Porous piezoelectric polymer with directionally arranged holes and preparation method thereof

Abstract

The invention discloses a porous piezoelectric polymer with directionally arranged holes and a preparation method thereof, the polymer comprises a polymer matrix obtained by directionally freezing a piezoelectric polymer material nano powder solution, cylindrical holes directionally arranged in the polymer matrix, and different charges generated on the surfaces of the holes through polarization, the electrodes are coated on two opposite surfaces of the polymer matrix; the preparation method comprises the following steps: performing temperature gradient directional freezing on a nano powder solution to realize directional crystallization of ice crystals, and then drying and sublimating a solvent of a nano particle solution under a vacuum condition to obtain the porous piezoelectric polymer with directionally arranged holes. The invention discloses a preparation method of the polymer.

Description

Technical Field

[0001] The present invention belongs to the technical field of piezoelectric polymers, and particularly relates to a porous piezoelectric polymer with oriented pores and a preparation method thereof. Background Art

[0002] With the rapid development of disciplines such as polymer polymers and piezoelectric materials, piezoelectric polymers are widely used in the fields of medicine, transportation, aerospace, etc. Researchers are committed to developing piezoelectric polymers that are easy to prepare. Currently, the preparation of piezoelectric ceramic materials is relatively complex and requires high-temperature processes such as sintering and annealing. The raw materials contain lead elements, and the risk factor is high. Summary of the Invention

[0003] In order to overcome the problems existing in the above-mentioned prior art, the purpose of the present invention is to provide a porous piezoelectric polymer with oriented pores and a preparation method thereof. By using low-temperature crystallization and low-pressure sublimation, a large number of oriented micropores are generated, and an equivalent piezoelectric effect is generated through corona polarization. The polymer has the characteristics of simple structure, easy preparation, and safe and convenient preparation.

[0004] To achieve the above object, the technical solution adopted by the present invention is:

[0005] A porous piezoelectric polymer with oriented pores includes a polymer substrate 1, columnar pores 2 arranged in an array in the polymer substrate 1 with the vertical direction as the axis, and conductive electrodes 3 attached to two opposite side surfaces of the polymer substrate 1; opposite surfaces of the columnar pores 2 arranged in an array store opposite charges, forming multiple pairs of dipoles, and exhibiting a piezoelectric effect externally.

[0006] The polymer substrate 1 uses piezoelectric polymer material nano-powder as a raw material, and by applying a temperature gradient to the nano-powder solution for directional freezing, the directional crystallization of solvent ice crystals is realized, and then the solvent ice crystals are dried and sublimated under vacuum conditions to obtain the polymer substrate 1 with columnar pores 2 arranged in an array inside.

[0007] The polymer substrate 1 is in the shape of a cube.

[0008] The preparation method of the porous piezoelectric polymer with oriented pores includes the following steps:

[0009] Step 1: Prepare a nano-powder solution; disperse the piezoelectric polymer material nano-powder in an organic solvent at a certain mass fraction, and then heat and stir it to fully dissolve it into a nano-powder solution;

[0010] Step 2: Place the nanopowder solution in a container, apply low temperature at the bottom of the container using a low temperature source, and place the top of the container in room temperature air to form a temperature gradient from the bottom of the container to the top; in this temperature gradient, the solvent will crystallize and solidify in an orderly and directional manner from the bottom of the container to the top of the container to form a cylindrical array crystal;

[0011] Step 3: placing the crystallized nanopowder solution solid at room temperature and in a vacuum environment to dry it, the solvent sublimates to leave columnar holes 2, and the solute piezoelectric polymer material nanopowder forms a polymer substrate 1;

[0012] Step 4: Coat the two opposite sides of the polymer substrate 1 with columnar holes 2 distributed inside with low-temperature conductive silver paste or magnetron sputtered silver as conductive electrodes 3, and use needle tip discharge under high voltage to perform corona polarization on the porous piezoelectric polymer. The two opposite sides of the columnar holes 2 are charged and store opposite charges, thereby forming dipoles to show piezoelectric effect to the outside.

[0013] Preferably, the piezoelectric polymer material nanopowder in step 1 is polyvinylidene fluoride powder or polyvinylidene fluoride-co-trifluoroethylene, polyvinylidene fluoride-co-hexafluoropropylene and multiple piezoelectric material copolymer nanopowders. The above materials have the following advantages in piezoelectricity, mechanics, and processability: in terms of piezoelectricity, they have a high piezoelectric coefficient after polarization, and their dielectric constant is low, which is suitable for the detection and sensing of small forces; in terms of mechanics, they have a low modulus and large deformation capacity, and can be applied to the field of flexible sensing; in terms of processability, they can be dissolved by dimethyl sulfoxide, and can be made into porous materials using freeze-drying, and the processing difficulty is low.

[0014] Preferably, the mass ratio of the piezoelectric polymer material nanopowder to the organic solvent in step 1 is 0.2:10 to 1.5:10, and the nanopowder solution prepared within this mass ratio range can form a porous piezoelectric polymer with a higher equivalent piezoelectric coefficient after freeze-drying.

[0015] Preferably, the organic solvent in step 1 is a thermally stable organic solvent. Furthermore, the thermally stable organic solvent is dimethyl sulfoxide, which can efficiently dissolve polyvinylidene fluoride and its copolymer nanopowders, has a moderate volatilization rate during drying, avoids defects caused by rapid drying, and has low toxicity and recyclability, is safer and environmentally friendly.

[0016] Preferably, the low temperature source in step 2 is liquid nitrogen or low temperature ethanol, which can quickly solidify the nanopowder solution, has a relatively uniform temperature distribution and has good chemical stability.

[0017] Compared with the prior art, the present invention has the following advantages:

[0018] 1. The polymer of the present invention has a compact and lightweight structure and good compatibility with a variety of application scenarios.

[0019] 2. The holes in the present invention are arranged directionally, enabling the polymer skeleton to form a continuous load-bearing network in the direction parallel to the holes. Stress is efficiently transmitted along the main chain of the skeleton, forming a structure similar to a truss. Therefore, it has excellent mechanical properties in the direction of the holes.

[0020] 3. The present invention adopts the design of freeze crystallization - vacuum drying to form charge storage holes, realizing the equivalent piezoelectric effect in the polymer.

[0021] 4. Using piezoelectric polymer material nano-powder as the raw material, the material has a high safety factor, low preparation cost, and a simple process. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a schematic structural diagram of the porous piezoelectric polymer of the present invention.

[0023] Figure 2 It is a preparation flow chart of the porous piezoelectric polymer of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0024] The present invention will be further described in detail below with reference to the drawings and specific embodiments.

[0025] As Figure 1 shown, a porous piezoelectric polymer with directionally arranged holes includes a cubic polymer substrate 1, circular holes 2 arranged directionally in an array inside the cubic polymer substrate 1 with the vertical direction as the axis, and conductive electrodes 3 attached to the opposite surfaces of the cubic polymer substrate 1. Opposite surfaces of the directionally arranged cylindrical holes 2 store opposite charges, forming multiple pairs of dipoles, and exhibiting a piezoelectric effect externally.

[0026] The cubic polymer substrate 1 uses piezoelectric polymer material nano-powder as the raw material. By applying a temperature gradient to the nano-powder solution for directional freezing, the directional crystallization of solvent ice crystals is achieved. Then, the solvent ice crystals are dried and sublimated under vacuum conditions to obtain a cubic polymer substrate 1 with directionally arranged cylindrical holes 2 inside.

[0027] As Figure 2 shown, the preparation method of a porous piezoelectric polymer with directionally arranged holes according to the present invention includes the following steps:

[0028] Step 1: Prepare a nano-powder solution; disperse the piezoelectric polymer material nano-powder in an organic solvent at a certain mass fraction, and then heat and stir to fully dissolve it into a nano-powder solution; wherein, the mass ratio of the piezoelectric polymer material nano-powder to the organic solvent is 1:10.

[0029] Step 2: Place the nano-powder solution in a container with a cube shape. Apply low temperature at the bottom of the container using a low-temperature source (such as liquid nitrogen, low-temperature ethanol, etc.), and place the top of the container in room-temperature air to form a temperature gradient from the bottom to the top of the container; in the above temperature gradient, the solvent will crystallize and solidify orderly from the bottom to the top of the container to form a cylindrical array of crystals;

[0030] Step 3: Place the solidified nano-powder solution after crystallization in a room-temperature and vacuum environment to dry it. The solvent sublimes leaving columnar holes 2, and the solute (piezoelectric polymer material nano-powder) forms a polymer substrate 1 with a cube shape.

[0031] Step 4: Coat the opposite surfaces of the cube-shaped polymer substrate (1) with columnar holes 2 inside with low-temperature conductive silver paste as conductive electrodes 3, and use needle tip discharge under high voltage to corona polarize the porous piezoelectric polymer. Two opposite sides of the columnar holes 2 are charged, storing opposite charges, and then forming dipoles to exhibit piezoelectric effect externally.

[0032] The piezoelectric polymer material nano-powder described in Step 1 is polyvinylidene fluoride (PVDF) powder, or it can also be nano-powder copolymers of various piezoelectric materials such as polyvinylidene fluoride - co-trifluoroethylene, polyvinylidene fluoride - co-hexafluoropropylene, etc.

[0033] The mass ratio of the piezoelectric polymer material nano-powder to the organic solvent described in Step 1 is 0.2 / 10 to 1.5 / 10.

[0034] The organic solvent is dimethyl sulfoxide (DMSO) or other thermally stable organic solvents.

Claims

1. A porous piezoelectric polymer with holes arranged in an oriented manner, characterized in that: The invention comprises a polymer substrate (1), columnar holes (2) arranged in a direction and distributed in an array inside the polymer substrate (1) with the vertical direction as the axis, and conductive electrodes (3) attached to two opposite sides of the polymer substrate (1); opposite surfaces of the columnar holes (2) arranged in a direction store charges of opposite signs to form multiple pairs of dipoles, which show a piezoelectric effect externally.

2. The porous piezoelectric polymer with holes arranged directionally according to claim 1, wherein: The polymer substrate (1) uses piezoelectric polymer material nanopowder as raw material, applies temperature gradient directional freezing to the nanopowder solution to achieve directional crystallization of solvent ice crystals, and then dries and sublimates the solvent ice crystals under vacuum conditions to obtain a polymer substrate (1) with directional columnar pores (2) distributed inside.

3. A porous piezoelectric polymer with holes arranged directionally according to claim 1, characterized in that: The polymer substrate (1) is in the shape of a cube.

4. A method for preparing a porous piezoelectric polymer with holes arranged directionally according to any one of claims 1 to 3, characterized in that: The steps include: Step 1: preparing a nanopowder solution; dispersing the piezoelectric polymer material nanopowder in an organic solvent at a certain mass fraction, and then heating and stirring to fully dissolve it into a nanopowder solution; Step 2: Place the nanopowder solution in a container, apply low temperature at the bottom of the container using a low temperature source, and place the top of the container in room temperature air to form a temperature gradient from the bottom of the container to the top; in this temperature gradient, the solvent will crystallize and solidify in an orderly and directional manner from the bottom of the container to the top of the container to form a cylindrical array crystal; Step 3: placing the crystallized nanopowder solution solid at room temperature and in a vacuum environment to dry it, so that the solvent sublimates to leave columnar holes (2), and the solute piezoelectric polymer material nanopowder forms a polymer substrate (1); Step 4: The two opposite sides of the polymer substrate (1) with columnar holes (2) distributed inside are coated with low-temperature conductive silver paste or magnetron sputtered silver as conductive electrodes (3), and the porous piezoelectric polymer is corona polarized using needle tip discharge under high voltage. The two opposite sides of the columnar holes (2) are charged, storing charges of opposite signs, and then forming dipoles to show piezoelectric effect externally.

5. The preparation method according to claim 4, characterized in that: The piezoelectric polymer material nanopowder in step 1 is polyvinylidene fluoride powder or polyvinylidene fluoride-co-trifluoroethylene, polyvinylidene fluoride-co-hexafluoropropylene and other piezoelectric material copolymer nanopowders.

6. The preparation method according to claim 4, characterized in that: The mass ratio of the piezoelectric polymer material nanopowder to the organic solvent in step 1 is 0.2:10 to 1.5:

10.

7. The preparation method according to claim 4, characterized in that: The organic solvent in step 1 is a thermally stable organic solvent.

8. The preparation method according to claim 7, characterized in that: The thermally stable organic solvent is dimethyl sulfoxide.

9. The preparation method according to claim 4, characterized in that: The low temperature source in step 2 is liquid nitrogen or low temperature ethanol.

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