Fiber composite material for insulating support cylinder as well as preparation method and application of fiber composite material

Abstract

The invention discloses a fiber composite material for an insulating support cylinder and a preparation method and application thereof, and relates to the technical field of composite materials. The fiber composite material for the insulating support cylinder, provided by the invention, comprises 5-15 parts of boron nitride nanotubes, 30-40 parts of epoxy resin and 50-60 parts of fibers, the boron nitride nanotubes are subjected to fluoridation treatment, so that the boron nitride nanotubes have surface electronegativity and can be directionally arranged under the induction of an external electric field to form a heat conduction path, and the heat conductivity coefficient of the composite material can be increased to 0.45 W / mK or above, and meanwhile, the boron nitride nanotubes subjected to fluoridation treatment have higher surface roughness, so that the heat conductivity coefficient of the composite material can be increased to 0.45 W / mK or above. The binding force between the fiber and the resin can be improved, so that the insulativity of the composite material can be improved, and the resistivity of the composite material is up to 3.7 * 10 < 15 > omega.cm.

Description

Technical Field

[0001] The present invention relates to the technical field of composite materials, and in particular to a fiber composite material for an insulating support tube, a preparation method and application thereof. Background Art

[0002] The insulating support tube is a key component in the dry-type transformer. Its main function is to insulate the high-voltage winding and the low-voltage winding respectively and serve as the supporting skeleton of the dry-type transformer. When the dry-type transformer is in operation, the high-voltage and low-voltage windings will generate a lot of heat. At this time, the insulating support tube will also serve as the main airway for the heat dissipation of the windings, which places high demands on the insulation and thermal conductivity of the insulating support tube material.

[0003] Existing insulation support tube materials are usually composite materials of epoxy resin and glass fiber or aramid fiber. However, due to the smooth surface and chemical inertness of glass fiber and aramid fiber, their dispersion is poor and their interfacial bonding ability with epoxy resin is insufficient, which easily leads to defects such as dry spots and air gaps inside the insulation tube support, which in turn leads to a significant decrease in the insulation and thermal conductivity of the insulation support tube. Therefore, the interfacial bonding between the reinforcing fiber and the epoxy resin has important engineering practical value for improving the performance of the insulation support tube. Summary of the invention

[0004] In order to solve the deficiencies of the prior art, the present invention provides a fiber composite material for an insulating support tube, wherein the fluorinated boron nitride nanotubes have a higher surface roughness, thereby promoting the interface bonding between the epoxy resin and the fiber, and the fluorinated boron nitride nanotubes can be oriented under the induction of an external electric field to form a heat conduction path, and also reduce the probability of agglomeration. Therefore, the composite material provided by the present invention has excellent insulation and thermal conductivity.

[0005] Another object of the present invention is to provide a method for preparing a fiber composite material for an insulating support tube.

[0006] Another object of the present invention is to provide an insulating support cylinder.

[0007] The above-mentioned purpose of the present invention is achieved through the following technical solutions:

[0008] A fiber composite material for an insulating support tube, comprising the following components calculated by mass:

[0009] 5-15 parts of boron nitride nanotubes, 30-40 parts of epoxy resin, and 50-60 parts of fiber;

[0010] The boron nitride nanotubes are arranged in a directional manner in the fiber composite material for the insulating support tube;

[0011] The boron nitride nanotubes are subjected to fluorination treatment, and the fluorination treatment temperature is ≤60°C.

[0012] Introducing boron nitride nanoparticles in fiber composite materials is a common way to modify composite materials, which can significantly improve the thermal conductivity of materials, but this approach is very easy to cause particle agglomeration, resulting in a significant decrease in the thermal conductivity of the prepared product. Therefore, in the composite material provided by the present invention, nanotube-shaped boron nitride is selected as a thermal conductive filler, and the boron nitride nanotubes are fluorinated and modified at the same time. The resulting fluorinated boron nitride nanotubes have electronegativity on the surface, and can be oriented under the induction of an external electric field, similar to "turning in place", and then arranged in a directional manner in the fiber composite material for the insulating support tube, forming a good thermal conductive path, and the presence of surface electronegativity causes the nanotube-shaped boron nitride to have charge repulsion between each other, so the probability of filler agglomeration decreases. In addition, due to the fluorination modification, the roughness of the surface of the boron nitride nanotube increases, and the specific surface area increases therewith, which is conducive to improving the interface bonding between epoxy resin and fiber in the fiber composite material, so the insulation performance of the composite material for the insulating support tube can be significantly improved.

[0013] It should be noted that in order to take into account both the thermal conductivity and insulation performance of the fiber composite material for the insulating support tube, it is necessary to control the temperature of the fluorination modification of the boron nitride nanotubes and the amount of fluorinated boron nitride nanotubes added to the composite material. If the temperature of the fluorination modification is too high, it is not conducive to improving the insulation performance. It is speculated that this may be because the degree of fluorination on the surface of the boron nitride is increased, which in turn leads to an increase in the conductivity of the filler. Adding too much fluorinated boron nitride nanotubes will also lead to an increase in conductivity.

[0014] Preferably, the boron nitride nanotube has a length of 5 to 10 μm and a diameter of 30 to 50 nm.

[0015] The inventors have experimentally confirmed that the boron nitride nanotubes with the above morphological characteristics can be oriented parallel to the direction of the electric field under the induction of an external electric field after fluorination modification, which is beneficial to forming a heat conduction path and improving the thermal conductivity of the insulating support tube.

[0016] Preferably, the fluorination treatment of the boron nitride nanotubes is carried out using fluorine-nitrogen gas, and the fluorine-nitrogen gas comprises fluorine gas and nitrogen gas in a volume ratio of (15-25):(75-85).

[0017] Preferably, the pressure of the fluorine-nitrogen gas is 2-5 kPa.

[0018] Preferably, the fluorination treatment time is ≤90 min.

[0019] More preferably, the fluorination treatment time is 15 to 60 minutes.

[0020] In a specific embodiment of the present invention, the boron nitride nanotubes further include a drying step before the fluorination treatment. More specifically, the drying step is performed at 60-80° C. for 3-8 hours.

[0021] Preferably, the fiber includes at least one of glass fiber and aramid fiber, and the epoxy resin includes bisphenol A epoxy resin.

[0022] In a specific embodiment of the present invention, the glass fibers include E-glass fibers.

[0023] Preferably, the fiber composite material for the insulating support tube comprises the following components calculated by mass:

[0024] 5-15 parts of boron nitride nanotubes, 34-38 parts of epoxy resin, and 51-57 parts of fibers.

[0025] The present invention also protects a method for preparing the fiber composite material for the insulating support tube, comprising the following steps:

[0026] Boron nitride nanotubes, epoxy resin and fibers are mixed, a direct current electric field is applied to induce directional arrangement of the boron nitride nanotubes, and then the fiber composite material for the insulating support tube is obtained after curing at 80 to 140°C.

[0027] Preferably, the intensity of the DC electric field is 10-1000 V / mm.

[0028] More preferably, the intensity of the DC electric field is 100-200 V / mm.

[0029] Preferably, the time for applying the DC electric field to induce the oriented arrangement of the boron nitride nanotubes is 30 to 90 minutes.

[0030] Preferably, the curing is performed at 80-120° C. for 2-4 hours and then at 120-140° C. for 3-5 hours.

[0031] In a specific embodiment of the present invention, the mixing is to mix the boron nitride nanotubes and the epoxy resin, and then add them into the mold wrapped with the fiber.

[0032] More specifically, the step of mixing the boron nitride nanotubes and the epoxy resin is to mechanically stir the mixture of the boron nitride nanotubes and the epoxy resin, and the mechanical stirring time is 30 minutes.

[0033] More specifically, the mold comprises two concentric metal cylinders, the inner cylinder has a diameter of 9 to 13 cm, the outer cylinder has a diameter of 13 to 30 cm, and the outer cylinder has a diameter greater than the inner cylinder. More specifically, the metal cylinder is a stainless steel cylinder.

[0034] In a specific embodiment of the present invention, the DC electric field is a DC electric field applied between two concentric metal cylinders, and the direction of the DC electric field can be from the outer cylinder to the inner cylinder, or from the inner cylinder to the outer cylinder.

[0035] In a specific embodiment of the present invention, the fiber layers in the fiber-wrapped mold are 4 to 10 layers.

[0036] The present invention also protects an insulating support tube made of the above-mentioned fiber composite material for the insulating support tube.

[0037] Compared with the prior art, the present invention has the following beneficial effects:

[0038] In the fiber composite material for the insulating support tube provided by the present invention, the boron nitride nanotubes after fluorination treatment have surface electronegativity, can be oriented and arranged to form a heat conduction path under the induction of an external electric field, and can increase the thermal conductivity of the composite material to above 0.45 W / m·K. At the same time, the fluorinated boron nitride nanotubes have a higher surface roughness, which can improve the bonding force between the fiber and the resin, thereby improving the insulation of the composite material. The resistivity of the composite material is as high as 3.7×10 15 Ω·cm. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 The present invention is a flow chart of a method for preparing a fiber composite material for an insulating support tube. DETAILED DESCRIPTION

[0040] The present invention is further described below in conjunction with specific embodiments, but the embodiments do not limit the present invention in any form. Unless otherwise specified, the raw materials and reagents used in the embodiments of the present invention are conventionally purchased raw materials and reagents. Among them, the raw material information used in each embodiment and comparative example is as follows:

[0041] Boron nitride nanotubes: Product model BNNT-103, purchased from Shanghai Boron Ju New Material Technology Co., Ltd., with a specific surface area of ​​40m 2 / g, length 5-10μm, diameter 30-50nm.

[0042] Epoxy resin: EPIKOTE 828 bisphenol A epoxy resin, purchased from Hexion, USA.

[0043] Example 1

[0044] A fiber composite material for an insulating support tube, comprising the following components calculated by mass:

[0045] 5 parts of boron nitride nanotubes, 38 parts of epoxy resin, 57 parts of E-glass fiber;

[0046] The boron nitride nanotubes are subjected to fluorination treatment, comprising the following steps:

[0047] The boron nitride nanotubes are dried at 70° C. for 5 hours, and then fluorinated under fluorine-nitrogen gas at room temperature for 15 minutes to obtain the boron nitride nanotubes; the pressure of the fluorine-nitrogen gas is 3 kPa, and the volume proportion of fluorine gas in the fluorine-nitrogen gas is 20%.

[0048] The method for preparing the fiber composite material for the insulating support tube in this embodiment includes the following steps:

[0049] The glass fiber is wound in parallel on the inner cylinder of a mold including inner and outer concentric stainless steel cylinders, and a mixture of boron nitride nanotubes and epoxy resin is added after winding for 5 layers; the diameter of the inner cylinder in the mold is 9 cm, and the diameter of the outer cylinder is 13 cm; the mixture of boron nitride nanotubes and epoxy resin is prepared by mixing the boron nitride nanotubes and epoxy resin and mechanically stirring for 30 minutes;

[0050] The DC high voltage is connected to the inner cylinder of the mold through a protective resistor, the outer cylinder is grounded, and a DC electric field of 100V / mm is applied to induce the directional arrangement of the boron nitride nanotubes. The DC electric field is applied for 60 minutes. After induction, it is cured at 100°C for 3 hours, and then continued to cure at 130°C for 4 hours to obtain a fiber composite material for the insulating support cylinder.

[0051] Example 2

[0052] A fiber composite material for an insulating support tube, which is different from Example 1 only in that:

[0053] The time for the fluorination treatment of the boron nitride nanotubes is 30 minutes, and the mass proportions of the boron nitride nanotubes, epoxy resin and glass fiber are 15 parts, 34 parts and 51 parts respectively.

[0054] The method for preparing the fiber composite material for the insulating support tube in this embodiment is different from that in Embodiment 1 only in that:

[0055] The strength of the DC electric field is 150 V / mm.

[0056] Example 3

[0057] A fiber composite material for an insulating support tube, which is different from Example 1 only in that:

[0058] The mass proportions of boron nitride nanotubes, epoxy resin and glass fiber are 10 parts, 35 parts and 55 parts respectively.

[0059] The preparation method of the fiber composite material for the insulating support tube in this embodiment is consistent with that in Embodiment 1.

[0060] Example 4

[0061] A fiber composite material for an insulating support tube, which is different from Example 1 only in that:

[0062] The fluorination time of the boron nitride nanotubes is 75 minutes.

[0063] The preparation method of the fiber composite material for the insulating support tube in this embodiment is consistent with that in Embodiment 1.

[0064] Example 5

[0065] A fiber composite material for an insulating support tube, which is different from Example 1 only in that:

[0066] The pressure of the fluorine-nitrogen gas used in the fluorination treatment of the boron nitride nanotubes is 5 kPa, wherein the volume proportion of the fluorine gas is 15%.

[0067] The preparation method of the fiber composite material for the insulating support tube in this embodiment is consistent with that in Embodiment 1.

[0068] Example 6

[0069] A fiber composite material for an insulating support tube, which is different from Example 1 only in that:

[0070] The pressure of the fluorine-nitrogen gas used in the fluorination treatment of the boron nitride nanotubes is 2 kPa, wherein the volume proportion of the fluorine gas is 25%.

[0071] The preparation method of the fiber composite material for the insulating support tube in this embodiment is consistent with that in Embodiment 1.

[0072] Example 7

[0073] A fiber composite material for an insulating support tube, which is different from Example 1 only in that:

[0074] In the method for preparing the fiber composite material for the insulating support tube in this embodiment, the intensity of the DC electric field is 1000 V / mm.

[0075] Example 8

[0076] A fiber composite material for an insulating support tube, which is different from Example 1 only in that:

[0077] In the method for preparing the fiber composite material for the insulating support tube in this embodiment, the intensity of the DC electric field is 10 V / mm.

[0078] Comparative Example 1

[0079] A fiber composite material for an insulating support tube, which is different from Example 1 only in that:

[0080] The pressure of fluorine-nitrogen gas used in the fluorination treatment of boron nitride nanotubes is 5 kPa, the fluorination time is 60 minutes, and the mass proportions of boron nitride nanotubes, epoxy resin and glass fiber are 30 parts, 28 parts and 42 parts respectively.

[0081] The preparation method of the fiber composite material for the insulating support tube in this comparative example is different from that in Example 1 only in that:

[0082] The strength of the DC electric field is 200 V / mm.

[0083] Comparative Example 2

[0084] A fiber composite material for an insulating support tube, which is different from Example 1 only in that:

[0085] The fluorination treatment of the boron nitride nanotubes was carried out under fluorine and nitrogen gas at 200°C.

[0086] The preparation method of the fiber composite material for the insulating support tube in this comparative example is different from that in Example 1 only in that:

[0087] The strength of the DC electric field is 200 V / mm.

[0088] Performance Testing

[0089] The fiber composite materials for insulating support tubes prepared in the examples and comparative examples were tested for thermal conductivity and resistivity, and specific performance test data are shown in Table 1 below:

[0090] Table 1. Thermal conductivity and resistivity of materials obtained in Examples and Comparative Examples

[0091] Group Thermal conductivity (W / m·K) Resistivity (Ω·cm) Example 1 0.45 <![CDATA[5.00×10 15 ]]> Example 2 0.51 <![CDATA[4.80×10 15 ]]> Example 3 0.65 <![CDATA[5.50×10 15 ]]> Example 4 0.51 <![CDATA[4.39×10 15 ]]> Example 5 0.49 <![CDATA[4.83×10 15 ]]> Example 6 0.45 <![CDATA[5.10×10 15 ]]> Example 7 0.55 <![CDATA[3.70×10 15 ]]> Example 8 0.32 <![CDATA[4.50×10 15 ]]> Comparative Example 1 0.85 <![CDATA[1.20×10 15 ]]> Comparative Example 2 0.77 <![CDATA[2.00×10 15 ]]>

[0092] As can be seen from Table 1 above, the fiber composite material for the insulating support tube prepared in the present invention uses nanotube-shaped boron nitride as a thermally conductive filler, and the boron nitride nanotubes are fluorinated. The resulting fluorinated boron nitride nanotubes have negative electronegativity on the surface and can undergo dipole polarization orientation under the induction of an external electric field, similar to "turning on the spot", and then are arranged in a directional manner in the fiber composite material for the insulating support tube, forming a good thermal conductive path. The presence of surface electronegativity makes the nanotube-shaped boron nitride have charge repulsion between each other, so the probability of filler agglomeration is reduced. In addition, due to the fluorination modification, the roughness of the surface of the boron nitride nanotube increases, and the specific surface area increases accordingly, which is beneficial to improve the interface bonding between the epoxy resin and the fiber in the fiber composite material, so that the insulation and thermal conductivity of the composite material for the insulating support tube can be significantly improved, and the thermal conductivity coefficient can reach more than 0.45W / m·K, and the resistivity is as high as 3.7×10 15 Ω·cm or more.

[0093] According to Examples 1 to 3, in the fiber composite material for the insulating support tube provided by the present invention, when the mass fractions of each component are 10 parts of boron nitride nanotubes, 35 parts of epoxy resin and 55 parts of glass fiber (Example 3), the performance of the obtained composite material is optimal, while the mass fractions of the three components are increased or decreased respectively, and the comprehensive performance of the obtained composite material is reduced (Examples 1 to 2). Therefore, the preferred composite material of the present invention includes 5 to 15 parts of boron nitride nanotubes, 34 to 38 parts of epoxy resin, and 51 to 57 parts of fiber.

[0094] According to Examples 1 and 4, the fluorination time of boron nitride nanotubes reaches 75 minutes, and the insulation and thermal conductivity of the obtained composite material are reduced, indicating that too high a degree of fluorination will also lead to performance degradation. Therefore, the present invention preferably has a fluorination time of ≤90 minutes, and more preferably a fluorination time of 15 to 60 minutes.

[0095] According to Examples 1, 5-6, the boron nitride nanotubes may be fluorinated using fluorine-nitrogen gas at a pressure of 2-5 kPa and a volume ratio of fluorine gas to nitrogen of (15-25):(75-85).

[0096] According to Examples 1, 7 to 8, when a direct current electric field is used to induce directional alignment of boron nitride nanotubes, when the intensity of the electric field is within the more preferred range of 100 to 200 V / mm (Example 1) of the present invention, the comprehensive performance of the obtained composite material is better.

[0097] According to Comparative Example 1, the amount of fluorinated boron nitride nanotubes added is too much. Although the thermal conductivity is improved, the electrical conductivity of the composite material is also increased, which is not conducive to improving the insulation performance.

[0098] According to Comparative Example 2, when the boron nitride nanotubes were fluorinated with fluorine and nitrogen, the temperature was too high, which was not conducive to improving the insulation performance. It is speculated that this may be because the degree of fluorination on the surface of the boron nitride increased, which in turn led to an increase in the conductivity of the filler.

[0099] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the essence and scope of the technical solution of the present invention.

Claims

1. A fiber composite material for an insulating support tube, characterized in that: It includes the following components calculated by mass: 5-15 parts of boron nitride nanotubes, 30-40 parts of epoxy resin, and 50-60 parts of fiber; The boron nitride nanotubes are arranged in a directional manner in the fiber composite material for the insulating support tube; The boron nitride nanotubes are subjected to fluorination treatment, and the fluorination treatment temperature is ≤60°C.

2. The fiber composite material for the insulating support tube according to claim 1, characterized in that: The boron nitride nanotube has a length of 5 to 10 μm and a diameter of 30 to 50 nm.

3. The fiber composite material for the insulating support tube according to claim 1, characterized in that: The boron nitride nanotubes are fluorinated using fluorine-nitrogen gas, wherein the fluorine-nitrogen gas comprises fluorine gas and nitrogen gas in a volume ratio of (15-25):(75-85).

4. The fiber composite material for the insulating support tube according to claim 3, characterized in that: The pressure of the fluorine and nitrogen gas is 2-5 kPa.

5. The fiber composite material for the insulating support tube according to claim 1, characterized in that: The fluorination treatment time is 15 to 60 minutes.

6. The fiber composite material for the insulating support tube according to claim 1, characterized in that: The fiber includes at least one of glass fiber and aramid fiber, and the epoxy resin includes bisphenol A epoxy resin.

7. The method for preparing the fiber composite material for the insulating support tube according to any one of claims 1 to 6, characterized in that: The steps include: Boron nitride nanotubes, epoxy resin and fibers are mixed, a direct current electric field is applied to induce the directional arrangement of the boron nitride nanotubes, and then the fiber composite material for the insulating support tube is obtained after curing at 80 to 140°C.

8. The preparation method according to claim 7, characterized in that: The intensity of the DC electric field is 100-200 V / mm.

9. The preparation method according to claim 8, characterized in that: The time for applying the direct current electric field to induce the directional arrangement of the boron nitride nanotubes is 30 to 90 minutes.

10. An insulating support tube made of the fiber composite material for an insulating support tube according to any one of claims 1 to 6.

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