In another aspect of the present disclosure, the polyvinyl fluoride-based composite material is applied to the inner lining layer of a flexible pipe for marine use.

[0022] This disclosure presents a polyvinylidene fluoride (PVDF) vinyl composite material, its preparation method, and its applications. The preparation method includes: mixing graphene oxide and dimethyl phthalate (DMP@GO) for a modification reaction to obtain a DMP@GO dispersion; subjecting the DMP@GO dispersion to solid-liquid separation and drying to obtain a DMP@GO solid product; and using the DMP@GO solid product and PVDF as raw materials to prepare the PVDF vinyl composite material. The PVDF vinyl composite material prepared by this disclosure exhibits a significantly reduced gas permeability coefficient, excellent gas barrier properties, and also excellent mechanical properties (including tensile strength and elongation at break), making it well-suited for use as an inner lining for flexible marine pipes. Attached Figure Description

[0023] Figure 1 This is a flowchart illustrating a specific embodiment of the method for preparing polyvinylidene fluoride composite materials disclosed herein.

[0024] Figure 2 A comparison diagram of the yield strength of the GO / PVDF material prepared in Comparative Example 1 and the KH550@GO / PVDF material prepared in Comparative Example 3 of this disclosure;

[0025] Figure 3 A comparison diagram of the elongation at break of the GO / PVDF material prepared in Comparative Example 1 and the KH550@GO / PVDF material prepared in Comparative Example 3 of this disclosure;

[0026] Figure 4 A comparison graph showing the gas permeability coefficients of the GO / PVDF material prepared in Comparative Example 1 and the KH550@GO / PVDF material prepared in Comparative Example 3 of this disclosure;

[0027] Figure 5 The results show the comparison of the yield strength of the materials prepared in Comparative Example 4 of this disclosure. Detailed Implementation

[0028] To enable those skilled in the art to better understand the technical solutions of this disclosure, the disclosure will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only used to explain this disclosure and represent a part of the embodiments of this disclosure, not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this disclosure without creative effort are within the protection scope of this disclosure.

[0029] As shown in Figure 1, one aspect of this disclosure provides a method S100 for preparing polyvinylidene fluoride composite material, specifically including the following steps S110~S130:

[0030] S110. Graphene oxide (GO) and dimethyl phthalate (DMP) are mixed and modified to obtain a DMP@GO dispersion.

[0031] In some preferred embodiments, the mass ratio of graphene oxide to dimethyl phthalate is 1:(2~10), for example, 1:2, 1:4, 1:5, 1:6, 1:8, 1:10, etc. are preferred, and 1:5 is even more preferred.

[0032] In some other preferred embodiments, the modification reaction is carried out under ultrasonic conditions, and the temperature of the modification reaction is room temperature, and the time is 8 to 12 hours, for example, 8 hours, 10 hours, or 12 hours are preferred.

[0033] S120. The DMP@GO dispersion is subjected to solid-liquid separation and drying treatment in sequence to obtain DMP@GO solid product.

[0034] It should be noted that the solid-liquid separation in step S120 can preferably be centrifugal separation, the solid product after centrifugation is washed, and then the washed solid product is dried. Among them, washing can preferably be performed with anhydrous ethanol, and the number of washings can preferably be 3 times.

[0035] In some preferred embodiments, drying can preferably be carried out in a drying oven at a temperature of 60-70°C, for example, 60°C, 65°C, 70°C, etc., for a time of 12-24 hours, for example, 12 hours, 15 hours, 20 hours, 24 hours, etc.

[0036] S130. Polyvinylidene fluoride composite material was prepared using DMP@GO solid product and polyvinylidene fluoride as raw materials.

[0037] Specifically, step S130 includes the following process:

[0038] The DMP@GO solid product was dispersed in an organic solvent and ultrasonically treated to obtain an ultrasonically treated solution. The ultrasonically treated solution was mixed with a first polyvinylidene fluoride (PVDF) to obtain a mixed solution. The mixed solution was then subjected to alcohol precipitation and drying to obtain a PVDF composite masterbatch. The PVDF composite masterbatch and a second PVDF were melt-blended to obtain the PVDF vinyl composite material.

[0039] In this embodiment, the DMP@GO solid product is further subjected to ultrasonic treatment in an organic solvent to achieve the exfoliation of the DMP@GO solid product, thereby enabling the DMP@GO solid product to exist in a uniformly dispersed form in the PVDF matrix; improving the gas barrier properties of the composite material; at the same time, the masterbatch method is also used to further improve the dispersibility of GO in the PVDF matrix, further improving the gas barrier properties and mechanical properties of the composite material.

[0040] It should be noted that this embodiment does not specifically limit the conditions for mixing the ultrasonic treatment solution and the first polyvinylidene fluoride, as long as the two are mixed evenly. For example, it is preferable to carry out the mixing under stirring conditions, and the mixing temperature is preferably room temperature, and the mixing time is preferably 8 to 12 hours.

[0041] It should be further noted that this embodiment does not specifically limit the solvent used for alcohol precipitation, such as anhydrous ethanol, and the solid product obtained by alcohol precipitation should be dried. The drying temperature is preferably 60~70°C and the drying time is preferably 24~48h.

[0042] In some preferred embodiments, the mass ratio of the first polyvinylidene fluoride to the second polyvinylidene fluoride is 1:(4~9), for example, 1:4, 1:5, 1:6, 1:7, 1:8, 1:9 are preferred, and 1:4 is even more preferred.

[0043] In some other preferred embodiments, the ratio of DMP@GO solid product to the organic solvent is (0.2~0.5) g:100 mL, for example, preferably 0.2:100 mL, 0.3:100 mL, 0.4:100 mL, or 0.5:100 mL.

[0044] In some other preferred embodiments, the organic solvent includes N,N-dimethylformamide.

[0045] In some other preferred embodiments, the DMP@GO solid product is dispersed in an organic solvent and subjected to ultrasonic treatment for 1 to 2 hours.

[0046] In some other preferred embodiments, the temperature for melt blending the polyvinylidene fluoride composite masterbatch and the second polyvinylidene fluoride is 180~200℃, the screw speed is 50~100r / min, and the time is 6~10min.

[0047] It should be noted that this embodiment does not specifically limit the equipment for melt blending polyvinylidene fluoride composite masterbatch and second polyvinylidene fluoride, for example, melt blending can be carried out in a Brabender torque rheometer.

[0048] Furthermore, the mass percentage of the DMP@GO solid product in the polyvinylidene fluoride composite material obtained in this embodiment is 0.2-0.9%, for example, it can be 0.2%, 0.3%, 0.4%, 0.6% or 0.9%.

[0049] This disclosure utilizes the hydrolysis of dimethyl phthalate (DMP) during the modification reaction to generate carboxyl groups (-COOH), which then undergo esterification with hydroxyl groups (-OH) or epoxy groups on the surface of graphene oxide, thereby achieving surface modification of graphene oxide. The benzene ring and ester group structure of DMP can improve the processing performance of PVDF, increase the compatibility between graphene oxide and PVDF, improve the aggregation problem of graphene oxide, and enhance the dispersibility of graphene oxide in the polyvinylidene fluoride (PVDF) matrix; thereby improving the gas barrier properties and mechanical properties of polyvinylidene fluoride composite materials.

[0050] In another aspect of this disclosure, a polyvinylidene fluoride (PVDF) composite material is provided, which is prepared by the preparation method described above. For details of the preparation process, please refer to the above description, which will not be repeated here.

[0051] The polyvinylidene fluoride composite material prepared in this embodiment has a significantly reduced gas permeability coefficient and excellent gas barrier properties, as well as excellent mechanical properties (including tensile strength and elongation at break), making it well-suited for use as an inner lining for flexible marine pipes.

[0052] In another aspect of this disclosure, an application of a polyvinylidene fluoride (PVDF) composite material is proposed, wherein the PVDF composite material described above is used in the lining of a flexible marine pipe.

[0053] The following will further illustrate the polyvinylidene fluoride (PVDF) composite material and its preparation method with specific examples:

[0054] Example 1

[0055] (1) Preparation of DMP@GO

[0056] 1.0 g of graphene oxide (GO) was added to 5.0 g of dimethyl phthalate (DMP), and the mixture was sonicated for 12 hours to obtain a uniform DMP@GO dispersion. The dispersion was then centrifuged, washed three times with anhydrous ethanol, and finally dried in a 70°C oven for 24 hours to obtain DMP@GO solid particles.

[0057] (2) Preparation of DMP@GO / PVDF composite material by masterbatch method

[0058] First, DMP@GO solid particles were dispersed in 100 mL of N,N-dimethylformamide (DMF) solvent and ultrasonically dispersed for 1 hour. Then, 10.0 g of polyvinylidene fluoride (PVDF) was added, and the mixture was stirred continuously at room temperature for 12 hours to ensure complete dissolution. Anhydrous ethanol was then added to precipitate the solute, and the resulting precipitate was dried at 70 °C for 48 hours to obtain the PVDF composite masterbatch.

[0059] Finally, the obtained masterbatch was melt-blended with 40.0 g of the second PVDF using a Brabender torque rheometer at 200 °C, with a screw speed of 50 r / min, a mixing temperature of 200 °C, and a mixing time of 6 min, to finally prepare the DMP@GO / PVDF composite material.

[0060] In this embodiment, DMP@GO / PVDF composite materials with different solid particle contents were prepared by adjusting the content of DMP@GO solid particles. For example, the mass percentage of DMP@GO solid particles in the DMP@GO / PVDF composite material was 0.3%, 0.6%, or 0.9%, and the corresponding composite materials were denoted as (0.3%DMP@GO / PVDF)-m, (0.6%DMP@GO / PVDF)-m, and (0.9%DMP@GO / PVDF)-m, respectively.

[0061] The (0.6% DMP@GO / PVDF)-m molded sheet material prepared in Example 1 is opaque, which indicates that the DMP@GO solid particles are uniformly dispersed in the matrix.

[0062] Comparative Example 1

[0063] Graphene oxide (GO) and PVDF were melt-blended using a Brabender torque rheometer at 200°C with a screw speed of 50 r / min, a mixing temperature of 200°C, and a mixing time of 6 min, ultimately yielding a PVDF / GO composite material.

[0064] In this comparative example, composite materials with different GO contents were prepared by adjusting the content of graphene oxide (GO). For example, in the PVDF / GO composite material, the GO mass content was 0%, 0.2%, 0.3%, 0.4%, 0.6%, or 0.9%, and the corresponding composite materials were denoted as PVDF, 0.2%GO / PVDF, 0.3%GO / PVDF, 0.4%GO / PVDF, 0.6%GO / PVDF, or 0.9%GO / PVDF, respectively.

[0065] The 0.6% GO / PVDF molded sheet material prepared in Comparative Example 1 is transparent, but the presence of focused black particles is clearly visible, indicating that the GO solid particles are not uniformly dispersed in the matrix.

[0066] Comparative Example 2

[0067] GO was dispersed in 100 mL of N,N-dimethylformamide (DMF) solvent and ultrasonically dispersed for 1 hour. Then, 10.0 g of polyvinylidene fluoride (PVDF) was added, and the mixture was stirred continuously at room temperature for 12 hours until fully dissolved. Anhydrous ethanol was then added to precipitate the solute, and the resulting precipitate was dried at 70 °C for 48 hours to obtain PVDF / GO masterbatch. The obtained PVDF / GO masterbatch was melt-blended with 40 g of PVDF using a Brabender torque rheometer at 200 °C, with a screw speed of 50 r / min, a mixing temperature of 200 °C, and a mixing time of 6 min, ultimately yielding the composite material.

[0068] In this comparative example, composite materials with different GO contents were prepared by adjusting the content of graphene oxide (GO). For example, the mass content of GO in the composite materials was 0.3%, 0.6% and 0.9%, and the corresponding composite materials were denoted as (0.3%GO / PVDF)-m, (0.6%GO / PVDF)-m or (0.9%GO / PVDF)-m, respectively.

[0069] Furthermore, the products prepared in Example 1, Comparative Example 1, and Comparative Example 2 were subjected to gas permeability tests. The test results are shown in Table 1. The composite material of Example 1 has a low permeability coefficient and a low diffusion coefficient, and has excellent gas barrier properties.

[0070] Table 1. Permeability and diffusion coefficients of materials prepared in Examples 1 and Comparative Examples 1-2

[0071]

[0072] Furthermore, the tensile strength and elongation at break properties of the products prepared in Example 1, Comparative Example 1, and Comparative Example 2 were tested. The test results are shown in Table 2. The mechanical properties of the composite material in Example 1 are still relatively high and basically consistent with PVDF. This indicates that the composite material in Example 1 has good mechanical properties while having low gas permeability coefficient and diffusion coefficient and good gas barrier properties.

[0073] Table 2. Tensile strength and elongation at break of the materials prepared in Examples 1 and Comparative Examples 1-2

[0074]

[0075] Comparative Example 3

[0076] Mix 5 mL KH550, 100 mL deionized water and 150 mL anhydrous ethanol, then add 1.0 g GO and carry out the modification reaction at room temperature for 24 h. Subsequently, the dispersion is centrifuged and washed three times with anhydrous ethanol. Finally, it is dried in an oven at 70 °C for 24 h to obtain KH550 modified GO solid particles (KH550@GO).

[0077] KH550@GO and PVDF were melt-blended at 200℃ using a Brabender torque rheometer with a screw speed of 50 r / min, a mixing temperature of 200℃, and a mixing time of 6 min, to finally obtain the PVDF / KH550@GO composite material.

[0078] In this comparative example, composite materials with different KH550@GO contents were prepared by adjusting the content of KH550 modified GO solid particles (KH550@GO). For example, in the PVDF / KH550@GO composite material, the mass content of KH550@GO was 0.2%, 0.4%, or 0.6%, and the corresponding composite materials were denoted as 0.2%KH550@GO / PVDF, 0.4%KH550@GO / PVDF, and 0.6%KH550@GO / PVDF, respectively.

[0079] Figure 2 This is a comparison graph showing the yield strength of the GO / PVDF material prepared in Comparative Example 1 and the KH550@GO / PVDF material prepared in Comparative Example 3. Figure 3 This is a comparison chart of the elongation at break of the GO / PVDF material prepared in Comparative Example 1 and the KH550@GO / PVDF material prepared in Comparative Example 3. Figure 4 A comparison graph showing the gas permeability coefficients of the GO / PVDF material prepared in Comparative Example 1 and the KH550@GO / PVDF material prepared in Comparative Example 3. Figure 4 The permeability coefficient was tested at a temperature of 90℃.

[0080] Depend on Figure 2 , Figure 3 and Figure 4 It can be seen that in Comparative Example 3, the properties of the composite material obtained before and after modification by KH550 did not change significantly, indicating that the KH550 modification did not enhance the direct interaction between GO and PVDF.

[0081] Comparative Example 4

[0082] DMP and PVDF were melt-blended using a Brabender torque rheometer at 200°C. The screw speed was 50 r / min, the mixing temperature was 200°C, and the time was 6 min, resulting in a PVDF / DMP blend. The mass content of DMP was 1% (denoted as PVDF / 1%DMP) and 2% (denoted as PVDF / 2%DMP).

[0083] Graphene oxide (GO) was added to dimethyl phthalate (DMP) and ultrasonically treated for 12 hours to obtain a uniform DMP / GO dispersion. The dispersion was then melt-blended with PVDF using a Brabender torque rheometer at 200°C, with a screw speed of 50 r / min, a mixing temperature of 200°C, and a mixing time of 6 min, to finally prepare the PVDF / DMP / GO composite material.

[0084] In this comparative example, composite materials with different GO and DMP contents were prepared by adjusting the contents of dimethyl phthalate (DMP) and graphene oxide (GO). For example, in the PVDF / DMP / GO composite material, when the mass content of DMP is 1% and the mass content of GO is 0.2%, the corresponding composite material is denoted as PVDF / 1%DMP / 0.2%GO; in the PVDF / DMP / GO composite material, when the mass content of DMP is 2% and the mass content of GO is 0.2%, the corresponding composite material is denoted as PVDF / 2%DMP / 0.2%GO; and in the PVDF / DMP / GO composite material, when the mass content of DMP is 2% and the mass content of GO is 0.4%, the corresponding composite material is denoted as PVDF / 2%DM / 0.4%GO.

[0085] The gas permeability of the PVDF prepared in Comparative Example 1 and the product prepared in Comparative Example 4 was tested, and the test results are shown in Table 3.

[0086] Table 3 Gas permeability coefficients of materials prepared in Comparative Example 4

[0087]

[0088] The mechanical properties of PVDF, 0.2%GO / PVDF, and 0.4%GO / PVDF prepared in Comparative Example 1, and PVDF / 1%DMP, PVDF / 1%DMP / 0.2%GO, PVDF / 2%DMP, PVDF / 2%DMP / 0.2%GO, and PVDF / 2%DMP / 0.4%GO prepared in Comparative Example 4 were tested. The test results are as follows: Figure 5 As shown.

[0089] From Table 3 and Figure 5It can be seen that the composite material prepared in Comparative Example 4 has decreased mechanical properties and worse gas barrier properties compared to the material prepared in Comparative Example 1. This is because DMP is a small molecule liquid, and its direct incorporation into PVDF disrupts the crystalline structure of PVDF, leading to a decrease in material performance. However, comparing the mechanical properties (Table 2) and gas permeation data (Table 1) of the composite material prepared in Example 1 with those of PVDF and the material prepared in Comparative Example 1, the material prepared in Example 1 shows improved barrier properties while maintaining essentially unchanged mechanical properties. This indicates that removing excess DMP and employing a masterbatch method in Example 1 is more effective in improving the barrier properties and maintaining excellent mechanical properties of the composite material.

[0090] In summary, as demonstrated by the above embodiments, this disclosure utilizes the acid groups or hydroxyl groups generated from the hydrolysis of dimethyl phthalate (DMP) to react with graphene oxide, thereby activating and modifying the graphene oxide and improving its dispersibility in a polyvinylidene fluoride (PVDF) matrix. Furthermore, the benzene rings and ester groups of DMP enhance its compatibility with PVDF, further improving the compatibility of the DMP@GO solid product with PVDF and its flowability within the PVDF matrix. This results in good dispersibility of graphene oxide in the PVDF matrix, significantly improving the barrier properties and mechanical properties of the PVDF composite material. In other words, the PVDF composite material prepared according to this disclosure exhibits a significantly reduced gas permeability coefficient, demonstrating excellent gas barrier properties, while also possessing excellent mechanical properties (including tensile strength and elongation at break).

[0091] This disclosure proposes a polyvinylidene fluoride (PVDF) composite material, its preparation method, and its application. Compared with the prior art, it has the following beneficial effects: the gas permeability coefficient of the PVDF composite material prepared by this disclosure is significantly reduced, and it has excellent gas barrier properties. It also has excellent mechanical properties (including tensile strength and elongation at break), and can be well applied to the inner lining of flexible pipes for marine use.

[0092] It is understood that the above embodiments are merely exemplary embodiments used to illustrate the principles of this disclosure, and this disclosure is not limited thereto. For those skilled in the art, various modifications and improvements can be made without departing from the spirit and substance of this disclosure, and these modifications and improvements are also considered to be within the scope of protection of this disclosure.

Claims

1. A method for preparing a polyvinylidene fluoride composite material, characterized in that, The preparation method includes: Graphene oxide and dimethyl phthalate were mixed and modified to obtain a DMP@GO dispersion. The mass ratio of graphene oxide to dimethyl phthalate was 1:(2~10). In the modification reaction, the carboxyl groups generated by the hydrolysis of dimethyl phthalate underwent esterification with the hydroxyl or epoxy groups on the surface of graphene oxide, thereby achieving surface modification of graphene oxide. The benzene ring and ester group structure of dimethyl phthalate can improve the processing performance of polyvinylidene fluoride and increase the compatibility and dispersibility between graphene oxide and polyvinylidene fluoride. The DMP@GO dispersion was subjected to solid-liquid separation and drying processes to obtain the DMP@GO solid product. A polyvinylidene fluoride composite material was prepared using the DMP@GO solid product and polyvinylidene fluoride as raw materials, comprising: The DMP@GO solid product was dispersed in an organic solvent and subjected to ultrasonic treatment to obtain an ultrasonically treated solution. The ultrasonic treatment solution and the first polyvinylidene fluoride were mixed to obtain a mixed solution. The mixed solution was then subjected to alcohol precipitation and drying in sequence to obtain polyvinylidene fluoride composite masterbatch. The polyvinylidene fluoride composite masterbatch and the second polyvinylidene fluoride were melt-blended to obtain a polyvinylidene fluoride vinyl composite material; The composite material has low gas permeability and diffusion coefficients, good acid gas barrier properties, and good mechanical properties.

2. The preparation method according to claim 1, characterized in that, The modification reaction was carried out under ultrasonic conditions at room temperature for 8-12 hours.

3. The preparation method according to claim 1, characterized in that, The drying process is carried out at a temperature of 60-70°C for 12-24 hours.

4. The preparation method according to claim 1, characterized in that, The mass ratio of the first polyvinylidene fluoride to the second polyvinylidene fluoride is 1:(4~9); The ratio of the DMP@GO solid product to the organic solvent is (0.2~0.5) g: 100 mL.

5. The preparation method according to claim 1, characterized in that, The temperature for melting and blending the polyvinylidene fluoride composite masterbatch and the second polyvinylidene fluoride is 180~200℃, the screw speed is 50~100r / min, and the time is 6~10min.

6. The preparation method according to claim 1, characterized in that, The mass percentage of the DMP@GO solid product in the polyvinylidene fluoride composite material is 0.2-0.9%.

7. A polyvinylidene fluoride composite material, characterized in that, The polyvinylidene fluoride composite material is prepared by the preparation method according to any one of claims 1 to 6.

8. An application of a polyvinylidene fluoride composite material, characterized in that, The polyvinylidene fluoride composite material described in claim 7 is used in the inner lining of a flexible marine pipe.

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