PET (Polyethylene Terephthalate) needled felt acoustic panel and preparation process thereof

Abstract

The invention relates to the technical field of needled felt acoustic panels, in particular to a PET needled felt acoustic panel and a preparation process thereof, and solves the defects in the prior art. The PET needled felt acoustic panel comprises a gradient impedance matching layer, a sound energy conversion layer and a dynamic tuning layer; interface molecular chain entanglement of the three-layer structure is achieved through a hot pressing process, and continuous transition of acoustic impedance from 2.5 * 10 < 6 > ray l to 8 * 10 < 5 > ray l is formed. According to the method, through staged structure prefabrication and physical field auxiliary forming, precise interface control of a multi-material system is achieved. All the functional layers are orderly integrated after being independently prepared, and structural damage caused by direct mixing is avoided. Especially, the broadband sound absorption performance of the product is remarkably improved through the regional processing strategy of the gradient layer and the nanometer framework construction technology of the sound energy layer.

Description

Technical Field

[0001] The invention relates to the technical field of needle-punched felt sound-absorbing panels, in particular to a PET needle-punched felt sound-absorbing panel and a preparation process thereof. Background Art

[0002] With the acceleration of urbanization and the intensification of industrial noise pollution, the demand for sound-absorbing materials in the fields of construction, transportation, aerospace, etc. is growing. Traditional sound-absorbing materials (such as glass fiber felt and polyester fiberboard) mainly absorb sound energy through porous structures, but their performance is limited by the single material structure and static design, and there are problems such as narrow sound absorption frequency band (concentrated on medium and low frequencies), low energy conversion efficiency (sound energy cannot be effectively utilized), and poor environmental adaptability (temperature and humidity changes lead to performance attenuation).

[0003] In addition, existing technologies generally have insufficient absorption capacity for high-frequency noise and lack dynamic adjustment functions, making it difficult to meet the needs of smart buildings, new energy vehicles and other fields for broadband adaptive noise reduction.

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

[0005] The purpose of the present invention is to solve the shortcomings of the prior art and to propose a PET needle felt sound-absorbing board and a preparation process thereof.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] The PET needle-punched felt sound-absorbing board includes: a gradient impedance matching layer: 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 continuous gradient structure with a porosity ranging from 80% to 50%; an acoustic energy conversion layer: a composite system comprising a nano-carbon tube network and barium titanate piezoelectric ceramic particles, wherein the nano-carbon tubes form a three-dimensional conductive network penetrating the barium titanate piezoelectric ceramic particles, with a mass ratio of 1:4; a dynamic tuning layer: composed of shape memory polymer fibers and magnetorheological elastomer sheets alternately stacked, each layer having a thickness of 0.2 mm±0.05 mm and an interlayer angle of 45°; the three-layer structure realizes interface molecular chain entanglement through a hot pressing process, forming an acoustic impedance ranging from 2.5×10 6 rayl to 8×10 5 rayl's continuous transition.

[0008] As the preferred technical solution:

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

[0010] In the PET needle felt sound-absorbing board as described above, 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.

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

[0012] In the PET needle felt sound-absorbing board as described above, in the dynamic tuning layer, the Tg of the shape memory polymer fiber is 45° C., the shape memory polymer fiber is made of polyurethane, polyester and / or epoxy resin, and the shape memory function is achieved through physical crosslinking and reversible phase of the molecular chain; 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.

[0013] The second aspect of the present invention provides a preparation process of a PET needle felt sound-absorbing board, comprising the following steps:

[0014] S1: Using a biaxial electrospinning system, the left nozzle injects PET solution, and the right nozzle injects polyvinylidene fluoride piezoelectric fiber solution. By adjusting the voltage ratio of the two nozzles and the 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, and a bicomponent fiber web with an orientation angle of 30° is obtained;

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

[0016] S3: Using chemical vapor deposition, a multi-walled carbon nanotube network is grown on a nickel template, and then the nickel template is etched away with a FeCl3 / HCl solution to obtain an independent three-dimensional carbon nanotube network;

[0017] S4: barium titanate nanoparticles and PVDF-TrFE solution were ball-milled and mixed for 2 h, and the mixed slurry was infiltrated into the independent three-dimensional carbon tube network by vacuum impregnation method. After the solvent was evaporated at 80 °C, a 10 kV / mm electric field polarization treatment was applied to obtain a composite piezoelectric body;

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

[0019] S6: polyurethane and epoxy resin are dissolved in tetrahydrofuran, extruded through a slit to form a 50 μm thick liquid film, stretched and oriented in an alternating magnetic field, and thermally cured to obtain a shape memory polymer film;

[0020] S7: Mixing the polyurethane prepolymer with 40 vol% carbonyl iron powder, injecting it into a mold, applying a 1 T magnetic field to arrange the particles in a chain shape, and cutting it into 0.2 mm thin sheets after curing at 80° C. to obtain magnetorheological elastomer sheets;

[0021] S8: Alternately stack the shape memory polymer film and the magnetorheological elastomer sheet at a 45° cross angle, and use a laser positioning system to ensure that the interlayer angle tolerance is <1° to complete the tuning layer;

[0022] S9: stacking the gradient layer, the acoustic energy layer, and the tuning layer in order, and adopting a segmented hot pressing process to obtain a PET needle-punched felt sound-absorbing board.

[0023] The preparation process of the PET needle felt sound-absorbing board as described above, in S2, the layered processing step includes: top layer: spraying 0.5% polyethylene glycol solution by ultrasonic atomization, locally softening the fiber at 120°C, forming a porosity of 80%; middle layer: adopting pulse hot pressing, pressure 5MPa, temperature 150°C, pulse frequency 10Hz, to reduce the porosity to 65%; bottom layer: after impregnation with 0.1% silane coupling agent solution, thermal curing at 180°C to form a porosity of 50%.

[0024] The preparation process of the PET needle felt sound-absorbing board as described above, in S9, the segmented hot pressing process includes: the first segment: 180°C / 5MPa, maintained for 2 minutes, so that the molecular chain entanglement is generated at the interface between the gradient layer and the acoustic energy layer; the second segment: 120°C / 3MPa, maintained for 5 minutes, to achieve the bonding of the tuning layer and the acoustic energy layer; the third segment: 60°C / 1MPa, maintained for 10 minutes, to eliminate residual stress.

[0025] The preparation process of the PET needle felt sound-absorbing board as described above also includes depositing Ag / TiO on the surface by magnetron sputtering. 2 Core-shell structure, Ag target power 200W, TiO 2 The reactive sputtering time was 30 s, and the density was controlled by mask to be 1×10 8 Pieces / cm 2 .

[0026] Compared with the prior art, the present invention has the following beneficial effects:

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

[0028] Carbon nanotubes penetrate barium titanate particles to form a "nanospring" structure. The carbon tube conductive network improves carrier mobility. The piezoelectric potential of barium titanate particles is bridged by carbon tubes to form a macroscopic potential. 2 The surface plasmon resonance of the core-shell structure is coupled with the piezoelectric effect. The localized surface plasmon resonance of the Ag nanowire enhances the local electric field. 2 The shell forms a potential barrier to prevent charge recombination, making the acoustic-to-electric conversion efficiency reach 12% (conventional piezoelectric materials <5%).

[0029] Shape memory forms a dual response mechanism: when the temperature is >45℃, the shape memory layer shrinks, and when the magnetic field is >0.3T, the modulus of the magnetorheological layer increases by 2 orders of magnitude, synergistically adjusting the structural stiffness, the 45° stacked structure waveguide effect, and alternating stacking to form a spiral sound channel, causing the residual sound waves to produce multiple reflection attenuation between layers.

[0030] In summary, the components of the present invention achieve system-level performance breakthroughs through size matching (micrometer-nano multi-level structure), physical property complementation (conductive, electrical, dielectric synergy), and energy transfer (mechanical, electrical, and thermal coupling), reflecting the paradigm shift in material system design from simple superposition to directional assembly. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 It is a schematic diagram of a fourth embodiment of the present invention;

[0032] Figure 2 It is a data line chart of the embodiments and comparative examples of the present invention. DETAILED DESCRIPTION

[0033] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the invention belongs. In the event of a conflict, the definitions in the specification shall prevail. "When mass, concentration, temperature, time, or other value or parameter is expressed as a range, a preferred range, or a range defined by a series of upper preferred values ​​and lower preferred values, this should be understood to specifically disclose all ranges formed by any pairing of any upper range limit or preferred value with any lower range limit or preferred value, regardless of whether the range is disclosed separately. For example, a range of 1-50 should be understood to include 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, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91 6, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, or 50, any number, combination of numbers, or subrange, and all decimal values ​​between the above integers, for example, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, and 1.9. With respect to subranges, "nested subranges" extending from any endpoint within the range are specifically contemplated. For example, nested subranges of the exemplary range 1-50 may include 1-10, 1-20, 1-30, and 1-40 in one direction, or 50-40, 50-30, 50-20, and 50-10 in the other direction."

[0034] The present invention is further explained below in conjunction with specific examples. The experimental methods described in the following examples are conventional methods unless otherwise specified; the reagents and materials described are all commercially available unless otherwise specified.

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

[0036] The three-layer structure achieves interfacial molecular chain entanglement through a hot pressing process, forming a continuous transition of 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 boron nitride nanosheets and graphene oxide, with a stacking period of 5nm±0.5nm; a surface plasmon resonance unit: a silver nanowire and a titanium dioxide core-shell structure, with a stacking period of 10 per square centimeter. 8 The density of the layers is evenly distributed; the layer achieves an acoustic-to-electric conversion efficiency of ≥12% in the frequency band of 3800-5000 Hz, while maintaining an NRC coefficient of >0.95.

[0038] Specifically, in the gradient impedance matching layer, the diameter of the PET fiber is 10-50μm, and the diameter of the polyvinylidene fluoride piezoelectric fiber is 10-15μm; in the acoustic energy conversion layer, the diameter of the nanocarbon tube network is 8-15nm, and the particle size of the barium titanate piezoelectric ceramic particles is 180-200nm; in the dynamic tuning layer, the Tg of the shape memory polymer fiber is 45°C, and the shape memory polymer fiber is made of polyurethane, polyester and / or epoxy resin, and the shape memory function is achieved through physical crosslinking and reversible phase of the molecular chain; 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.

[0039] Embodiment 1

[0040] A preparation process of a PET needle felt sound-absorbing board comprises the following steps:

[0041] S1: Using a biaxial electrospinning system, the left nozzle injects a PET solution (10% concentration, the solvent is hexafluoroisopropanol), and the right nozzle injects a PVDF piezoelectric fiber solution (10% concentration, the solvent is a DMF / acetone mixture). By adjusting the voltage ratio of the two nozzles (3:2) and the speed of the collecting roller (1800rpm), 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), and the fiber diameters are PET 25μm and PVDF 11μm, respectively. The collector surface temperature is maintained at 50°C to allow the fibers to initially melt and crosslink, and a two-component fiber web with an orientation angle of 30° is obtained;

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

[0043] Top layer (air contact surface): 0.5% polyethylene glycol solution was sprayed by ultrasonic atomization to soften the fiber locally at 110°C to form 80% porosity;

[0044] Middle layer: pulse hot pressing (pressure 4MPa, temperature 130℃, pulse frequency 8Hz) was used to reduce the porosity to 65%;

[0045] Bottom layer: After being impregnated with 0.1% silane coupling agent solution, it is thermally cured at 160°C to form a 50% porosity;

[0046] Complete the gradient layer;

[0047] S3: Using chemical vapor deposition (CVD), a multi-walled carbon nanotube network was grown on a nickel template. The growth parameters were set as follows: acetylene flow rate 50 sccm, temperature 650°C, and growth time 25 min. The nickel template was then etched away with FeCl3 / HCl solution to obtain an independent three-dimensional carbon tube network (tube diameter 10 nm);

[0048] S4: barium titanate nanoparticles (particle size 185nm) and PVDF-TrFE solution (mass ratio 4:1) were ball-milled and mixed for 2h. The mixed slurry was infiltrated into the independent three-dimensional carbon tube network by vacuum impregnation method. After the solvent was evaporated at 75°C, an electric field polarization treatment of 8kV / mm was applied to obtain a composite piezoelectric body;

[0049] S5: Boron nitride (precursor triethylboron + NH3) and graphene oxide (O2 plasma assisted) are alternately deposited on the surface of the composite piezoelectric body using atomic layer deposition (ALD), and the deposition amount per cycle is controlled to form a 4.9nm periodic structure. The total deposition cycle is 90 cycles to complete the acoustic energy layer;

[0050] S6: Dissolve polyurethane / epoxy resin (mass ratio 7:3) in tetrahydrofuran, extrude through a slit to form a 50 μm thick liquid film, stretch and orient in an alternating magnetic field (frequency 1 kHz), and heat cure at 120°C to form a shape memory film with Tg = 45°C, thereby obtaining a shape memory polymer film;

[0051] S7: Mix the polyurethane prepolymer with 40 vol% carbonyl iron powder (particle size 4 μm), inject it into the mold, and apply a 1 T magnetic field to arrange the particles in a chain. After curing at 70°C, cut it into 0.2 mm slices to obtain magnetorheological elastomer slices;

[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), and a laser positioning system is used to ensure that the inter-layer angle tolerance is <1° to complete the tuning layer;

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

[0054] The first stage: 180℃ / 5MPa, hold for 2min, to generate molecular chain entanglement at the interface between the gradient layer and the acoustic energy layer;

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

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

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

[0058] In the embodiment, the Ag / TiO 2 Core-shell structure, Ag target power 200W, TiO 2 The reactive sputtering time was 30 s, and the density was controlled by mask to be 1×10 8 Pieces / cm 2； A cyclic temperature field (40°C) and an alternating magnetic field (0.5T, frequency 10Hz) are applied to the finished product to complete the coordinated training of shape memory effect and magnetorheological effect.

[0059] Embodiment 2

[0060] A preparation process of a PET needle felt sound-absorbing board comprises the following steps:

[0061] S1: Using a biaxial electrospinning system, the left nozzle injects a PET solution (10% concentration, the solvent is hexafluoroisopropanol), and the right nozzle injects a PVDF piezoelectric fiber solution (12% concentration, the solvent is a DMF / acetone mixture). By adjusting the voltage ratio of the two nozzles (3:2) and the speed of the collecting roller (2000rpm), 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), and the fiber diameters are PET 30μm and PVDF 12μm, respectively. The collector surface temperature is maintained at 60°C to allow the fibers to initially melt and crosslink, and a two-component fiber web with an orientation angle of 30° is obtained;

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

[0063] Top layer (air contact surface): 0.5% polyethylene glycol solution was sprayed by ultrasonic atomization to soften the fiber locally at 120°C to form 80% porosity;

[0064] Middle layer: pulse hot pressing (pressure 5 MPa, temperature 150°C, pulse frequency 10 Hz) was used to reduce the porosity to 65%;

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

[0066] Complete the gradient layer;

[0067] S3: Using chemical vapor deposition (CVD), a multi-walled carbon nanotube network was grown on a nickel template. The growth parameters were set as follows: acetylene flow rate 50 sccm, temperature 680°C, and growth time 30 min. The nickel template was then etched away with FeCl3 / HCl solution to obtain an independent three-dimensional carbon nanotube network (tube diameter 12 nm);

[0068] S4: barium titanate nanoparticles (particle size 190nm) and PVDF-TrFE solution (mass ratio 4:1) were ball-milled and mixed for 2h. The mixed slurry was infiltrated into the independent three-dimensional carbon tube network by vacuum impregnation method. After the solvent was evaporated at 80°C, a 10kV / mm electric field polarization treatment was applied to obtain a composite piezoelectric body;

[0069] S5: Boron nitride (precursor triethylboron + NH 3 ) and graphene oxide (O 2 Plasma assisted), controlling the deposition amount per cycle to form a 5.2nm periodic structure, with a total deposition of 100 cycles to complete the acoustic energy layer;

[0070] S6: Dissolve polyurethane / epoxy resin (mass ratio 7:3) in tetrahydrofuran, extrude through a slit to form a 50 μm thick liquid film, stretch and orient in an alternating magnetic field (frequency 1 kHz), and heat cure at 120°C to form a shape memory film with Tg = 45°C, thereby obtaining a shape memory polymer film;

[0071] S7: Mix the polyurethane prepolymer with 40 vol% carbonyl iron powder (particle size 5 μm), inject it into the mold, and apply a 1 T magnetic field to arrange the particles in a chain. After curing at 80°C, cut it into 0.2 mm slices to obtain magnetorheological elastomer slices;

[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), and a laser positioning system is used to ensure that the inter-layer angle tolerance is <1° to complete the tuning layer;

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

[0074] The first stage: 180℃ / 5MPa, hold for 2min, to generate molecular chain entanglement at the interface between the gradient layer and the acoustic energy layer;

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

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

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

[0078] In the embodiment, the Ag / TiO 2 Core-shell structure, Ag target power 200W, TiO 2 The reactive sputtering time was 30 s, and the density was controlled by mask to be 1×10 8 Pieces / cm 2; Apply a cyclic temperature field (45°C) and an alternating magnetic field (0.7T, frequency 12Hz) to the finished product to complete the coordinated training of shape memory effect and magnetorheological effect.

[0079] Embodiment 3

[0080] A preparation process of a PET needle felt sound-absorbing board comprises the following steps:

[0081] S1: Using a biaxial electrospinning system, the left nozzle injects a PET solution (10% concentration, the solvent is hexafluoroisopropanol), and the right nozzle injects a PVDF piezoelectric fiber solution (12% concentration, the solvent is a DMF / acetone mixture). By adjusting the voltage ratio of the two nozzles (3:2) and the speed of the collecting roller (2000rpm), 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), and the fiber diameters are 32μm for PET and 13μm for PVDF, respectively. The surface temperature of the collector is maintained at 60°C to allow the fibers to initially melt and crosslink, and a two-component fiber web with an orientation angle of 30° is obtained;

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

[0083] Top layer (air contact surface): 0.5% polyethylene glycol solution was sprayed by ultrasonic atomization to soften the fiber locally at 130°C to form 80% porosity;

[0084] Middle layer: pulse hot pressing (pressure 5MPa, temperature 160°C, pulse frequency 11Hz) was used to reduce the porosity to 65%;

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

[0086] Complete the gradient layer;

[0087] S3: Using chemical vapor deposition (CVD), a multi-walled carbon nanotube network was grown on a nickel template. The growth parameters were set as follows: acetylene flow rate 50 sccm, temperature 685°C, and growth time 30 min. The nickel template was then etched away with FeCl3 / HCl solution to obtain an independent three-dimensional carbon tube network (tube diameter 13 nm);

[0088] S4: barium titanate nanoparticles (particle size 192nm) and PVDF-TrFE solution (mass ratio 4:1) were ball-milled and mixed for 2h. The mixed slurry was infiltrated into the independent three-dimensional carbon tube network by vacuum impregnation method. After the solvent was evaporated at 80°C, a 10kV / mm electric field polarization treatment was applied to obtain a composite piezoelectric body;

[0089] S5: Boron nitride (precursor triethylboron + NH3) and graphene oxide (O2 plasma assisted) are alternately deposited on the surface of the composite piezoelectric body using atomic layer deposition (ALD), and the deposition amount per cycle is controlled to form a 5.4nm periodic structure. The total deposition cycle is 110 cycles to complete the acoustic energy layer;

[0090] S6: polyurethane / epoxy resin (mass ratio 7:3) was dissolved in tetrahydrofuran, and extruded through a slit to form a 50 μm thick liquid film. The film was stretched and oriented in an alternating magnetic field (frequency 1 kHz), and thermally cured at 130°C to form a shape memory film with Tg = 45°C, thereby obtaining a shape memory polymer film;

[0091] S7: Mix the polyurethane prepolymer with 40 vol% carbonyl iron powder (particle size 5 μm), inject it into the mold, and apply a 1 T magnetic field to arrange the particles in a chain. After curing at 85 ° C, cut it into 0.2 mm slices to obtain magnetorheological elastomer slices;

[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), and a laser positioning system is used to ensure that the inter-layer angle tolerance is <1° to complete the tuning layer;

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

[0094] The first stage: 180℃ / 5MPa, hold for 2min, to generate molecular chain entanglement at the interface between the gradient layer and the acoustic energy layer;

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

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

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

[0098] In the embodiment, the Ag / TiO 2 Core-shell structure, Ag target power 200W, TiO 2 The reactive sputtering time was 30 s, and the density was controlled by mask to be 1×10 8 Pieces / cm 2 ; A cyclic temperature field (48°C) and an alternating magnetic field (0.7T, frequency 13Hz) are applied to the finished product to complete the coordinated training of shape memory effect and magnetorheological effect.

[0099] Embodiment 4

[0100] A preparation process of a PET needle felt sound-absorbing board comprises the following steps:

[0101] S1: Using a biaxial electrospinning system, the left nozzle injects a PET solution (10% concentration, the solvent is hexafluoroisopropanol), and the right nozzle injects a PVDF piezoelectric fiber solution (12% concentration, the solvent is a DMF / acetone mixture). By adjusting the voltage ratio of the two nozzles (3:2) and the speed of the collecting roller (2100rpm), 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), and the fiber diameters are PET 35μm and PVDF 14μm, respectively. The collector surface temperature is maintained at 60°C to allow the fibers to initially melt and crosslink, and a two-component fiber web with an orientation angle of 30° is obtained;

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

[0103] Top layer (air contact surface): 0.5% polyethylene glycol solution was sprayed by ultrasonic atomization to soften the fiber locally at 130°C to form 80% porosity;

[0104] Middle layer: pulse hot pressing (pressure 7MPa, temperature 160℃, pulse frequency 13Hz) was used to reduce the porosity to 65%;

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

[0106] Complete the gradient layer;

[0107] S3: Using chemical vapor deposition (CVD), a multi-walled carbon nanotube network was grown on a nickel template. The growth parameters were set as follows: acetylene flow rate 50 sccm, temperature 680°C, and growth time 30 min. The nickel template was then etched away with FeCl3 / HCl solution to obtain an independent three-dimensional carbon nanotube network (tube diameter 14 nm);

[0108] S4: barium titanate nanoparticles (particle size 195nm) and PVDF-TrFE solution (mass ratio 4:1) were ball-milled and mixed for 2h. The mixed slurry was infiltrated into the independent three-dimensional carbon tube network by vacuum impregnation method. After the solvent was evaporated at 80°C, a 10kV / mm electric field polarization treatment was applied to obtain a composite piezoelectric body;

[0109] S5: Boron nitride (precursor triethylboron + NH3) and graphene oxide (O2 plasma assisted) are alternately deposited on the surface of the composite piezoelectric body using atomic layer deposition (ALD), and the deposition amount per cycle is controlled to form a 5.5nm periodic structure. The total deposition cycle is 110 cycles to complete the acoustic energy layer;

[0110] S6: Dissolve polyurethane / epoxy resin (mass ratio 7:3) in tetrahydrofuran, extrude through a slit to form a 50 μm thick liquid film, stretch and orient in an alternating magnetic field (frequency 1 kHz), and heat cure at 120°C to form a shape memory film with Tg = 45°C, thereby obtaining a shape memory polymer film;

[0111] S7: Mix the polyurethane prepolymer with 40 vol% carbonyl iron powder (particle size 5 μm), inject it into the mold, and apply a 1 T magnetic field to arrange the particles in a chain. After curing at 80°C, cut it into 0.2 mm slices to obtain magnetorheological elastomer slices;

[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), and a laser positioning system is used to ensure that the inter-layer angle tolerance is <1° to complete the tuning layer;

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

[0114] The first stage: 180℃ / 5MPa, hold for 2min, to generate molecular chain entanglement at the interface between the gradient layer and the acoustic energy layer;

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

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

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

[0118] In the embodiment, the Ag / TiO 2 Core-shell structure, Ag target power 200W, TiO 2 The reactive sputtering time was 30 s, and the density was controlled by mask to be 1×10 8 Pieces / cm 2； A cyclic temperature field (50°C) and an alternating magnetic field (0.8T, frequency 14Hz) are applied to the finished product to complete the coordinated training of shape memory effect and magnetorheological effect.

[0119] Comparative Example 1

[0120] A preparation process of a PET needle felt sound-absorbing board is basically the same as that of the fourth embodiment, except that the gradient layer delamination process is missing (the S2 step only maintains a uniform porosity).

[0121] Comparative Example 2

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

[0123] Comparative Example 3

[0124] A preparation process of a PET needle felt sound-absorbing board is basically the same as that of the fourth embodiment, 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] A preparation process of a PET needle felt sound-absorbing board is basically the same as that of Example 4, except that: a plasma resonance unit is missing (Ag / TiO is skipped in step S9) 2 sputtering).

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

[0128] 1. Sound absorption performance test

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

[0130] Detection method:

[0131] The sample (size 500 mm×500 mm) was placed in a reverberation chamber, and a full-band sound source (125 Hz to 5000 Hz) was used to excite the sound field.

[0132] The sound pressure decay time was measured, the noise reduction coefficient (NRC) was calculated, and the average value of the sound absorption coefficient in the four frequency bands of 250Hz, 500Hz, 1000Hz, and 2000Hz was taken.

[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 test

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

[0136] Detection method:

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

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

[0139] 3. Mechanical properties testing

[0140] Area density and size deviation:

[0141] Standard basis: JC / T 2704-2022 "Polyester fiber decorative sound-absorbing board"

[0142] Testing method: electronic balance to measure surface density (allowable deviation ±5%), vernier caliper to measure thickness (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 veneer wood-based panels"

[0145] Test method: three-point bending test, span 300mm, loading rate 5mm / min, measuring maximum deflection (qualified limit ≤3mm).

[0146] 4. Acoustic-electrical conversion efficiency test

[0147] Standard basis: GB / T 16731 ​​"Sound absorption performance classification of building sound absorption products" (supplementary piezoelectric characteristics test)

[0148] Detection method:

[0149] In the anechoic chamber, input a sound wave with a sound pressure level of 85dB (3800-5000Hz) and measure the output voltage.

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

[0151] The results are shown in Table 1:

[0152] Table 1

[0153]

[0154] From the above Table 1, it can be directly determined that the performance of Examples 1 to 4 is good. By optimizing the parameters of the gradient layer, refining the nanostructure of the acoustic energy layer, increasing the density of the plasma unit and strengthening the dynamic tuning training, the peak performance of NRC and acoustic-electric efficiency is gradually achieved. The performance of each example in terms of combustion level and durability is highly consistent, which verifies the reliability of the core process.

[0155] Reference Figure 1-2In Example 4 and Comparative Example 1, where other conditions are the same, Comparative Example 1: lacks the gradient layer delamination process; performance degradation: NRC drops to 0.72 (Example: 0.96), and the sound absorption coefficient in the high frequency band (>3000Hz) is significantly attenuated (from 0.98→0.55). The combustion level is reduced to B2 (flammable), because the bottom layer is not cured by the silane coupling agent, and the thermal stability of the material is reduced.

[0156] Mechanism: Uniform porosity (65%) leads to a sudden change in acoustic impedance and an increase in reflection loss (reflectivity from 5% to 23%). The unlayered fiber mesh lacks a gradient transition and cannot achieve broadband sound absorption (only covers 500 to 3000 Hz).

[0157] Comparative Example 2: Lack of acoustic energy layer carbon nanotube network; performance degradation: acoustic-electric efficiency is only 5.8% (Example: 12.5%), efficiency above 3800Hz is <3%. Durability is reduced (NRC attenuation 9.5%), because barium titanate particles are not supported by carbon tube network and are easy to fall off.

[0158] Mechanism: Barium titanate particles are directly dispersed in the PVDF-TrFE matrix, the conductive network is discontinuous, and the carrier mobility is reduced (from 200→50cm 2 / Vs). Without the buffering effect of the carbon tube skeleton, micro cracks will appear in the piezoelectric ceramics under cyclic stress, resulting in performance degradation.

[0159] Comparative Example 3: Missing dynamic tuning layer; performance degradation: NRC decays to 0.88 (Example: 0.96), and the sound absorption coefficient in the high frequency band (>4000Hz) decreases by 15%. Durability is significantly reduced (NRC decays by 6.3%), because there is no dynamic tuning function, and the internal stress of the material cannot be released.

[0160] mechanism:

[0161] The lack of 45° cross-laminated spiral waveguide structure reduces the number of sound wave reflections (from 7 times to 3 times), and the energy dissipation is insufficient. There is no shape memory effect (Tg = 45°C) to adjust the porosity, and the sound absorption stability is poor when the temperature fluctuates (the fluctuation rate is from 5% to 18%).

[0162] Comparative Example 4: Plasma resonance unit missing; performance degradation: high frequency band (3800-5000 Hz) acoustic-electric efficiency decreased to 10.1% (Example: 12.5%). NRC decreased from 0.96 to 0.91, and high frequency sound absorption coefficient decreased (from 0.98 to 0.89).

[0163] mechanism:

[0164] Ag / TiO 2The lack of core-shell structure leads to the disappearance of localized surface plasmon resonance (LSPR) effect, and the electric field enhancement factor changes from 50 to 1. High-frequency sound waves cannot enhance the piezoelectric response through plasma coupling, and the energy conversion efficiency is limited.

[0165] In summary, the gradient layer stratification treatment in the present invention is the core guarantee of broadband sound absorption (NRC ≥ 0.95), contributing 34% 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 skeleton significantly improves the carrier mobility. The dynamic tuning layer improves the high-frequency sound absorption stability (durability contributes 67%) through a 45° stacking design and shape memory effect. Although the plasma resonance unit contributes less to the overall performance, it can specifically optimize the sound-to-electric conversion efficiency in the high-frequency band (3800-5000Hz) (+19%).

[0166] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. PET needle felt sound-absorbing board, characterized by include: Gradient impedance matching layer: It is composed of PET fiber and polyvinylidene fluoride piezoelectric fiber interwoven in a volume ratio of 7:

3. The fiber orientation angle is controlled at 30°±5°, forming a continuous gradient structure with a porosity ranging from 80% to 50%; Acoustic energy conversion layer: a composite system comprising a carbon nanotube network 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; Dynamic tuning layer: It is composed of shape memory polymer fibers and magnetorheological elastomer sheets alternately stacked, with each layer thickness of 0.2mm±0.05mm and an angle between layers of 45°; The three-layer structure is entangled with the interface molecular chain through hot pressing process, forming an acoustic impedance from 2.5×10 6 rayl to 8×10 5 rayl's continuous transition.

2. The PET needle felt sound-absorbing board according to claim 1, characterized in that The acoustic energy conversion layer further comprises: The quantum confinement structure of alternating stacks of boron nitride nanosheets and graphene oxide, with a stacking period of 5nm±0.5nm; Surface plasmon resonance unit: silver nanowire and titanium dioxide core-shell structure, 10 per square centimeter 8 The density of the digits is evenly distributed; The layer achieves an acoustic-to-electric conversion efficiency of ≥12% in the frequency band of 3800-5000 Hz while maintaining an NRC coefficient of >0.

95.

3. The PET needle 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.

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

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

6. A process for preparing the PET needle felt sound-absorbing board according to any one of claims 1 to 5, characterized in that: The following steps are involved: S1: Using a biaxial electrospinning system, the left nozzle injects PET solution, and the right nozzle injects polyvinylidene fluoride piezoelectric fiber solution. By adjusting the voltage ratio of the two nozzles and the 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, and a bicomponent fiber web with an orientation angle of 30° is obtained; S2: The above two-component fiber web is layered according to the porosity gradient requirements to complete the gradient layer; S3: Using chemical vapor deposition, a multi-walled carbon nanotube network is grown on a nickel template, and then the nickel template is etched away with a FeCl 3 / HCl solution to obtain an independent three-dimensional carbon nanotube network; S4: barium titanate nanoparticles and PVDF-TrFE solution were ball-milled and mixed for 2 h, and the mixed slurry was infiltrated into the independent three-dimensional carbon tube network by vacuum impregnation method. After the solvent was evaporated at 80 °C, a 10 kV / mm electric field polarization treatment was applied to obtain a composite piezoelectric body; S5: using atomic layer deposition to alternately deposit boron nitride and graphene oxide on the surface of the composite piezoelectric body, controlling the deposition amount per cycle to form a 5.2±0.3nm periodic structure, with a total deposition of 100 cycles to complete the acoustic energy layer; S6: polyurethane and epoxy resin are dissolved in tetrahydrofuran, extruded through a slit to form a 50 μm thick liquid film, stretched and oriented in an alternating magnetic field, and thermally cured to obtain a shape memory polymer film; S7: Mixing the polyurethane prepolymer with 40 vol% carbonyl iron powder, injecting it into a mold, applying a 1 T magnetic field to arrange the particles in a chain shape, and cutting it into 0.2 mm thin sheets after curing at 80° C. to obtain magnetorheological elastomer sheets; S8: Alternately stack the shape memory polymer film and the magnetorheological elastomer sheet at a 45° cross angle, and use a laser positioning system to ensure that the interlayer angle tolerance is <1° to complete the tuning layer; S9: stacking the gradient layer, the acoustic energy layer, and the tuning layer in order, and adopting a segmented hot pressing process to obtain a PET needle-punched felt sound-absorbing board.

7. The preparation process of the PET needle felt sound-absorbing board according to claim 6, characterized in that: In S2, the layered processing step includes: Top layer: 0.5% polyethylene glycol solution was sprayed by ultrasonic atomization to soften the fiber locally at 120°C to form 80% porosity; Middle layer: pulse hot pressing, pressure 5MPa, temperature 150℃, pulse frequency 10Hz, to reduce porosity to 65%; Bottom layer: After being impregnated with 0.1% silane coupling agent solution, it was thermally cured at 180°C to form a porosity of 50%.

8. The preparation process of the PET needle felt sound-absorbing board according to claim 6, characterized in that: In S9, the segmented hot pressing process includes: The first stage: 180℃ / 5MPa, hold for 2min, to generate molecular chain entanglement at the interface between the gradient layer and the acoustic energy layer; The second stage: 120℃ / 3MPa, hold for 5min to achieve bonding between the tuning layer and the acoustic energy layer; The third stage: 60℃ / 1MPa, hold for 10min to eliminate residual stress.

9. The preparation process of the PET needle felt sound-absorbing board according to claim 6, characterized in that The Ag / TiO2 core-shell structure was deposited on the surface by magnetron sputtering, with an Ag target power of 200 W, a TiO2 reactive sputtering time of 30 s, and a density of 1×10 8 Pieces / cm 2 .

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