A waste branch fiber reinforced mold integrated composite porous material and a preparation method thereof

Abstract

The application relates to the technical field of functional composite materials, and discloses a waste branch fiber reinforced mold integrated composite porous material and a preparation method thereof. The composite porous material is obtained by taking waste branch particles as a main body and combining a binder, through multi-scale pore design and a natural wood fiber-polymer coupling effect, the high acoustic attenuation, heat preservation and insulation, high damping loss performance of the material are synergistically improved. By adjusting and controlling key parameters such as the content, length, equivalent diameter and porosity of the waste branches, the customizable design of the performance of the composite material is realized, the material with comprehensive performance advantages is developed according to the requirements of different application scenes, and through multi-stage grading of the branches, optimization design of the mold and modification of the binder, the cross-scale pore construction in the material is realized, the material has the performances of light weight, sound absorption and insulation, heat insulation and impact resistance, and the high-value utilization of the agricultural and forestry waste is effectively promoted.

Description

Technical Field

[0001] This invention relates to the field of functional composite materials technology, and more specifically to an integrated composite porous material for molds reinforced with waste branch fibers and its preparation method. Background Technology

[0002] Biomass-based materials are renewable and biodegradable, and have great research value and application prospects in materials science. However, the process of directly using them to prepare porous materials is complicated and costly, and they only focus on a single function, making it difficult to meet the multi-functional requirements of sound absorption, heat insulation, and vibration reduction at the same time. In the process of large-scale production, there are also problems such as difficulty in quality control and unstable product performance.

[0003] Thorny economic trees such as wolfberry, oleaster, and jujube are important specialty crops in Northwest my country. Their planting and maintenance generate a large number of waste branches annually, mainly including: robust, overly vigorous, and excessively dense branches pruned during the autumn / winter dormancy period and summer growing season; broken and weak fruit-bearing branches generated during the peak fruit harvesting period; diseased and insect-infested branches removed during the growing season due to pest and disease control, especially concentrated during periods of high pest and disease incidence; and broken and frost-damaged branches caused by extreme weather events such as spring sandstorms and early autumn frosts. These waste branches are abundant and widely distributed, possessing significant biomass resource attributes.

[0004] Every year, a large amount of waste goji berry branches are generated nationwide. The biomass raw material itself has extremely low acquisition costs, even near-zero cost in some regions. However, due to the highly dispersed, bulky, thorny, and easily damaged nature of these waste branches, as well as their low transportation and storage efficiency, the costs of collection, transportation, and pre-processing increase significantly. Therefore, in the overall cost structure, raw material costs account for a relatively small proportion, with core costs concentrated in logistics, crushing, and subsequent high-value processing.

[0005] Currently, the main methods for disposing of waste branches are still open burning or landfilling. Burning generates large amounts of smoke, greenhouse gases, and toxic substances, polluting the atmosphere. Landfilling occupies land resources, and the leachate and methane produced during anaerobic decomposition cause secondary pollution to soil and groundwater. Methane's greenhouse effect potential is more than twenty times that of carbon dioxide. Although some resource utilization methods exist (such as using crushed branches as organic feed), the stable structure of cellulose and lignin in these branches makes them difficult for animals to digest directly. Pretreatment using high-temperature, high-pressure, acid-alkali treatment, or enzymatic fermentation is necessary, and supplementation with concentrated feeds such as soybean meal and corn is required, resulting in high overall costs and poor economic efficiency.

[0006] Therefore, how to develop an integrated composite porous material for molds reinforced with waste branch fibers and its preparation method is a problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0007] In view of this, the present invention provides an integrated composite porous material for waste branch fiber reinforced mold and its preparation method. The composite porous material is obtained by using waste branch particles as the main body and combining them with a binder. Through multi-scale pore design and natural wood fiber-polymer coupling effect, the material’s high acoustic attenuation, thermal insulation and high damping loss performance are synergistically improved.

[0008] To achieve the above objectives, the present invention adopts the following technical solution:

[0009] A method for preparing an integrated composite porous material for molds reinforced with waste branch fibers includes the following steps: (1) Pretreatment: Dry the waste branches, remove the residual leaves on the surface, soak them in water to remove surface impurities, and then dry them; (2) Dismantling and grading: The dried waste branches are dismantled into roots, trunk and lateral branches; the roots, trunk and lateral branches with equivalent diameter >10mm are crushed to a particle size <10mm, and then screened through multiple stages to obtain three types of particles with particle sizes <3mm, 3~6mm and 6~10mm; the lateral branches are cut into lateral branch segments with a length of 0~100mm, and divided into three grades of 0~3mm, 3~6mm and 6~10mm according to the equivalent diameter; (3) Fiber modification: Take some particles with a particle size <3mm and grind them to obtain fiber bundles with a particle size of 60~180μm. Add coupling agent and compatibilizer to modify them to obtain modified fiber bundles. Combine the modified fiber bundles with the three types of particles obtained in step (2) to obtain compound particles. (4) Preparation of binder: Add delayed catalyst and thickener to binder, disperse at high speed and control foaming rate ≤15% to obtain polymer binder; (5) Injection molding: The side branch segments are laid in the mold and vibrated to compact them. Then the compounded particles are mixed with the polymer binder to form a slurry, which is injected into the mold gap and pressure is applied for injection molding. (6) Curing and molding: After injection molding, a constant pressure is applied and the mixture is left to stand. After the pressure is removed, the mixture is ventilated and cured to obtain a composite porous material.

[0010] Preferably, the raw material for the waste branches is agricultural and forestry waste plants of vines or shrubs.

[0011] Preferably, the plants include wolfberry, grape, honeysuckle, oleaster, mulberry, and catalpa.

[0012] Preferably, in step (1), plant saponin surfactant, citric acid solution or sodium bicarbonate solution are added during water soaking and stirred.

[0013] Adding additives during water soaking can more effectively remove pesticide residues, waxes, and organic contaminants, and improve the subsequent bonding strength between fibers and binders.

[0014] Preferably, in step (1), the method for removing surface impurities is selected from one of rinsing, mechanical tumbling, and ultrasonic treatment.

[0015] Preferably, the compound particles comprise the following components: 10% modified fiber bundles, 40%~50% particles with a particle size <3mm, 25%~30% particles with a particle size of 3~6mm, and 15%~20% particles with a particle size of 6~10mm.

[0016] Within the aforementioned particle size distribution, small particles fill the gaps between large particles, achieving close packing and improving material density; medium-sized particles provide the main support; and long particles enhance toughness. Simultaneously, this gradation facilitates slurry flow, ensuring uniform binder penetration during injection molding. If the proportion of small particles exceeds 60%, the slurry viscosity becomes too high, leading to injection molding difficulties and uneven foaming; if the proportion of large particles exceeds 30%, voids are easily formed, reducing material strength; and if the proportion of side-branch segments is too high, it may hinder binder flow, resulting in poor filling.

[0017] The mechanism of graded processing is based on particle size distribution theory: by rationally combining particles of different sizes, porosity is reduced, interfacial bonding is enhanced, and rheological properties are improved. Combined with the design of venting holes and flow channels in the mold, foaming can be effectively controlled (foaming rate ≤15%), preventing voids and improving the overall performance of the composite material.

[0018] Preferably, in step (3), the coupling agent is selected from one of silane coupling agents, aminosilane coupling agents, titanate coupling agents, and zirconate coupling agents; the amount of coupling agent added is 3.5% of the fiber bundle mass; the compatibilizer is selected from one of maleic anhydride-grafted polyethylene, maleic anhydride-grafted polypropylene, acrylic acid-grafted polyolefin, and polyurethane prepolymer; the amount of compatibilizer added is 2.5% of the fiber bundle mass.

[0019] Coupling agents and compatibilizers synergistically improve the interfacial compatibility and adhesion between fibers and polymer matrices. The principle is as follows: the surface of discarded fiber branches is rich in polar groups such as hydroxyl groups, exhibiting strong hydrophilicity, while the polymer matrix (such as polyurethane) is hydrophobic. The significant difference in interfacial polarity between the two makes direct composite bonding prone to debonding. Coupling agents (such as silane coupling agents) have a bifunctional structure; one end forms a covalent bond with the hydroxyl groups on the fiber surface, while the other end reacts with the polymer matrix, constructing a "molecular bridge" at the interface. Through this bridging effect, the interfacial energy between the fiber and polymer is reduced, allowing the two materials to bond tightly and preventing debonding or delamination. Compatibilizers, through their polar groups, form hydrogen bonds or chemical bonds with the fibers, while their nonpolar backbone is well-compatible with the polymer matrix, forming a transition layer and reducing interfacial tension. The synergistic effect of both significantly improves interfacial bonding strength, wettability, and stress transfer efficiency, thereby enhancing the mechanical properties, pore structure stability, and various properties of the composite material, such as sound absorption, heat insulation, and vibration damping.

[0020] More preferably, in step (3), the silane coupling agent is KH-550; and the compatibilizer is maleic anhydride-grafted polyethylene.

[0021] Preferably, in step (4), the adhesive is selected from polyurethane, epoxy foam, phenolic foam, and thermoplastic microsphere foaming agent.

[0022] More preferably, in step (4), the adhesive is polyurethane, which includes black material and white material; the black material is liquefied MDI with an NCO content of 28%~30%; the white material is polyether polyol with a hydroxyl value of 350~380mgKOH / g; and the mass ratio of the black material to the white material is 1:1.1.

[0023] The size of the waste branch particles is matched with the polyurethane structural unit, which can significantly enhance the pore connectivity. At the same time, as a biomass material with inherent viscoelastic damping properties, waste branches can convert sound energy into heat energy through molecular chain and structural friction during compression-rebound, thereby improving the problem of insufficient sound absorption performance of traditional closed-cell polymers. The performance conflict between sound absorption and heat insulation is balanced by a mixed pore strategy. By stacking branch particles to form discontinuous rigid units, a mass-spring system is constructed with the polyurethane elastic matrix, thereby significantly improving the vibration reduction and impact resistance of the material.

[0024] Preferably, in step (4), 0.5-1 wt% of nanocellulose or elastomer microparticles are added to the adhesive.

[0025] Nanocellulose or elastomer microparticles can improve the impact toughness and crack resistance of composite materials.

[0026] Preferably, in step (4), ammonium polyphosphate or aluminum hydroxide flame retardant is added to the adhesive.

[0027] Flame retardants can meet the flame retardancy requirements of building materials.

[0028] Preferably, in step (4), the delayed catalyst is selected from one of stannous octoate, organobismuth, and dibutyltin dilaurate; the amount of delayed catalyst added is 1% of the mass of the binder; the tackifier is selected from one of rosin resin, hydrogenated rosin, terpene resin, and fumed silica; the amount of tackifier added is 0.5% of the mass of the binder.

[0029] The role of delayed-action catalysts is to regulate the balance and rate between the gelation reaction (isocyanate reacts with polyols to form polyurethane) and the foaming reaction (isocyanate reacts with water to form CO2), providing sufficient working time to complete injection molding. Subsequently, they rapidly gel and solidify, fixing the positions of the branches and fibers and inhibiting over-foaming, thereby controlling the material's density and pore structure. Tackifiers rapidly increase the viscosity of the system, preventing less dense branches and fiber bundles from floating, delaminating, or distributing unevenly in the binder due to buoyancy, ensuring the homogeneity of the composite material.

[0030] More preferably, in step (4), the delayed catalyst is stannous octoate; and the tackifier is rosin resin.

[0031] Preferably, in step (5), the material of the mold is selected from PLA, PP, ABS; the inner wall of the mold is sandblasted with 80-mesh diamond sand and coated with an epoxy interface agent with a dry film thickness of 10~15μm, and the inner wall is welded with reinforcing ribs; the mold is provided with venting holes, injection ports, guide grooves and pressure relief grooves.

[0032] More preferably, the vent hole has a diameter φ of 1.5mm, is located at the bottom of the mold fold and the intersection of the reinforcing rib, and is externally connected to an air extraction device with a negative pressure value of -0.02MPa; the injection port has 2 sets on each side of the mold length direction, for a total of 4 sets, with a diameter of 12mm, and the opening direction is inclined at a 30° angle to the mold center with respect to the inner wall of the mold; the pressure relief groove is 5mm wide and 3mm deep, is located on both sides of the mold width direction, and is connected to the vent hole.

[0033] The air extraction device removes air from the gaps between branches during injection molding, preventing air stagnation and the formation of voids. The angled injection port prevents the adhesive from directly impacting the branches and causing localized displacement. When the adhesive reaches the edges, excess adhesive flows into the pressure relief groove, preventing excessive local pressure and over-foaming (foaming rate controlled ≤15%). Simultaneously, the curing state of the adhesive within the pressure relief groove allows for a visual assessment of the overall filling fullness.

[0034] More preferably, the flow channel layout is selected from one of the following: dendritic, radial, and mesh-like; the reinforcing ribs are selected from one of the following: cross-shaped, dotted, and mesh-like.

[0035] More preferably, the inner cavity of the mold has dimensions of 1800mm×900mm×50mm, and the frame has a 50mm wide folded edge with a φ8mm mounting hole pre-reserved on the folded edge; the flow guide channels are arranged in a tree-like pattern from the injection port to the edge of the mold, with the main channel being 3mm wide, the branch channels being 2mm wide, the spacing between the flow guide channels being 50mm, and the bottom of the channels slightly sloping towards the center of the mold with a slope of 0.5%; the reinforcing ribs are cross-shaped, 10mm high, and spaced 150mm apart.

[0036] The guide channel utilizes the combined effects of gravity and injection pressure to guide the adhesive to penetrate evenly into the gaps between the branches, especially solving the problem of insufficient filling in the edge areas far from the injection port.

[0037] More preferably, the inner cavity of the mold is adjustable in size via a movable partition; the frame is provided with a folded edge, which adopts a quick-connect structure, including a spring pin or a buckle.

[0038] Preferably, in step (5), the thickness of the side branch segments is 30~45mm, and after laying, they are lightly vibrated for 10s using a vibration platform; the mass ratio of the compound granules to the polymer binder is 3:1, the injection pressure is 6~8MPa, the injection rate is 100~120mL / s, and the barrel temperature is 50~55℃.

[0039] Preferably, in step (6), the constant pressure is 0.5~0.8MPa, the pressure is removed after standing at room temperature for 2 hours, and the mixture is ventilated and left to cure for 48 hours.

[0040] Under pressure, the adhesive fully penetrates into the gaps between the branches and fiber bundles, eliminating air bubbles and ensuring tight contact at the interface; it also inhibits excessive foaming and prevents a decrease in strength due to excessively large pores.

[0041] The present invention also provides a composite porous material obtained by the above preparation method.

[0042] Compared with the prior art, the present invention has the following beneficial effects: 1. Waste branches, stacked to form millimeter-scale pores, absorb low-frequency noise, while the polymer binder itself has micron-scale pores, absorbing high-frequency noise. This cross-scale coupling forms a composite porous material, achieving broadband sound absorption. The binder's adhesion prevents the branches from rearranging due to vibration or pressure, thus preventing pore structure failure and ensuring long-term stable sound absorption performance. The stacked waste branches have a very low flow resistance, and the binder covers the surface of the branches and the pores, completely filling all gaps between particles, forming a continuous, non-perforated, sealed whole. This blocks the propagation path of the airborne sound medium, effectively weakening sound wave transmission and increasing the viscous resistance of sound waves traveling through the pores. This allows for more thorough friction between the sound waves and the pore walls, converting sound energy into heat energy more efficiently.

[0043] 2. Discarded branches are inherently brittle and prone to breakage. The binder acts as an energy buffer and transfer agent. When impacted, the binder absorbs energy through deformation and distributes stress to multiple branch particles, preventing stress concentration that could lead to brittle fracture. This improves the toughness and impact resistance of the composite porous material.

[0044] 3. The waste branch particles are in point or line contact, forming solid thermal bridges through which heat is efficiently conducted. The interconnected and open internal pores created by the stacking allow air to circulate within the pores when there is a temperature difference between the two sides of the material. This airflow efficiently carries away heat, severely compromising the insulation effect. The adhesive, however, completely encapsulates each waste branch particle, forming a solid film with extremely low thermal conductivity. This film completely blocks the direct contact between the branch particles, transforming the original solid thermal bridges into a broken bridge structure connected by the insulating material, greatly reducing heat conduction through the solid material. During the bonding process, numerous independent and closed pores are formed, isolating airflow, eliminating convective heat transfer, and increasing insulation performance.

[0045] 4. The elastic modulus of waste branches is fixed, and the binder can be adjusted to prepare materials with different elastic moduli, achieving precise control of material properties. This simple operation allows for wide application in various industrial fields such as interior acoustic decoration, prefabricated building components, integrated exterior wall insulation and sound absorption, vehicle interiors, and noise control in industrial equipment. Especially in the construction field, it can be used as a key component in sound-absorbing ceilings, sound-absorbing wall panels, partition core materials, floor vibration damping layers, and soundproof doors, significantly improving the indoor acoustic environment and enhancing building sound insulation and thermal insulation performance. Simultaneously, it has multi-functional expansion potential in areas such as industrial noise reduction and rail transit equipment, aligning with the development direction of low-carbon environmental protection and high-value utilization of agricultural and forestry waste, and possessing broad engineering applications and market prospects.

[0046] 5. Compared with pure polyurethane adhesives, the composite porous material of this invention maintains its lightweight properties while achieving a sound absorption coefficient approaching 1 in certain frequency bands. According to GB / T 18696.2-2002 standard, using the transfer function method, the composite porous material of this invention exhibits excellent sound absorption performance in the core noise frequency band of 500–2000 Hz when the cylindrical specimen is 30 mm high. The optimal specimen achieves a sound absorption coefficient of over 0.95 at 1000 Hz. In the high-frequency band of 2500–6400 Hz, the sound absorption coefficient generally remains above 0.60, with some frequency points reaching as high as 0.84. The optimal sample forms three stable sound absorption peaks at 1000 Hz, 3200 Hz, and 6000 Hz, with a stable sound absorption coefficient above 0.4 across the entire frequency band and an average sound absorption coefficient reaching 0.7. The sound absorption uniformity and continuity are far superior to conventional comparative samples. Attached Figure Description

[0047] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0048] Figure 1 This is a schematic diagram of the structure of the composite porous material of the present invention.

[0049] Figure 2 This is the composite porous material of Example 1.

[0050] Figure 3 This is the composite porous material of Example 2.

[0051] Figure 4 This is the composite porous material of Example 3.

[0052] Figure 5 This is the composite porous material of Example 4.

[0053] Figure 6 This is the composite porous material of Example 5.

[0054] Figure 7 This is the composite porous material of Example 6.

[0055] Figure 8 This is the composite porous material of Example 7.

[0056] Figure 9 The graph shows the sound absorption coefficient of the composite porous material in Example 1 at 200~6400Hz.

[0057] Figure 10 The graph shows the sound absorption coefficient of the composite porous material in Example 2 at 200~6400Hz.

[0058] Figure 11 The graph shows the sound absorption coefficient of the composite porous material in Example 3 at 200~6400Hz.

[0059] Figure 12 The graph shows the sound absorption coefficient of the composite porous material in Example 4 at 200~6400Hz.

[0060] Figure 13 The graph shows the sound absorption coefficient of the composite porous material in Example 5 at 200~6400Hz.

[0061] Figure 14 The graph shows the sound absorption coefficient of the composite porous material in Example 6 at 200~6400Hz.

[0062] Figure 15 The graph shows the sound absorption coefficient of the composite porous material in Example 7 at 200~6400Hz. Detailed Implementation

[0063] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0064] This invention uses discarded wolfberry branches as raw materials.

[0065] Example 1 A method for preparing an integrated composite porous material for molds reinforced with waste branch fibers includes the following steps: (1) Pretreatment: Dry the waste wolfberry branches, remove the residual leaves on the surface, soak and rinse them in water to remove surface impurities, and then dry them; (2) Dismantling and grading: The dried waste branches are dismantled into roots, trunk and lateral branches; the roots, trunk and lateral branches with equivalent diameter >10mm are crushed to a particle size <10mm, and then screened through multiple stages to obtain three types of particles with particle sizes <3mm, 3~6mm and 6~10mm; the lateral branches are cut into lateral branch segments with a length of 0~100mm, and divided into three grades of 0~3mm, 3~6mm and 6~10mm according to the equivalent diameter; (3) Fiber modification: Take some particles with a particle size <3mm and grind them to obtain fiber bundles of 60~180μm. Add silane coupling agent KH-550 and compatibilizer maleic anhydride grafted polyethylene for modification to obtain modified fiber bundles; combine the modified fiber bundles with the three types of particles obtained in step (2) to obtain compound particles. By weight percentage, the compounded particles comprise the following components: 10% modified fiber bundles, 40% particles with a diameter <3mm, 30% particles with a diameter of 3-6mm, and 20% particles with a diameter of 6-10mm; The coupling agent is added at 3.5% of the fiber bundle mass; the compatibilizer is added at 2.5% of the fiber bundle mass. (4) Preparation of binder: Add delayed catalyst and thickener to binder, disperse at high speed and control foaming rate ≤15% to obtain polymer binder; The binder is polyurethane, which comprises a black component and a white component; the black component is liquefied MDI with an NCO content of 28%~30%; the white component is polyether polyol with a hydroxyl value of 350~380 mgKOH / g; the mass ratio of the black component to the white component is 1:1.1; the delayed catalyst is stannous octoate; the tackifier is rosin resin; the amount of delayed catalyst added is 1% of the binder mass; the amount of tackifier added is 0.5% of the binder mass; (5) Injection molding: The side branch segments with a length of 40~60mm and an equivalent diameter of 3~6mm are laid in the mold and vibrated to compact them. Then, the compounded particles are mixed with the polymer binder to form a slurry, which is injected into the mold gap and pressure is applied for injection molding. The mold is made of PLA; the inner wall of the mold is sandblasted with 80-mesh diamond abrasive and coated with an epoxy interface agent with a dry film thickness of 10~15μm; reinforcing ribs are welded to the inner wall; the mold is equipped with vent holes, injection ports, flow channels, and pressure relief channels; the vent holes have a diameter φ of 1.5mm, are located at the bottom of the mold's folded edge and the intersection of the reinforcing ribs, and are connected to an external negative pressure value of - The system includes a 0.02MPa suction device; four injection ports, two on each side of the mold along its length, each with a diameter of 12mm, and openings angled at 30° towards the mold center; pressure relief grooves, 5mm wide and 3mm deep, located on both sides of the mold's width and connected to the vent holes; the mold's internal dimensions are 1800mm × 900mm × 50mm, with a 50mm wide folded edge on the frame, and φ8mm mounting holes pre-drilled on the folded edge; the flow guide channels are arranged in a tree-like pattern from the injection port towards the mold edge, with a main channel width of 3mm, branch channels width of 2mm, and a channel spacing of 50mm, the bottom of the channels slightly inclined towards the mold center with a slope of 0.5%; and cross-shaped reinforcing ribs, 10mm high and spaced 150mm apart. The cut segments are laid with a thickness of 35mm, and after laying, they are gently vibrated for 10s using a vibration platform; the mass ratio of the compound granules to the polymer binder is 3:1, the injection pressure is 7MPa, the injection rate is 110mL / s, and the barrel temperature is 50℃. (6) Curing and molding: After injection molding, apply a constant pressure of 0.7 MPa and let stand at room temperature for 2 hours. After removing the pressure, let stand in the air for 48 hours to cure, and obtain the composite porous material.

[0066] Example 2 The difference from Example 1 is that in step (3), the compound particles, by mass percentage, include the following components: 10% modified fiber bundles, 45% particles with a diameter <3mm, 25% particles with a diameter of 3~6mm, and 20% particles with a diameter of 6~10mm; in step (5), the length of the side branch segments is 20~40mm, the equivalent diameter is 0~3mm, and the laying thickness is 30mm. The rest are the same.

[0067] Example 3 The difference from Example 1 is that in step (3), the compound particles, by mass percentage, include the following components: 10% modified fiber bundles, 45% particles with a diameter <3mm, 30% particles with a diameter of 3~6mm, and 15% particles with a diameter of 6~10mm; in step (5), the length of the side branch segments is 20~40mm, and the laying thickness is 30mm. The rest are the same.

[0068] Example 4 The difference from Example 1 is that in step (3), the compound particles, by mass percentage, include the following components: 10% modified fiber bundles, 50% particles with a diameter <3mm, 25% particles with a diameter of 3~6mm, and 15% particles with a diameter of 6~10mm; in step (5), the length of the side branch segments is 20~40mm, the equivalent diameter is 0~3mm, and the laying thickness is 40mm. The rest are the same.

[0069] Example 5 The difference from Example 1 is that in step (3), the compound particles, by mass percentage, include the following components: 10% modified fiber bundles, 45% particles with a diameter <3mm, 25% particles with a diameter of 3~6mm, and 20% particles with a diameter of 6~10mm; in step (5), the equivalent diameter of the side branch segments is 0~3mm. The rest are the same.

[0070] Example 6 The difference from Example 1 is that in step (5), the thickness of the lateral branch segments is 40 mm. The rest are the same.

[0071] Example 7 The difference from Example 1 is that in step (3), the compound particles, by mass percentage, include the following components: 10% modified fiber bundles, 45% particles with a diameter <3mm, 30% particles with a diameter of 3~6mm, and 15% particles with a diameter of 6~10mm; in step (5), the equivalent diameter of the side branch segments is 6~10mm. The rest are the same.

[0072] Performance testing Sound absorption performance: The composite porous materials obtained in each embodiment were cut into cylindrical specimens with a diameter of 30 mm and a height of 30 mm. The sound absorption performance was tested using the transfer function method according to GB / T 18696.2-2002 standard.

[0073] according to Figure 9 The composite porous material of Example 1 has a significant effect on mid-frequency noise control, and the high-frequency sound absorption coefficient continues to rise to over 0.8, demonstrating excellent high-frequency sound absorption performance and outstanding ability to dissipate high-frequency noise.

[0074] according to Figure 10 The composite porous material of Example 2 exhibits similar sound absorption performance in the mid-frequency range to that of Example 1, with stable noise dissipation efficiency and a continuously increasing sound absorption coefficient in the high-frequency range, reaching a peak value of 0.65~0.7 after 5000Hz.

[0075] according to Figure 11 The composite porous material in Example 3 has a sound absorption peak of 0.85 at 1000Hz, covering the core noise frequency band of 500~2000Hz, and has excellent sound absorption effect.

[0076] according to Figure 12 The composite porous material of Example 4 has a sound absorption coefficient of over 0.95 at 1000Hz, achieving efficient attenuation of mid-to-low frequency noise. In a wide frequency range of 500~6500Hz, the sound absorption coefficient is consistently maintained above 0.4, and multiple sound absorption peaks are formed at 1000Hz, 3200Hz and 6000Hz, with an average sound absorption coefficient of up to 0.7.

[0077] according to Figure 13 In Example 5, the composite porous material steadily increased its sound absorption coefficient to 0.6 in the mid-frequency range, with no fluctuations in the sound absorption process and strong stability. In the high-frequency range, the sound absorption coefficient increased to 0.7, indicating good high-frequency sound absorption performance.

[0078] according to Figure 14 The composite porous material in Example 6 has weak sound absorption performance at low frequencies, but its sound absorption coefficient increases to 0.65 at high frequencies.

[0079] according to Figure 15 The composite porous material of Example 7 has a stable sound absorption coefficient of 0.6~0.7 in the mid-to-high frequency range, indicating good sound absorption in the mid-to-high frequency range.

[0080] Vibration reduction performance test: The composite porous materials obtained in each embodiment were cut into 30×30×30mm specimens, and their elastic modulus was measured to be in the range of 20~35N / mm.

[0081] The thermal conductivity of the composite porous materials obtained in each embodiment was measured using the transient planar heat source method, ranging from 0.010 to 0.110 W / (m·K).

[0082] The properties of the composite porous materials obtained in Examples 1-7 are shown in Table 1. The average sound insulation refers to the average normal incidence transmission loss (TLn) over the range of 200–6400 Hz. The average sound absorption coefficient is the average value over the range of 200–6400 Hz. It is evident that the density, sound absorption coefficient, and sound insulation properties of the composite porous materials obtained in this invention are highly sensitive to the morphology of the side branch segments, particle size distribution, fiber bundle ratio, and foaming process parameters. The fundamental reason for this is that side branch segments, particles, and fiber bundles of different sizes construct a multi-level porous topology in the polyurethane matrix, consisting of macroscopic voids, mesoscopic particle packing pores, and microscopic fiber bundle interface pores. By controlling the particle size distribution and side branch morphology, the material's packing density, porosity, pore size distribution, air resistance, and sound wave propagation path can be precisely controlled. When the compound ratio is unbalanced or the side branch shape is not suitable, it will directly cause the porosity and flow resistance of the material to deviate from the optimal range, resulting in problems such as blind spots in the sound absorption frequency band, reduced sound insulation performance, or insufficient mechanical stability. However, through optimized particle size distribution and side branch shape design, the three can be synergistically controlled, enabling the material to have excellent sound absorption and sound insulation performance in a wide frequency range.

[0083] Table 1

[0084] As can be seen from Table 1 and the sound absorption coefficient curve, the composite porous material obtained by the present invention has good performance in the fields of heat insulation, impact resistance and sound absorption and noise reduction. The quality of the compounding of different fiber bundles and particles, the length of the side branch segments, the equivalent diameter, and the laying thickness directly affect its various properties.

[0085] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing an integrated composite porous material for a mold reinforced with waste branch fibers, characterized in that, Includes the following steps: (1) Pretreatment: Dry the waste branches, remove the residual leaves on the surface, soak them in water to remove surface impurities, and then dry them; (2) Dismantling and grading: The dried waste branches are dismantled into roots, trunk and lateral branches; the roots, trunk and lateral branches with equivalent diameter >10mm are crushed to a particle size <10mm, and then screened through multiple stages to obtain three types of particles with particle sizes <3mm, 3~6mm and 6~10mm; the lateral branches are cut into lateral branch segments with a length of 0~100mm, and divided into three grades of 0~3mm, 3~6mm and 6~10mm according to the equivalent diameter; (3) Fiber modification: Take some particles with a particle size <3mm and grind them to obtain fiber bundles with a particle size of 60~180μm. Add coupling agent and compatibilizer to modify them to obtain modified fiber bundles. The modified fiber bundles are compounded with the three types of particles obtained in step (2) to obtain compound particles; (4) Preparation of binder: Add delayed catalyst and thickener to binder, disperse at high speed and control foaming rate ≤15% to obtain polymer binder; (5) Injection molding: The side branch segments are laid in the mold and vibrated to compact them. Then the compounded particles are mixed with the polymer binder to form a slurry, which is injected into the mold gap and pressure is applied for injection molding. (6) Curing and molding: After injection molding, a constant pressure is applied and the mixture is left to stand. After the pressure is removed, it is ventilated and cured to obtain a composite porous material.

2. The preparation method according to claim 1, characterized in that, In step (3), the compound particles comprise the following components by mass percentage: 10% modified fiber bundles, 40%~50% particles with a diameter <3mm, 25%~30% particles with a diameter of 3~6mm, and 15%~20% particles with a diameter of 6~10mm.

3. The preparation method according to claim 1, characterized in that, In step (3), the coupling agent is selected from one of silane coupling agents, aminosilane coupling agents, titanate coupling agents, and zirconate coupling agents; the amount of coupling agent added is 3.5% of the fiber bundle mass; the compatibilizer is selected from one of maleic anhydride-grafted polyethylene, maleic anhydride-grafted polypropylene, acrylic acid-grafted polyolefin, and polyurethane prepolymer; the amount of compatibilizer added is 2.5% of the fiber bundle mass.

4. The preparation method according to claim 1, characterized in that, In step (4), the adhesive is selected from polyurethane, epoxy foam, phenolic foam, and thermoplastic microsphere foaming agent.

5. The preparation method according to claim 1, characterized in that, In step (4), the delayed catalyst is selected from one of stannous octoate, organobismuth, and dibutyltin dilaurate; the amount of delayed catalyst added is 1% of the mass of the binder; the tackifier is selected from one of rosin resin, hydrogenated rosin, terpene resin, and fumed silica; the amount of tackifier added is 0.5% of the mass of the binder.

6. The preparation method according to claim 1, characterized in that, In step (5), the material of the mold is selected from PLA, PP, ABS; the inner wall of the mold is sandblasted with 80-mesh diamond sand and coated with an epoxy interface agent with a dry film thickness of 10~15μm, and the inner wall is welded with reinforcing ribs; the mold is provided with venting holes, injection ports, guide grooves and pressure relief grooves.

7. The preparation method according to claim 6, characterized in that, The vent hole has a diameter φ of 1.5mm and is located at the bottom of the mold fold and the intersection of the reinforcing rib, and is connected to an external suction device with a negative pressure value of -0.02MPa; the injection port has 2 sets on each side of the mold length direction, for a total of 4 sets, with a diameter of 12mm, and the opening direction is inclined at a 30° angle to the mold center with respect to the inner wall of the mold; the pressure relief groove is 5mm wide and 3mm deep, located on both sides of the mold width direction, and is connected to the vent hole.

8. The preparation method according to claim 1, characterized in that, In step (5), the thickness of the side branch segments is 30~45mm, and after laying, they are lightly vibrated for 10s using a vibration platform; the mass ratio of the compound granules to the polymer binder is 3:1, the injection pressure is 6~8MPa, the injection rate is 100~120mL / s, and the barrel temperature is 50~55℃.

9. The preparation method according to claim 1, characterized in that, In step (6), the constant pressure is 0.5~0.8MPa, the pressure is removed after standing at room temperature for 2 hours, and the mixture is then ventilated and left to cure for 48 hours.

10. The composite porous material obtained by the preparation method according to any one of claims 1 to 9.

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