PET needle punched felt sound absorption board and its preparation process

Abstract

The present application relates to the technical field of needle-punched felt sound absorption board, and particularly relates to a PET needle-punched felt sound absorption board and a preparation process thereof, which solves the problems existing in the prior art, and comprises a gradient impedance matching layer, a sound energy conversion layer and a dynamic tuning layer; the three-layer structure realizes interface molecular chain entanglement through a hot-pressing process, and forms a continuous transition of acoustic impedance from 2.5*106 ray l to 8*105 ray l. The present application realizes precise interface control of a multi-material system through stage-by-stage structure prefabrication and physical field assisted forming. After independent preparation, the functional layers are integrated in order, avoiding structural damage caused by direct mixing. In particular, the sub-regional processing strategy of the gradient layer and the nano-skeleton construction technology of the sound energy layer significantly improve the broadband sound absorption performance of the product.

Description

Technical Field

[0001] This invention relates to the field of needle-punched felt sound-absorbing panels, and more particularly to PET needle-punched felt sound-absorbing panels and their preparation process. Background Technology

[0002] With the acceleration of urbanization and the aggravation of industrial noise pollution, the demand for sound-absorbing materials in fields such as construction, transportation, and aerospace is increasing. Traditional sound-absorbing materials (such as fiberglass mats and polyester fiberboards) mainly achieve sound energy absorption through porous structures, but their performance is limited by the single material structure and static design, resulting in problems such as a narrow sound absorption frequency band (concentrated in the mid and low frequencies), low energy conversion efficiency (sound energy cannot be effectively utilized), and poor environmental adaptability (performance degradation due to changes in temperature and humidity).

[0003] In addition, existing technologies generally lack the ability to absorb high-frequency noise and lack dynamic adjustment functions, making it difficult to meet the needs of broadband adaptive noise reduction in fields such as smart buildings and new energy vehicles.

[0004] Therefore, we propose a PET needle-punched felt sound-absorbing board and its preparation process to solve the above problems. Summary of the Invention

[0005] The purpose of this invention is to address the shortcomings of existing technologies by proposing a PET needle-punched felt sound-absorbing board and its preparation process.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] The PET needle-punched felt sound-absorbing panel comprises: a gradient impedance matching layer, composed of PET fibers and polyvinylidene fluoride piezoelectric fibers interwoven in a 7:3 volume ratio, with the fiber orientation angle controlled at 30°±5°, forming a continuous gradient structure with a porosity ranging from 80% to 50%; a sound energy conversion layer, comprising a composite system of carbon nanotube networks and barium titanate piezoelectric ceramic particles, wherein the carbon nanotubes form a three-dimensional conductive network penetrating the barium titanate piezoelectric ceramic particles, with a mass ratio of 1:4; and a dynamic tuning layer, composed of alternating layers of shape memory polymer fibers and magnetorheological elastomer sheets, each layer being 0.2mm±0.05mm thick with an interlayer angle of 45°; the three-layer structure achieves interfacial molecular chain entanglement through a hot-pressing process, forming an acoustic impedance ranging from 2.5×10⁻⁶. 6 rayl to 8×10 5 Continuous transitions in Rayl.

[0008] As a preferred technical solution:

[0009] As described above, the PET needle-punched felt sound-absorbing panel further comprises, in its sound energy conversion layer: a quantum confinement structure of alternating stacked boron nitride nanosheets and graphene oxide, with a stacking period of 5 nm ± 0.5 nm; and surface plasmon resonance units: silver nanowires and titanium dioxide core-shell structures, at a density of 10 nanometers per square centimeter. 8 The density of the particles is uniformly distributed; the layer achieves an acoustic-to-electric conversion efficiency of ≥12% in the 3800-5000Hz frequency band, while maintaining an NRC coefficient >0.95.

[0010] In the PET needle-punched felt sound-absorbing board described above, the diameter of the PET fibers in the gradient impedance matching layer is 10-50 μm, and the diameter of the polyvinylidene fluoride piezoelectric fibers is 10-15 μm.

[0011] In the PET needle-punched felt sound-absorbing board described above, the diameter of the carbon nanotube network in the sound energy conversion layer is 8-15 nm, and the particle size of the barium titanate piezoelectric ceramic particles is 180-200 nm.

[0012] As described above, in the PET needle-punched felt sound-absorbing board, the shape memory polymer fiber in the dynamic tuning layer has a Tg of 45°C. The shape memory polymer fiber is made of polyurethane, polyester, and / or epoxy resin, and achieves shape memory function through physical cross-linking of molecular chains and reversible phase. The magnetorheological elastomer sheet is composed of polyurethane and carbonyl iron powder, and the thickness of the magnetorheological elastomer sheet is 0.2±0.05mm.

[0013] A second aspect of the present invention provides a manufacturing process for a PET needle-punched felt sound-absorbing panel, comprising the following steps:

[0014] S1: Using a biaxial electrospinning system, a PET solution is injected into the left nozzle and a polyvinylidene fluoride piezoelectric fiber solution is injected into the right nozzle. By adjusting the voltage ratio of the two nozzles and the rotation speed of the collecting roller, a mixed fiber web with a fiber orientation angle of 28°±2° is formed on the rotating collector. The surface temperature of the collector is maintained at 60°C to allow the fibers to initially melt and crosslink, thereby obtaining a bicomponent fiber web with an orientation angle of 30°.

[0015] S2: The above-mentioned bicomponent fiber web is layered according to the porosity gradient requirements to complete the gradient layer;

[0016] S3: A multi-walled carbon nanotube network was grown on a nickel template using chemical vapor deposition, and then the nickel template was removed by etching with FeCl3 / HCl solution to obtain an independent three-dimensional carbon nanotube network.

[0017] S4: Barium titanate nanoparticles were ball-milled and mixed with PVDF-TrFE solution for 2 hours. The mixed slurry was then impregnated into an independent three-dimensional carbon nanotube network using a vacuum impregnation method. After evaporating the solvent at 80°C, a 10kV / mm electric field polarization treatment was applied to obtain a composite piezoelectric material.

[0018] S5: Boron nitride and graphene oxide are alternately deposited on the surface of the composite piezoelectric material using atomic layer deposition, and the deposition amount per cycle is controlled to form a periodic structure of 5.2±0.3nm. A total of 100 deposition cycles are completed to complete the acoustic energy layer.

[0019] S6: Polyurethane and epoxy resin are dissolved in tetrahydrofuran, and a 50μm thick liquid film is formed by slit extrusion. The film is stretched and oriented in an alternating magnetic field and then thermo-cured to obtain a shape memory polymer film.

[0020] S7: Mix polyurethane prepolymer with 40 vol% carbonyl iron powder, inject into a mold and apply a 1T magnetic field to make the particles arrange in a chain. After curing at 80℃, cut into 0.2 mm thin sheets to obtain magnetorheological elastomer thin sheets.

[0021] S8: The shape memory polymer film and the magnetorheological elastomer sheet are alternately stacked at a 45° cross angle. A laser positioning system is used to ensure that the interlayer angle tolerance is <1° to complete the tuning layer.

[0022] S9: The PET needle-punched felt sound-absorbing board is obtained by stacking the gradient layer, sound energy layer and tuning layer in the order of gradient layer, and using a segmented hot pressing process.

[0023] As described above, in the preparation process of the PET needle-punched felt sound-absorbing board, the layering process in step S2 includes: Top layer: 0.5% polyethylene glycol solution is sprayed by ultrasonic atomization, and the fibers are locally softened at 120°C to form 80% porosity; Middle layer: Pulsed hot pressing is used at a pressure of 5MPa, a temperature of 150°C, and a pulse frequency of 10Hz to reduce the porosity to 65%; Bottom layer: After impregnation with 0.1% silane coupling agent solution, it is heat-cured at 180°C to form 50% porosity.

[0024] As described above, in the preparation process of the PET needle-punched felt sound-absorbing board, the segmented hot-pressing process in S9 includes: the first segment: 180℃ / 5MPa, held for 2min, to generate molecular chain entanglement at the interface between the gradient layer and the sound energy layer; the second segment: 120℃ / 3MPa, held for 5min, to achieve bonding between the tuning layer and the sound energy layer; and the third segment: 60℃ / 1MPa, held for 10min, to eliminate residual stress.

[0025] The fabrication process of the PET needle-punched felt sound-absorbing panel described above also includes depositing an Ag / TiO2 core-shell structure on the surface using magnetron sputtering, with an Ag target power of 200W, a TiO2 reaction sputtering time of 30s, and a density controlled by a mask of 1×10⁻⁶. 8 pcs / cm 2 .

[0026] Compared with the prior art, the beneficial effects of the present invention are:

[0027] The diameter gradient distribution of PET fibers and PVDF piezoelectric fibers forms a multi-scale porous structure, which generates an acoustic phase interference effect at a 30° orientation angle. The coarse fibers construct the main framework, and the fine fibers fill the gaps, achieving progressive absorption of acoustic waves over a wide frequency range.

[0028] Carbon nanotubes penetrate barium titanate particles to form a "nanospring" structure. The conductive network of carbon nanotubes enhances carrier mobility, and the piezoelectric potential of barium titanate particles is bridged by carbon nanotubes to form a macroscopic potential. The surface plasmon resonance of the Ag / TiO2 core-shell structure couples with the piezoelectric effect. The local surface plasmon resonance of Ag nanowires enhances the local electric field, and the TiO2 shell forms a potential barrier to prevent charge recombination, resulting in an acoustic-electric conversion efficiency of 12% (compared to <5% for traditional piezoelectric materials).

[0029] The shape memory layer forms a dual response mechanism: when the temperature is >45℃, the shape memory layer shrinks; when the magnetic field is >0.3T, the magnetorheological layer modulus increases by two orders of magnitude, which synergistically adjusts the structural stiffness. The 45° stacked structure has a waveguide effect, and the alternating stacking forms a spiral acoustic channel, causing the residual sound waves to undergo multiple reflections and attenuation between the layers.

[0030] In summary, the components of this invention achieve breakthroughs in system-level performance through size matching (micron-nano multi-level structure), complementary physical properties (coordination of conductivity and dielectric properties), and energy transfer (mechanical-electrothermal coupling), reflecting a paradigm shift in material system design from simple superposition to directional assembly. Attached Figure Description

[0031] Figure 1 This is a schematic diagram of Embodiment 4 of the present invention;

[0032] Figure 2 The following is a line graph illustrating the data of an embodiment and comparative example of the present invention. Detailed Implementation

[0033] Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. In case of conflict, the definitions in this specification shall prevail. When a mass, concentration, temperature, time, or other value or parameter is expressed as a range, preferred range, or a series of upper and lower preferred values, this shall be understood as specifically disclosing all ranges formed by any pair of any upper or preferred value with any lower or preferred value, regardless of whether such range is disclosed individually. For example, a range of 1-50 should be understood to include selections from 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 3 Any number, combination of numbers, or subrange of numbers between the integers 6, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, or 50, and all decimal values ​​between the integers listed above, such as 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, and 1.9. Regarding subranges, specifically consider “nested subranges” extending from any endpoint of the range. For example, nested subranges of the exemplary range 1-50 could include 1-10, 1-20, 1-30, and 1-40 in one direction, or 50-40, 50-30, 50-20, and 50-10 in another direction.

[0034] The present invention will be further explained below with reference to specific embodiments. Unless otherwise specified, the experimental methods described in the following embodiments are conventional methods; unless otherwise specified, the reagents and materials can be obtained commercially.

[0035] A PET needle-punched felt sound-absorbing panel includes: a gradient impedance matching layer: composed of PET fibers and polyvinylidene fluoride piezoelectric fibers interwoven in a 7:3 volume ratio, with the fiber orientation angle controlled at 30°±5°, forming a continuous gradient structure with a porosity from 80% to 50%; a sound energy conversion layer: comprising a composite system of carbon nanotube networks and barium titanate piezoelectric ceramic particles, wherein the carbon nanotubes form a three-dimensional conductive network penetrating the barium titanate piezoelectric ceramic particles, with a mass ratio of 1:4; and a dynamic tuning layer: composed of shape memory polymer fibers and magnetorheological elastomer sheets alternately stacked, each layer having a thickness of 0.2mm±0.05mm and an interlayer angle of 45°.

[0036] The three-layer structure achieves interfacial molecular chain entanglement through hot pressing, forming a continuous transition in acoustic impedance from 2.5×10⁶ rayl to 8×10⁵ rayl.

[0037] The acoustic energy conversion layer also includes: a quantum confinement structure of alternating stacks of boron nitride nanosheets and graphene oxide, with a stacking period of 5 nm ± 0.5 nm; and surface plasmon resonance units: silver nanowires and titanium dioxide core-shell structures, at a density of 10 nanometers per square centimeter. 8 The density of the particles is uniformly distributed; the layer achieves an acoustic-to-electric conversion efficiency of ≥12% in the 3800-5000Hz frequency band, while maintaining an NRC coefficient >0.95.

[0038] Specifically, in the gradient impedance matching layer, the diameter of the PET fiber is 10-50 μm, and the diameter of the polyvinylidene fluoride piezoelectric fiber is 10-15 μm; in the sound energy conversion layer, the diameter of the carbon nanotube network is 8-15 nm, and the particle size of the barium titanate piezoelectric ceramic particles is 180-200 nm; in the dynamic tuning layer, the shape memory polymer fiber has a Tg of 45℃, and the shape memory polymer fiber is made of polyurethane, polyester and / or epoxy resin, achieving shape memory function through physical cross-linking of molecular chains and reversible phase; the magnetorheological elastomer sheet is composed of polyurethane and carbonyl iron powder, and the thickness of the magnetorheological elastomer sheet is 0.2±0.05 mm.

[0039] Example 1

[0040] A manufacturing process for a PET needle-punched felt sound-absorbing panel includes the following steps:

[0041] S1: Using a biaxial electrospinning system, a PET solution (10% concentration, hexafluoroisopropanol as solvent) is injected from the left nozzle, and a PVDF piezoelectric fiber solution (10% concentration, DMF / acetone mixture as solvent) is injected from the right nozzle. By adjusting the voltage ratio of the two nozzles (3:2) and the speed of the collecting roller (1800 rpm), a mixed fiber web with a fiber orientation angle of 26° is formed on the rotating collector. The collection volume ratio is controlled (PET:PVDF = 7:3), with fiber diameters of 25 μm for PET and 11 μm for PVDF. The collector surface temperature is maintained at 50°C to allow the fibers to initially melt and crosslink, obtaining a bicomponent fiber web with an orientation angle of 30°.

[0042] S2: The above-mentioned bicomponent fiber web is layered according to the porosity gradient requirements:

[0043] Top layer (air contact surface): A 0.5% polyethylene glycol solution is sprayed by ultrasonic atomization, which locally softens the fibers at 110°C, forming an 80% porosity.

[0044] Intermediate layer: The porosity is reduced to 65% by pulse hot pressing (pressure 4MPa, temperature 130℃, pulse frequency 8Hz);

[0045] Bottom layer: After impregnation with 0.1% silane coupling agent solution, it is thermo-cured at 160℃ to form a porosity of 50%;

[0046] Complete the gradient layer;

[0047] S3: A multi-walled carbon nanotube network was grown on a nickel template using chemical vapor deposition (CVD). The growth parameters were set as follows: acetylene flow rate 50 sccm, temperature 650℃, and growth time 25 min. Subsequently, the nickel template was removed by etching with FeCl3 / HCl solution to obtain an independent three-dimensional carbon nanotube network (10 nm in diameter).

[0048] S4: Barium titanate nanoparticles (185 nm in diameter) were ball-milled with PVDF-TrFE solution (mass ratio 4:1) for 2 h. The mixed slurry was impregnated into an independent three-dimensional carbon nanotube network using a vacuum impregnation method. After evaporating the solvent at 75 °C, an electric field of 8 kV / mm was applied for polarization treatment to obtain a composite piezoelectric material.

[0049] S5: Atomic layer deposition (ALD) is used to alternately deposit boron nitride (precursor triethylboron + NH3) and graphene oxide (O2 plasma assisted) on the surface of the composite piezoelectric, controlling the deposition amount per cycle to form a 4.9nm periodic structure, with a total of 90 deposition cycles to complete the acoustic energy layer;

[0050] S6: Polyurethane / epoxy resin (mass ratio 7:3) is dissolved in tetrahydrofuran and extruded through a slit to form a 50μm thick liquid film. The film is stretched and oriented in an alternating magnetic field (frequency 1kHz) and then thermosetting at 120℃ to form a shape memory film with a Tg of 45℃, thus obtaining a shape memory polymer film.

[0051] S7: A polyurethane prepolymer was mixed with 40 vol% carbonyl iron powder (4 μm particle size), injected into a mold, and then subjected to a 1T magnetic field to cause the particles to arrange in a chain. After curing at 70°C, it was cut into 0.2 mm thin sheets to obtain magnetorheological elastomer sheets.

[0052] S8: The shape memory polymer film and the magnetorheological elastomer sheet are alternately stacked at a 45° cross angle (0.2 mm per layer, 6 layers in total). A laser positioning system is used to ensure that the interlayer angle tolerance is <1° to complete the tuning layer.

[0053] S9: Stacked in the order of gradient layer - acoustic energy layer - tuning layer, using a segmented hot-pressing process:

[0054] First stage: 180℃ / 5MPa, maintain for 2min, so that molecular chain entanglement occurs at the interface between the gradient layer and the acoustic energy layer;

[0055] Second stage: 120℃ / 3MPa, hold for 5 minutes to achieve bonding between the tuning layer and the acoustic energy layer;

[0056] Third stage: 60℃ / 1MPa, hold for 10min to eliminate residual stress;

[0057] PET needle-punched felt sound-absorbing board was obtained.

[0058] In this embodiment, the Ag / TiO2 core-shell structure is deposited on the surface using magnetron sputtering, with an Ag target power of 200W and a TiO2 reactive sputtering time of 30s. The density is controlled to be 1×10⁻⁶ using a mask. 8 pcs / cm 2； A cyclic temperature field (40℃) and an alternating magnetic field (0.5T, frequency 10Hz) are applied to the finished product to complete the synergistic training of shape memory effect and magnetorheological effect.

[0059] Example 2

[0060] A manufacturing process for a PET needle-punched felt sound-absorbing panel includes the following steps:

[0061] S1: Using a biaxial electrospinning system, a PET solution (10% concentration, solvent: hexafluoroisopropanol) is injected into the left nozzle, and a PVDF piezoelectric fiber solution (12% concentration, solvent: DMF / acetone mixture) is injected into the right nozzle. By adjusting the voltage ratio of the two nozzles (3:2) and the speed of the collecting roller (2000 rpm), a mixed fiber web with a fiber orientation angle of 28° is formed on the rotating collector. The collection volume ratio is controlled (PET:PVDF = 7:3), with fiber diameters of 30 μm for PET and 12 μm for PVDF. The collector surface temperature is maintained at 60°C to allow the fibers to initially melt and crosslink, obtaining a bicomponent fiber web with a 30° orientation angle.

[0062] S2: The above-mentioned bicomponent fiber web is layered according to the porosity gradient requirements:

[0063] Top layer (air contact surface): A 0.5% polyethylene glycol solution is sprayed by ultrasonic atomization, which locally softens the fibers at 120°C, forming an 80% porosity.

[0064] Intermediate layer: The porosity is reduced to 65% by pulse hot pressing (pressure 5MPa, temperature 150℃, pulse frequency 10Hz);

[0065] Bottom layer: After impregnation with 0.1% silane coupling agent solution, it is thermo-cured at 180°C to form a porosity of 50%;

[0066] Complete the gradient layer;

[0067] S3: A multi-walled carbon nanotube network was grown on a nickel template using chemical vapor deposition (CVD). The growth parameters were set as follows: acetylene flow rate 50 sccm, temperature 680℃, and growth time 30 min. Subsequently, the nickel template was removed by etching with FeCl3 / HCl solution to obtain an independent three-dimensional carbon nanotube network (12 nm diameter).

[0068] S4: Barium titanate nanoparticles (190 nm in diameter) were ball-milled with PVDF-TrFE solution (mass ratio 4:1) for 2 h. The mixed slurry was impregnated into an independent three-dimensional carbon nanotube network using a vacuum impregnation method. After evaporating the solvent at 80 °C, a 10 kV / mm electric field polarization treatment was applied to obtain a composite piezoelectric material.

[0069] S5: Atomic layer deposition (ALD) is used to alternately deposit boron nitride (precursor triethylboron + NH3) and graphene oxide (O2 plasma assisted) on the surface of the composite piezoelectric material, controlling the deposition amount per cycle to form a 5.2nm periodic structure, with a total of 100 deposition cycles to complete the acoustic energy layer;

[0070] S6: Polyurethane / epoxy resin (mass ratio 7:3) is dissolved in tetrahydrofuran and extruded through a slit to form a 50μm thick liquid film. The film is stretched and oriented in an alternating magnetic field (frequency 1kHz) and then thermosetting at 120℃ to form a shape memory film with a Tg of 45℃, thus obtaining a shape memory polymer film.

[0071] S7: A polyurethane prepolymer was mixed with 40 vol% carbonyl iron powder (5 μm particle size), injected into a mold, and then subjected to a 1T magnetic field to cause the particles to arrange in a chain. After curing at 80℃, it was cut into 0.2 mm thin sheets to obtain magnetorheological elastomer sheets;

[0072] S8: The shape memory polymer film and the magnetorheological elastomer sheet are alternately stacked at a 45° cross angle (0.2 mm per layer, 6 layers in total). A laser positioning system is used to ensure that the interlayer angle tolerance is <1° to complete the tuning layer.

[0073] S9: Stacked in the order of gradient layer - acoustic energy layer - tuning layer, using a segmented hot-pressing process:

[0074] First stage: 180℃ / 5MPa, maintain for 2min, so that molecular chain entanglement occurs at the interface between the gradient layer and the acoustic energy layer;

[0075] Second stage: 120℃ / 3MPa, hold for 5 minutes to achieve bonding between the tuning layer and the acoustic energy layer;

[0076] Third stage: 60℃ / 1MPa, hold for 10min to eliminate residual stress;

[0077] PET needle-punched felt sound-absorbing board was obtained.

[0078] In this embodiment, the Ag / TiO2 core-shell structure is deposited on the surface using magnetron sputtering, with an Ag target power of 200W and a TiO2 reactive sputtering time of 30s. The density is controlled to be 1×10⁻⁶ using a mask. 8 pcs / cm 2A cyclic temperature field (45℃) and an alternating magnetic field (0.7T, frequency 12Hz) are applied to the finished product to complete the synergistic training of shape memory effect and magnetorheological effect.

[0079] Example 3

[0080] A manufacturing process for a PET needle-punched felt sound-absorbing panel includes the following steps:

[0081] S1: Using a biaxial electrospinning system, a PET solution (10% concentration, solvent: hexafluoroisopropanol) is injected into the left nozzle, and a PVDF piezoelectric fiber solution (12% concentration, solvent: DMF / acetone mixture) is injected into the right nozzle. By adjusting the voltage ratio of the two nozzles (3:2) and the speed of the collecting roller (2000 rpm), a mixed fiber web with a fiber orientation angle of 29° is formed on the rotating collector. The collection volume ratio is controlled (PET:PVDF = 7:3), with fiber diameters of 32 μm for PET and 13 μm for PVDF. The collector surface temperature is maintained at 60°C to allow the fibers to initially melt and crosslink, obtaining a bicomponent fiber web with an orientation angle of 30°.

[0082] S2: The above-mentioned bicomponent fiber web is layered according to the porosity gradient requirements:

[0083] Top layer (air contact surface): A 0.5% polyethylene glycol solution is sprayed by ultrasonic atomization, which locally softens the fibers at 130°C, forming an 80% porosity.

[0084] Intermediate layer: The porosity is reduced to 65% by pulse hot pressing (pressure 5MPa, temperature 160℃, pulse frequency 11Hz);

[0085] Bottom layer: After impregnation with 0.1% silane coupling agent solution, it is thermo-cured at 185°C to form a porosity of 50%;

[0086] Complete the gradient layer;

[0087] S3: A multi-walled carbon nanotube network was grown on a nickel template using chemical vapor deposition (CVD). The growth parameters were set as follows: acetylene flow rate 50 sccm, temperature 685℃, and growth time 30 min. Subsequently, the nickel template was removed by etching with FeCl3 / HCl solution to obtain an independent three-dimensional carbon nanotube network (13 nm in diameter).

[0088] S4: Barium titanate nanoparticles (192 nm in diameter) were ball-milled with PVDF-TrFE solution (mass ratio 4:1) for 2 h. The mixed slurry was impregnated into an independent three-dimensional carbon nanotube network using a vacuum impregnation method. After evaporating the solvent at 80 °C, a 10 kV / mm electric field polarization treatment was applied to obtain a composite piezoelectric material.

[0089] S5: Atomic layer deposition (ALD) is used to alternately deposit boron nitride (precursor triethylboron + NH3) and graphene oxide (O2 plasma assisted) on the surface of the composite piezoelectric material, controlling the deposition amount per cycle to form a 5.4nm periodic structure, with a total of 110 deposition cycles to complete the acoustic energy layer;

[0090] S6: Polyurethane / epoxy resin (mass ratio 7:3) is dissolved in tetrahydrofuran and extruded through a slit to form a 50μm thick liquid film. The film is stretched and oriented in an alternating magnetic field (frequency 1kHz) and then thermosetting at 130℃ to form a shape memory film with a Tg of 45℃, thus obtaining a shape memory polymer film.

[0091] S7: A polyurethane prepolymer was mixed with 40 vol% carbonyl iron powder (particle size 5 μm), injected into a mold, and then subjected to a 1T magnetic field to cause the particles to arrange in a chain. After curing at 85℃, it was cut into 0.2 mm thin sheets to obtain magnetorheological elastomer sheets;

[0092] S8: The shape memory polymer film and the magnetorheological elastomer sheet are alternately stacked at a 45° cross angle (0.2 mm per layer, 6 layers in total). A laser positioning system is used to ensure that the interlayer angle tolerance is <1° to complete the tuning layer.

[0093] S9: Stacked in the order of gradient layer - acoustic energy layer - tuning layer, using a segmented hot-pressing process:

[0094] First stage: 180℃ / 5MPa, maintain for 2min, so that molecular chain entanglement occurs at the interface between the gradient layer and the acoustic energy layer;

[0095] Second stage: 120℃ / 3MPa, hold for 5 minutes to achieve bonding between the tuning layer and the acoustic energy layer;

[0096] Third stage: 60℃ / 1MPa, hold for 10min to eliminate residual stress;

[0097] PET needle-punched felt sound-absorbing board was obtained.

[0098] In this embodiment, the Ag / TiO2 core-shell structure is deposited on the surface using magnetron sputtering, with an Ag target power of 200W and a TiO2 reactive sputtering time of 30s. The density is controlled to be 1×10⁻⁶ using a mask. 8 pcs / cm 2 A cyclic temperature field (48℃) and an alternating magnetic field (0.7T, frequency 13Hz) are applied to the finished product to complete the synergistic training of shape memory effect and magnetorheological effect.

[0099] Example 4

[0100] A manufacturing process for a PET needle-punched felt sound-absorbing panel includes the following steps:

[0101] S1: Using a biaxial electrospinning system, a PET solution (10% concentration, solvent: hexafluoroisopropanol) is injected into the left nozzle, and a PVDF piezoelectric fiber solution (12% concentration, solvent: DMF / acetone mixture) is injected into the right nozzle. By adjusting the voltage ratio of the two nozzles (3:2) and the speed of the collecting roller (2100 rpm), a mixed fiber web with a fiber orientation angle of 30° is formed on the rotating collector. The collection volume ratio is controlled (PET:PVDF = 7:3), with fiber diameters of 35 μm for PET and 14 μm for PVDF. The collector surface temperature is maintained at 60°C to allow the fibers to initially melt and crosslink, obtaining a bicomponent fiber web with a 30° orientation angle.

[0102] S2: The above-mentioned bicomponent fiber web is layered according to the porosity gradient requirements:

[0103] Top layer (air contact surface): A 0.5% polyethylene glycol solution is sprayed by ultrasonic atomization, which locally softens the fibers at 130°C, forming an 80% porosity.

[0104] Intermediate layer: The porosity is reduced to 65% by pulse hot pressing (pressure 7MPa, temperature 160℃, pulse frequency 13Hz);

[0105] Bottom layer: After impregnation with 0.1% silane coupling agent solution, it is thermo-cured at 180°C to form a porosity of 50%;

[0106] Complete the gradient layer;

[0107] S3: A multi-walled carbon nanotube network was grown on a nickel template using chemical vapor deposition (CVD). The growth parameters were set as follows: acetylene flow rate 50 sccm, temperature 680℃, and growth time 30 min. Subsequently, the nickel template was removed by etching with FeCl3 / HCl solution to obtain an independent three-dimensional carbon nanotube network (14 nm diameter).

[0108] S4: Barium titanate nanoparticles (195 nm in diameter) were ball-milled with PVDF-TrFE solution (mass ratio 4:1) for 2 h. The mixed slurry was impregnated into an independent three-dimensional carbon nanotube network using a vacuum impregnation method. After evaporating the solvent at 80 °C, a 10 kV / mm electric field polarization treatment was applied to obtain a composite piezoelectric material.

[0109] S5: Atomic layer deposition (ALD) is used to alternately deposit boron nitride (precursor triethylboron + NH3) and graphene oxide (O2 plasma assisted) on the surface of the composite piezoelectric material, controlling the deposition amount per cycle to form a 5.5nm periodic structure, with a total of 110 deposition cycles to complete the acoustic energy layer;

[0110] S6: Polyurethane / epoxy resin (mass ratio 7:3) is dissolved in tetrahydrofuran and extruded through a slit to form a 50μm thick liquid film. The film is stretched and oriented in an alternating magnetic field (frequency 1kHz) and then thermosetting at 120℃ to form a shape memory film with a Tg of 45℃, thus obtaining a shape memory polymer film.

[0111] S7: A polyurethane prepolymer was mixed with 40 vol% carbonyl iron powder (5 μm particle size), injected into a mold, and then subjected to a 1T magnetic field to cause the particles to arrange in a chain. After curing at 80℃, it was cut into 0.2 mm thin sheets to obtain magnetorheological elastomer sheets;

[0112] S8: The shape memory polymer film and the magnetorheological elastomer sheet are alternately stacked at a 45° cross angle (0.2 mm per layer, 6 layers in total). A laser positioning system is used to ensure that the interlayer angle tolerance is <1° to complete the tuning layer.

[0113] S9: Stacked in the order of gradient layer - acoustic energy layer - tuning layer, using a segmented hot-pressing process:

[0114] First stage: 180℃ / 5MPa, maintain for 2min, so that molecular chain entanglement occurs at the interface between the gradient layer and the acoustic energy layer;

[0115] Second stage: 120℃ / 3MPa, hold for 5 minutes to achieve bonding between the tuning layer and the acoustic energy layer;

[0116] Third stage: 60℃ / 1MPa, hold for 10min to eliminate residual stress;

[0117] PET needle-punched felt sound-absorbing board was obtained.

[0118] In this embodiment, the Ag / TiO2 core-shell structure is deposited on the surface using magnetron sputtering, with an Ag target power of 200W and a TiO2 reactive sputtering time of 30s. The density is controlled to be 1×10⁻⁶ using a mask. 8 pcs / cm 2； A cyclic temperature field (50℃) and an alternating magnetic field (0.8T, frequency 14Hz) are applied to the finished product to complete the synergistic training of shape memory effect and magnetorheological effect.

[0119] Comparative Example 1

[0120] The preparation process of a PET needle-punched felt sound-absorbing board is basically the same as that in Example 4, except that the gradient layer layering process is missing (step S2 only maintains uniform porosity).

[0121] Comparative Example 2

[0122] The preparation process of a PET needle-punched felt sound-absorbing board is basically the same as that in Example 4, except that the carbon nanotube network of the sound energy layer is missing (step S3 is skipped, and barium titanate / PVDF-TrFE composite is used directly).

[0123] Comparative Example 3

[0124] The preparation process of a PET needle-punched felt sound-absorbing board is basically the same as that in Example 4, except that the dynamic tuning layer is missing (steps S6 to S8 are skipped, and only a single PET layer is retained).

[0125] Comparative Example 4

[0126] The preparation process of a PET needle-punched felt sound-absorbing board is basically the same as that in Example 4, except that the plasma resonance unit is missing (step S9 skips Ag / TiO2 sputtering).

[0127] The PET needle-punched felt sound-absorbing panels prepared in Examples 1 to 4 and Comparative Examples 1 to 4 were tested:

[0128] 1. Sound absorption performance testing

[0129] Standard basis: GB / T 20247 "Acoustic Reverberation Chamber Sound Absorption Measurement"

[0130] Detection method:

[0131] The sample (500mm × 500mm) was placed in a reverberation chamber and the sound field was excited using a full-band sound source (125Hz~5000Hz).

[0132] Measure the sound pressure decay time, calculate the noise reduction coefficient (NRC), and take the average sound absorption coefficient of the four frequency bands of 250Hz, 500Hz, 1000Hz, and 2000Hz.

[0133] The measured data must meet the sound absorption performance classification specified in JC / T 2704-2022 (Level 1 NRC≥0.85, Level 2 ≥0.75, Level 3 ≥0.65).

[0134] 2. Combustion performance testing

[0135] Standard basis: GB 8624 "Classification of Burning Performance of Building Materials and Products"

[0136] Detection method:

[0137] Single-unit combustion test (SBI) was used to measure parameters such as heat release rate and smoke production.

[0138] Flame-retardant materials must meet the B1 grade (flame-retardant grade): total heat release (THR) ≤ 7.5 MJ / m2, smoke generation rate ≤ 0.25 m2 / s15.

[0139] 3. Mechanical property testing

[0140] areal density and dimensional tolerance:

[0141] Standard basis: JC / T 2704-2022 "Polyester Fiber Decorative Sound Absorbing Boards"

[0142] Testing methods: Weigh the surface density with an electronic balance (allowable deviation ±5%), and measure the thickness with a vernier caliper (allowable deviation ±0.2mm).

[0143] Bending deformation:

[0144] Standard basis: GB / T 17657 "Test Methods for Physical and Chemical Properties of Wood-based Panels and Decorative Wood-based Panels"

[0145] Test method: Three-point bending test, span 300mm, loading rate 5mm / min, measure the maximum deflection (pass limit ≤3mm).

[0146] 4. Sound-to-electricity conversion efficiency testing

[0147] Standard basis: GB / T 16731 ​​"Classification of Sound Absorption Performance of Building Sound Absorption Products" (Supplementary Piezoelectric Characteristic Test)

[0148] Detection method:

[0149] In the anechoic chamber, an 85dB sound pressure level (3800~5000Hz) sound wave is input, and the output voltage is measured.

[0150] Calculate the sound-to-electricity conversion efficiency: in (S is the sample area).

[0151] The results are shown in Table 1 below:

[0152] Table 1

[0153]

[0154] Table 1 above clearly shows that all four examples exhibit superior performance. Through gradient layer parameter optimization, refinement of the acoustic energy layer nanostructure, increase in plasma unit density, and dynamic tuning training, peak performance in NRC and acoustic-electric efficiency is gradually achieved. The examples demonstrate high consistency in flammability and durability, verifying the reliability of the core process.

[0155] Reference Figure 1-2 In Example 4 and Comparative Example 1, all other conditions were the same. Comparative Example 1: lacked gradient layer layering treatment; performance deteriorated: NRC decreased to 0.72 (Example: 0.96), and the high-frequency (>3000Hz) sound absorption coefficient decreased significantly (from 0.98 to 0.55). The flammability rating decreased to B2 (combustible) because the bottom layer was not cured by silane coupling agent, resulting in reduced material thermal stability.

[0156] Mechanism: Uniform porosity (65%) leads to abrupt changes in acoustic impedance, increasing reflection loss (reflectivity from 5% to 23%). Unlayered fiber mesh lacks a gradient transition and cannot achieve broadband sound absorption (covering only 500–3000 Hz).

[0157] Comparative Example 2: Carbon nanotube network lacking acoustic energy layer; performance degradation: acoustic-electric efficiency only 5.8% (Example: 12.5%), efficiency <3% in the frequency band above 3800Hz. Durability decreased (NRC attenuation 9.5%), as barium titanate particles are prone to detachment due to the lack of carbon nanotube network support.

[0158] Mechanism: Barium titanate particles are directly dispersed in the PVDF-TrFE matrix, resulting in a discontinuous conductive network and a decrease in carrier mobility (from 200→50cm). 2 Without the buffering effect of the carbon nanotube framework, piezoelectric ceramics develop microcracks under cyclic stress, leading to performance degradation.

[0159] Comparative Example 3: Lack of dynamic tuning layer; performance degradation: NRC attenuation to 0.88 (Example: 0.96), and a 15% decrease in the high-frequency (>4000Hz) sound absorption coefficient. Durability is significantly reduced (NRC attenuation of 6.3%), as the internal stress of the material cannot be released due to the lack of dynamic tuning function.

[0160] mechanism:

[0161] The lack of a 45° cross-layered helical waveguide structure reduces the number of sound wave reflections (from 7 to 3), resulting in insufficient energy dissipation. Furthermore, the absence of shape memory effect (Tg = 45℃) for adjusting porosity leads to poor sound absorption stability under temperature fluctuations (fluctuation rate increases from 5% to 18%).

[0162] Comparative Example 4: Missing plasma resonant unit; performance degradation: high-frequency (3800–5000 Hz) acoustic-electric efficiency decreased to 10.1% (Example: 12.5%). NRC changed from 0.96 to 0.91, and the high-frequency absorption coefficient decreased (from 0.98 to 0.89).

[0163] mechanism:

[0164] The absence of the Ag / TiO2 core-shell structure leads to the disappearance of the localized surface plasmon resonance (LSPR) effect, and the electric field enhancement factor changes from 50 to 1. High-frequency acoustic waves cannot enhance the piezoelectric response through plasma coupling, thus limiting energy conversion efficiency.

[0165] In summary, the gradient layer layering process in this invention is the core guarantee for broadband sound absorption (NRC≥0.95), contributing 34% to the improvement in sound absorption performance. The carbon nanotube network plays a decisive role in the sound-to-electric conversion efficiency (contributing 53%), and its three-dimensional conductive framework significantly improves carrier mobility. The dynamic tuning layer, through its 45° stacking design and shape memory effect, enhances high-frequency sound absorption stability (contributing 67% to durability). Although the plasma resonant unit contributes less to the overall performance, it can specifically optimize the sound-to-electric conversion efficiency in the high-frequency range (3800~5000Hz) (+19%).

[0166] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A PET felt sound-absorbing board, characterized in that, include: Gradient impedance matching layer: It is composed of PET fibers and polyvinylidene fluoride piezoelectric fibers interwoven in a volume ratio of 7:3, with the fiber orientation angle controlled at 30°±5°, forming a gradient distribution of porosity from 80% on the surface to 50% on the bottom layer. Sound energy conversion layer: a composite system containing carbon nanotube network and barium titanate piezoelectric ceramic particles. The composite system is obtained by ball milling barium titanate nanoparticles with PVDF-TrFE solution for 2 hours, infiltrating the mixed slurry into an independent three-dimensional carbon nanotube network using a vacuum impregnation method, evaporating the solvent at 80°C, and then applying a 10kV / mm electric field polarization treatment. The acoustic energy conversion layer also includes: a quantum confinement structure of alternating stacks of boron nitride nanosheets and graphene oxide, with a stacking period of 5 nm ± 0.5 nm; and surface plasmon resonance units: silver nanowires and titanium dioxide core-shell structures, at a density of 10 nanometers per square centimeter. 8 The density of the particles is uniformly distributed; this layer achieves an acoustic-to-electric conversion efficiency of ≥12% in the 3800-5000Hz frequency band, while maintaining an NRC coefficient >0.95; Dynamic tuning layer: It is composed of alternating layers of shape memory polymer film and magnetorheological elastomer sheet, each layer is 0.2mm ± 0.05mm thick, and the interlayer angle is 45°; The three-layer structure achieves interfacial molecular chain entanglement through a hot-pressing process, resulting in an acoustic impedance of 2.5 × 10⁻⁶. 6 rayl to 8×10 5 Continuous transitions in Rayl.

2. The PET felt sound-absorbing board according to claim 1, characterized in that, In the gradient impedance matching layer, the diameter of the PET fiber is 10-50 μm, and the diameter of the polyvinylidene fluoride piezoelectric fiber is 10-15 μm.

3. The PET felt sound-absorbing board according to claim 2, characterized in that, In the acoustic energy conversion layer, the diameter of the carbon nanotube network is 8-15 nm, and the particle size of the barium titanate piezoelectric ceramic particles is 180-200 nm.

4. The PET felt sound-absorbing board according to claim 3, characterized in that, In the dynamic tuning layer, the shape memory polymer film has a Tg of 45°C. The shape memory polymer film is made of polyurethane, polyester and / or epoxy resin, and achieves shape memory function through physical cross-linking of molecular chains and reversible phase. The magnetorheological elastomer sheet is composed of polyurethane and carbonyl iron powder, and the thickness of the magnetorheological elastomer sheet is 0.2±0.05 mm.

5. A manufacturing process for a PET felt sound-absorbing panel according to any one of claims 1 to 4, characterized in that, Includes the following steps: S1: Using a biaxial electrospinning system, a PET solution is injected into the left nozzle and a polyvinylidene fluoride piezoelectric fiber solution is injected into the right nozzle. By adjusting the voltage ratio of the two nozzles and the rotation speed of the collecting roller, a mixed fiber web with a fiber orientation angle of 28°±2° is formed on the rotating collector. The surface temperature of the collector is maintained at 60°C to allow the fibers to initially melt and crosslink, thereby obtaining a bicomponent fiber web with an orientation angle of 30°. S2: The above-mentioned bicomponent fiber web is layered according to the porosity gradient requirements to complete the gradient layer; S3: A multi-walled carbon nanotube network was grown on a nickel template using chemical vapor deposition, and then the nickel template was removed by etching with FeCl3 / HCl solution to obtain an independent three-dimensional carbon nanotube network. S4: Barium titanate nanoparticles were ball-milled and mixed with PVDF-TrFE solution for 2 hours. The mixed slurry was then impregnated into an independent three-dimensional carbon nanotube network using a vacuum impregnation method. After evaporating the solvent at 80°C, a 10kV / mm electric field polarization treatment was applied to obtain a composite piezoelectric material. S5: Boron nitride and graphene oxide are alternately deposited on the surface of the composite piezoelectric material using atomic layer deposition (ALD), with the deposition amount per cycle controlled to form a periodic structure of 5.2 ± 0.3 nm. A total of 100 deposition cycles are completed to form the acoustic energy layer. S6: Polyurethane and epoxy resin are dissolved in tetrahydrofuran, and a 50μm thick liquid film is formed by slit extrusion. The film is stretched and oriented in an alternating magnetic field and then thermo-cured to obtain a shape memory polymer film. S7: Mix polyurethane prepolymer with 40 vol% carbonyl iron powder, inject into a mold and apply a 1T magnetic field to make the particles arrange in a chain. After curing at 80℃, cut into 0.2 mm thin sheets to obtain magnetorheological elastomer thin sheets. S8: The shape memory polymer film and the magnetorheological elastomer sheet are alternately stacked at a 45° cross angle. A laser positioning system is used to ensure that the interlayer angle tolerance is <1° to complete the tuning layer. S9: The PET felt sound-absorbing board is obtained by stacking the gradient layer, sound energy layer and tuning layer in the order of gradient layer, and using a segmented hot pressing process.

6. The manufacturing process of the PET felt sound-absorbing panel according to claim 5, characterized in that, In step S2, the layering process includes: Top layer: A 0.5% polyethylene glycol solution is sprayed by ultrasonic atomization, and the fibers are locally softened at 120°C to form an 80% porosity. Intermediate layer: Pulsed hot pressing is used at a pressure of 5 MPa, a temperature of 150℃, and a pulse frequency of 10 Hz to reduce the porosity to 65%. Bottom layer: After impregnation with 0.1% silane coupling agent solution, it is heat-cured at 180℃ to form a porosity of 50%.

7. The manufacturing process of the PET felt sound-absorbing panel according to claim 6, characterized in that, In step S9, the segmented hot pressing process includes: First stage: 180℃ / 5MPa, maintain for 2min, so that molecular chain entanglement occurs at the interface between the gradient layer and the acoustic energy layer; Second stage: 120℃ / 3MPa, hold for 5 minutes to achieve bonding between the tuning layer and the acoustic energy layer; Third stage: 60℃ / 1MPa, hold for 10 minutes to eliminate residual stress.

8. The manufacturing process of the PET felt sound-absorbing panel according to claim 5, characterized in that... It also includes the deposition of Ag / TiO2 core-shell structures on the surface using magnetron sputtering, with an Ag target power of 200W, a TiO2 reactive sputtering time of 30s, and a density controlled by a mask of 1×10⁻⁶. 8 pcs / cm 2 .

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