Piezoelectric elastomer material for underwater acoustic transducer and preparation method and application thereof

Abstract

This invention relates to the field of piezoelectric elastomer materials, specifically to a piezoelectric elastomer material for underwater acoustic transducers, its preparation method, and its application. The material comprises an elastomer matrix, a piezoelectric filler, a lead-silicon bridging agent containing phosphate groups, a conductive agent, and additives. The elastomer matrix is ​​an interpenetrating network, with the piezoelectric filler dispersed within it. One end of the lead-silicon bridging agent forms a bond with the metal ions of the piezoelectric filler, anchoring the lead-silicon bridging agent to the surface of the piezoelectric filler. The other end, after hydrolysis, undergoes condensation cross-linking with the elastomer matrix to form a covalent network. The mass ratio of the elastomer matrix, piezoelectric filler, and lead-silicon bridging agent containing phosphate groups is 86.5~119:41~73:1~5. This invention introduces a lead-silicon bridging agent to improve the material's piezoelectric constant, integrity, and long-term durability in underwater environments, solving the problems of insufficient piezoelectric performance, reliability, and environmental stability in existing piezoelectric elastomer materials for underwater acoustic transducers.

Description

Technical Field

[0001] This invention relates to the field of piezoelectric elastomer materials technology, specifically to a piezoelectric elastomer material for underwater acoustic transducers, its preparation method, and its application. Background Technology

[0002] To improve the performance and reliability of underwater acoustic transducers under complex operating conditions, the development of flexible piezoelectric materials has become an important direction. Piezoelectric elastomers, due to their unique acoustic impedance matching capabilities and adaptability, have become a research hotspot. Currently, the technological accumulation in this field mainly revolves around the following two types of materials:

[0003] One type is polymer composites constructed by introducing piezoelectric fillers. These materials use flexible polymers such as silicone rubber, polyurethane, and epoxy resin as the matrix, and achieve piezoelectric functionality by incorporating piezoelectric ceramic powders such as lead zirconate titanate (PZT) and barium titanate (BT). Recent studies have shown that piezoelectric output and mechanical flexibility of composite materials can be improved through filler surface modification and interface engineering. For example, some studies have achieved high-content uniform dispersion and excellent interfacial bonding by introducing interface-modified PZT filler into thermoplastic polyurethane (TPU) and in-situ reducing silver nanoparticles, resulting in composite fibers with excellent mechanical properties. However, existing technologies still suffer from weak interfacial bonding between inorganic piezoelectric fillers and organic elastomer matrices, easily leading to stress transfer failure and energy loss; uneven distribution of the interfacial electric field makes it difficult to fully utilize piezoelectric activity; and weak interfacial bonding causes accelerated performance degradation due to water penetration during long-term underwater operation, severely restricting the reliability and service life of underwater acoustic transducers.

[0004] Another category is intrinsically piezoelectric polymeric materials. These materials do not require composite piezoelectric fillers; they generate piezoelectric effects through the polar structure or crystalline phase of the molecular chains themselves. Typical examples include polyvinylidene fluoride (PVDF) and its copolymers, as well as novel piezoelectric elastomers. PVDF-based materials have attracted widespread attention in flexible sensing and energy harvesting due to their flexibility, processability, and biocompatibility. However, their piezoelectric activity mainly depends on the formation of the polar β phase, usually requiring complex polarization or annealing treatments, and their piezoelectric coefficient is limited. Recently, research has reported intrinsically piezoelectric elastomers based on cross-linked polyacrylonitrile (PAN), achieving a piezoelectric coefficient of approximately 40 pC / N and 100% hyperelastic recovery, while also exhibiting ultra-high compressibility. Although these intrinsically piezoelectric materials avoid the interface problems between fillers and the matrix, they still face challenges such as complex piezoelectric activity regulation and the need to verify long-term stability. Furthermore, their application research in the field of underwater acoustic transducers is still in its early stages.

[0005] In summary, the current development of underwater acoustic transducers is limited by the limitations of piezoelectric elastomer materials. The primary challenge lies in the weak interfacial bonding between inorganic piezoelectric fillers and organic elastomer matrices, which easily leads to stress transmission failure and energy loss. Secondly, the uneven distribution of the electric field at the material interface makes it difficult to maximize piezoelectric activity. In addition, the weak interfacial bonding makes the material prone to accelerated performance degradation due to permeation when working in a long-term underwater environment, thus restricting reliability and service life. Summary of the Invention

[0006] To address the aforementioned problems, this invention provides a piezoelectric elastomer material for underwater acoustic transducers, its preparation method, and its application. This invention incorporates a lead-silicon bridging agent into the piezoelectric elastomer material. The specific functional groups at both ends of the lead-silicon bridging agent molecule form strong chemical bonds between the piezoelectric filler surface and the elastomer matrix, constructing a robust connection, reducing the interfacial energy barrier, and improving stress transmission efficiency. Furthermore, it induces a local electric field enhancement effect under an applied polarized electric field, synergistically improving piezoelectric output and long-term stability. This effectively solves the problem of insufficient piezoelectric performance, reliability, and environmental stability in current piezoelectric elastomer materials for underwater acoustic transducers due to weak interfacial bonding between the filler and matrix.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: The first objective of this invention is to provide a piezoelectric elastomer material for underwater acoustic transducers, comprising: an elastomer matrix, wherein the elastomer matrix is ​​an interpenetrating network structure obtained by crosslinking silicone rubber and polyurethane rubber as raw materials in a catalyst and crosslinking agent system; the mass ratio of silicone rubber to polyurethane rubber is 70-85:15-30. A piezoelectric filler, dispersed in the elastomer matrix, is obtained by surface treatment with an amino-containing silane coupling agent using lead zirconate titanate and barium titanate as matrices; the mass ratio of lead zirconate titanate, barium titanate, and the amino-containing silane coupling agent is 30-50:10-20:1-3. A lead-silicon bridging agent containing phosphate groups is used to connect the elastomer matrix and the piezoelectric filler, wherein one end of the lead-silicon bridging agent containing phosphate groups forms a bond with the metal ions of the piezoelectric filler, anchoring the lead-silicon bridging agent on the surface of the piezoelectric filler, and the other end, after hydrolysis, undergoes condensation crosslinking with the elastomer matrix to form a covalent network. The conductive agent forms a three-dimensional conductive network with the elastomer matrix through physical entanglement. The mass ratio of the elastomer matrix, piezoelectric filler, and lead-silicon bridging agent containing phosphate groups is 86.5~119:41~73:1~5.

[0008] In a preferred embodiment of the present invention, the amino-containing silane coupling agent is KH-550, KH-540 or KH-792; the amino-containing silane coupling agent is more preferably KH-550 silane coupling agent, whose amino functional group can react with the hydroxyl groups on the filler surface, and can also react with isocyanate crosslinking agents to participate in the construction of crosslinking networks.

[0009] In a preferred embodiment of the present invention, the mass ratio of conductive agent to silicone rubber is 0.5~2:70~85; the mass ratio of catalyst, crosslinking agent and silicone rubber is 0.5~1.5:1~2.5:70~85.

[0010] In a preferred embodiment of the present invention, the piezoelectric elastomer material used in the underwater acoustic transducer further includes additives, including plasticizers, antioxidants and defoamers, wherein the mass ratio of plasticizers, antioxidants, defoamers and silicone rubber is 5~15:0.5~1.5:1~3:70~85.

[0011] In a preferred embodiment of the present invention, the piezoelectric elastomer material used in the underwater acoustic transducer comprises the following raw materials in parts by weight: 70-85 parts silicone rubber; 15-30 parts polyurethane rubber; 30-50 parts lead zirconate titanate; 10-20 parts barium titanate; 5-15 parts plasticizer; 0.5-2 parts conductive agent; 1-3 parts amino-containing silane coupling agent; 0.5-1.5 parts antioxidant; 1-3 parts defoamer; 0.5-1.5 parts catalyst; 1-2.5 parts crosslinking agent; and 1.0-5.0 parts lead-silicon bridging agent containing phosphate groups. Wherein, lead zirconate titanate is lead zirconate titanate powder, barium titanate is barium titanate nanoparticles, the plasticizer is dioctyl phthalate, the conductive agent is carbon nanotubes, the catalyst is a platinum catalyst, and the crosslinking agent is an isocyanate crosslinking agent.

[0012] In this invention, the lead-silicon bridging agent is the core inventive point. Its specific functional groups at both ends establish strong chemical bonds between the piezoelectric ceramic filler surface and the elastomer matrix, fundamentally solving the problem of weak interfacial bonding between inorganic fillers and organic matrices. Silicone rubber and polyurethane rubber are compounded to form the elastomer matrix, providing excellent flexibility and water resistance while imparting good mechanical strength to the material. Lead zirconate titanate powder and barium titanate nanoparticles are compounded as the piezoelectric functional phase; the former provides high-voltage electrical properties, while the latter fills voids and enhances the local electric field through nano-effects. Carbon nanotubes construct a conductive network, promoting polarization charge migration. An amino-containing silane coupling agent performs primary surface treatment on the filler, improving dispersibility and providing anchor points for the lead-silicon bridging agent. Dioctyl phthalate acts as a plasticizer to optimize processing flowability. Isocyanate crosslinking agents and platinum catalysts catalyze the crosslinking reactions of polyurethane and silicone rubber, respectively, forming a dual network structure that anchors the interfacial bonds. Antioxidants and defoamers ensure the performance stability and structural density of the material during processing and use. In short, this invention uses a lead-silicon bridging agent as a link to firmly anchor piezoelectric fillers in an elastomer network. Combined with conductive, reinforcing, and crosslinking additives, it synergistically achieves a comprehensive improvement in piezoelectric properties, interfacial bonding strength, and environmental durability.

[0013] It should be noted that this invention utilizes the specific coordinating groups in the molecular structure of the lead-silicon bridging agent to form strong chemical bonds with metal ions on the surface of piezoelectric ceramic fillers such as lead zirconate titanate powder and barium titanate nanopowder. Simultaneously, the hydrolytic functional groups at the other end of the bridging agent undergo cross-linking reactions with organic elastomer matrices such as silicone rubber and polyurethane rubber. This amphiphilic structure forms a strong connection between the inorganic filler and the organic polymer, significantly enhancing the bonding force at the interface between the two phases. This allows external stress to be transferred more efficiently from the flexible matrix to the rigid piezoelectric functional phase, reducing energy loss due to interface debonding and improving the integrity, fatigue resistance, and reliability of the composite material under dynamic deformation. Furthermore, the dipole moment formed on the surface of fillers such as lead zirconate titanate powder and barium titanate nanopowder by the lead-silicon bridging agent can effectively modulate the local electric field distribution in the interface region when the material is polarized by applying an external electric field. This reduces the energy barrier for domain flipping and promotes a more complete and thorough directional arrangement of some domains within the piezoelectric ceramic grains, thereby increasing the piezoelectric constant of the composite material. Under stress, it can generate a stronger electrical signal output, improving the transmission sensitivity and reception efficiency of the underwater acoustic transducer. Finally, through the covalent bonding network formed within the composite system by the lead-silicon bridging agent, piezoelectric fillers such as lead zirconate titanate powder and barium titanate nanopowder are firmly anchored in the elastomer matrix. This tough interfacial structure inhibits the migration or detachment of fillers that may occur due to repeated deformation during use, while blocking the penetration path of environmental media such as water along the interface between the filler and the matrix. This slows down the decay rate of the piezoelectric properties of the material when it is placed in harsh environments such as underwater high pressure and salt corrosion for a long time, ensuring that the underwater acoustic transducer made from it has a longer service life and more stable acoustic performance.

[0014] In a preferred embodiment of the present invention, the preparation method of the lead-silicon bridging agent containing phosphate groups includes the following steps: S1. In the first solvent system, vinylphosphonic acid and 3-aminopropyltriethoxysilane were subjected to an aza-Michael addition reaction to obtain an intermediate. The chemical formula of the intermediate is CH2=CH-P(O)(OH)-NH-(CH2)3-Si(OCH2CH3)3.

[0015] In a preferred embodiment of the present invention, in step S1, the molar ratio of vinylphosphonic acid to 3-aminopropyltriethoxysilane is 1:1 to 1.2, the first solvent is anhydrous ethanol, the reaction temperature is 60°C to 80°C, and the reaction time is 4h to 6h.

[0016] S2. In the system of the second solvent, a coordination reaction is carried out using the intermediate and lead acetate as raw materials to obtain a lead-containing siloxane complex. Subsequently, the lead-containing siloxane complex is precipitated to obtain a lead-silicon bridging agent containing phosphate groups.

[0017] The specific process for S2 is as follows: The intermediate and lead acetate are added together to a dimethyl sulfoxide solvent and stirred to react, causing the lead ions to coordinate with the phosphate groups in the intermediate to form a lead-containing siloxane complex. The lead-containing siloxane complex is then cooled to room temperature, and a precipitant is added to precipitate the product. After filtration, washing, and vacuum drying, a lead-silicon bridging agent containing phosphate groups is obtained.

[0018] The reaction mechanism of the lead-silicon bridging agent containing phosphate groups is as follows: First, in the synthesis stage, the carbon-carbon double bond in vinylphosphonic acid undergoes an aza-Michael addition reaction with the amino group in 3-aminopropyltriethoxysilane to generate an intermediate containing both phosphonic acid and siloxane groups. Subsequently, the phosphate group in the intermediate undergoes a coordination reaction with the lead ions provided by lead acetate to form a lead-containing siloxane complex. This complex is precipitated from the reaction system, and after filtration, washing, and drying, the final product, the lead-silicon bridging agent containing phosphate groups, is obtained.

[0019] In a preferred embodiment of the present invention, in step S2, the molar ratio of the intermediate to lead acetate is 1:0.5~0.6, the second solvent is dimethyl sulfoxide, and the precipitation process uses a precipitant, which is water or anhydrous ethanol.

[0020] In a preferred embodiment of the present invention, in step S2, the stirring reaction temperature is 80℃~100℃ and the reaction time is 10h~11h.

[0021] In a preferred embodiment of the present invention, in step S2, the vacuum drying temperature is 50℃~60℃ and the time is 6h~8h.

[0022] Secondly, the present invention provides a method for preparing the above-mentioned piezoelectric elastomer material for underwater acoustic transducers, comprising the following steps: S1. Weigh each raw material according to its weight composition.

[0023] S2. Mix the elastomer matrix, piezoelectric filler, lead-silicon bridging agent containing phosphate groups, conductive agent and additives to obtain a mixed colloid, and then perform curing, aging and polarization treatments in sequence to obtain a piezoelectric elastomer material for underwater acoustic transducers.

[0024] The specific process of S2 is as follows: (1) Lead zirconate titanate powder and barium titanate nanoparticles were dried at 120℃ for 4h, and then surface-treated with KH-550 silane coupling agent; a lead-silicon bridging agent containing phosphate groups was dissolved in anhydrous ethanol and ball-milled together with the surface-treated lead zirconate titanate powder and barium titanate nanoparticles to obtain the pretreated piezoelectric functional filler. The ball milling speed was 300rpm, the ball milling time was 2h, and the ball-to-material ratio was 5:1.

[0025] (2) Add silicone rubber and polyurethane rubber to a mixing device and premix for 10 min; add plasticizer dioctyl phthalate and defoamer, and continue mixing for 10 min to form a uniform colloid.

[0026] (3) Add the pretreated piezoelectric functional filler and carbon nanotubes to the colloid in batches, gradually increase the rotation speed to 500 rpm to 800 rpm, mix for 60 min to 90 min, and control the temperature to not exceed 50℃ to obtain the mixture.

[0027] (4) Degas the mixture under a vacuum of -0.095MPa for 20-30 minutes; then add isocyanate crosslinking agent, platinum catalyst, antioxidant and defoamer, and mix at 300rpm for 10 minutes.

[0028] (5) The mixed colloid is injected into the mold, pressure is applied in the flat vulcanizing machine, and gradient curing is carried out; after demolding, the material is cured at room temperature for 24 hours, and then electrode preparation and polarization treatment are carried out.

[0029] It should be noted that the preparation process of the piezoelectric elastomer material of the present invention is based on a multi-step chemical and physical synergy: First, an amino-containing silane coupling agent reacts with the hydroxyl groups on the surface of lead zirconate titanate and barium titanate fillers through its amino groups, introducing organic functional groups on the filler surface to achieve primary interface modification; subsequently, a lead-silicon bridging agent forms strong coordination bonds with metal ions on the filler surface through the coordination groups in its molecules, while its terminal siloxane groups hydrolyze in subsequent processing and undergo condensation reaction with the silicone rubber matrix, thereby constructing a covalent bridge between the filler and the matrix; in the mixing stage, carbon nanotubes form a three-dimensional conductive network with the matrix through physical entanglement, while isocyanate crosslinking agents react with the active groups of polyurethane rubber and together with the platinum catalytic addition crosslinking system of silicone rubber to form a double crosslinking network, anchoring the interfacial chemical bonds therein; finally, during gradient curing and high-temperature polarization, the internal structure of the material tends to be dense, and under the action of a strong electric field, the electric domains of the piezoelectric ceramic grains are oriented along the direction of the electric field, endowing the material with macroscopic piezoelectric activity. The entire process, through the synergy of chemical bonding and physical cross-linking, firmly integrates inorganic fillers into the elastomer network, achieving a unified approach to interface enhancement, piezoelectric performance improvement, and environmental durability optimization.

[0030] In the preparation of piezoelectric elastomer materials, lead-silicon bridging agents play a dual interfacial bonding role: on the one hand, the lead ions and phosphate groups in the bridging agent form strong coordination bonds with the metal ions on the surface of the piezoelectric fillers, namely lead zirconate titanate and barium titanate, anchoring the bridging agent to the filler surface; on the other hand, the siloxane groups at the end of the bridging agent undergo condensation crosslinking reactions with the silicone rubber and polyurethane rubber matrix after hydrolysis, forming a covalent network. Through this bifunctional structure of "anchoring the filler at one end and crosslinking the matrix at the other end," the lead-silicon bridging agent constructs a strong chemical bond bridge between the inorganic filler and the organic matrix, fundamentally solving the problem of weak interfacial bonding.

[0031] In a preferred embodiment of the present invention, during the preparation of the mixture, the rotation speed is 500 rpm to 800 rpm and the mixing time is 60 min to 90 min.

[0032] In a preferred embodiment of the present invention, during the vacuum degassing process, the vacuum degree is -0.095MPa and the time is 20min~30min.

[0033] In a preferred embodiment of the present invention, the curing is carried out by gradient curing, which specifically involves curing at 60°C for 2 hours, at 100°C for 2 hours, and at 120°C for 1 hour in sequence; the pressure of gradient curing is 5MPa~10MPa.

[0034] In a preferred embodiment of the present invention, the polarization treatment temperature is 80℃~100℃, the electric field is 2kV / mm~4kV / mm, and the polarization time is 30min~60min.

[0035] In a preferred embodiment of the present invention, the specific conditions for the polarization treatment are as follows: the material is placed in silicone oil, and a DC electric field of 2kV / mm to 4kV / mm is applied at 80℃ to 100℃ for 30min to 60min.

[0036] A third objective of this invention is to provide the application of a piezoelectric elastomer material for use in the fabrication of underwater acoustic transducers.

[0037] In a preferred embodiment of the present invention, the material is used to prepare the core vibrating element of an underwater acoustic transducer, specifically applied to an underwater sonar transmitting / receiving unit, an underwater communication sensor, or a marine environmental monitoring vibration sensing module.

[0038] The specific application process is as follows: The piezoelectric elastomer material prepared in this invention is cut into the required size, and silver paste is applied to the upper and lower surfaces as electrodes. After polarization treatment, it is assembled with a matching layer and a backing material, and encapsulated to form a single unit of underwater acoustic transducer. This unit is then arrayed to form an underwater sonar transmitting / receiving array for underwater target detection and imaging. The matching layer is one or more layers of material located between the piezoelectric material and the water medium, specifically epoxy resin composite material, rigid polyurethane, etc. The backing material is a layer of material located on the back side of the piezoelectric material, i.e., the side opposite to the radiating surface, specifically epoxy resin composite material, rubber composite material, etc. In this application, the thickness and size of each layer are not limited. Preferably, the thickness ratio of the matching layer:piezoelectric material:backing material is 1:2:5.

[0039] Compared with the prior art, the beneficial effects of the present invention are: 1. This invention provides a piezoelectric elastomer material for underwater acoustic transducers. By adding a lead-silicon bridging agent containing phosphate groups to the piezoelectric elastomer material, the specific coordinating groups of the lead-silicon bridging agent containing phosphate groups form strong chemical bonds with metal ions on the surface of lead zirconate titanate powder and barium titanate nanoparticles. Simultaneously, the hydrolytic functional groups at the other end crosslink with silicone rubber, polyurethane rubber, etc. This amphiphilic structure forms a strong connection between the inorganic filler and the organic polymer, enhancing the interfacial bonding force between the two phases. This allows external stress to be transferred more efficiently from the flexible matrix to the rigid piezoelectric functional phase, reducing energy loss due to interfacial debonding, and improving the integrity, fatigue resistance, and reliability of the composite material under dynamic deformation. This effectively solves the problem of insufficient piezoelectric performance, reliability, and environmental stability of current piezoelectric elastomer materials for underwater acoustic transducers due to weak interfacial bonding between the filler and the matrix.

[0040] 2. This invention uses a lead-silicon bridging agent containing phosphate groups to form a dipole moment on the surface of fillers such as lead zirconate titanate powder and barium titanate nanopowder. When the material is polarized by applying an external electric field, the dipole layer effectively modulates the local electric field distribution in the interface region, reduces the energy barrier for domain flipping, and promotes a more complete and thorough directional arrangement of some domains within the piezoelectric ceramic grains. This improves the piezoelectric constant of the composite material, enabling it to generate a stronger electrical signal output under stress and enhancing the transmission sensitivity and reception efficiency of the underwater acoustic transducer.

[0041] 3. This invention utilizes a lead-silicon bridging agent containing phosphate groups to form a covalently bonded network within the composite system, anchoring filler particles and sealing interfacial channels. This inhibits filler migration and detachment; blocks the penetration of environmental media such as moisture and salt spray; and maintains over 80% piezoelectric performance retention under salt water immersion and high temperature and humidity environments, significantly extending service life. Specifically, the covalently bonded network formed by the lead-silicon bridging agent anchors piezoelectric fillers such as lead zirconate titanate powder and barium titanate nanoparticles within the elastomer matrix. This robust interfacial structure inhibits the migration or detachment of fillers that may occur due to repeated deformation during use, while blocking the penetration path of environmental media such as moisture along the filler-matrix interface. This slows down the decay rate of the piezoelectric performance of the material under harsh environments such as long-term underwater high pressure and salt corrosion, ensuring that the underwater acoustic transducer made from it has a longer service life and more stable acoustic performance.

[0042] 4. In the preparation method of the piezoelectric elastomer material for underwater acoustic transducers provided by the present invention, the filler is subjected to dual interface modification by pretreatment with an amino-containing silane coupling agent and co-milling with a lead-silicon bridging agent; a gradient curing process is implemented, combined with vacuum degassing and segmented mixing. This ensures uniform dispersion of the filler and avoids agglomeration; improves the density and structural consistency of the material; and is conducive to large-scale, repeatable preparation. Attached Figure Description

[0043] Figure 1 The images are scanning electron microscope (SEM) images of the piezoelectric elastomer materials used in underwater acoustic transducers in Embodiment 2 and Comparative Example 2 of the present invention. Figure 1 Figure A is a scanning electron microscope (SEM) image of Example 2, and Figure B is a scanning electron microscope (SEM) image of Comparative Example 2.

[0044] Figure 2 The diagram shows the effect of enhanced interfacial bonding of piezoelectric elastomer materials with different formulations for underwater acoustic transducers according to the present invention.

[0045] Figure 3 This is a performance comparison chart of piezoelectric elastomer materials with different formulations for underwater acoustic transducers according to the present invention.

[0046] Figure 4 The graph shows the durability results of piezoelectric elastomer materials with different formulations for underwater acoustic transducers according to the present invention. Detailed Implementation

[0047] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0048] It should be noted that the technical terms used in this invention are only for the purpose of describing specific embodiments and are not intended to limit the scope of protection of this invention. Unless otherwise specified, all raw materials, reagents, instruments and equipment used in the following embodiments of this invention can be purchased from the market or prepared by existing methods.

[0049] In this invention, the silicone rubber was purchased from Bluestar Organosilicon International Co., Ltd., model 107, with a viscosity of 20000 mPa·s ± 5000 mPa·s. The polyurethane rubber was purchased from Wanhua Chemical Group Co., Ltd., model polyester TPU, with a hardness of 80A ± 5A. The lead zirconate titanate powder was purchased from Guangdong Fenghua Advanced Technology Co., Ltd., with a purity of 99.5% and an average particle size of 1μm~3μm. The barium titanate nanoparticles were purchased from Guoci Materials Co., Ltd., with a purity of 99.9% and an average particle size of 50nm~100nm. The dioctyl phthalate was chemically pure, with a purity ≥99%, and was purchased from Zibo Qixiang Tengda Chemical Co., Ltd. The carbon nanotubes were purchased from Shenzhen Nanoport Co., Ltd., in multi-wall form, with a purity >95% and a diameter of 10nm~20nm. The KH-550 silane coupling agent was chemically pure, with a purity ≥98%, and was purchased from Nanjing Shuguang Silane Chemical Co., Ltd. Antioxidant 1010, reagent grade, purity ≥99%, purchased from Beijing Jiyi Chemical Co., Ltd. Defoamer, silicone-based, 100% active ingredient, purchased from Shenzhen Defeng Chemical Co., Ltd. Platinum catalyst, platinum content 3000ppm~5000ppm, purchased from Hangzhou Jessica Chemical Co., Ltd. Isocyanate crosslinking agent, model TDI-100, purity ≥99.5%, purchased from Cangzhou Dahua Group Co., Ltd. Isopropyl tris(dioctyl phosphate) titanate purchased from Nanjing Herun Coupling Agent Co., Ltd.

[0050] In the following examples and comparative examples, the antioxidant is antioxidant 1010.

[0051] The following specific examples will provide further explanation.

[0052] Example 1 A piezoelectric elastomer material for underwater acoustic transducers includes an elastomer matrix, a piezoelectric filler, a lead-silicon bridging agent containing phosphate groups, a conductive agent, and additives. The elastomer matrix is ​​an interpenetrating network structure obtained by crosslinking silicone rubber and polyurethane rubber in a platinum catalyst and isocyanate crosslinking agent system. The piezoelectric filler, dispersed in the elastomer matrix, is obtained by surface treatment with an amino-containing silane coupling agent using lead zirconate titanate and barium titanate as the matrix. The lead-silicon bridging agent containing phosphate groups connects the elastomer matrix and the piezoelectric filler. One end forms a bond with the metal ions of the piezoelectric filler, anchoring the lead-silicon bridging agent to the surface of the piezoelectric filler; the other end hydrolyzes and undergoes condensation crosslinking with the elastomer matrix to form a covalent network. The conductive agent, carbon nanotubes, forms a three-dimensional conductive network with the elastomer matrix through physical entanglement. The mass ratio of the elastomer matrix, piezoelectric filler, and lead-silicon bridging agent containing phosphate groups is 86.5:41:1; the mass ratio of silicone rubber and polyurethane rubber is 70:15. The mass ratio of lead zirconate titanate, barium titanate, and amino-containing silane coupling agent is 30:10:1.

[0053] The material comprises the following raw materials in parts by weight: 70 parts silicone rubber; 15 parts polyurethane rubber; 30 parts lead zirconate titanate powder; 10 parts barium titanate nanopowder; 5 parts dioctyl phthalate; 0.5 parts carbon nanotubes; 1 part KH-550 silane coupling agent; 0.5 parts antioxidant; 1 part defoamer; 0.5 parts platinum catalyst; 1 part isocyanate crosslinking agent; and 1.0 part lead-silicon bridging agent containing phosphate groups.

[0054] The preparation method of the above-mentioned piezoelectric elastomer material for underwater acoustic transducers includes the following steps: S1. Preparation of lead-silicon bridging agents containing phosphate groups: 0.1 mol of vinylphosphonic acid and 0.1 mol of 3-aminopropyltriethoxysilane were dissolved in 100 mL of anhydrous ethanol at a molar ratio of 1:1 and reacted at 60 °C for 4 hours to obtain an intermediate. 0.1 mol of the intermediate and 0.05 mol of lead acetate were added to 150 mL of dimethyl sulfoxide solvent at a molar ratio of 1:0.5 and stirred at 80 °C for 10 hours to allow lead ions to coordinate with the phosphate groups in the intermediate, forming a lead-containing siloxane complex. The lead-containing siloxane complex was cooled to room temperature, and deionized water was added as a precipitant to precipitate the product. After filtration and washing, the product was dried under vacuum at 50 °C for 6 hours to obtain a lead-silicon bridging agent containing phosphate groups.

[0055] S2. 30 parts of lead zirconate titanate powder and 10 parts of barium titanate nanoparticles were dried at 120℃ for 4 hours, and then surface-treated with 1 part of KH-550 silane coupling agent. 1 part of a lead-silicon bridging agent containing phosphate groups was dissolved in 50 mL of anhydrous ethanol and ball-milled together with the surface-treated lead zirconate titanate powder and barium titanate nanoparticles at 300 rpm for 2 hours at a ball-to-material ratio of 5:1 to obtain the pretreated piezoelectric functional filler. 70 parts of silicone rubber and 15 parts of polyurethane rubber were added to a mixing device and premixed for 10 minutes; then 5 parts of dioctyl phthalate and 0.5 parts of defoamer were added, and mixing continued for 10 minutes to form a homogeneous colloid. The pretreated piezoelectric functional filler and 0.5 parts of carbon nanotubes were added to the colloid in portions, gradually increasing the rotation speed to 500 rpm and mixing for 60 minutes, controlling the temperature to not exceed 50℃ to obtain a mixture. The mixture was degassed under a vacuum of -0.095 MPa for 20 minutes; then 1 part of isocyanate crosslinking agent, 0.5 part of platinum catalyst, 0.5 part of antioxidant and 0.5 part of defoamer were added, and the mixture was mixed at 300 rpm for 10 minutes to obtain a mixed colloid.

[0056] S3. Inject the mixed colloid into the mold, apply a pressure of 5MPa in a flat vulcanizing machine, and perform gradient curing, that is, cure at 60℃ for 2 hours, at 100℃ for 2 hours, and at 120℃ for 1 hour in sequence. After demolding, let the material mature at room temperature for 24 hours, and then perform electrode preparation and polarization treatment. The polarization treatment conditions are to place the material in silicone oil, apply a DC electric field of 2kV / mm at 80℃, and polarize for 30 minutes to obtain the piezoelectric elastomer material for underwater acoustic transducers.

[0057] This material is used to prepare the core vibrating element of underwater acoustic transducers, specifically for underwater sonar transmitting / receiving units, underwater communication sensors, or vibration sensing modules for marine environmental monitoring.

[0058] Example 2 A piezoelectric elastomer material for underwater acoustic transducers includes an elastomer matrix, a piezoelectric filler, a lead-silicon bridging agent containing phosphate groups, a conductive agent, and additives. The elastomer matrix is ​​an interpenetrating network structure obtained by crosslinking silicone rubber and polyurethane rubber in a platinum catalyst and isocyanate crosslinking agent system. The piezoelectric filler, dispersed in the elastomer matrix, is obtained by surface treatment with an amino-containing silane coupling agent using lead zirconate titanate and barium titanate as the matrix. The lead-silicon bridging agent containing phosphate groups connects the elastomer matrix and the piezoelectric filler. One end forms a bond with the metal ions of the piezoelectric filler, anchoring the lead-silicon bridging agent to the surface of the piezoelectric filler; the other end hydrolyzes and undergoes condensation crosslinking with the elastomer matrix to form a covalent network. The conductive agent, carbon nanotubes, forms a three-dimensional conductive network with the elastomer matrix through physical entanglement. The mass ratio of the elastomer matrix, piezoelectric filler, and lead-silicon bridging agent containing phosphate groups is 102.75:57:3; the mass ratio of silicone rubber and polyurethane rubber is 77.5:22.5. The mass ratio of lead zirconate titanate, barium titanate, and amino-containing silane coupling agent is 40:15:2.

[0059] The material comprises the following raw materials in parts by weight: 77.5 parts silicone rubber; 22.5 parts polyurethane rubber; 40 parts lead zirconate titanate powder; 15 parts barium titanate nanopowder; 10 parts dioctyl phthalate; 1.25 parts carbon nanotubes; 2 parts KH-550 silane coupling agent; 1 part antioxidant; 2 parts defoamer; 1 part platinum catalyst; 1.75 parts isocyanate crosslinking agent; and 3.0 parts lead-silicon bridging agent containing phosphate groups.

[0060] The preparation method of the above-mentioned piezoelectric elastomer material for underwater acoustic transducers includes the following steps: S1. Preparation of lead-silicon bridging agents containing phosphate groups: 0.1 mol of vinylphosphonic acid and 0.11 mol of 3-aminopropyltriethoxysilane were dissolved in 100 mL of anhydrous ethanol at a molar ratio of 1:1.1 and reacted at 70 °C for 5 hours to obtain an intermediate. 0.1 mol of the intermediate and 0.055 mol of lead acetate at a molar ratio of 1:0.55 were added to 150 mL of dimethyl sulfoxide solvent and stirred at 90 °C for 10.5 hours to allow lead ions to coordinate with the phosphate groups in the intermediate, forming a lead-containing siloxane complex. The lead-containing siloxane complex was cooled to room temperature, and deionized water was added as a precipitant to precipitate the product. After filtration and washing, the product was dried under vacuum at 55 °C for 7 hours to obtain a lead-silicon bridging agent containing phosphate groups.

[0061] S2. 40 parts of lead zirconate titanate powder and 15 parts of barium titanate nanoparticles were dried at 120℃ for 4 hours, and then surface-treated with 2 parts of KH-550 silane coupling agent. 3 parts of a lead-silicon bridging agent containing phosphate groups were dissolved in 80 mL of anhydrous ethanol and ball-milled together with the surface-treated lead zirconate titanate powder and barium titanate nanoparticles at 300 rpm for 2 hours at a ball-to-material ratio of 5:1 to obtain the pretreated piezoelectric functional filler. 77.5 parts of silicone rubber and 22.5 parts of polyurethane rubber were added to a mixing device and premixed for 10 minutes; then 10 parts of dioctyl phthalate and 1 part of defoamer were added, and mixing continued for 10 minutes to form a homogeneous colloid. The pretreated piezoelectric functional filler and 1.25 parts of carbon nanotubes were added to the colloid in portions, gradually increasing the rotation speed to 650 rpm and mixing for 75 minutes, controlling the temperature to not exceed 50℃, to obtain the final mixture. The mixture was degassed under a vacuum of -0.095 MPa for 25 minutes; then 1.75 parts of isocyanate crosslinking agent, 1 part of platinum catalyst, 1 part of antioxidant and 1 part of defoamer were added, and the mixture was mixed at 300 rpm for 10 minutes to obtain a mixed colloid.

[0062] S3. Inject the mixed colloid into the mold, apply a pressure of 7.5 MPa in a flat vulcanizing machine, and perform gradient curing, that is, cure at 60℃ for 2 hours, at 100℃ for 2 hours, and at 120℃ for 1 hour in sequence. After demolding, let the material mature at room temperature for 24 hours, and then perform electrode preparation and polarization treatment. The polarization treatment conditions are to place the material in silicone oil, apply a DC electric field of 3 kV / mm at 90℃, and polarize for 45 minutes to obtain the piezoelectric elastomer material for underwater acoustic transducers.

[0063] This material is used to prepare the core vibrating element of underwater acoustic transducers, specifically for underwater sonar transmitting / receiving units, underwater communication sensors, or vibration sensing modules for marine environmental monitoring.

[0064] Example 3 A piezoelectric elastomer material for underwater acoustic transducers includes an elastomer matrix, a piezoelectric filler, a lead-silicon bridging agent containing phosphate groups, a conductive agent, and additives. The elastomer matrix is ​​an interpenetrating network structure obtained by crosslinking silicone rubber and polyurethane rubber in a platinum catalyst and isocyanate crosslinking agent system. The piezoelectric filler, dispersed in the elastomer matrix, is obtained by surface treatment with an amino-containing silane coupling agent using lead zirconate titanate and barium titanate as the matrix. The lead-silicon bridging agent containing phosphate groups connects the elastomer matrix and the piezoelectric filler. One end forms a bond with the metal ions of the piezoelectric filler, anchoring the lead-silicon bridging agent to the surface of the piezoelectric filler; the other end hydrolyzes and undergoes condensation crosslinking with the elastomer matrix to form a covalent network. The conductive agent, carbon nanotubes, forms a three-dimensional conductive network with the elastomer matrix through physical entanglement. The mass ratio of the elastomer matrix, piezoelectric filler, and lead-silicon bridging agent containing phosphate groups is 119:73:5; the mass ratio of silicone rubber and polyurethane rubber is 85:30. The mass ratio of lead zirconate titanate, barium titanate, and amino-containing silane coupling agent is 50:20:3.

[0065] The material comprises the following raw materials in parts by weight: 85 parts silicone rubber; 30 parts polyurethane rubber; 50 parts lead zirconate titanate powder; 20 parts barium titanate nanopowder; 15 parts dioctyl phthalate; 2 parts carbon nanotubes; 3 parts KH-550 silane coupling agent; 1.5 parts antioxidant; 3 parts defoamer; 1.5 parts platinum catalyst; 2.5 parts isocyanate crosslinking agent; and 5.0 parts lead-silicon bridging agent containing phosphate groups.

[0066] The preparation method of the above-mentioned piezoelectric elastomer material for underwater acoustic transducers includes the following steps: S1. Preparation of lead-silicon bridging agents containing phosphate groups: 0.1 mol of vinylphosphonic acid and 0.12 mol of 3-aminopropyltriethoxysilane were dissolved in 100 mL of anhydrous ethanol at a molar ratio of 1:1.2 and reacted at 80 °C for 6 hours to obtain an intermediate. 0.1 mol of intermediate A and 0.06 mol of lead acetate were added to 150 mL of dimethyl sulfoxide solvent at a molar ratio of 1:0.6 and stirred at 100 °C for 11 hours to allow lead ions to coordinate with the phosphate groups in the intermediate, forming a lead-containing siloxane complex. The lead-containing siloxane complex was cooled to room temperature, and deionized water was added as a precipitant to precipitate the product. After filtration and washing, the product was dried under vacuum at 60 °C for 8 hours to obtain a lead-silicon bridging agent containing phosphate groups.

[0067] S2. 50 parts of lead zirconate titanate powder and 20 parts of barium titanate nanoparticles were dried at 120℃ for 4 hours, and then surface-treated with 3 parts of KH-550 silane coupling agent. 5 parts of lead-silicon bridging agent containing phosphate groups were dissolved in 80 mL of anhydrous ethanol and ball-milled together with the surface-treated lead zirconate titanate powder and barium titanate nanoparticles at 300 rpm for 2 hours at a ball-to-material ratio of 5:1 to obtain the pretreated piezoelectric functional filler. 85 parts of silicone rubber and 30 parts of polyurethane rubber were added to a mixing device and premixed for 10 minutes; then 15 parts of dioctyl phthalate and 1.5 parts of defoamer were added, and mixing continued for 10 minutes to form a homogeneous colloid. The pretreated piezoelectric functional filler and 2 parts of carbon nanotubes were added to the colloid in portions, gradually increasing the rotation speed to 800 rpm and mixing for 90 minutes, controlling the temperature not to exceed 50℃, to obtain the final mixture. The mixture was degassed under a vacuum of -0.095 MPa for 30 minutes; then 2.5 parts of isocyanate crosslinking agent, 1.5 parts of platinum catalyst, 1.5 parts of antioxidant and 1.5 parts of defoamer were added, and the mixture was mixed at 300 rpm for 10 minutes to obtain a mixed colloid.

[0068] S3. Inject the mixed colloid into the mold, apply a pressure of 10MPa in a flat vulcanizing machine, and perform gradient curing, that is, cure at 60℃ for 2 hours, at 100℃ for 2 hours, and at 120℃ for 1 hour in sequence. After demolding, let the material mature at room temperature for 24 hours, and then perform electrode preparation and polarization treatment. The polarization treatment conditions are to place the material in silicone oil, apply a DC electric field of 4kV / mm at 100℃, and polarize for 60 minutes to obtain the piezoelectric elastomer material for underwater acoustic transducers.

[0069] This material is used to prepare the core vibrating element of underwater acoustic transducers, specifically for underwater sonar transmitting / receiving units, underwater communication sensors, or vibration sensing modules for marine environmental monitoring.

[0070] Comparative Example 1 A piezoelectric elastomer material for underwater acoustic transducers comprises the following raw materials in parts by weight: 70 parts silicone rubber; 15 parts polyurethane rubber; 30 parts lead zirconate titanate powder; 10 parts barium titanate nanopowder; 5 parts dioctyl phthalate; 0.5 parts carbon nanotubes; 1 part KH-550 silane coupling agent; 0.5 parts antioxidant; 1 part defoamer; 0.5 parts platinum catalyst; and 1 part isocyanate crosslinking agent.

[0071] A method for preparing a piezoelectric elastomer material for underwater acoustic transducers includes the following steps: S1. 30 parts of lead zirconate titanate powder and 10 parts of barium titanate nanoparticles were dried at 120℃ for 4 hours, then surface-treated with 1 part of KH-550 silane coupling agent, followed by ball milling at 300 rpm for 2 hours at a ball-to-material ratio of 5:1 to obtain the pretreated piezoelectric functional filler. 70 parts of silicone rubber and 15 parts of polyurethane rubber were added to a mixing device and premixed for 10 minutes; then 5 parts of dioctyl phthalate and 0.5 parts of defoamer were added, and mixing continued for 10 minutes to form a homogeneous colloid. The pretreated piezoelectric functional filler and 0.5 parts of carbon nanotubes were added to the colloid in portions, gradually increasing the rotation speed to 500 rpm and mixing for 60 minutes, controlling the temperature to not exceed 50℃ to obtain a mixture. The mixture was degassed under a vacuum of -0.095 MPa for 20 minutes; then 1 part of isocyanate crosslinking agent, 0.5 part of platinum catalyst, 0.5 part of antioxidant and 0.5 part of defoamer were added, and the mixture was mixed at 300 rpm for 10 minutes to obtain a mixed colloid.

[0072] S3. Inject the mixed colloid into the mold, apply a pressure of 5MPa in a flat vulcanizing machine, and perform gradient curing, that is, cure at 60℃ for 2 hours, at 100℃ for 2 hours, and at 120℃ for 1 hour in sequence. After demolding, let the material mature at room temperature for 24 hours, and then perform electrode preparation and polarization treatment. The polarization treatment conditions are to place the material in silicone oil, apply a DC electric field of 2kV / mm at 80℃, and polarize for 30 minutes to obtain the piezoelectric elastomer material for underwater acoustic transducers.

[0073] The difference between Comparative Example 1 and Example 1 is that no lead-silicon bridging agent containing phosphate groups was added.

[0074] Comparative Example 2 A piezoelectric elastomer material for underwater acoustic transducers comprises the following raw materials in parts by weight: 70 parts silicone rubber; 15 parts polyurethane rubber; 30 parts lead zirconate titanate powder; 10 parts barium titanate nanopowder; 5 parts dioctyl phthalate; 0.5 parts carbon nanotubes; 1 part KH-550 silane coupling agent; 0.5 parts antioxidant; 1 part defoamer; 0.5 parts platinum catalyst; 1 part isocyanate crosslinking agent; and 1.0 part isopropyl tris(dioctyl phosphate) titanate.

[0075] The preparation method of the above-mentioned piezoelectric elastomer material for underwater acoustic transducers includes the following steps: S1. 30 parts of lead zirconate titanate powder and 10 parts of barium titanate nanoparticles were dried at 120℃ for 4 hours, and then surface-treated with 1 part of KH-550 silane coupling agent. 1 part of isopropyl tris(dioctyl phosphate) titanate was dissolved in 50 mL of anhydrous ethanol and ball-milled together with the surface-treated lead zirconate titanate powder and barium titanate nanoparticles at 300 rpm for 2 hours at a ball-to-material ratio of 5:1 to obtain the pretreated piezoelectric functional filler. 70 parts of silicone rubber and 15 parts of polyurethane rubber were added to a mixing device and premixed for 10 minutes; then 5 parts of dioctyl phthalate and 0.5 parts of defoamer were added, and mixing continued for 10 minutes to form a homogeneous colloid. The pretreated piezoelectric functional filler and 0.5 parts of carbon nanotubes were added to the colloid in portions, gradually increasing the rotation speed to 500 rpm and mixing for 60 minutes, controlling the temperature to not exceed 50℃, to obtain the final mixture. The mixture was degassed under a vacuum of -0.095 MPa for 20 minutes; then 1 part of isocyanate crosslinking agent, 0.5 part of platinum catalyst, 0.5 part of antioxidant and 0.5 part of defoamer were added, and the mixture was mixed at 300 rpm for 10 minutes to obtain a mixed colloid.

[0076] S3. Inject the mixed colloid into the mold, apply a pressure of 5MPa in a flat vulcanizing machine, and perform gradient curing, that is, cure at 60℃ for 2 hours, at 100℃ for 2 hours, and at 120℃ for 1 hour in sequence. After demolding, let the material mature at room temperature for 24 hours, and then perform electrode preparation and polarization treatment. The polarization treatment conditions are to place the material in silicone oil, apply a DC electric field of 2kV / mm at 80℃, and polarize for 30 minutes to obtain the piezoelectric elastomer material for underwater acoustic transducers.

[0077] The difference between Comparative Example 2 and Example 1 is that the lead-silicon bridging agent containing phosphate groups is replaced with a titanate coupling agent, which is isopropyl tris(dioctyl phosphate) titanate.

[0078] Comparative Example 3 A piezoelectric elastomer material for underwater acoustic transducers comprises the following raw materials in parts by weight: 70 parts silicone rubber; 15 parts polyurethane rubber; 30 parts lead zirconate titanate powder; 10 parts barium titanate nanopowder; 5 parts dioctyl phthalate; 0.5 parts carbon nanotubes; 1 part KH-550 silane coupling agent; 0.5 parts antioxidant; 1 part defoamer; 0.5 parts platinum catalyst; 1 part isocyanate crosslinking agent; and 1.0 part KH-560 silane coupling agent.

[0079] The preparation method of the above-mentioned piezoelectric elastomer material for underwater acoustic transducers includes the following steps: S1. 30 parts of lead zirconate titanate powder and 10 parts of barium titanate nanoparticles were dried at 120℃ for 4 hours, and then surface-treated with 1 part of KH-550 silane coupling agent. 1 part of KH-560 silane coupling agent was dissolved in 50 mL of anhydrous ethanol and ball-milled together with the surface-treated lead zirconate titanate powder and barium titanate nanoparticles at 300 rpm for 2 hours at a ball-to-material ratio of 5:1 to obtain the pretreated piezoelectric functional filler. 70 parts of silicone rubber and 15 parts of polyurethane rubber were added to a mixing device and premixed for 10 minutes; then 5 parts of dioctyl phthalate and 0.5 parts of defoamer were added, and mixing continued for 10 minutes to form a homogeneous colloid. The pretreated piezoelectric functional filler and 0.5 parts of carbon nanotubes were added to the colloid in portions, gradually increasing the rotation speed to 500 rpm and mixing for 60 minutes, controlling the temperature to not exceed 50℃, to obtain the final mixture. The mixture was degassed under a vacuum of -0.095 MPa for 20 minutes; then 1 part of isocyanate crosslinking agent, 0.5 part of platinum catalyst, 0.5 part of antioxidant and 0.5 part of defoamer were added, and the mixture was mixed at 300 rpm for 10 minutes to obtain a mixed colloid.

[0080] S3. Inject the mixed colloid into the mold, apply a pressure of 5MPa in a flat vulcanizing machine, and perform gradient curing, that is, cure at 60℃ for 2 hours, at 100℃ for 2 hours, and at 120℃ for 1 hour in sequence. After demolding, let the material mature at room temperature for 24 hours, and then perform electrode preparation and polarization treatment. The polarization treatment conditions are to place the material in silicone oil, apply a DC electric field of 2kV / mm at 80℃, and polarize for 30 minutes to obtain the piezoelectric elastomer material for underwater acoustic transducers.

[0081] The difference between Comparative Example 3 and Example 1 is that the lead-silicon bridging agent containing phosphate groups was replaced with KH-560 silane coupling agent, which is γ-glycidoxypropyltrimethoxysilane.

[0082] The structure and performance of the materials in Examples 1 to 3 and Comparative Examples 1 to 3 were measured.

[0083] First, the mechanical properties and interfacial bonding quality of this invention were tested. The specific process was as follows: First, piezoelectric elastomer material samples were prepared according to the formulations of Examples 1-3 and Comparative Examples 1-3. At least five standard tensile and fatigue specimens were prepared for each formulation. The process included drying and surface treatment of the piezoelectric filler, mixing with the rubber matrix, vacuum degassing, gradient curing and polarization in a flat vulcanizing machine. Then, tensile tests were performed, and stress-strain curves were recorded at a rate of 500 mm / min to calculate the fracture strength and Young's modulus. The interfacial bonding quality was evaluated by observing the tensile fracture surface using an electron microscope. Next, fatigue tests were performed, applying a cyclic load at a frequency of 5 Hz with a maximum stress of 50% of the material's tensile strength until 1,000,000 cycles or specimen failure, monitoring changes in dynamic modulus and crack propagation. Finally, the performance differences between the example groups and the comparative example groups were compared through statistical analysis.

[0084] Figure 1 The images are scanning electron microscope (SEM) images of the piezoelectric elastomer materials used in underwater acoustic transducers in Embodiment 2 and Comparative Example 2 of the present invention. Figure 1 Figure A is a scanning electron microscope (SEM) image of Example 2, and Figure B is a scanning electron microscope (SEM) image of Comparative Example 2. Figure 1 As shown, the microstructure of the fracture surface of Comparative Example 2 shows that the filler and matrix interface are more tightly and firmly bonded, while the material of Comparative Example 2 partially debonded at the interface, and the cracks propagated along the interface. This demonstrates the excellent effect of the lead-silicon bridging agent of the present invention in enhancing the interfacial bonding force between inorganic fillers and organic polymer matrix, and significantly improving the integrity and durability of composite materials.

[0085] Figure 2 The diagram shows the enhanced interfacial bonding force of piezoelectric elastomer materials with different formulations for underwater acoustic transducers according to the present invention. Figure 2 As shown, Examples 1 to 3, which use lead-silicon bridging agents, are significantly superior to Comparative Examples 1 to 3, which do not use or use other types of coupling agents, in terms of mechanical properties and fatigue resistance. Specifically, the materials in the Example group exhibit higher fracture strength, modulus, and longer fatigue life.

[0086] Next, the piezoelectric and dielectric properties of this invention were tested. Specific steps included preparing a circular sample with a diameter of 20 mm and a thickness of 1 mm; preparing and polarizing electrodes according to the methods of Examples 1-3 and Comparative Examples 1-3; measuring the piezoelectric constant d33; applying a force of 0.25 N at a frequency of 10 Hz and averaging five points; then testing electrical properties, including measuring the dielectric constant and dielectric loss at a frequency of 1 kHz; and applying a maximum electric field of 4 kV / mm at a frequency of 10 Hz to perform hysteresis loop testing to obtain residual polarization and coercive field. A simple transducer prototype was then fabricated to test acoustic sensitivity. Finally, the data from the example group and the comparative group were compared, and the differences were analyzed using a t-test. The results are shown in Table 1 and... Figure 3 As shown.

[0087] Table 1 compares the performance of piezoelectric elastomer materials with different formulations used in underwater acoustic transducers. Figure 3 This is a performance comparison chart of piezoelectric elastomer materials with different formulations for underwater acoustic transducers according to the present invention. (Table 1 and...) Figure 3 It can be seen that all the sample groups using lead-silicon bridging agents showed significantly better piezoelectric, dielectric, and acoustic sensitivity than the control group samples without or using other types of coupling agents. With the increase of lead-silicon bridging agent dosage, the piezoelectric constant, dielectric constant, and remanent polarization intensity of the material showed a gradual increasing trend, while the dielectric loss and coercive field decreased accordingly, demonstrating the significant effect of the bridging agent on improving the overall electrical performance of the material. In contrast, the control group without any bridging agent showed the worst performance in all aspects, confirming the key role of interface modification in piezoelectric composite materials. Overall, the introduction of lead-silicon bridging agents effectively optimized the material system, enabling the piezoelectric elastomer to have superior performance.

[0088] Table 1 compares the performance of piezoelectric elastomer materials with different formulations used in underwater acoustic transducers. In addition, the present invention conducted environmental durability tests on materials with different formulations. The testing process was as follows: First, circular samples with a diameter of 20 mm and a thickness of 1 mm were prepared and polarized. Ten samples were prepared for each formulation, of which five were used for salt water immersion tests and five were used for high temperature and high humidity tests. For the salt water immersion test, the samples were immersed in a 3.5% NaCl solution at 25°C for 30 days. The weight change was measured every 7 days to calculate the water absorption rate and to detect the d33 value and dielectric properties. The high temperature and high humidity test was conducted at 85°C and 85% relative humidity for 1000 hours, with d33 and dielectric properties measured every 100 hours. After aging, the sample cross-section and surface were observed through microstructure analysis to evaluate filler migration and interface conditions. The water penetration path was analyzed in conjunction with elemental distribution. Subsequently, the piezoelectric property retention rate was calculated and the dielectric constant and loss changes were recorded. Finally, the performance degradation rate was analyzed by comparing the example group and the control group using linear regression.

[0089] Figure 4 The graph shows the durability results of piezoelectric elastomer materials with different formulations for underwater acoustic transducers according to the present invention. Figure 4As shown, the sample group of examples with added lead-silicon bridging agent exhibited significantly higher piezoelectric property retention and lower water absorption after salt water immersion and high temperature and humidity aging, and this effect increased with the increase of lead-silicon bridging agent dosage. In contrast, the performance degradation of Comparative Example 1 sample without any bridging agent was the most significant, while the durability of the comparative example sample using other types of coupling agents was better than that of Comparative Example 1, but still significantly inferior to that of the example group. This result fully demonstrates the unique and effective role of lead-silicon bridging agent in improving the environmental durability of piezoelectric elastomer materials.

[0090] Finally, the material obtained in this invention is applied to the core vibrating element of a hydroacoustic transducer, specifically in underwater sonar transmitting / receiving units, underwater communication sensors, or marine environmental monitoring vibration sensing modules. The specific application process is as follows: the piezoelectric elastomer material from Example 1 is cut to the required size, and silver paste is applied to the upper and lower surfaces as electrodes, with a silver paste coating amount of 0.07 g / cm³. 2 After polarization treatment, the material is assembled with a matching layer and a backing material. The matching layer has a double-layer structure: the first matching layer is a composite material of glass microspheres and epoxy resin, with the glass microspheres accounting for 40% by volume; the second matching layer is a blend of polyurethane and epoxy resin, located on the front surface of the piezoelectric material, on the side in contact with the water medium, used to achieve gradient acoustic impedance matching between the piezoelectric material and the water medium. The thickness of the matching layer is determined to be one-quarter wavelength based on the transducer's operating frequency. The backing material is a composite material of tungsten powder and epoxy resin, with the tungsten powder accounting for 50% by volume, located on the rear surface of the piezoelectric material, on the side opposite to the radiating surface, used to absorb backward radiated sound waves, broaden the transducer bandwidth, and provide mechanical support. The thickness of the backing material must be sufficient to attenuate backward radiated sound waves. The matching layer was custom-made by a professional transducer component manufacturer, Baoding Xinwei Electronic Technology Co., Ltd. The tungsten powder was purchased from Aladdin, with a particle size of 1μm~5μm and a purity ≥99.9%; the epoxy resin was purchased from Shanghai Litai New Mold Material Co., Ltd., using P99 resin. The matching layer, piezoelectric material, and backing material have a thickness ratio of 1:2:5. After arranging these elements, an underwater sonar transmitting / receiving array is fabricated for underwater target detection and imaging.

[0091] Tests showed that the flexible underwater acoustic transducer based on PZT / silicone rubber composite material in Example 1, with a transmit voltage response of 186.5 dB, improved the electroacoustic conversion efficiency by approximately 7 dB compared to a rigid transducer of the same size. Furthermore, its electroacoustic performance remained stable under different bending conditions, making it suitable for conformal installation on underwater vehicles of various sizes. The rigid transducer was a PZT-5H piezoelectric ceramic sheet, purchased from the 26th Research Institute of China Electronics Technology Group Corporation.

[0092] It should be noted that when numerical ranges are involved in this invention, it should be understood that both endpoints of each numerical range, as well as any value between the two endpoints, can be selected. Since the steps and methods used are the same as in the embodiments, preferred embodiments are described here to avoid redundancy. Although preferred embodiments of this invention have been described, those skilled in the art, once they understand the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended scope of protection is intended to be interpreted as including the preferred embodiments and all changes and modifications falling within the scope of this invention.

[0093] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of protection of this invention and its equivalents, this invention also intends to include these modifications and variations.

Claims

1. A piezoelectric elastomer material for underwater acoustic transducers, characterized in that, Piezoelectric elastomer materials used in underwater acoustic transducers include: The elastomer matrix is ​​an interpenetrating network structure obtained by crosslinking silicone rubber and polyurethane rubber in a catalyst and crosslinking agent system; the mass ratio of silicone rubber to polyurethane rubber is 70~85:15~30. The piezoelectric filler is dispersed in the elastomer matrix. The piezoelectric filler is obtained by surface treatment with an amino-containing silane coupling agent, with lead zirconate titanate and barium titanate as the matrix. The mass ratio of lead zirconate titanate, barium titanate and amino-containing silane coupling agent is 30~50:10~20:1~3. Lead-silicon bridging agents containing phosphate groups are used to connect elastomer matrices and piezoelectric fillers. One end of the lead-silicon bridging agent containing phosphate groups forms a bond coordination with the metal ions of the piezoelectric filler, anchoring the lead-silicon bridging agent on the surface of the piezoelectric filler. The other end undergoes hydrolysis and condensation crosslinking with the elastomer matrix to form a covalent network. The conductive agent forms a three-dimensional conductive network with the elastomer matrix through physical entanglement; The mass ratio of the elastomer matrix, piezoelectric filler, and lead-silicon bridging agent containing phosphate groups is 86.5~119:41~73:1~5.

2. The piezoelectric elastomer material for underwater acoustic transducers according to claim 1, characterized in that, The preparation method of the lead-silicon bridging agent containing phosphate groups includes the following steps: In the first solvent system, vinylphosphonic acid and 3-aminopropyltriethoxysilane were used as raw materials to carry out an aza-Michael addition reaction to obtain an intermediate; In the second solvent system, a coordination reaction was carried out using an intermediate and lead acetate as raw materials to obtain a lead-containing siloxane complex. Subsequently, the lead-containing siloxane complex was precipitated to obtain a lead-silicon bridging agent containing phosphate groups.

3. The piezoelectric elastomer material for underwater acoustic transducers according to claim 2, characterized in that, The molar ratio of vinylphosphonic acid to 3-aminopropyltriethoxysilane is 1:1 to 1.2, and the first solvent is anhydrous ethanol.

4. The piezoelectric elastomer material for underwater acoustic transducers according to claim 2, characterized in that, The molar ratio of the intermediate to lead acetate is 1:0.5~0.6, the second solvent is dimethyl sulfoxide, and the precipitation process uses a precipitant, which is water or anhydrous ethanol.

5. The piezoelectric elastomer material for underwater acoustic transducers according to claim 1, characterized in that, The amino-containing silane coupling agent is KH-550, KH-540 or KH-792; the mass ratio of conductive agent to silicone rubber is 0.5~2:70~85; the mass ratio of catalyst, crosslinking agent and silicone rubber is 0.5~1.5:1~2.5:70~85.

6. The piezoelectric elastomer material for underwater acoustic transducers according to claim 1, characterized in that, The piezoelectric elastomer material used in the underwater acoustic transducer also includes additives, including plasticizers, antioxidants, and defoamers. The mass ratio of plasticizers, antioxidants, defoamers, and silicone rubber is 5~15:0.5~1.5:1~3:70~85.

7. A method for preparing a piezoelectric elastomer material for a hydroacoustic transducer according to any one of claims 1 to 6, characterized in that, Includes the following steps: Weigh each raw material according to its weight composition; An elastomer matrix, piezoelectric filler, lead-silicon bridging agent containing phosphate groups, conductive agent, and additives are mixed to obtain a mixed colloid. This colloid is then subjected to curing, aging, and polarization treatments to obtain a piezoelectric elastomer material for underwater acoustic transducers.

8. The piezoelectric elastomer material for underwater acoustic transducers according to claim 7, characterized in that, The curing process employs a gradient curing method, specifically curing at 60℃ for 2 hours, 100℃ for 2 hours, and 120℃ for 1 hour sequentially; the pressure for gradient curing is 5MPa~10MPa.

9. The piezoelectric elastomer material for underwater acoustic transducers according to claim 7, characterized in that, The polarization treatment temperature is 80℃~100℃, the electric field is 2kV / mm~4kV / mm, and the polarization time is 30min~60min.

10. The use of a piezoelectric elastomer material for underwater acoustic transducers according to any one of claims 1 to 6 in the preparation of underwater acoustic transducers.

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