CN115627040B - Composite material resistant to low temperature of-50 ℃ for sealing, preparation method and sensor - Google Patents

Abstract

The invention belongs to the technical field of sealing composite materials, and specifically relates to a sealing composite material that can withstand low temperatures of -50°C. A modified nano-zirconium-based metal-organic framework material (UiO- 66-NH ₂ ) is a functional filler. It benefits from the lower polarity of the alkyl long-chain dodecaldehyde grafted on the outer surface of the modified UiO-66-NH ₂ particles, and the interaction between it and the fluororubber matrix. Compatibility is improved, and the composite has excellent bond strength and mechanical properties at low temperatures. The invention also provides a preparation method of the composite material and a sensor using the composite material. Suitable for use in low temperature environments in the power industry.

Description

A sealing composite material that is resistant to -50°C low temperature, preparation method and sensor

Technical field

The invention belongs to the technical field of sealing composite materials for electronic products, and specifically discloses a sealing composite material that is resistant to -50°C low temperature, a preparation method thereof, and a sensor using the sealing composite material that is resistant to -50°C low temperature.

Background technique

Protection and sealing are key processes in the sensor manufacturing process. Improper handling may cause sensor failure or errors beyond the allowable range. Taking the load cell as an example, if the protective sealing effect is not good, the resistance strain gauge and strain adhesive will easily absorb moisture in the air, which is likely to cause conduction between the strain gauge wire grids or wire grid corrosion, and may also cause It causes the size of the base of the pasted strain gauge, the bonding layer between the wire grid and the base to change, resulting in a decrease in insulation resistance, bonding strength and stiffness, and a change in the resistance value of the strain gauge, causing zero point drift of the sensor, poor insulation and even failure. The sensor fails, so the sensor must be effectively protected and sealed to improve its moisture-proof, waterproof, enzyme-proof, salt-spray-proof and other properties as well as its ability to resist vibration and impact, and further increase the service life of the sensor.

At a certain temperature, the sealing performance of the sensor sealing ring depends on its degree of recovery after tension and compression deformation at that temperature. As the temperature decreases, the recovery after tension and compression deformation becomes slower and slower, and the material gradually becomes harder. After passing through a leather state, it finally becomes as hard and brittle as glass, that is, vitrification, which causes At low temperatures, the sealing ring may crack and age, leading to sealing failure.

As a high-performance elastomer that can operate in special environments such as high and low temperatures and strong corrosiveness, fluorine rubber meets special needs that ordinary elastomers cannot meet. Therefore, it is widely used in national defense, industry, life and other fields. At the same time, with the opening of the smart industrial era, high-precision science and technology and new smart materials have begun to spread to industry. The harsh operating environment has challenged traditional polymer-based functional materials. However, like fluorine rubber, most of them have excellent performance None of the polymer-based functional materials are qualified for ultra-low temperature environments, which poses a challenge to the normal operation of outdoor sensors in extremely cold climates.

Contents of the invention

In order to solve the technical problems listed in the background art, the present invention provides a method for preparing a sealing composite material that is resistant to -50°C low temperature. The specific technical solution is as follows:

Mix 1 to 3 mmol/L UiO-66-NH ₂ nanoparticles/ethanol dispersion with an equal volume of 0.1 to 0.5 mol/L dodecaldehyde/ethanol solution, add the catalyst, and reflux at 68-72°C for 12 to 24 hours. , collect the product and wash to remove excess dodecaldehyde to obtain surface-modified UiO-66-NH2 nanoparticles;

Add 10-20wt% silane coupling agent A-1100 to the 60-80wt% fluororubber/methanol solution and stir evenly, then add 5-15wt% bisphenol AF and 5-15wt% bisphenol AF in sequence. 10wt% tetrabutylammonium bisulfate, stir until completely dissolved; add the surface-modified UiO-66-NH ₂ nanoparticles with a mass fraction of 5 to 30wt%, and ultrasonic for 18-22 minutes to disperse, and extract uniform The dispersion is evaporated and dried to obtain the sealing material.

Preferably, the catalyst is glacial acetic acid.

Preferably, the cleaning agent used for cleaning is absolute ethanol.

Preferably, the volatilization and drying process involves pouring the dispersion onto a horizontal stainless steel plate and casting a film, and after the solvent volatilization is completed, the dispersion is sent to a blast oven for drying.

Further, the process conditions of the drying treatment are to raise the temperature to 200°C for 2 hours, and then maintain the temperature for 3.5-4.5 hours.

The invention also provides a sealing composite material prepared by the above method and resistant to low temperatures of -50°C.

Another aspect of the present invention is a sensor that uses a film made of the above-mentioned sealing composite material to seal the housing.

Further, the thickness of the above-mentioned film used by the sensor is 5-20 μm.

Compared with the existing technology, the beneficial effects produced by the present invention are as follows:

Surface modification of nanoparticles with long alkyl chains can significantly improve the dispersion of metal-organic framework materials in fluororubber solutions and the compatibility between metal-organic materials and fluororubber matrix.

The modified metal-organic framework particles are used as functional filler materials, which can greatly improve the bonding strength and mechanical properties of fluorine rubber at low temperatures.

Description of the drawings

Figure 1 is the XRD spectrum of UiO-66-NH ₂ nanoparticles before and after surface modification in the embodiment;

Figure 2 is the FTIR spectrum of UiO-66-NH ₂ nanoparticles before and after surface modification in the embodiment;

Figure 3 is a surface SEM image of UiO-66-NH ₂ nanoparticles before and after surface modification in the embodiment;

Figure 4 is a cross-sectional view of the sealing composite material at a low temperature of -50°C in the embodiment.

Detailed ways

In order to make the purpose, technical solutions and advantages of the present invention clearer, the present invention will be described below in conjunction with the accompanying drawings and specific embodiments. Obviously, the described embodiments are only some of the embodiments of the present invention, but not all of the embodiments. Based on this embodiment, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the scope of protection of the present invention. 1. Preparation of UiO-66-NH ₂

Weigh zirconium tetrachloride (ZrCl ₄ , 2.5mmol, 0.56g) respectively and dissolve it in 75ml N,N-dimethylformamide (DMF). After stirring to complete the dissolution, add 2-amino-p-benzene. Dicarboxylic acid (NH ₂ -BDC, 2.5mmol, 0.42g), continue stirring until it is completely dissolved, add the reaction liquid into a 100ml polytetrafluoroethylene reactor, and heat to 120°C in a blast drying oven. React for 24 hours. After naturally cooling to room temperature, the product was separated and collected by centrifugation (10000 r/min, 15 min), and washed three times with DMF and methanol to remove impurities in the pores of the material. Finally, the obtained solid powder was dried in a vacuum oven at 80°C to obtain the required UiO-66- _NH2 nanoporous material.

2. Surface modification of UiO-66-NH2

The UiO-66-NH ₂ nanoparticles washed with absolute ethanol were redispersed in absolute ethanol (2mmol/L), ultrasonicated for 1.5 hours, and then centrifuged at a lower speed (3000rpm) for 10 minutes to remove larger particles. Nanoparticles. Take the supernatant, add an equal volume of pre-configured 0.3 mol/L dodecaldehyde/absolute ethanol solution, add a few drops of glacial acetic acid as a catalyst, and reflux at 70°C for 18 hours. After the reaction is completed, the resulting product is collected by centrifugation, and then washed repeatedly with absolute ethanol to remove excess dodecaldehyde to obtain surface-modified UiO-66-NH2 nanoparticles.

Figure 1 shows the XRD spectrum of modified UiO-66-NH ₂ nanoparticles through surface modification. The XRD spectrum of UiO-66-NH ₂ is consistent with the results of the standard card, and before and after modification, the XRD spectrum of the material has no Obvious changes occurred, indicating that the structure of UiO-66-NH ₂ was not destroyed during the surface modification process, mainly because the functionalization of the -NH ₂ group inside the UiO-66-NH ₂ structure was affected by the diffusion of dodecaldehyde molecules. Due to the limitation, the modified groups are mainly distributed on the outer surface of the MOF particles and have no effect on the crystal structure of UiO-66- _NH2 . Figure 2 shows the FTIR spectrum of UiO-66-NH ₂ nanoparticles modified by surface modification. There are two obvious differences in the FTIR spectrum before and after modification, among which the absorption peak at 3100cm-1 ~ 3500cm-l Corresponding to the symmetric stretching and asymmetric stretching of -CH ₂ groups in alkanes, the absorption peak at 1088cm-l in the light brown area belongs to the CC stretching vibration of linear alkanes. The above spectral analysis verified that through surface modification, dodecaldehyde molecules were successfully grafted on the surface of UiO-66-NH ₂ particles, and modified UiO-66-NH ₂ particle materials were obtained.

3. Preparation of cross-linked composite materials

The fluororubber system uses bisphenol AF as the vulcanizing agent. First, slowly add silane coupling agent A-1100 (mass fraction 15wt%) to the fluororubber/methanol solution with a mass fraction of 70wt% and stir evenly. Then add bisphenol AF ( Mass fraction 10wt%) and tetrabutylammonium hydrogen sulfate (mass fraction 5wt%) were stirred until completely dissolved.

The surface-modified UiO-66-NH ₂ nanoparticles (mass fraction 20 wt%) were added and dispersed by ultrasonic for 20 minutes to obtain a uniform dispersion. The mixed system is then poured onto a horizontal stainless steel plate to cast a film, and the mixed rubber is obtained after the solvent evaporates. Finally, the prepared mixed rubber was placed in a blast oven for drying treatment. The conditions were to raise the temperature to 200°C for 2 hours, and then keep it at 200°C for 4 hours. Finally, a composite sealing film was obtained. The thickness of the film was 15 μm, and its cross-section was shown in Figure 4. Show.

In order to intuitively analyze the morphology and structure of the synthetic materials, SEM tests were conducted, and the results are shown in Figure 3. It can be seen from the figure that the morphology of UiO-66-NH ₂ particles before and after modification has not changed significantly. However, the compatibility between unmodified UiO-66-NH ₂ and fluororubber in the left figure is not Very good, UiO-66- _NH2 is not completely dissolved inside the fluororubber. The compatibility between the modified UiO-66-NH ₂ and fluororubber in the picture on the right is good. The modified UiO-66-NH ₂ is all dissolved inside the fluororubber. This is because the long alkyl chain is relatively low. The polarity effect can improve the compatibility between nano-metal organic framework particles and fluororubber matrix.

By randomly measuring 100 UiO-66- _NH2 particles in the SEM image and taking the average, it can be known that the size of the particles is about 20nm. Such a small particle size provides the possibility to prepare composite materials with higher compatibility and better performance.

The composite materials made by this method and general composite materials were tested for performance in a -50°C environment. The test results are as shown in the following table:

fluororubber This patented composite material Dielectric strength (kV/mm) 28 39 Dielectric constant (1.2MHz) 2.8 3.3 Volume resistivity (Ω·cm) 1.2×10 ¹⁶ 1.8×10 ¹⁶ Linear expansion coefficient [m/(m·k)] 1.6×10 ^-4 1.2× ^10-4 Tensile Strength 45.2 65.8

It can be seen that the composite material prepared by this patent has higher dielectric strength, dielectric constant and volume resistivity, lower linear expansion coefficient and higher tensile strength.

The above embodiments complete the description of a sealing composite material and preparation method that is resistant to -50°C low temperature. A sensor made of this film as a housing seal of the sensor constitutes another technical solution of the present application "a sensor" ” embodiment.

Finally, it should be noted that the above are only preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, for those skilled in the art, it is still The technical solutions described in the foregoing embodiments may be modified, or some of the technical features may be equivalently replaced. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention shall be included in the protection scope of the present invention.

Claims (8)

1. A method for preparing a sealing composite material that is resistant to -50°C low temperature, which is characterized by comprising the following steps: Mix 1 to 3 mmol/L UiO-66-NH ₂ nanoparticles/ethanol dispersion with an equal volume of 0.1 to 0.5 mol/L dodecaldehyde/ethanol solution, add the catalyst, and reflux at 68-72°C for 12 to 24 hours. , collect the product and wash to remove excess dodecaldehyde to obtain surface-modified UiO-66-NH2 nanoparticles; Add 10-20wt% silane coupling agent A-1100 to the 60-80wt% fluororubber/methanol solution and stir evenly, then add 5-15wt% bisphenol AF and 5-15wt% bisphenol AF in sequence. 10wt% tetrabutylammonium bisulfate, stir until completely dissolved; add the surface-modified UiO-66-NH ₂ nanoparticles with a mass fraction of 5 to 30wt%, and ultrasonic for 18-22 minutes to disperse, and extract uniform The dispersion is evaporated and dried to obtain the sealing material. 2. The method for preparing a sealing composite material that can withstand low temperatures of -50°C as claimed in claim 1, characterized in that: the catalyst is glacial acetic acid. 3. The method for preparing a sealing composite material that can withstand low temperatures of -50°C as claimed in claim 2, characterized in that the cleaning agent used for cleaning is absolute ethanol. 4. A method for preparing a sealing composite material that is resistant to -50°C low temperature as claimed in claim 3, characterized in that: the volatilization and drying process involves pouring the dispersion onto a horizontal stainless steel plate and casting a film. , after the solvent evaporates, it is sent to a blast oven for drying. 5. A method for preparing a sealing composite material that is resistant to -50°C low temperature as claimed in claim 4, characterized in that: the process conditions of the drying treatment are to raise the temperature to 200°C in 2 hours, and then maintain the temperature for 3.5-4.5 hours. h. 6. A sealing composite material that is resistant to low temperatures of -50°C, characterized in that it is prepared by the preparation method described in any one of claims 1-5. 7. A sensor, characterized in that the outer shell is sealed using a film made of a sealing composite material that is resistant to -50°C low temperature as claimed in claim 6. 8. A sensor as claimed in claim 7, characterized in that: the film thickness of the sealing composite material that is resistant to -50°C low temperature is 5-20 μm.