A method for directly producing a ptf film using a polytetrafluoroethylene dispersion

Abstract

The application belongs to the technical field of polytetrafluoroethylene, and particularly relates to a method for directly preparing a PTFE film from a polytetrafluoroethylene dispersion liquid. The method uses the polytetrafluoroethylene dispersion liquid as a raw material, modifies the polytetrafluoroethylene dispersion liquid through a small molecule modifier, and then directly prepares the PTFE film by film forming, drying and sintering the modified polytetrafluoroethylene dispersion liquid, so that the preparation process is simple and feasible and can be continuously formed. The obtained PTFE film has a film thickness that can be as thin as 1 micrometer and can be flexibly controlled between 1 micrometer and 200 micrometers, the film structure of the obtained film is uniform and stable, the width of the film is large, the thickness uniformity of the film is good, and the mechanical properties of the film are excellent.

Description

Technical Field

[0001] This invention belongs to the technical field of polytetrafluoroethylene, specifically relating to a method for directly preparing PTFE films using a polytetrafluoroethylene dispersion. Background Technology

[0002] Polytetrafluoroethylene (PTFE) is polymerized from tetrafluoroethylene monomers and is the most important fluoropolymer. The PTFE molecular chain consists of strictly alternating carbon and fluorine units in a helical configuration. The molecular structure is highly symmetrical, with carbon atoms surrounded by small-radius, highly electronegative fluorine atoms. The CF bonds have high bond energy (460 kJ / mol) and short bond distances. Therefore, PTFE possesses outstanding dielectric properties, chemical corrosion resistance, lubricity, and weather resistance.

[0003] PTFE film is a polymer material made of polytetrafluoroethylene resin. It has stable chemical properties such as resistance to extreme temperatures (-150~260℃) and acid and alkali resistance. It has wide applications in electrical and electronic, aerospace, petrochemical, defense and military and medical fields. It is also an indispensable material in the fields of high frequency communication and microelectronics.

[0004] Existing PTFE films are generally produced by molding and sintering cylindrical preforms, cutting them into films using a machine tool, and then calendering them. Depending on the processing method, they can be classified into three types: oriented films, semi-oriented films, and non-oriented films. However, in the current PTFE film preparation process, PTFE is subjected to multi-dimensional force fields such as pressure and shear force, as well as temperature gradient fields, which easily leads to uneven stress transmission, resulting in uneven resin particle packing and density distribution. During the sintering stage, due to PTFE's poor thermal conductivity, temperature gradients occur, leading to significant differences in the strength of the inner and outer interfaces of the preform, and poor material uniformity in the cut film. Furthermore, the strong cutting forces of the machine tool during film formation cause significant anisotropy in the film material properties, generating large internal stresses that cannot be completely eliminated in a short time, leading to phenomena such as film curling and affecting the long-term performance of the film material.

[0005] With the increasing demands for lightweight, miniaturized, and highly stable performance in high-frequency communication and microelectronics, more stringent requirements have been placed on polytetrafluoroethylene (PTFE) films used in these fields in terms of film thickness, uniformity, and width.

[0006] Polytetrafluoroethylene (PTFE) dispersions are concentrated dispersions of PTFE obtained through emulsion polymerization in the presence of nonionic surfactants. In emulsion polymerization, in addition to PTFE monomers and initiators, surfactants and various auxiliaries are added to allow polymerization to occur within surfactant micelles. The resulting particles are uniformly dispersed in the solution. PTFE particles in PTFE dispersions are typically spherical or rod-shaped, negatively charged, and hydrophobic. They are characterized by small particle size, narrow particle size distribution, controllable particle morphology, and excellent processing and product properties. While granular polymers obtained from suspension polymerization can be further processed, PTFE dispersions cannot be directly used for molding and are mainly used for paste extrusion, impregnation of fabrics or porous metals, and coating on other substrates to form coatings. However, there are no reports of using PTFE emulsions directly to produce pure PTFE films. Summary of the Invention

[0007] The purpose of this invention is to provide a method for directly preparing PTFE films using polytetrafluoroethylene dispersion. The method uses PTFE dispersion as raw material, modifies the polytetrafluoroethylene dispersion with a small molecule modifier, and then forms, dries, and sinters the modified polytetrafluoroethylene dispersion to directly prepare PTFE films. The preparation process is simple, feasible, and can be continuously formed.

[0008] The resulting PTFE film can be as thin as 1 μm and can be flexibly adjusted between 1 and 200 μm. The resulting film has a uniform and stable structure, a large width and good thickness uniformity, and excellent mechanical properties.

[0009] During their research, the inventors discovered the following technical obstacles to directly preparing PTFE films using polytetrafluoroethylene (PTFE) dispersions: Due to the weak interaction forces between latex particles in the PTFE dispersion, significant cracks occur during the drying process due to capillary forces. This makes it difficult to achieve molecular chain entanglement and film formation through simple sintering. Therefore, existing PTFE dispersions cannot be directly used to form complete and continuous films like other polymer solutions; they must first be coated and dried to form a powder film before sintering. Normal drying film formation results in molecular chain entanglement and strong interaction forces, directly forming a film with strength. However, powder films differ from conventional drying film formation. They are simply PTFE particles stacked after drying the PTFE dispersion, lacking molecular chain entanglement. Therefore, there are no significant interaction forces between the PTFE particles, resulting in virtually no strength.

[0010] Based on the above problems, the inventors innovatively conceived the following technical approach: introducing a small molecule modifier that is immiscible with water but has better wettability to PTFE particles in a polytetrafluoroethylene dispersion than water. This small molecule modifier establishes a three-dimensional physical cross-linked network (e.g., ...) in the polytetrafluoroethylene dispersion. Figure 1 As shown in the figure, the interaction force between PTFE particles is increased. The presence of the three-dimensional physical network reduces the drying rate of the film, which is beneficial for the uniform release of internal stress during the drying process. This significantly reduces the width of micro-defects in the film, improves the uniformity of PTFE particle distribution after drying, and enhances the overall performance of the PTFE film.

[0011] Furthermore, the small molecule modifier introduced is different from polymers with flexible molecular chains. The addition of the small molecule modifier will not have a fatal impact on the film after sintering, that is, it will not produce micropores. Thus, it will not affect the application of the obtained PTFE film in the field of dielectric materials.

[0012] The specific technical solution of the present invention is as follows:

[0013] A method for directly preparing PTFE films using a polytetrafluoroethylene (PTFE) dispersion involves using the PTFE dispersion as a raw material, and directly preparing PTFE films through film formation, drying, sintering, and winding.

[0014] Specifically, the following steps are included:

[0015] (1) Add a small molecule modifier to a polytetrafluoroethylene dispersion; stir; and obtain a modified polytetrafluoroethylene dispersion; wherein the small molecule modifier is a non-polar liquid with a molecular weight of less than 1000; and the three-phase contact angle between the small molecule modifier and PTFE particles and water in the polytetrafluoroethylene dispersion is less than 90°.

[0016] (2) The modified polytetrafluoroethylene dispersion is cast or coated onto the substrate material and dried to form a film; then it is sintered and molded.

[0017] (3) The sintered film is peeled off from the substrate material and wound up to directly prepare a PTFE film. The substrate material can be a flat and high-temperature resistant material such as steel strip or glass plate.

[0018] In this invention, the solid content of the polytetrafluoroethylene dispersion in step (1) of the method for directly preparing PTFE film using polytetrafluoroethylene dispersion is 55-65 wt%; the number average molecular weight of polytetrafluoroethylene in the polytetrafluoroethylene dispersion is 500,000 to 2,000,000; and the size of PTFE particles in the dispersion is 150 to 220 nm.

[0019] If the number-average molecular weight of polytetrafluoroethylene in the polytetrafluoroethylene dispersion is too small, it will not achieve the practical mechanical strength of the film; if it is too large, it will lead to excessive melt viscosity and make it difficult to form a film. Therefore, the polytetrafluoroethylene selected in this invention has a number-average molecular weight of 500,000 to 2,000,000.

[0020] If the PTFE particle size is too small, it will increase the size of film defects; while if the PTFE particle size is too large, it will be detrimental to the storage stability of the dispersion. Therefore, a PTFE particle size of 150–220 nm was selected.

[0021] In this invention, the small molecule modifier in step (1) of the method for directly preparing PTFE film using polytetrafluoroethylene dispersion is one or more of n-pentadecanol, n-decane, white oil or paraffin oil.

[0022] Pentadecane, n-decane, white oil, or paraffin oil can all achieve a three-phase contact angle of less than 90° with PTFE particles and water, and are immiscible with water. Their wettability to PTFE particles is stronger than that of water; they connect between PTFE particles and remain stable, forming a three-dimensional physical network throughout the entire PTFE dispersion. During film formation, this increases the interaction between PTFE particles, improving and reducing defects formed in the PTFE film during drying.

[0023] In this invention, the amount of small molecule modifier added in step (1) of the method for directly preparing PTFE film using polytetrafluoroethylene dispersion is 0.01-6% of the solid mass of polytetrafluoroethylene dispersion.

[0024] In this invention, the specific stirring operation in step (1) of the method for directly preparing PTFE film using polytetrafluoroethylene dispersion is as follows: first, stir at high speed of 800-2500 rpm for 5-20 min, and then stir at low speed of 300-500 rpm for 5-10 min.

[0025] In this invention, step (1) of the method for directly preparing PTFE film using polytetrafluoroethylene dispersion is further enhanced by adding a synergist, which is one or more of modified hydrogenated castor oil, organobentonite, or polymethyl methacrylate.

[0026] The aforementioned synergist is an oil-soluble material that is immiscible with water. It can swell or form hydrogen bonds in the small molecule modifier, thereby increasing the viscosity of the polytetrafluoroethylene dispersion.

[0027] In this invention, the amount of synergist added in step (1) of the method for directly preparing PTFE film using polytetrafluoroethylene dispersion is 0-6% of the mass of small molecule modifier.

[0028] In this invention, in step (2) of the method for directly preparing PTFE film using polytetrafluoroethylene dispersion, the film-forming drying temperature is 20-60℃ and the film-forming drying time is 5-90min; the sintering temperature is 340-400℃ and the sintering time is 10-60min.

[0029] A PTFE film is prepared directly from a polytetrafluoroethylene dispersion according to the above method; the PTFE film has a thickness of 1-200 μm, a width of 0.05-2 m, a tensile strength of 22-31 MPa, an elongation at break of 190-300%, and a dielectric loss of 0.0003-0.0008.

[0030] An application of the PTFE film prepared by the above-mentioned method of directly preparing PTFE film using polytetrafluoroethylene dispersion in the field of dielectric materials.

[0031] The beneficial effects of this invention are as follows: This invention proposes a method for directly preparing PTFE films using a polytetrafluoroethylene dispersion. The method involves coating the film with the polytetrafluoroethylene dispersion, drying to remove the solvent, sintering to form a film, and peeling and winding it up. During the preparation process, there is no significant stress inside the film, and the film is thin and heated evenly at all locations. Therefore, compared with traditional preparation methods, the prepared polytetrafluoroethylene film has a deeper degree of molecular chain entanglement, better product uniformity, no significant internal stress, and excellent mechanical and dielectric properties.

[0032] The PTFE film prepared by the method can have a minimum thickness of 1 μm, which meets the current demand for ultra-thin and high-performance PTFE film materials in dielectric materials. Moreover, its film thickness can be precisely controlled in the range of 1 to 200 micrometers by adjusting the thickness of a single coating and multiple coatings, and the thickness uniformity can be significantly improved compared with existing methods.

[0033] The modified polytetrafluoroethylene dispersion overcomes the uneven flow phenomenon that occurs in the coating and drying process of existing polytetrafluoroethylene dispersions, effectively improves defects such as microcracks in the film formation process, and significantly improves the mechanical and dielectric properties of the obtained film material.

[0034] The small molecule modifier introduced is different from polymers with flexible molecular chains. The addition of the small molecule modifier will not have a fatal impact on the film after sintering, that is, it will not produce micropores. Thus, it will not affect the application of the obtained PTFE film in the field of dielectric materials. Attached Figure Description

[0035] Figure 1 This is a schematic diagram of the three-dimensional physical network structure in the modified polytetrafluoroethylene dispersion described in this invention.

[0036] Figure 2 This is a process flow diagram of the preparation method described in this invention.

[0037] Figure 3 This is a comparison diagram of the crack size of the polytetrafluoroethylene film obtained in Example 1 and Comparative Example 1. Detailed Implementation

[0038] The technical solution of the present invention will now be described in detail with reference to the accompanying drawings.

[0039] 1. The polytetrafluoroethylene dispersion used below was purchased from Shandong Dongyue Polymer Materials Co., Ltd.

[0040] 2. The yield stress of the modified polytetrafluoroethylene dispersion was determined using a rotational rheometer.

[0041] 3. PTFE film thickness testing method: The thickness of the film sample is tested using a digital thickness gauge in accordance with GB / T 6672-2001, with 20 thickness test points.

[0042] 4. The tensile properties of the PTFE film were tested using a universal testing machine.

[0043] Example 1

[0044] The specific steps of the method for directly preparing PTFE films using polytetrafluoroethylene dispersion are as follows:

[0045] (1) Add 0.15g of small molecule modifier n-pentadecanol (analytical grade) to 100g of polytetrafluoroethylene dispersion with a solid content of 60wt%; wherein the number average molecular weight of polytetrafluoroethylene in the polytetrafluoroethylene dispersion is 700,000; and the size of PTFE particles in the dispersion is 150nm.

[0046] First, stir at a high speed of 1500 rpm for 10 min, then stir at a low speed of 400 rpm for 10 min; to obtain a modified polytetrafluoroethylene dispersion.

[0047] (2) The modified polytetrafluoroethylene dispersion was cast onto the substrate material, dried at 40°C for 10 min, and then sintered at 365°C for 15 min to form the product.

[0048] (3) The sintered film is peeled off from the substrate material and wound up to directly prepare a PTFE film with a thickness of 35±0.2μm and a width of 1.2m. Commercially available 35-micron-level machined PTFE film material, after testing, has a thickness of 35±1.2μm. The comparison shows that the PTFE film prepared in this embodiment has better thickness uniformity; the thickness fluctuation range of the film obtained in this embodiment is only 0.2μm, while the thickness fluctuation range of commercially available machined films of the same thickness is 1.2μm.

[0049] Depend on Figure 1 It is evident that the three-dimensional physical structure between PTFE particles is more compact.

[0050] Before sintering, the dry films of Example 1 and Comparative Example 1 were observed using an optical microscope. Figure 3 As can be seen, compared to the morphology of the dry film in Comparative Example 1, the dry film in Example 1 has a more uniform distribution of cracks and defects, and a smaller width. This ensures that after subsequent sintering, the dry film in Example 1 has better molecular chain entanglement, resulting in better mechanical and dielectric properties.

[0051] The dielectric property test results show that the film prepared in this embodiment retains the original dielectric properties of polytetrafluoroethylene (PTFE) at 10 GHz. Due to fewer defects and better interfacial bonding, its dielectric loss is reduced from 0.002 to 0.0008 compared to Comparative Example 1. This indicates that the uniformity, mechanical strength, and dielectric properties of the PTFE film material prepared in this embodiment are significantly improved, and it can be applied in fields such as machinery, automotive, and aerospace.

[0052] Example 2

[0053] The specific steps of the method for directly preparing PTFE films using polytetrafluoroethylene dispersion are as follows:

[0054] (1) Add 0.2g of small molecule modifier n-pentadecanol (analytical grade) to 100g of polytetrafluoroethylene dispersion with a solid content of 60wt%; wherein the number average molecular weight of polytetrafluoroethylene in the polytetrafluoroethylene dispersion is 700,000; and the size of PTFE particles in the dispersion is 150nm.

[0055] First, stir at a high speed of 1500 rpm for 10 min, then stir at a low speed of 400 rpm for 10 min; to obtain a modified polytetrafluoroethylene dispersion.

[0056] (2) The modified polytetrafluoroethylene dispersion was cast onto the substrate material, dried at 60°C for 10 min, and then sintered at 365°C for 20 min to form the product.

[0057] (3) The sintered film is peeled off from the substrate material and wound up to directly prepare a PTFE film with a thickness of 40±0.2μm and a width of 1.2m.

[0058] Example 3

[0059] The specific steps of the method for directly preparing PTFE films using polytetrafluoroethylene dispersion are as follows:

[0060] (1) First, 0.0015g of synergist modified hydrogenated castor oil was added to 0.15g of small molecule modifier n-pentadecanol (analytical grade) to prepare a composite reinforcing modifier;

[0061] Then, the obtained composite reinforcing modifier was added to 100g of polytetrafluoroethylene dispersion with a solid content of 60wt%; wherein the number average molecular weight of polytetrafluoroethylene in the polytetrafluoroethylene dispersion was 700,000; and the PTFE particle size in the dispersion was 150nm.

[0062] First, stir at a high speed of 1500 rpm for 10 min, then stir at a low speed of 400 rpm for 10 min; to obtain a modified polytetrafluoroethylene dispersion.

[0063] (2) The modified polytetrafluoroethylene dispersion was cast onto the substrate material, dried at 40°C for 10 min, and then sintered at 365°C for 10 min to form the product.

[0064] (3) The sintered film is peeled off from the substrate material and wound up to directly prepare a PTFE film with a thickness of 2±0.01μm and a width of 1.0m.

[0065] The minimum thickness of polytetrafluoroethylene (PTFE) film materials prepared by traditional turning processes is 20-30 μm, and the thickness uniformity is poor, making it impossible to obtain PTFE film materials with a thickness of 2±0.2 μm.

[0066] Example 4

[0067] The specific steps of the method for directly preparing PTFE films using polytetrafluoroethylene dispersion are as follows:

[0068] (1) First, 0.0015g of synergist polymethyl methacrylate (molecular weight 2000) was added to 0.2g of small molecule modifier n-decane (analytical grade) to prepare a composite reinforcing modifier;

[0069] Then, the obtained composite reinforcing modifier was added to 100g of polytetrafluoroethylene dispersion with a solid content of 60wt%; wherein the number average molecular weight of polytetrafluoroethylene in the polytetrafluoroethylene dispersion was 700,000; and the PTFE particle size in the dispersion was 150nm.

[0070] First, stir at a high speed of 1500 rpm for 10 min, then stir at a low speed of 400 rpm for 10 min; to obtain a modified polytetrafluoroethylene dispersion.

[0071] (2) The modified polytetrafluoroethylene dispersion was cast onto the substrate material, dried at 50°C for 10 min, and then sintered at 365°C for 20 min to form the product.

[0072] (3) The sintered film is peeled off from the substrate material and wound up to directly prepare a PTFE film with a thickness of 10±0.03μm and a width of 1.0m.

[0073] Optical microscopy revealed that the sintered film in Example 4 was basically free of micro-defects such as cracks.

[0074] Example 5

[0075] The specific steps of the method for directly preparing PTFE films using polytetrafluoroethylene dispersion are as follows:

[0076] (1) Add 0.5g of small molecule modifier n-pentadecanol (analytical grade) to 100g of polytetrafluoroethylene dispersion with a solid content of 60wt%; wherein the number average molecular weight of polytetrafluoroethylene in the polytetrafluoroethylene dispersion is 700,000; and the size of PTFE particles in the dispersion is 150nm.

[0077] First, stir at a high speed of 1500 rpm for 20 min, then stir at a low speed of 500 rpm for 10 min; to obtain a modified polytetrafluoroethylene dispersion.

[0078] (2) The modified polytetrafluoroethylene dispersion was cast onto the substrate material, dried at 20°C for 40 min, and then sintered at 390°C for 20 min to form the product.

[0079] (3) The sintered film is peeled off from the substrate material and wound up to directly prepare a PTFE film with a thickness of 10±0.01μm and a width of 1.5m.

[0080] Comparative Example 1

[0081] The difference between this comparative example and Example 1 is that the small molecule modifier n-pentadecanol was not added; otherwise, it is the same as Example 1, including the thickness of the resulting film.

[0082] Comparative Example 2

[0083] The difference between this comparative example and Example 2 is that the small molecule modifier n-pentadecanol was not added; otherwise, it is the same as Example 1, including the thickness of the resulting film.

[0084] Comparative Example 3

[0085] The difference between this comparative example and Example 3 is that the small molecule modifier n-pentadecanol was not added; otherwise, it is the same as Example 1, including the thickness of the resulting film.

[0086] Due to the large number of micro-defects in the film obtained in Comparative Example 3, only film fragments with an area of ​​about 1×1cm could be peeled off, and large-area complete polytetrafluoroethylene films could not be obtained. Therefore, subsequent mechanical property tests could not be performed.

[0087] Comparative Example 4

[0088] The difference between this comparative example and Example 4 is that the small molecule modifier n-decane was not added; otherwise, it is the same as Example 1, including the thickness of the resulting film.

[0089] Due to the large number of micro-defects in the film obtained in Comparative Example 4, only film fragments with an area of ​​about 2×2cm could be peeled off, and large-area complete polytetrafluoroethylene films could not be obtained. Therefore, subsequent mechanical property tests could not be performed.

[0090] Comparative Example 5

[0091] The difference between this comparative example and Example 5 is that the small molecule modifier n-pentadecanol was not added; otherwise, it is the same as Example 1, including the thickness of the resulting film.

[0092] Due to the large number of micro-defects in the film obtained in Comparative Example 5, it was impossible to obtain a large-format, complete polytetrafluoroethylene film, and therefore subsequent mechanical property tests could not be performed.

[0093] Comparative Example 6

[0094] The specific steps of the method for directly preparing PTFE films using polytetrafluoroethylene dispersion are as follows:

[0095] (1) Add 0.15g of ethanol (analytical grade) to 100g of polytetrafluoroethylene dispersion with a solid content of 60wt%; wherein the number average molecular weight of polytetrafluoroethylene in the polytetrafluoroethylene dispersion is 700,000; and the size of PTFE particles in the dispersion is 150nm.

[0096] First, stir at a high speed of 1500 rpm for 10 min, then stir at a low speed of 400 rpm for 10 min; to obtain a modified polytetrafluoroethylene dispersion.

[0097] (2) The modified polytetrafluoroethylene dispersion was cast onto the substrate material, dried at 40°C for 10 min, and then sintered at 365°C for 15 min to form the product.

[0098] (3) Separate the sintered film from the substrate material.

[0099] Although both are alcohols, ethanol cannot form a three-dimensional physical network between PTFE particles and polytetrafluoroethylene dispersions. During the drying process, there are too many film cracks, and only film fragments with an area of ​​about 0.5×0.5cm and a thickness of 25μm can be peeled off. It is impossible to obtain a large-format complete polytetrafluoroethylene film, so subsequent tests cannot be carried out.

[0100] The properties of the modified polytetrafluoroethylene dispersions and the resulting PTFE films described in Examples 1-5 and Comparative Examples 1-5 were measured below, and the detailed indicators are shown in Table 1.

[0101] Table 1

[0102]

Claims

1. A method for directly preparing PTFE films using a polytetrafluoroethylene dispersion, characterized in that, Polytetrafluoroethylene (PTFE) films are directly prepared from PTFE dispersions through film formation, drying, sintering, and winding. Specifically, the following steps are included: (1) Add a small molecule modifier to the polytetrafluoroethylene dispersion; stir; and obtain a modified polytetrafluoroethylene dispersion; wherein the small molecule modifier is a non-polar liquid with a molecular weight of less than 1000; and the three-phase contact angle between the small molecule modifier and PTFE particles and water in the polytetrafluoroethylene dispersion is less than 90°. The small molecule modifier is one or more of n-pentadecanol, n-decane, white oil or paraffin oil. The amount of the small molecule modifier added is 0.01-6% of the solid mass of the polytetrafluoroethylene dispersion; (2) The modified polytetrafluoroethylene dispersion is cast or coated onto the substrate material and dried to form a film; then it is sintered and molded. (3) The sintered film is peeled off from the substrate material and wound up to directly prepare a PTFE film.

2. The method for directly preparing PTFE films using polytetrafluoroethylene dispersion according to claim 1, characterized in that, The solid content of the polytetrafluoroethylene dispersion in step (1) is 55-65 wt%; the number average molecular weight of polytetrafluoroethylene in the polytetrafluoroethylene dispersion is 500,000 to 2,000,000; and the particle size of PTFE in the dispersion is 150 to 220 nm.

3. The method for directly preparing PTFE films using polytetrafluoroethylene dispersion according to claim 1, characterized in that, The specific operation of stirring in step (1) is as follows: first stir at high speed of 800~2500 rpm for 5~20 min, then stir at low speed of 300~500 rpm for 5~10 min.

4. The method for directly preparing PTFE films using polytetrafluoroethylene dispersion according to claim 1, characterized in that, In step (1), an synergist is also added, which is one or more of modified hydrogenated castor oil, organobentonite, or polymethyl methacrylate.

5. The method for directly preparing PTFE films using polytetrafluoroethylene dispersion according to claim 4, characterized in that, In step (1), the amount of synergist added is 0-6% of the mass of the small molecule modifier.

6. The method for directly preparing PTFE films using polytetrafluoroethylene dispersion according to claim 1, characterized in that, In step (2), the film-forming drying temperature is 20-60℃ and the film-forming drying time is 5-90min; the sintering temperature is 340~400℃ and the sintering time is 10-60min.

7. A PTFE film, characterized in that, The PTFE film is prepared directly from a polytetrafluoroethylene dispersion according to any one of claims 1-6; the thickness of the PTFE film is 1-200 μm; the width is 0.05-2 m; the tensile strength of the film is 22-31 MPa; the elongation at break is 190-300%; and the dielectric loss is 0.0003-0.0008.

8. The application of a PTFE film prepared by the method of directly preparing PTFE film using polytetrafluoroethylene dispersion as described in any one of claims 1-6 in the field of dielectric materials.

Images