Polyimide-based piezoelectric damping heat generation material and preparation method thereof

Abstract

The invention discloses a polyimide-based piezoelectric damping heat generation material and a preparation method thereof. The piezoelectric damping heat generation material comprises the following components in parts by weight: 85-95 parts of a modified polyimide matrix, 3-8 parts of hydroxylated carbon nanotubes and 2-5 parts of a metal organic framework, and the piezoresistive sensitivity of the piezoelectric damping heat generation material is 1.8-3.2 kPa <-1 >; through the design of the modified polyimide matrix and the hydroxylated CNT-MOF composite filler, a uniform conductive network and a porous heat dissipation adjusting structure are constructed, the heating efficiency is improved to 65% or above, meanwhile, the piezoresistive sensitivity and the damping coefficient are guaranteed, and the technical problems that an existing material is low in heating efficiency, poor in uniformity and difficult to cooperate in performance are solved.

Description

Technical Field

[0001] This invention belongs to the field of piezoresistive damping heat-generating materials, and particularly relates to a polyimide-based piezoresistive damping heat-generating material and its preparation method. Background Technology

[0002] Piezoresistive damping heating materials have become core candidate materials for electronic skin because they can integrate pressure sensing, damping buffering and self-heating functions.

[0003] Existing technologies suffer from problems such as uneven dispersion of conductive networks, low heating efficiency (typically 30%-60%), and uneven temperature distribution. For example, PI-based materials with the simple addition of carbon nanotubes (CNTs) suffer from local hot spot temperature differences exceeding 10°C due to the tendency of CNTs to agglomerate, and the heating efficiency is difficult to exceed 60%. At the same time, increasing the content of conductive fillers to improve heating performance leads to a decrease in material flexibility and a reduction in damping coefficient (<0.3), making it impossible to achieve a synergistic performance of "heating-piezoresistive-damping". Summary of the Invention

[0004] The purpose of this invention is to provide a polyimide-based piezoresistive damping heat-generating material and its preparation method, so as to solve the problems of low heating efficiency, poor uniformity and difficulty in synergistic performance of existing materials.

[0005] This invention employs the following technical solution: a polyimide-based piezoresistive damping heating material, comprising the following components by weight: 85-95 parts of modified polyimide matrix, 3-8 parts of hydroxylated carbon nanotubes, and 2-5 parts of metal-organic framework; the piezoresistive sensitivity of the piezoresistive damping heating material is 1.8-3.2 kPa. -1 .

[0006] A method for preparing a polyimide-based piezoresistive damping heat-generating material includes: Step 1: Add pyromellitic dianhydride, 4,4'-diaminodiphenyl ether and 4-hydroxybenzoic acid to N-methylpyrrolidone and stir at 50-70℃ for 2-4 hours to obtain a polyimide precursor polyamic acid solution. Step 2: Add hydroxylated carbon nanotubes and interfacial compatibilizer to N-methylpyrrolidone, ultrasonically disperse for 30-60 min, then add metal-organic framework, and continue ultrasonication for 1-2 h to obtain composite filler dispersion; Step 3: Add the composite filler dispersion to the polyamic acid solution and stir at 80-100℃ for 3-5 hours to form a slurry; Step 4: The slurry is coated onto the substrate and subjected to heat treatment at 80℃ / 2h, 150℃ / 1h, 250℃ / 1h, and 350℃ / 1h. After cooling, it is peeled off to obtain the piezoresistive damping heat-generating material.

[0007] The beneficial effects of this invention are: This invention constructs a uniform conductive network and a porous heat dissipation regulation structure through the design of "modified polyimide matrix + hydroxylated CNT-MOF composite filler". While improving the heating efficiency to more than 65%, it ensures the piezoresistive sensitivity and damping coefficient, solving the technical problems of low heating efficiency, poor uniformity and difficulty in synergistic performance of existing materials. The material prepared by this invention has a uniform conductive network, and the MOF porous structure regulates the heat distribution. The heating efficiency reaches 65%-75% at 10V, the temperature rise rate is ≥8℃ / s (from room temperature to 60℃), and the hot spot temperature difference is ≤3℃. The piezoresistive sensitivity of the material prepared by this invention is 1.8-3.2 kPa. -1 (Pressure range: 0.1-150 kPa), damping coefficient: 0.4-0.6 (frequency range: 1-100 Hz), performance retention rate: ≥90% after 1000 thermal cycles (-20℃ to 80℃); The material prepared by this invention has an elongation at break of ≥35%, a resistance change rate of ≤8% after 1000 bending cycles (bending radius 5mm), and an interfacial bonding strength improvement of more than 40% (compared to unmodified PI-based materials). Detailed Implementation

[0008] The present invention will now be described in detail with reference to specific embodiments.

[0009] This invention discloses a polyimide-based piezoresistive damping heating material, comprising the following components by weight: 85-95 parts of modified polyimide matrix, 3-8 parts of hydroxylated carbon nanotubes, and 2-5 parts of metal-organic framework. The piezoresistive sensitivity of the piezoresistive damping heating material is 1.8-3.2 kPa. -1 .

[0010] It also includes 0.5-2 parts by weight of interface compatibilizer.

[0011] The hydroxyl content of hydroxylated carbon nanotubes is 3-10%.

[0012] The hydroxylated carbon nanotubes have a diameter of 5-20 nm and a length of 1-5 μm.

[0013] Among them, the particle size of metal-organic frameworks is 100-300nm.

[0014] The modified polyimide matrix is ​​prepared by copolymerization of pyromellitic dianhydride, 4,4'-diaminodiphenyl ether and 4-hydroxybenzoic acid.

[0015] In the modified polyimide matrix, the mass fraction of 4-hydroxybenzoic acid is 5%~10%.

[0016] Metal-organic frameworks (MOFs) are selected from one or more of ZIF-8 (particle size 50-200nm), HKUST-1 (particle size 100-300nm), or MIL-101 (particle size 150-400nm). Their porous structure can regulate heat distribution, avoid local overheating, and at the same time increase the specific surface area of ​​the material and enhance piezoresistive sensitivity.

[0017] This invention also discloses a method for preparing a polyimide-based piezoresistive damping heat-generating material, comprising: Step 1: Add pyromellitic dianhydride, 4,4'-diaminodiphenyl ether and 5-10 wt% of 4-hydroxybenzoic acid to N-methylpyrrolidone, stir at 50-70℃ for 2-4 h to obtain a polyimide precursor polyamic acid solution.

[0018] The modified polyimide of this application is prepared by copolymerization of pyromellitic dianhydride (PMDA), 4,4'-diaminodiphenyl ether (ODA) and 5-10 wt% 4-hydroxybenzoic acid (HBA). The hydroxyl groups of HBA can form hydrogen bonds with the hydroxyl groups of CNT-OH to enhance interfacial bonding.

[0019] Step 2: Add hydroxylated carbon nanotubes and interfacial compatibilizer to N-methylpyrrolidone, ultrasonically disperse for 30-60 min, then add metal-organic framework, and continue ultrasonication for 1-2 h to obtain composite filler dispersion; Step 3: Add the composite filler dispersion to the polyamic acid solution and stir at 80-100℃ for 3-5 hours to form a slurry; Step 4: The slurry is coated onto the substrate and subjected to heat treatment at 80℃ / 2h, 150℃ / 1h, 250℃ / 1h, and 350℃ / 1h. After cooling, it is peeled off to obtain the piezoresistive damping heat-generating material.

[0020] Example 1

[0021] Components (parts by weight): Modified polyimide precursor (HBA content 5%): 92 parts; Hydroxylated carbon nanotubes (CNT-OH, 3% hydroxyl content, 10 nm diameter, 3 μm length): 5 parts; Metal-organic framework (MOF) (ZIF-8, particle size 100 nm): 2 parts; Interface compatibilizer KH550: 1 part.

[0022] Preparation process: A piezoresistive damping heat-generating material with a thickness of 100 μm was prepared according to steps 1-4.

[0023] The material properties test method obtained in Example 1 is as follows: (1) Heating efficiency at 10V: Refer to the “Test Method for Performance of Flexible Electric Heating Materials” and the specification for calculating thermal power conversion efficiency, and test according to the group standard: T / CIET1400—2025 (General Technical Conditions for Flexible Electric Heating Materials). The test environment is controlled at 23±2℃ and 50±10%RH.

[0024] (2) Temperature rise rate: The temperature rise rate of flexible materials shall be measured in accordance with the “Method for Determining Temperature Rise Rate of Flexible Materials” specified in GB / T2423.22-2012 (Environmental Test Temperature Change Test N Method), using an infrared thermal imager (such as FLIRE8) with a resolution ≥0.1℃.

[0025] (3) Hot spot temperature difference: The surface of the material is scanned with an infrared thermal imager (scanning accuracy ≤ 0.5 mm), and the difference between the highest temperature point (hot spot) and the average temperature of the surrounding area is identified as the hot spot temperature difference. During the test, the material is in a steady-state heating state (temperature fluctuation ≤ 0.5℃ / min).

[0026] (4) Piezoresistive sensitivity (0.1-125kPa): Tested according to the “Method for Determining Sensitivity of Piezoresistive Flexible Pressure Sensor” specified in GB / T36390-2018 (General Technical Conditions for Flexible Pressure Sensors).

[0027] (5) Damping coefficient (50Hz): According to GB / T29020-2012 (Dynamic Mechanical Properties Test Method), a DMA tester (such as TAQ800) is used. In tensile mode, the frequency is set to 50Hz and the temperature to 23℃. The damping coefficient tanδ=E'' / E' is calculated by measuring the energy storage modulus (E') and the loss modulus (E'').

[0028] (6) Performance retention rate after 1000 thermal cycles: Tested according to the “Method for Calculating Performance Retention Rate of Flexible Materials for Thermal Cycling Durability Test” specified in GB / T2423.22-2012 (Environmental Test Temperature Change Test N Method).

[0029] (7) Elongation at break: The tensile properties of flexible film materials were tested using a universal testing machine in accordance with GB / T1040.3-2006 (Determination of tensile properties of plastics - Part 3: Films and sheets).

[0030] After testing, the properties of the material in this embodiment are as follows: At 10V, the heating efficiency is 68%, the temperature rise rate is 8.2℃ / s (room temperature → 62℃, 10s), the hot spot temperature difference is 2.8℃; the piezoresistive sensitivity is 2.8kPa⁻¹ (0.1-120kPa); the damping coefficient is 0.48 (50Hz); the performance retention rate after 1000 thermal cycles is 91%; and the elongation at break is 38%.

[0031] Example 2

[0032] The steps in this embodiment are the same as those in Embodiment 1, except that: Components (parts by weight): Modified polyimide precursor (HBA content 8%): 90 parts; CNT-OH (hydroxyl content 8%, tube diameter 8nm, length 2μm): 6 parts; MOF (ZIF-8, particle size 100nm): 3 parts; KH550: 0.5 parts.

[0033] A material with a thickness of 120 μm was obtained. After testing, the performance of the material in this embodiment is as follows: At 10V, the heating efficiency is 72%, the temperature rise rate is 9.5℃ / s (room temperature → 65℃, 9s), the hot spot temperature difference is 2.2℃; the piezoresistive sensitivity is 3.1kPa⁻¹ (0.1-130kPa); the damping coefficient is 0.52 (50Hz); the performance retention rate after 1000 thermal cycles is 93%; and the elongation at break is 36%.

[0034] Example 3

[0035] The steps in this embodiment are the same as those in Embodiment 1, except that: Components (parts by weight): Modified polyimide precursor (HBA content 5%): 95 parts; CNT-OH (5% hydroxyl content, 10nm diameter, 3μm length): 3 parts; MOF (HKUST-1, particle size 200nm): 2 parts KH550: 1 copy; A material with a thickness of 90 μm was obtained. After testing, the properties of the material in this embodiment are as follows: At 10V, the heating efficiency is 66%, the temperature rise rate is 8.0℃ / s (room temperature → 60℃, 10s), the hot spot temperature difference is 2.5℃; the piezoresistive sensitivity is 1.8kPa⁻¹ (0.1-110kPa); the damping coefficient is 0.46 (50Hz); the performance retention rate after 1000 thermal cycles is 90%; and the elongation at break is 40%.

[0036] Example 4

[0037] The steps in this embodiment are the same as those in Embodiment 1, except that: Components (parts by weight): Modified polyimide precursor (HBA content 10%): 85 parts; CNT-OH (hydroxyl content 10%, tube diameter 6nm, length 1μm): 8 parts; MOF (MIL-101, particle size 300nm): 4 parts; KH550: 1.5 portions.

[0038] A material with a thickness of 150 μm was obtained. After testing, the properties of the material in this embodiment are as follows: At 10V, the heating efficiency is 75%, the temperature rise rate is 10.3℃ / s (room temperature → 68℃, 8s), the hot spot temperature difference is 1.8℃; the piezoresistive sensitivity is 3.2kPa⁻¹ (0.1-140kPa); the damping coefficient is 0.55 (50Hz); the performance retention rate after 1000 thermal cycles is 95%; and the elongation at break is 34%.

[0039] Example 5

[0040] The steps in this embodiment are the same as those in Embodiment 1, except that: Components (parts by weight): Modified polyimide precursor (HBA content 6%): 91 parts; CNT-OH (6% hydroxyl content, tube diameter 12nm, length 4μm): 5 parts; ZIF-8 / HKUST-1 (mass ratio 1:1, particle size 100 / 200nm): 3 parts; KH550: 1 copy.

[0041] A material with a thickness of 110 μm was obtained. After testing, the properties of the material in this embodiment are as follows: At 10V, the heating efficiency is 70%, the temperature rise rate is 9.0℃ / s (room temperature → 64℃, 9.5s), the hot spot temperature difference is 2.0℃; the piezoresistive sensitivity is 2.9kPa⁻¹ (0.1-125kPa); the damping coefficient is 0.50 (50Hz); the performance retention rate after 1000 thermal cycles is 92%; and the elongation at break is 37%.

[0042] Example 6

[0043] The steps in this embodiment are the same as those in Embodiment 1, except that: Components (parts by weight): Modified polyimide precursor (HBA content 7%): 89 parts; CNT-OH (7% hydroxyl content, tube diameter 15nm, length 5μm): 6 parts; MOF (MIL-101, particle size 400nm): 5 parts; KH550: 2 copies.

[0044] A material with a thickness of 130 μm was obtained. After testing, the properties of the material in this embodiment are as follows: At 10V, the heating efficiency is 73%, the temperature rise rate is 9.8℃ / s (room temperature → 66℃, 8.5s), the hot spot temperature difference is 2.1℃; the piezoresistive sensitivity is 3.0kPa⁻¹ (0.1-135kPa); the damping coefficient is 0.53 (50Hz); the performance retention rate after 1000 thermal cycles is 94%; and the elongation at break is 35%.

[0045] Comparative Example 1 (Unmodified PI + Unmodified CNT) Components (parts by weight): A material with a thickness of 110 μm was obtained by mixing 95 parts pure PI, 5 parts unmodified CNTs, and no MOF or KH550. The properties of the material in this comparative example are as follows: At 10V, the heating efficiency is 52%, the temperature rise rate is 5.1℃ / s (room temperature → 55℃, 15s), the hot spot temperature difference is 12.3℃, the piezoresistive sensitivity is 1.2kPa-1, the damping coefficient is 0.28, the performance retention rate after 1000 thermal cycles is 75%, and the elongation at break is 25%.

[0046] Comparative Example 2 (Modified PI + No MOF) Components (parts by weight): A material with a thickness of 120 μm was obtained by using 95 parts of modified PI (5% HBA content), 5 parts of CNT-OH, and no MOF. The properties of the material in this comparative example are as follows: At 10V, the heating efficiency is 58%, the temperature rise rate is 6.8℃ / s (room temperature → 58℃, 12s), the hot spot temperature difference is 8.5℃; the piezoresistive sensitivity is 2.0Pa-1; the damping coefficient is 0.35; the performance retention rate after 1000 thermal cycles is 82%; and the elongation at break is 32%.

[0047] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A polyimide-based piezoresistive damping heat-generating material, characterized in that, The material comprises, by weight, 85-95 parts of modified polyimide matrix, 3-8 parts of hydroxylated carbon nanotubes, and 2-5 parts of metal-organic framework, wherein the piezoresistive damping heating material has a piezoresistive sensitivity of 1.8-3.2 kPa. -1 .

2. The polyimide-based piezoresistive damping heat-generating material according to claim 1, characterized in that, It also includes 0.5-2 parts by weight of interface compatibilizer.

3. The polyimide-based piezoresistive damping heat-generating material according to claim 1, characterized in that, The hydroxyl content of the hydroxylated carbon nanotubes is 3-10%.

4. The polyimide-based piezoresistive damping heat-generating material according to claim 1, characterized in that, The hydroxylated carbon nanotubes have a diameter of 5-20 nm and a length of 1-5 μm.

5. The polyimide-based piezoresistive damping heat-generating material according to claim 1, characterized in that, The particle size of the metal-organic framework is 100-300 nm.

6. The polyimide-based piezoresistive damping heat-generating material according to claim 1, characterized in that, The modified polyimide matrix is ​​prepared by copolymerization of pyromellitic dianhydride, 4,4'-diaminodiphenyl ether and 4-hydroxybenzoic acid.

7. The polyimide-based piezoresistive damping heat-generating material according to claim 1, characterized in that, In the modified polyimide matrix, the mass fraction of 4-hydroxybenzoic acid is 5%~10%.

8. A method for preparing the polyimide-based piezoresistive damping heat-generating material according to claims 1-7, characterized in that, include: Step 1: Add pyromellitic dianhydride, 4,4'-diaminodiphenyl ether and 4-hydroxybenzoic acid to N-methylpyrrolidone and stir at 50-70℃ for 2-4 hours to obtain a polyimide precursor polyamic acid solution. Step 2: Add hydroxylated carbon nanotubes and interfacial compatibilizer to N-methylpyrrolidone, ultrasonically disperse for 30-60 min, then add metal-organic framework, and continue ultrasonication for 1-2 h to obtain composite filler dispersion; Step 3: Add the composite filler dispersion to the polyamic acid solution and stir at 80-100℃ for 3-5 hours to form a slurry; Step 4: The slurry is coated onto the substrate and subjected to heat treatment at 80℃ / 2h, 150℃ / 1h, 250℃ / 1h, and 350℃ / 1h. After cooling, it is peeled off to obtain the piezoresistive damping heat-generating material.