Preparation method of high-temperature-resistant insulating adhesive based on crosslinking of boron nitride whiskers and organic silicon microspheres

Abstract

The invention discloses a preparation method of a high-temperature-resistant insulating adhesive based on crosslinking of boron nitride whiskers and organic silicon microspheres, and relates to the technical field of phosphate adhesive modification. The purpose of the invention is to solve the problem that the traditional phosphate adhesive is low in bonding strength, high in brittleness and poor in insulating property due to the fact that most of the traditional phosphate adhesives are aluminum phosphate systems, so that the assembly requirements of aircraft sensors cannot be met. Magnesium dihydrogen phosphate and organic silicon microspheres in the adhesive have high volume resistance, so that the insulating property of the adhesive can be effectively improved; more importantly, the boron nitride whiskers and the organic silicon microspheres can form a network interpenetrating structure, the microspheres are distributed among whisker networks, the whisker networks can provide high strength and high modulus, and the microspheres absorb energy and prevent crack propagation through elastic deformation, so that the toughness and mechanical properties of the phosphate adhesive at high temperature are remarkably improved. The preparation method of the high-temperature-resistant insulating adhesive based on crosslinking of the boron nitride whiskers and the organic silicon microspheres can be obtained.

Description

Technical Field

[0001] The present invention relates to the technical field of phosphate adhesive modification, and particularly relates to a preparation method of a high-temperature resistant insulating adhesive based on crosslinking of boron nitride whiskers and silicone microspheres. Background Art

[0002] In the aerospace field, tungsten rhenium (W-Re) thermocouples are one of the most commonly used high-temperature sensors and are widely used in the real-time temperature monitoring system of aircraft. In order to ensure the safe operation of tungsten rhenium (W-Re) thermocouples under severe thermal and mechanical environments, high-temperature resistant insulating adhesives are usually used to bond and encapsulate the sensors. In recent years, with the rapid development of aircraft speed, the operating temperature of tungsten rhenium thermocouples under extreme conditions can reach above 1500 °C, which poses extremely harsh requirements on high-temperature resistant insulating adhesives.

[0003] Currently, room-temperature curing high-temperature resistant insulating adhesives (1500 °C) mainly include the following categories: organic-inorganic hybrid adhesives and inorganic adhesives. Among them, organic-inorganic hybrid adhesives have excellent mechanical properties, but are prone to produce volatile components at high temperatures. At the same time, after the organic components volatilize, a large number of pores are generated in the adhesive, and the high-temperature mechanical properties decrease sharply. Commonly used inorganic adhesives include two categories: phosphates and silicates. The service temperature of silicate adhesives is usually below 1200 °C, which is difficult to meet the working conditions requirements. Phosphate adhesives have advantages such as excellent dielectric resistance and low curing shrinkage rate, but have defects such as poor insulation performance and high-temperature mechanical properties.

[0004] In summary, currently traditional phosphate adhesives are mostly aluminum phosphate systems, and still have problems such as low bonding strength, brittleness, and poor insulation performance, resulting in inability to meet the assembly requirements of aircraft sensors. Summary of the Invention

[0005] The purpose of the present invention is to solve the problem that traditional phosphate adhesives are mostly aluminum phosphate systems, which have low bonding strength, brittleness, and poor insulation performance, and thus cannot meet the assembly requirements of aircraft sensors, and to provide a preparation method of a high-temperature resistant insulating adhesive based on crosslinking of boron nitride whiskers and silicone microspheres.

[0006] A preparation method of a high-temperature resistant insulating adhesive based on crosslinking of boron nitride whiskers and silicone microspheres is carried out according to the following steps:

[0007] Step S1, modification of silicone microspheres:

[0008] Add silicone microspheres and KH550 solution into absolute ethanol, heat to 58 - 62 °C, and stir and react at 58 - 62 °C for 9.9 - 10.1 min. Then raise the temperature to 78 - 82 °C, and magnetically stir at 78 - 82 °C for 2.99 - 3.01 h. Then dry at 58 - 62 °C to obtain KH550-modified silicone microspheres;

[0009] Step S2: Prepare zirconium dihydrogen phosphate resin:

[0010] Mix phosphoric acid and zirconium hydroxide, then place it in a condensing reflux device, react at 78 - 82 °C until the solution is clear, and continue to stir and react for 20 - 30 min; After the reaction, cool to room temperature to obtain zirconium dihydrogen phosphate resin;

[0011] Step S3: Prepare phosphate curing agent:

[0012] Mix the KH550-modified silicone microspheres obtained in step S1 with alumina and boron nitride whiskers, and after fully ball-milling and dispersing, obtain a phosphate curing agent;

[0013] The mass ratio of the KH550-modified silicone microspheres to the boron nitride whiskers is (0.99 - 1.01):(0.99 - 1.01);

[0014] Step S4: Prepare high-temperature resistant insulating adhesive:

[0015] Fully stir and mix the zirconium dihydrogen phosphate resin obtained in step S2 with the phosphate curing agent obtained in step S3, and then cure at 21 - 25 °C for 47.99 - 48.01 h to obtain a high-temperature resistant insulating adhesive cross-linked based on boron nitride whiskers and silicone microspheres;

[0016] The mass ratio of the zirconium dihydrogen phosphate resin to the phosphate curing agent is (0.99 - 1.01):(0.99 - 1.01).

[0017] Advantages of the present invention:

[0018] (1) In the present invention, both magnesium dihydrogen phosphate and silicone microspheres have high volume resistivity, which can effectively improve the insulation performance of the adhesive; More importantly, boron nitride whiskers and silicone microspheres can form an interpenetrating network structure. The microspheres are distributed among the whisker networks. The whisker network can provide high strength and high modulus, while the microspheres absorb energy through elastic deformation to prevent crack propagation, significantly improving the toughness and mechanical properties of the phosphate adhesive at high temperatures.

[0019] (2) The present invention uses zirconium hydroxide to modify the phosphate resin, which can significantly reduce the viscosity of the adhesive and improve its heat resistance and insulation performance.

[0020] (3) In the present invention, the adhesive is toughened and modified by introducing silicone microspheres to cause crosslinking between phosphorus and silicon elements in the phosphate resin, and it can effectively absorb stress in a high-temperature environment, thereby effectively improving the bonding performance of the adhesive.

[0021] The present invention can obtain a preparation method of a high-temperature resistant insulating adhesive based on the crosslinking of boron nitride whiskers and silicone microspheres. Description of the Drawings

[0022] Figure 1 It represents the SEM image of the high-temperature resistant insulating adhesive prepared in Example 1;

[0023] Figure 2 It represents the SEM image of the traditional aluminum phosphate adhesive. Detailed Embodiments

[0024] Detailed Embodiment 1: A preparation method of a high-temperature resistant insulating adhesive based on the crosslinking of boron nitride whiskers and silicone microspheres is carried out according to the following steps:

[0025] Step S1: Modification of silicone microspheres:

[0026] The silicone microspheres and KH550 solution are added to anhydrous ethanol, heated to 58 - 62 °C, and stirred and reacted at 58 - 62 °C for 9.9 - 10.1 min, then heated to 78 - 82 °C and magnetically stirred at 78 - 82 °C for 2.99 - 3.01 h, and then dried at 58 - 62 °C to obtain KH550-modified silicone microspheres;

[0027] Step S2: Preparation of zirconium dihydrogen phosphate resin:

[0028] Phosphoric acid and zirconium hydroxide are mixed and then placed in a reflux condenser, reacted at 78 - 82 °C until the solution becomes clear, and continue to stir and react for 20 - 30 min; after the reaction, it is cooled to room temperature to obtain zirconium dihydrogen phosphate resin;

[0029] Step S3: Preparation of phosphate curing agent:

[0030] The KH550-modified silicone microspheres obtained in Step S1 are mixed with alumina and boron nitride whiskers, and after fully ball-milling and dispersing, a phosphate curing agent is obtained;

[0031] The mass ratio of the KH550-modified silicone microspheres to the boron nitride whiskers is (0.99 - 1.01):(0.99 - 1.01);

[0032] Step S4: Preparation of high-temperature resistant insulating adhesive:

[0033] After thoroughly stirring and mixing the zirconium dihydrogen phosphate resin obtained in step S2 with the phosphate curing agent obtained in step S3, and then curing at a temperature of 21-25 °C for 47.99-48.01 h, a high-temperature resistant insulating adhesive crosslinked based on boron nitride whiskers and silicone microspheres is obtained;

[0034] The mass ratio of the zirconium dihydrogen phosphate resin to the phosphate curing agent is (0.99-1.01):(0.99-1.01).

[0035] Specific Embodiment 2: The difference between this embodiment and Specific Embodiment 1 is that the ratio of the mass of the silicone microspheres, the volume of the KH550 solution, and the volume of absolute ethanol described in step S1 is (9-11) g:(0.8-1.2) mL:(98-102) mL.

[0036] Other steps are the same as those in Specific Embodiment 1.

[0037] Specific Embodiment 3: The difference between this embodiment and Specific Embodiment 1 or 2 is that the silicone microspheres are polymethylsilsesquioxane.

[0038] Other steps are the same as those in Specific Embodiment 1 or 2.

[0039] Specific Embodiment 4: The difference between this embodiment and one of Specific Embodiments 1 to 3 is that in step S1, the reaction is stirred at a rate of 195-205 r / min at a temperature of 58-62 °C for 9.9-10.1 min.

[0040] Other steps are the same as those in Specific Embodiments 1 to 3.

[0041] Specific Embodiment 5: The difference between this embodiment and one of Specific Embodiments 1 to 4 is that in step S1, magnetic stirring is carried out at a rate of 195-205 r / min at a temperature of 78-82 °C for 2.99-3.01 h.

[0042] Other steps are the same as those in Specific Embodiments 1 to 4.

[0043] Specific Embodiment 6: The difference between this embodiment and one of Specific Embodiments 1 to 5 is that the molar ratio of P in phosphoric acid to Zr in zirconium hydroxide in step S2 is 4:1.

[0044] Other steps are the same as those in Specific Embodiments 1 to 5.

[0045] Specific Embodiment 7: The difference between this embodiment and one of Specific Embodiments 1 to 6 is that in step S2, the reaction is carried out at a temperature of 78-82 °C for 12-24 h.

[0046] Other steps are the same as those in Specific Embodiments 1 to 6.

[0047] Embodiment 8 in detail: The difference between this embodiment and any one of Embodiments 1 to 7 is that: in step S3, the mass ratio of the KH550-modified silicone microspheres to alumina is (0.9 to 1.1):(7.5 to 8.5).

[0048] Other steps are the same as those in Embodiments 1 to 7.

[0049] Embodiment 9 in detail: The difference between this embodiment and any one of Embodiments 1 to 8 is that: in step S3, ball milling and dispersing are performed at a rotation speed of 350 r·min -1 for 10 min.

[0050] Other steps are the same as those in Embodiments 1 to 8.

[0051] The following examples are used to verify the beneficial effects of the present invention:

[0052] Example 1: A preparation method of a high-temperature resistant insulating adhesive based on the crosslinking of boron nitride whiskers and silicone microspheres is carried out according to the following steps:

[0053] Step S1, modification of silicone microspheres:

[0054] 10 g of silicone microspheres, 1 mL of KH550 solution and 100 mL of absolute ethanol are added to a beaker, heated to 60 °C, and stirred and reacted at a rate of 200 r / min at a temperature of 60 °C for 10 min, then the temperature is raised to 80 °C, and magnetically stirred at a rate of 200 r / min at a temperature of 80 °C for 3 h, and then washed with deionized water, centrifuged and dried to obtain KH550-modified silicone microspheres;

[0055] The silicone microspheres are polymethylsilsesquioxane;

[0056] Step S2, preparation of magnesium dihydrogen phosphate resin:

[0057] Phosphoric acid and magnesium hydroxide are added to a three-necked flask, and then placed in a condensation reflux device, and reacted at a temperature of 80 °C for 12 h until the solution is clear, and stirring and reacting are continued for 20 to 30 min; after the reaction is completed, it is cooled to room temperature to obtain magnesium dihydrogen phosphate resin;

[0058] The molar ratio of P in phosphoric acid to Zr in zirconium hydroxide is 4:1;

[0059] Step S3, preparation of phosphate curing agent:

[0060] 10 g of the KH550-modified silicone microspheres obtained in step S1, 80 g of alumina and 10 g of boron nitride whiskers are transferred to a dispersing device, and at 350 r·min -1After ball milling and dispersing at a rotational speed for 10 min, a phosphate curing agent is obtained;

[0061] Step S4: Prepare a high-temperature resistant insulating adhesive:

[0062] After fully stirring and mixing 100 g of magnesium dihydrogen phosphate resin obtained in step S2 and 100 g of phosphate curing agent obtained in step S3, and then curing at a temperature of 23 °C for 48 h, a high-temperature resistant insulating adhesive crosslinked based on boron nitride whiskers and silicone microspheres is obtained.

[0063] Comparative Example 1: This comparative example does not set step S1, and the remaining steps are the same, that is: phosphoric acid reacts with aluminum hydroxide at a molar ratio of 3:1 to generate aluminum dihydrogen phosphate resin, and then alumina is used as a curing agent and mixed at a mass ratio of (98 - 102) g:(98 - 102) g, and finally an aluminum phosphate adhesive is obtained.

[0064] Figure 1 It represents the SEM image of the high-temperature resistant insulating adhesive prepared in Example 1; as Figure 1 shown, a interpenetrating network structure is formed between boron nitride whiskers and silicone microspheres in the high-temperature resistant insulating adhesive, and the whiskers are uniformly distributed in the adhesive, constituting a three-dimensional skeleton; the silicone microspheres (with a diameter of about 1 - 3 μm) are filled in the gaps between the whiskers, forming a synergistic toughening effect. Through the stress dispersion of the whiskers and the energy absorption of the microspheres, the initiation and propagation of cracks are significantly inhibited, and no obvious defects are observed on the surface of the adhesive.

[0065] Figure 2 It represents the SEM image of the traditional aluminum phosphate adhesive; as Figure 2 shown, obvious cracks appear in local areas, the crack length is about 1 - 5 μm, and it shows an irregular branched shape. After Figure 1 and Figure 2 comparison, it can be found that the composite design of boron nitride whiskers and silicone microspheres can effectively reduce the microcracks generated during the curing process of the adhesive.

[0066] After inspection, the high-temperature resistant insulating adhesive prepared in this example has a room temperature shear strength ≥ 10 MPa, a shear strength at 1000 °C ≥ 6 MPa, a shear strength at 1500 °C ≥ 4 MPa, a room temperature pot life of up to 60 min, and a normal temperature volume resistivity ≥ 1.1×10 11 Ω·cm. Compared with the traditional aluminum phosphate adhesive, the room temperature shear strength is increased by 58%, the room temperature shear strength at 1000 °C is increased by 47%, the room temperature shear strength at 1500 °C is increased by 64%, and the volume resistivity is increased by 38%.

[0067] Table 1 shows the comparative data of the bonding performance of the high-temperature resistant insulating adhesive prepared in this example and the traditional aluminum phosphate adhesive to the SiC / SiC composite material respectively;

[0068] Table 1

[0069]

Claims

1. A method for preparing a high temperature resistant insulating adhesive based on cross-linking of boron nitride whiskers and silicone microspheres, characterized in that The preparation method is carried out according to the following steps: Step S1, modification of organosilicon microspheres: Adding the organosilicon microspheres and KH550 solution into anhydrous ethanol, heating to 58-62° C., stirring the reaction at 58-62° C. for 9.9-10.1 min, then heating to 78-82° C., magnetically stirring at 78-82° C. for 2.99-3.01 h, and drying at 58-62° C. to obtain KH550-modified organosilicon microspheres; Step S2, preparing zirconium dihydrogen phosphate resin: Phosphoric acid and zirconium hydroxide are mixed, and then placed in a condensation reflux device, reacted at a temperature of 78 to 82° C. until the solution is clear, and the stirring reaction is continued for 20 to 30 minutes; after the reaction is completed, the mixture is cooled to room temperature to obtain zirconium dihydrogen phosphate resin; Step S3, preparing a phosphate curing agent: The KH550 modified organosilicon microspheres obtained in step S1 are mixed with alumina and boron nitride whiskers, and the mixture is fully dispersed by ball milling to obtain a phosphate curing agent; The mass ratio of the KH550 modified organosilicon microspheres to the boron nitride whiskers is (0.99-1.01): (0.99-1.01); Step S4, preparing a high temperature resistant insulating adhesive: The zirconium dihydrogen phosphate resin obtained in step S2 and the phosphate curing agent obtained in step S3 are fully stirred and mixed, and then cured at a temperature of 21 to 25° C. for 47.99 to 48.01 hours to obtain a high-temperature resistant insulating adhesive based on cross-linking of boron nitride whiskers and silicone microspheres; The mass ratio of the zirconium dihydrogen phosphate resin to the phosphate curing agent is (0.99-1.01): (0.99-1.01).

2. The method for preparing a high temperature resistant insulating adhesive based on cross-linking of boron nitride whiskers and silicone microspheres according to claim 1, characterized in that The ratio of the mass of the organosilicon microspheres, the volume of the KH550 solution and the volume of anhydrous ethanol described in step S1 is (9-11) g: (0.8-1.2) mL: (98-102) mL.

3. A method for preparing a high temperature resistant insulating adhesive based on crosslinking of boron nitride whiskers and silicone microspheres according to claim 1 or 2, characterized in that The organic silicon microspheres are polymethylsilsesquioxane.

4. The method for preparing a high temperature resistant insulating adhesive based on cross-linking of boron nitride whiskers and silicone microspheres according to claim 1, characterized in that In step S1, the reaction is stirred at a temperature of 58 to 62° C. and a rate of 195 to 205 r / min for 9.9 to 10.1 min.

5. The method for preparing a high temperature resistant insulating adhesive based on cross-linking of boron nitride whiskers and silicone microspheres according to claim 1, characterized in that In step S1, the mixture is magnetically stirred at a temperature of 78 to 82° C. and a rate of 195 to 205 r / min for 2.99 to 3.01 h.

6. The method for preparing a high temperature resistant insulating adhesive based on cross-linking of boron nitride whiskers and silicone microspheres according to claim 1, characterized in that In step S2, the molar ratio of P in phosphoric acid to Zr in zirconium hydroxide is 4:

1.

7. The method for preparing a high temperature resistant insulating adhesive based on crosslinking of boron nitride whiskers and silicone microspheres according to claim 1, characterized in that In step S2, the reaction is carried out at a temperature of 78 to 82° C. for 12 to 24 hours.

8. The method for preparing a high temperature resistant insulating adhesive based on cross-linking of boron nitride whiskers and organosilicon microspheres according to claim 1, characterized in that The mass ratio of KH550-modified organosilicon microspheres to alumina in step S3 is (0.9-1.1):(7.5-8.5).

9. The method for preparing a high temperature resistant insulating adhesive based on cross-linking of boron nitride whiskers and silicone microspheres according to claim 1, characterized in that In step S3, the -1 The mixture was dispersed by ball mill at a speed of 10 min.

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