Self-cleaning acid and alkali resistant composite air duct

Abstract

The application discloses a self-cleaning acid and alkali resistant composite air pipe and belongs to the technical field of air pipes. The air pipe comprises a pipe body, the pipe body is a multilayer composite structure, and corrosion-resistant inner lining layers, reinforcing structure layers and hydrophobic self-cleaning outer layers are sequentially compounded from inside to outside. Flanges are arranged at the end portions of the pipe body, the flanges are made of the same fiber reinforced composite material as the reinforcing structure layers and are coated with a corrosion-resistant inner lining layer material on the surface, and a conductive or electrostatic conductive functional layer and a flow guide protrusion can be selectively arranged. The air pipe solves the problems of the existing air pipes, such as the inability to cooperate, easy damage and high maintenance cost, has comprehensive performances such as acid and alkali resistance, high strength and self-cleaning, is safe and reliable, convenient to maintain, and is suitable for complex ventilation working conditions of corrosive media and high dust.

Description

Technical Field

[0001] This invention relates to the field of ventilation duct technology, specifically to a self-cleaning acid and alkali resistant composite duct. Background Technology

[0002] In the production processes of industries such as chemical, metallurgical, and pharmaceutical, ventilation systems often need to transport gases containing corrosive media such as acid mist and alkali mist, while the airflow easily carries impurities such as dust. Existing ventilation ducts mainly include metal ducts, ordinary plastic ducts, and traditional composite ducts, all of which have obvious defects: metal ducts have acceptable mechanical strength, but poor resistance to acid and alkali corrosion, and are prone to corrosion and perforation after long-term use, and the surface is prone to dust accumulation, requiring frequent maintenance; ordinary plastic ducts have better corrosion resistance, but suffer from insufficient mechanical strength and weak impact resistance, and are prone to deformation and damage in high-pressure ventilation or complex installation environments; traditional composite ducts are mostly simple composites of a single reinforcing layer and an anti-corrosion layer, which can achieve a certain level of strength and corrosion resistance, but generally do not have self-cleaning function, and pollutants can easily breed bacteria after adhering, affecting ventilation efficiency, and the anti-corrosion layer and reinforcing layer are prone to peeling off after long-term use, resulting in a short service life. In addition, when dust-laden airflow flows inside the duct, it is easy to generate static electricity due to friction with the duct wall. Static electricity accumulation may cause sparks, posing a safety hazard. Existing technologies are difficult to achieve the synergistic integration of functions such as acid and alkali resistance, high strength, self-cleaning, and antistatic properties, and cannot meet the usage requirements of complex working conditions.

[0003] Therefore, a composite duct is proposed that simultaneously possesses excellent acid and alkali corrosion resistance, self-cleaning function, reliable mechanical strength and antistatic properties, as well as stable structure and long service life. Summary of the Invention

[0004] To address the technical shortcomings of existing air ducts, this invention provides a self-cleaning acid and alkali resistant composite air duct. Through the synergistic design of a multi-layer composite structure, it achieves multiple functional integrations, improving the applicability and stability of the air duct under harsh working conditions.

[0005] The specific technical solution is as follows:

[0006] A self-cleaning acid and alkali resistant composite air duct includes a duct body, which is a multi-layer composite structure, consisting of a corrosion-resistant inner lining layer, a reinforcing structural layer, and a hydrophobic self-cleaning outer layer stacked from the inside out.

[0007] The corrosion-resistant inner lining is the inner surface layer facing the flowing medium and is made of acid and alkali resistant polymer material;

[0008] The hydrophobic self-cleaning outer layer is an outer surface layer exposed to the external environment. Its surface has a micro-nano composite structure and is coated or blended with low surface energy materials, so that the static water contact angle of the outer surface layer is greater than 150° and the roll-off angle is less than 10°.

[0009] The reinforced structural layer is composited between the corrosion-resistant inner lining and the hydrophobic self-cleaning outer layer, providing mechanical strength support for the pipe body.

[0010] In the aforementioned self-cleaning acid and alkali resistant composite air duct, the material of the corrosion-resistant inner lining is at least one of polyvinylidene fluoride, polytetrafluoroethylene, perfluoroethylene propylene, or chlorinated polyvinyl chloride.

[0011] In the aforementioned self-cleaning acid and alkali resistant composite duct, the reinforcing structural layer is a fiber-reinforced composite material layer, which includes fibers and a matrix resin. The fibers are glass fibers, carbon fibers, or basalt fibers, and the matrix resin is a corrosion-resistant unsaturated polyester resin, vinyl ester resin, or epoxy resin.

[0012] In the aforementioned self-cleaning acid and alkali resistant composite air duct, the reinforcing structural layer is at least one of a continuous fiber winding layer, a fiber fabric lay-up layer, or a chopped fiber felt layer; the fiber winding angle of the continuous fiber winding layer is 30°-60°.

[0013] In the aforementioned self-cleaning acid and alkali resistant composite duct, the micro-nano composite structure of the hydrophobic self-cleaning outer layer is formed in situ on the surface of the reinforcing structure layer by surface etching, template method or spraying nanoparticles; the low surface energy material is at least one of polydimethylsiloxane, perfluorooctyltriethoxysilane or fluorocarbon resin.

[0014] The aforementioned self-cleaning acid and alkali resistant composite duct further comprises a conductive or electrostatically conductive functional layer on the inner surface of the corrosion-resistant inner lining. The material of the conductive or electrostatically conductive functional layer is a conductive polymer material or a polymer composite material doped with conductive fillers. The conductive filler is at least one of carbon black, graphene, or metal nanoparticles. The surface resistivity of the conductive or electrostatically conductive functional layer is 10⁻⁶. 3 Ω-10 9 Ω.

[0015] In the aforementioned self-cleaning acid and alkali resistant composite air duct, a flange is provided at the end of the duct body, and the surface of the flange is at least covered with the corrosion resistant inner lining material; the flange is made of the same fiber-reinforced composite material as the reinforcing structural layer.

[0016] In the aforementioned self-cleaning acid and alkali resistant composite air duct, the thickness of the corrosion-resistant inner lining layer is 0.5mm-3mm, the thickness of the reinforcing structural layer is 2mm-10mm, and the thickness of the hydrophobic self-cleaning outer layer is 0.1mm-0.8mm.

[0017] In the aforementioned self-cleaning acid and alkali resistant composite air duct, the volume fraction of fibers in the reinforcing structural layer is 30%-60%.

[0018] In the aforementioned self-cleaning acid and alkali resistant composite air duct, the inner wall of the duct body is provided with a plurality of flow guiding protrusions along the axial direction. The flow guiding protrusions are integrally formed with the duct body, and their surfaces are covered with a corrosion-resistant inner lining material.

[0019] This invention also provides a method for preparing a self-cleaning acid and alkali resistant composite air duct, comprising the following steps:

[0020] Step S1: Prepare a corrosion-resistant inner lining layer

[0021] A corrosion-resistant inner lining layer with a thickness of 0.5 mm to 3 mm is formed by using at least one polymer material selected from polytetrafluoroethylene, polyvinylidene fluoride, perfluoroethylene propylene, or chlorinated polyvinyl chloride through extrusion or hot pressing. Optionally, a conductive or electrostatically conductive functional layer is laminated onto its inner surface, and the surface resistivity of the functional layer is controlled to be within 10 Ω·cm. 3 Ω to 10 9 Between Ω;

[0022] Step S2: Composite Reinforced Structural Layer

[0023] A matrix resin is coated on the outer surface of the corrosion-resistant inner lining, and fiber reinforcement material is introduced by at least one of continuous fiber winding, fiber fabric lay-up, or chopped fiber mat. The fiber is glass fiber, carbon fiber, or basalt fiber, and the matrix resin is vinyl ester resin, epoxy resin, or unsaturated polyester resin. The fiber volume fraction is controlled to be 30% to 60%, the winding angle is 30° to 60°, and after curing, a reinforced structural layer with a thickness of 2 mm to 10 mm is formed.

[0024] Step S3: Construct a hydrophobic self-cleaning outer layer

[0025] On the outer surface of the reinforcing structural layer, a micro-nano composite structure is constructed by surface etching, template method or spraying nanoparticles, and then coated or blended with a low surface energy material, wherein the low surface energy material is at least one of polydimethylsiloxane, perfluorooctyltriethoxysilane or fluorocarbon resin, forming a hydrophobic self-cleaning outer layer with a thickness of 0.1 mm to 0.8 mm, so that its static water contact angle is greater than 150° and its roll-off angle is less than 10°;

[0026] Step S4: Flange preparation and bonding

[0027] The flange is made of the same fiber-reinforced composite material as the reinforcing structural layer, and its surface is covered with a corrosion-resistant inner lining material. Finally, the flange is fixed to the end of the pipe body by bonding or bolting.

[0028] Step S5: Optional flow guide protrusions integrally molded

[0029] When preparing the corrosion-resistant inner liner, a flow-guiding protrusion is integrally formed along the axial direction through mold design, and its surface is covered with corrosion-resistant inner liner material.

[0030] By directly coating the surface of the corrosion-resistant lining (101) with resin and then composite it with a reinforcing layer (102), the use of traditional adhesives is avoided, weak points at the interlayer interface are eliminated, and the risk of peeling between the anti-corrosion layer and the reinforcing layer during long-term use is significantly reduced.

[0031] Step S5 uses a mold to integrally form the guide protrusion (1011) with the inner liner, avoiding damage to the pipe wall caused by secondary processing and installation of the guide plate, and ensuring the durability and stability of the airflow guiding function.

[0032] Through the dual process control of micro-nano structure construction and low surface energy material coating in step S3, the static water contact angle of the hydrophobic outer layer is greater than 150° and the roll-off angle is less than 10°, giving the outer surface of the duct excellent dustproof, scale-proof and self-cleaning capabilities.

[0033] The process-performance mapping relationship is clear: by controlling etching or spraying process parameters (such as roughness Ra) and the coverage of low surface energy materials (f... c The self-cleaning index S can be directionally adjusted. d This allows products to shift from experience-based manufacturing to designable manufacturing.

[0034] In step S2, the fiber winding angle (30°-60°) and volume fraction (30%-60%) are limited, which optimizes the strength distribution of the reinforcing layer in the circumferential and axial directions. This allows it to resist internal negative pressure collapse and withstand external impacts, avoiding the problem of excessive strength in one direction and insufficient strength in another.

[0035] While ensuring circumferential compressive strength (such as 9-18 MPa in the examples), a lighter weight than metal ducts is achieved through the composite process of fiber and resin, which facilitates transportation and installation.

[0036] The composite and resistivity control of the conductive functional layer in step S1 enable the duct to effectively conduct away static electricity and prevent sparks when transporting flammable dust gas, thus broadening the application scenarios of the duct in the field of explosion protection.

[0037] In step S4, the flange surface is covered with a corrosion-resistant lining material, which gives the duct connection the same acid and alkali resistance as the duct body, solving the problem of easy corrosion and leakage at traditional duct flanges.

[0038] This method completes multi-layer structures in a single molding cycle (e.g., the reinforcing layer is directly wound after the lining is formed), reducing the number of times semi-finished products are turned over and lowering the risk of contamination and damage.

[0039] By controlling processes such as vacuum-assisted molding or hot-press curing, bubbles and dry spots in the reinforcing layer are reduced, thereby improving the density and yield of the composite material.

[0040] The present invention has the following beneficial effects:

[0041] 1. Enhanced overall performance: Through the multi-layer composite structure design of the duct body, the corrosion resistance of the corrosion-resistant inner lining, the high strength of the reinforced structural layer, and the self-cleaning function of the hydrophobic self-cleaning outer layer are organically combined. This solves the problem that the single function of existing air ducts is difficult to adapt to complex working conditions, enabling the air duct to have multiple performances at the same time, ensuring stable use in corrosive media and dusty environments.

[0042] 2. Enhanced safety and reliability: The added conductive or electrostatic conductive functional layer can effectively avoid static electricity accumulation and reduce safety hazards in dusty airflow conditions; the design of the airflow guide protrusion not only optimizes airflow distribution but also reduces the generation of frictional static electricity, further improving the safety of use; the material matching and covering design of the flange ensures the strength and corrosion resistance of the connection parts, avoids leakage and other problems caused by connection failure, and improves the overall structural reliability.

[0043] 3. Optimized ease of use and economy: The hydrophobic self-cleaning outer layer reduces the adhesion of external pollutants, significantly reducing the frequency and cost of duct maintenance; the reasonable matching of the thickness of each layer and the material design of the reinforcing structural layer achieve lightweight duct body while ensuring performance, making it easy to transport and install; the overall structure is adaptable to a variety of corrosive working conditions, eliminating the need for separate duct design for different working conditions, thus improving the applicability and reducing the cost of use. Attached Figure Description

[0044] Figure 1 This is a schematic diagram of the structure of a self-cleaning acid and alkali resistant composite air duct provided in an embodiment of the present invention;

[0045] Figure 2 This is a partial cross-sectional view of the pipe wall in a self-cleaning acid and alkali resistant composite duct provided in an embodiment of the present invention.

[0046] In the attached image:

[0047] 1. Pipe body; 101. Corrosion-resistant inner lining; 102. Reinforcing structural layer; 103. Hydrophobic self-cleaning outer layer; 1011. Flow guiding protrusion; 2. Flange. Detailed Implementation

[0048] The technical solution of the present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0049] The accompanying drawings are for illustrative purposes only and are schematic diagrams, not actual images. They should not be construed as limiting the scope of this application. To better illustrate the embodiments of the present invention, some parts in the drawings may be omitted, enlarged, or reduced, and do not represent the actual dimensions of the product. It is understandable to those skilled in the art that some well-known structures and their descriptions may be omitted in the drawings.

[0050] In the accompanying drawings of the embodiments of the present invention, the same or similar reference numerals correspond to the same or similar components. In the description of the present invention, it should be understood that if terms such as "upper," "lower," "left," "right," "inner," and "outer" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, they are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, the terms used to describe positional relationships in the drawings are only for illustrative purposes and should not be construed as limiting the present application. For those skilled in the art, the specific meaning of the above terms can be understood according to the specific circumstances.

[0051] In the description of this invention, unless otherwise explicitly specified and limited, the term "connection" or similar designation indicating a connection between components should be interpreted broadly. For example, it can refer to a fixed connection, a detachable connection, or an integral part; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium; it can refer to the internal communication between two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0052] Reference Figure 1-2 As shown in the figure, this specific embodiment provides a self-cleaning acid and alkali resistant composite air duct, including a duct body 1. The duct body 1 has a multi-layer composite structure, in which a corrosion-resistant inner lining layer 101, a reinforcing structural layer 102, and a hydrophobic self-cleaning outer layer 103 are stacked sequentially from the inside to the outside. The corrosion-resistant inner lining layer 101 is the inner surface layer facing the flowing medium and is made of acid and alkali resistant polymer material. The hydrophobic self-cleaning outer layer 103 is the outer surface layer exposed to the external environment. Its surface has a micro-nano composite structure and is coated or blended with a low surface energy material, so that the static water contact angle of the outer surface layer is greater than 150° and the roll-off angle is less than 10°. The reinforcing structural layer 102 is composited between the corrosion-resistant inner lining layer 101 and the hydrophobic self-cleaning outer layer 103 to provide mechanical strength support for the duct body 1.

[0053] The pipe body 1 in this design adopts a multi-layer composite structure design consisting of a corrosion-resistant inner lining layer 101, a reinforcing structural layer 102, and a hydrophobic self-cleaning outer layer 103. Each layer works synergistically: the corrosion-resistant inner lining layer 101 directly faces the flowing medium, effectively isolating the pipe body 1 from corrosive media erosion and protecting its interior from corrosion damage; the reinforcing structural layer 102, located between the two layers, provides reliable mechanical strength support for the pipe body 1, ensuring its structural stability during use and preventing deformation and damage; the hydrophobic self-cleaning outer layer 103 is exposed to the external environment, and its micro-nano composite structure combined with low surface energy materials reduces the adhesion of external contaminants to its surface, achieving a self-cleaning effect and reducing the frequency of external maintenance of the pipe body 1. The overall structure gives the pipe body 1 comprehensive properties of acid and alkali resistance, high strength, and self-cleaning, making it suitable for complex operating conditions involving corrosive media flow.

[0054] The corrosion-resistant inner lining 101 is made of at least one of polyvinylidene fluoride, polytetrafluoroethylene, perfluoroethylene propylene, or chlorinated polyvinyl chloride. The material of the corrosion-resistant inner lining 101 is limited to a specific acid and alkali resistant polymer material. This type of material itself possesses excellent acid and alkali resistance stability, which can further enhance the corrosion resistance of the corrosion-resistant inner lining 101, ensuring that the corrosion-resistant inner lining 101 operates stably in corrosive media environments for a long time, avoiding premature damage to the inside of the pipe body 1 due to insufficient material corrosion resistance, and extending the service life of the pipe body 1.

[0055] The reinforcing structural layer 102 is a fiber-reinforced composite material layer, comprising fibers and a matrix resin. The fibers are glass fiber, carbon fiber, or basalt fiber, and the matrix resin is a corrosion-resistant unsaturated polyester resin, vinyl ester resin, or epoxy resin. The inclusion of a fiber-reinforced composite material layer 102, with specific types of fibers and matrix resin, allows for synergistic reinforcement, significantly improving the mechanical properties of the reinforcing structural layer 102. This enhances the compressive and impact resistance of the pipe body 1, ensuring its structural reliability under complex installation and operating conditions. Simultaneously, the selected matrix resin possesses corrosion resistance, reducing the erosion of the reinforcing structural layer 102 by corrosive environments, further guaranteeing its long-term support effect.

[0056] The reinforcing structural layer 102 is at least one of a continuous fiber winding layer, a fiber fabric lay-up, or a chopped fiber felt layer; the fiber winding angle of the continuous fiber winding layer is 30°-60°. By defining the specific structural form of the reinforcing structural layer 102, the structural design of the continuous fiber winding layer, fiber fabric lay-up, or chopped fiber felt layer can optimize the strength distribution of the reinforcing structural layer 102 and improve the bonding tightness between the reinforcing structural layer 102 and adjacent layers; the winding angle design of the continuous fiber winding layer can further balance the circumferential and axial strength of the pipe body 1, avoid local weakness in the strength of the pipe body 1, and improve the overall structural stability and load-bearing capacity of the pipe body 1.

[0057] The hydrophobic self-cleaning outer layer 103's micro-nano composite structure is formed in situ on the surface of the reinforcing structure layer 102 through surface etching, template method, or spraying nanoparticles. The low surface energy material is at least one of polydimethylsiloxane, perfluorooctyltriethoxysilane, or fluorocarbon resin. The formation method of the hydrophobic self-cleaning outer layer 103's micro-nano composite structure is clearly defined. The in-situ formation method ensures a strong bond between the micro-nano composite structure and the reinforcing structure layer 102, preventing the hydrophobic self-cleaning outer layer 103 from detaching. The defined type of low surface energy material further enhances the hydrophobic properties of the hydrophobic self-cleaning outer layer 103, strengthens the self-cleaning effect, reduces the adhesion of dust, water stains, and other contaminants from the external environment to the surface of the hydrophobic self-cleaning outer layer 103, and reduces the external cleaning and maintenance costs of the pipe body 1.

[0058] The inner surface of the corrosion-resistant lining 101 is further composited with a conductive or electrostatic functional layer. The material of this conductive or electrostatic functional layer is a conductive polymer material or a polymer composite material doped with conductive fillers. The conductive filler is at least one of carbon black, graphene, or metal nanoparticles. The surface resistivity of the conductive or electrostatic functional layer is 10⁻⁶. 3 Ω-10 9 A conductive or electrostatic conductive functional layer is added to the inner surface of the corrosion-resistant lining 101. The material properties of this functional layer enable it to effectively dissipate the static electricity generated by the friction of airflow inside the pipe body 1, preventing the accumulation of static electricity inside the pipe body 1. The reduction of static electricity accumulation can reduce the risk of spark generation, ensure the safety of the pipe body 1 in the flow of flammable and explosive media such as dust, and at the same time prevent the accumulation of contaminants on the surface of the corrosion-resistant lining 101 due to the adsorption of dust by static electricity.

[0059] The pipe body 1 has a flange 2 at one end, and the surface of the flange 2 is covered with at least a corrosion-resistant inner lining layer 101. The flange 2 is made of the same fiber-reinforced composite material as the reinforcing structural layer 102. The flange 2 at the end of the pipe body 1, made of the same fiber-reinforced composite material as the reinforcing structural layer 102, ensures that the flange 2 and the main body of the pipe body 1 are matched in strength, avoiding structural failure due to weak connection points. The corrosion-resistant inner lining layer 101 on the surface of the flange 2 improves its corrosion resistance, reduces the erosion of the flange 2 by corrosive environments, ensures the connection sealing and structural integrity of the flange 2, and thus guarantees the long-term reliable use of the connection points of the pipe body 1.

[0060] The corrosion-resistant inner lining 101 has a thickness of 0.5mm-3mm, the reinforcing structural layer 102 has a thickness of 2mm-10mm, and the hydrophobic self-cleaning outer layer 103 has a thickness of 0.1mm-0.8mm. By limiting the thickness range of each layer, a reasonable thickness matching ensures the corrosion resistance of the corrosion-resistant inner lining 101, the mechanical strength of the reinforcing structural layer 102, and the self-cleaning function of the hydrophobic self-cleaning outer layer 103, thereby achieving a lightweight design of the pipe body 1, facilitating its transportation and installation. Simultaneously, it avoids material waste or structural bulkiness due to excessive thickness of any one layer, or functional deficiencies due to insufficient thickness, thus improving the overall performance and economy of the pipe body 1.

[0061] The volume fraction of fibers in the reinforcing structural layer 102 is 30%-60%. This defined range of fiber volume fraction in the reinforcing structural layer 102 allows for an optimal balance between strength and toughness, preventing insufficient strength due to excessively low fiber content or insufficient fiber content leading to inadequate fiber coating by the matrix resin and reduced interlayer bonding. This ensures the stable support effect of the reinforcing structural layer 102 and extends the service life of the tube body 1.

[0062] The inner wall of the pipe body 1 is provided with several flow-guiding protrusions 1011 along the axial direction. The flow-guiding protrusions 1011 are integrally formed with the pipe body 1, and their surfaces are covered with a corrosion-resistant inner lining material 101. The flow-guiding protrusions 1011 on the inner wall of the pipe body 1 can optimize the airflow distribution inside the pipe body 1, reduce the formation of eddies in the airflow inside the pipe body 1, reduce airflow resistance and the degree of friction between the airflow and the inner wall of the pipe body 1, thereby reducing the generation of frictional static electricity. The integral formation of the flow-guiding protrusions 1011 with the pipe body 1 improves the structural stability, and the corrosion-resistant inner lining material 101 on the surface ensures the corrosion resistance of the flow-guiding protrusions 1011, preventing them from being eroded and damaged by corrosive media. At the same time, it reduces the adhesion of pollutants on the surface of the flow-guiding protrusions 1011, further improving the ventilation efficiency and operational stability of the pipe body 1.

[0063] Overall working principle:

[0064] This self-cleaning acid and alkali resistant composite duct achieves basic functions such as corrosion resistance, strength support, and self-cleaning through the synergistic effect of its multi-layered composite structure and functional components. Combined with optional anti-static and airflow optimization designs, it enhances overall performance. The specific principle is as follows:

[0065] 1. Basic protection and support synergy: In the multi-layer composite structure of the pipe body 1, the corrosion-resistant inner lining layer 101 is in direct contact with the flowing medium. Relying on the characteristics of acid and alkali resistant polymer materials, it isolates the medium from corrosion and avoids damage to the inside of the pipe body 1. The reinforcing structural layer 102 is located between the two layers. Through the composite effect of fibers and matrix resin, it disperses the internal and external pressures borne by the pipe body 1, provides stable mechanical strength support for the pipe body 1, and ensures structural integrity. The hydrophobic self-cleaning outer layer 103 is exposed to the external environment. Its surface micro-nano composite structure and low surface energy materials work together to reduce the adhesion of water and pollutants, making it difficult for pollutants to adhere or easy to be peeled off by natural external forces, thus achieving self-cleaning.

[0066] 2. Functional Optimization and Synergy: If a conductive or electrostatic conductive functional layer is added, its conductive properties can dissipate the static electricity generated by the friction between the airflow and the inner wall of the pipe body 1 in a timely manner, avoiding the accumulation of static electricity; the flow guiding protrusion 1011 on the inner wall of the pipe body 1 guides the airflow along the axial direction, reducing the generation of eddies, reducing airflow resistance and reducing frictional static electricity; the flange 2 at the end of the pipe body 1 adopts the same fiber-reinforced composite material as the reinforcing structural layer 102, ensuring that the strength of the connection part matches the main body of the pipe body 1, and in conjunction with the corrosion-resistant inner lining material 101 covering the surface, ensuring the corrosion resistance and sealing of the connection part.

[0067] Overall technical effect:

[0068] 1. Enhanced overall performance: Through the multi-layer composite structure design of the pipe body 1, the corrosion resistance of the corrosion-resistant inner lining layer 101, the high strength of the reinforcing structural layer 102, and the self-cleaning function of the hydrophobic self-cleaning outer layer 103 are organically combined, which solves the problem that the single function of the existing air duct is difficult to adapt to complex working conditions. This enables the air duct to have multiple core performances at the same time, ensuring stable use in corrosive media and dusty environments.

[0069] 2. Enhanced safety and reliability: The added conductive or electrostatic conductive functional layer can effectively avoid static electricity accumulation and reduce safety hazards in dusty airflow conditions; the design of the guide protrusion 1011 not only optimizes airflow distribution but also reduces the generation of frictional static electricity, further improving safety in use; the material matching and covering design of flange 2 ensures the strength and corrosion resistance of the connection parts, avoids leakage and other problems caused by connection failure, and improves the overall structural reliability.

[0070] 3. Optimization of ease of use and economy: The hydrophobic self-cleaning outer layer 103 reduces the adhesion of external pollutants, significantly reducing the frequency and cost of duct maintenance; the reasonable matching of the thickness of each layer and the material design of the reinforcing structural layer 102 achieve lightweight duct body 1 while ensuring performance, making it easy to transport and install; the overall structure is adaptable to a variety of corrosive working conditions, eliminating the need for separate duct design for different working conditions, thus improving the applicability and reducing the cost of use.

[0071] How to use:

[0072] 1. Installation preparation: Select the corresponding specifications of air duct according to the actual working conditions of the ventilation system, and check the integrity of the duct body 1, flange 2 and each functional layer (corrosion-resistant inner lining 101, reinforcing structural layer 102, hydrophobic self-cleaning outer layer 103, etc.) to ensure that there are no defects such as damage, cracks, or delamination; if the air duct contains a conductive functional layer or a flow guiding protrusion 1011, it is necessary to additionally check that the surface of the conductive functional layer is undamaged and the flow guiding protrusion 1011 is undeformed.

[0073] 2. Duct connection: Ducts are connected via flange 2 at the end of duct body 1. When connecting, ensure that the covering layer of flange 2 is aligned with the corrosion-resistant inner lining layer 101 of duct body 1. Tighten flange 2 with bolts, applying force evenly during the tightening process to ensure a tight seal at the connection and prevent leakage of corrosive media. If bends or branches are required, select matching special-shaped ducts and use the same flange connection method to ensure reliable connection.

[0074] 3. System debugging: After the connection is completed, the ventilation system is tested and checked for deformation or vibration of the duct body 1 and leakage at the flange 2 connection. If the duct has a conductive functional layer, the static dissipation effect can be tested with an electrostatic tester to ensure that there is no static accumulation. For ducts with guide protrusions 1011, it is necessary to confirm that the ventilation efficiency meets the design requirements.

[0075] 4. Routine maintenance: Regularly observe the surface condition of the hydrophobic self-cleaning outer layer 103. If stubborn contaminants are attached, gently rinse with low-pressure airflow or clean water. Avoid using hard tools to scrape, as this may damage the micro-nano composite structure. Regularly check the sealing performance of the flange 2 connection. If a seal failure is found, replace the seal promptly. After long-term use, if damage is found in the corrosion-resistant inner lining 101, repair or replace the duct in time to ensure that the corrosion resistance does not fail.

[0076] Among them, the dynamic self-cleaning performance index of the hydrophobic self-cleaning outer layer The following relationship must be satisfied:

[0077]

[0078] in:

[0079] Static water contact angle (unit: degrees);

[0080] The roll angle is measured in degrees.

[0081] The arithmetic mean roughness (unit: micrometers) of the hydrophobic self-cleaning outer surface micro / nano structure.

[0082] The coverage of low surface energy material on the surface (dimensionless, range 0–1).

[0083] The derivation process is explained below:

[0084] This equation is derived based on the following physical and surface chemical principles:

[0085] 1. Hydrophobic properties: Normalized superhydrophobic contact angle contribution, with 150° as the superhydrophobic threshold.

[0086] 2. Self-cleaning flowability: This reflects the water droplet's ability to roll off; the smaller the rolling angle, the stronger the self-cleaning ability.

[0087] 3. Surface morphology influence items: This indicates that appropriate roughness is beneficial for superhydrophobicity, but excessive roughness will trap pollutants, hence the negative index.

[0088] 4. Low surface energy coverage items: This reflects the contribution of low surface energy material coverage to hydrophobicity; higher coverage indicates better performance.

[0089] Example data: =158°; =8°; =0.15μm (assuming that the sprayed nanoparticles form a micro-nano structure). =0.90 (assuming good PDMS coverage).

[0090] Substitute into the calculation:

[0091]

[0092]

[0093] .

[0094] at this time A value less than 1.0 indicates a need to optimize surface roughness or coverage uniformity. This can be achieved by adjusting the process (e.g., reducing...). (to approximately 0.12 μm), which can make Meeting the target demonstrates the function of this equation in design optimization and performance prediction.

[0095] Technical benefits: It provides a quantitative evaluation and design optimization tool to ensure that the hydrophobic self-cleaning performance reaches its best; through multi-parameter collaborative optimization, it avoids over-design of a single parameter (such as excessive roughness leading to dust accumulation); it enhances the predictability and controllability of the solution and is suitable for customized design under different working conditions.

[0096] Working principle and process:

[0097] 1. Determine operating requirements → Set targets ≥1.0;

[0098] 2. Material and process selection → Preliminary design ;

[0099] 3. Substitute into the equation to verify → If <1.0, adjust parameters (such as replacing with low surface energy materials, optimizing the spraying process);

[0100] 4. Preparation and testing → Measured parameters feed back into the equation optimization to form a design closed loop.

[0101] This specific implementation also provides the following three embodiments.

[0102] Example 1

[0103] I. Technical Solution

[0104] A self-cleaning acid and alkali resistant composite air duct includes a duct body 1, which is a multi-layer composite structure, consisting of a corrosion-resistant inner lining layer 101, a reinforcing structural layer 102, and a hydrophobic self-cleaning outer layer 103 stacked from the inside to the outside.

[0105] The corrosion-resistant inner lining layer 101 is made of polytetrafluoroethylene with a thickness of 1.5 mm;

[0106] The reinforcing structural layer 102 is a fiber-reinforced composite material layer, composed of glass fiber and vinyl ester resin, wherein the volume fraction of glass fiber is 45%, the reinforcing structural layer 102 is a continuous fiber winding layer with a fiber winding angle of 45° and a thickness of 6mm.

[0107] The hydrophobic self-cleaning outer layer 103 is a micro-nano composite structure formed in situ on the surface of the reinforcing structure layer 102 by spraying nano-silica particles, and coated with polydimethylsiloxane low surface energy material with a thickness of 0.4 mm.

[0108] The end of the pipe body 1 is provided with a flange 2, which is made of the same glass fiber reinforced vinyl ester resin as the reinforcing structural layer 102, and the surface of the flange 2 is covered with polytetrafluoroethylene material.

[0109] II. Working Principle

[0110] 1. Acid and alkali resistance protection principle: The PTFE material of the corrosion-resistant inner lining 101 is in direct contact with the corrosive medium in the flow. It relies on the excellent acid and alkali resistance of the material itself to isolate the medium from corrosion and avoid damage to the inside of the pipe body 1; the PTFE coating on the surface of the flange 2 simultaneously isolates the corrosive environment from the corrosion of the flange 2, ensuring the corrosion resistance of the connection parts.

[0111] 2. Strength support principle: In the reinforcing structural layer 102, glass fiber and vinyl ester resin form a synergistic reinforcement system. The continuous fiber 45° winding structure makes the fiber evenly distributed, which can effectively disperse the internal and external pressure on the pipe body 1 and provide stable mechanical strength support for the pipe body 1. The flange 2 is made of the same material as the reinforcing structural layer 102, ensuring that the strength of the connection part matches the main body of the pipe body 1 and avoiding connection failure.

[0112] 3. Self-cleaning principle: The hydrophobic self-cleaning outer layer of 103 nano-silica particles forms a micro-nano rough structure, which, combined with low surface energy polydimethylsiloxane, reduces the adhesion between the surface and water and pollutants, making it difficult for pollutants to adhere, or causing them to fall off under the action of natural wind or a small amount of rain, thus achieving self-cleaning.

[0113] III. Experimental Data

[0114] 1. Acid and alkali resistance test: The duct was immersed in a 20% sulfuric acid solution and a 20% sodium hydroxide solution for 30 days. After removal, it was observed that the corrosion-resistant inner lining 101 showed no bulging, cracking, or dissolution, and the duct body 1 had an intact structure and no leakage.

[0115] 2. Mechanical strength test: The circumferential compressive strength of pipe body 1 was tested and the result was 12MPa, and the axial tensile strength was 8MPa, which meets the requirements of high-pressure ventilation conditions; when the flange 2 connection part was subjected to a pressure of 1.5MPa, there was no deformation or leakage.

[0116] 3. Self-cleaning test: The static water contact angle of the hydrophobic self-cleaning outer layer 103 was measured to be 158° and the roll-off angle was 8°. When dust (particle size 50-100μm) was evenly sprayed on the surface and blown by an airflow with a wind speed of 3m / s, the dust removal rate reached 98%.

[0117] IV. Technical Effects

[0118] As can be seen from the above scheme, this embodiment effectively improves the acid and alkali resistance of the pipe body 1 by selecting polytetrafluoroethylene as the corrosion-resistant inner lining material 101. The immersion test showed no corrosion damage, ensuring the long-term stable use of the duct in corrosive media environments. The reinforcing structural layer 102 adopts a continuous winding structure of glass fiber with a specific volume fraction, which significantly improves the compressive and tensile strength of the pipe body 1. Combined with flange 2 of the same material, it ensures the strength matching of the connection parts and avoids structural failure. The combination of the micro-nano structure and low surface energy material of the hydrophobic self-cleaning outer layer 103 gives the surface excellent hydrophobic self-cleaning performance, high dust removal rate, and greatly reduces the frequency of external maintenance. The overall scheme achieves a synergistic effect of acid and alkali resistance, high strength, and self-cleaning, and is suitable for ventilation conditions containing acid mist and alkali mist in the chemical industry.

[0119] V. Preparation method:

[0120] 1. Preparation of corrosion-resistant inner lining 101: Select polytetrafluoroethylene sheet, cut it according to the specifications of tube body 1, and then use hot pressing molding process to attach it to the inner wall of the mold to form a corrosion-resistant inner lining 101 with a thickness of 1.5mm. The molding temperature is controlled at 370-380℃, and after holding at the temperature for 2-3 hours, it is naturally cooled and demolded.

[0121] 2. Preparation of reinforcing structural layer 102: Vinyl ester resin is uniformly coated on the outer surface of corrosion-resistant inner lining layer 101. Glass fiber is continuously wound on the resin coating surface at a winding angle of 45°. Resin is added simultaneously during the winding process to ensure that the fiber is completely wetted. After winding, curing treatment is performed at a curing temperature of 80-90℃ and a curing time of 4-5h to form a reinforcing structural layer 102 with a volume fraction of 45% and a thickness of 6mm.

[0122] 3. Preparation of hydrophobic self-cleaning outer layer 103: Nano-silica particles are sprayed onto the outer surface of the reinforcing structure layer 102 using a high-pressure spraying process to form a micro-nano rough structure. After spraying, the material is allowed to dry naturally for 2 hours. Then, polydimethylsiloxane low surface energy material is uniformly coated using a roller coating process with a thickness controlled at 0.4 mm. Finally, the material is cured at room temperature for 3 hours.

[0123] 4. Preparation and assembly of flange 2: Select glass fiber and vinyl ester resin, prepare flange 2 blank according to the material ratio of reinforcing structural layer 102, process it to the specifications of pipe body 1, cover the surface of flange 2 with polytetrafluoroethylene material and heat press it together, and finally fix flange 2 to the end of pipe body 1 by bonding and bolting to complete the preparation of the whole duct.

[0124] Example 2

[0125] I. Technical Solution

[0126] A self-cleaning acid and alkali resistant composite air duct includes a duct body 1, which is a multi-layer composite structure, consisting of a corrosion-resistant inner lining layer 101, a reinforcing structural layer 102, and a hydrophobic self-cleaning outer layer 103 stacked from the inside to the outside.

[0127] The corrosion-resistant inner lining 101 is made of polyvinylidene fluoride (PVDF) with a thickness of 2 mm. A conductive functional layer is laminated onto the inner surface of the corrosion-resistant inner lining 101. This conductive functional layer is made of PVDF composite material doped with carbon black, with a surface resistivity of 10⁻⁶. 6 Ω;

[0128] The reinforcing structural layer 102 is a fiber-reinforced composite material layer, composed of carbon fiber and epoxy resin, wherein the volume fraction of carbon fiber is 50%, and the reinforcing structural layer 102 is a fiber fabric layup with a thickness of 8mm.

[0129] The hydrophobic self-cleaning outer layer 103 micro-nano composite structure is formed on the surface of the reinforcing structure layer 102 by template method, and is blended with perfluorooctyltriethoxysilane low surface energy material with a thickness of 0.6 mm.

[0130] The end of the pipe body 1 is provided with a flange 2, which is made of the same carbon fiber reinforced epoxy resin as the reinforcing structural layer 102, and the surface of the flange 2 is covered with polyvinylidene fluoride material.

[0131] II. Working Principle

[0132] 1. Synergistic principle of acid and alkali resistance and antistatic properties: The polyvinylidene fluoride of the corrosion-resistant inner lining 101 isolates it from the erosion of corrosive media, and the conductive functional layer on its inner side relies on the conductive properties of carbon black to dissipate the static electricity generated by the friction between the airflow and the inner wall of the pipe body 1 in a timely manner, thus avoiding the accumulation of static electricity.

[0133] 2. High-strength support principle: Carbon fiber itself has high strength characteristics. When combined with epoxy resin to form a reinforcing structural layer 102, and with the fiber fabric lay-up structure, the fibers are evenly spread, which can fully withstand the internal and external pressure of the pipe body 1 and improve the overall structural stability. The flange 2 is made of the same material as the reinforcing structural layer 102 to ensure that the strength of the connection part matches the main body of the pipe body 1.

[0134] 3. Self-cleaning principle: The micro-nano composite structure formed by the template method provides a structural basis for hydrophobic self-cleaning. The blended perfluorooctyltriethoxysilane further reduces the surface energy, making it difficult for water and pollutants to adhere to the surface, thus achieving self-cleaning.

[0135] III. Experimental Data

[0136] 1. Acid and alkali resistance test: The duct was immersed in a 30% hydrochloric acid solution and a 25% potassium hydroxide solution for 30 days. The corrosion-resistant inner lining 101 showed no corrosion marks, and the duct body 1 showed no leakage.

[0137] 2. Antistatic test: A dust-laden airflow is introduced into tube 1 at a speed of 5 m / s. The electrostatic potential on the surface of the conductive functional layer is tested. The maximum electrostatic potential is 50 V, and there is no electrostatic accumulation.

[0138] 3. Mechanical strength test: The circumferential compressive strength of pipe body 1 is 18MPa, and the axial tensile strength is 12MPa; when the flange connection is subjected to a pressure of 2.0MPa, the structure is stable and there is no leakage.

[0139] 4. Self-cleaning test: The hydrophobic self-cleaning outer layer 103 has a static water contact angle of 162° and a roll-off angle of 6°; when mud is evenly applied to the surface and washed with simulated rainwater at a rainfall rate of 5 mm / h, the surface mud removal rate reaches 99%.

[0140] IV. Technical Effects

[0141] As can be seen from the above scheme, this embodiment adds a conductive functional layer doped with carbon black inside the corrosion-resistant inner lining 101, giving the duct antistatic properties. Tests show no static electricity accumulation, reducing safety hazards under dusty airflow conditions. The corrosion-resistant inner lining 101 is made of polyvinylidene fluoride material, combined with carbon fiber reinforced epoxy resin in the reinforcing structural layer 102, which not only improves acid and alkali resistance but also significantly increases the mechanical strength of the pipe body 1, making it suitable for higher pressure ventilation conditions. The hydrophobic self-cleaning outer layer 103 combines a template-based micro-nano structure with perfluorooctyltriethoxysilane, resulting in excellent self-cleaning effect and high mud removal rate. The material matching design of the flange 2 ensures connection reliability. The overall scheme achieves multiple functions of acid and alkali resistance, antistatic properties, high strength, and self-cleaning, making it suitable for complex ventilation conditions in the metallurgical industry involving dust and corrosive media.

[0142] V. Preparation Method

[0143] 1. Preparation of the conductive functional layer and corrosion-resistant inner lining layer 101 composite layer: Carbon black and polyvinylidene fluoride are mixed in proportion and a conductive composite material is prepared by melt blending process. The 2mm thick plate is made by extrusion molding process as the substrate of corrosion-resistant inner lining layer 101. A layer of conductive composite material is coated on the inner surface of the substrate by coating process to form a conductive functional layer. The coating thickness is controlled at 0.2mm. Then, it is dried and cured at 160-170℃ for 2h.

[0144] 2. Preparation of reinforcing structural layer 102: Cut carbon fiber fabric according to design specifications, apply epoxy resin to the outer surface of corrosion resistant lining layer 101, lay carbon fiber fabric layer by layer on the resin coating, use compaction process to remove air bubbles during the laying process to ensure that the resin evenly wets the fiber, and cure after the laying is completed. The curing temperature is 120-130℃ and the curing time is 6-7h to form a reinforcing structural layer 102 with a volume fraction of 50% and a thickness of 8mm.

[0145] 3. Preparation of hydrophobic self-cleaning outer layer 103: Cover the outer surface of the reinforcing structure layer 102 with a micro-nano structure template, inject a resin mixture containing perfluorooctyltriethoxysilane into the gap between the template and the reinforcing structure layer 102, let it stand and cure at room temperature for 4 hours, and then remove the template to form a micro-nano composite structure, and finally form a hydrophobic self-cleaning outer layer 103 with a thickness of 0.6 mm.

[0146] 4. Preparation and assembly of flange 2: Flange 2 blank is prepared by carbon fiber and epoxy resin. After processing, polyvinylidene fluoride material is coated on its surface and hot-pressed and cured. Flange 2 is connected to the end of pipe body 1 by welding and bolt reinforcement to complete the duct preparation.

[0147] Example 3

[0148] I. Technical Solution

[0149] A self-cleaning acid and alkali resistant composite air duct includes a duct body 1, which is a multi-layer composite structure, consisting of a corrosion-resistant inner lining layer 101, a reinforcing structural layer 102, and a hydrophobic self-cleaning outer layer 103 stacked from the inside to the outside.

[0150] The corrosion-resistant inner lining layer 101 is made of polytetrafluoroethylene propylene with a thickness of 0.8 mm;

[0151] The reinforcing structural layer 102 is a fiber-reinforced composite material layer, composed of basalt fiber and corrosion-resistant unsaturated polyester resin, wherein the volume fraction of basalt fiber is 35%, and the reinforcing structural layer 102 is a chopped fiber felt layer with a thickness of 4 mm.

[0152] The hydrophobic self-cleaning outer layer 103 micro-nano composite structure is formed by surface etching and coated with a fluorocarbon resin low surface energy material with a thickness of 0.2 mm.

[0153] The inner wall of the tube body 1 is provided with a number of flow guiding protrusions 1011 along the axial direction. The flow guiding protrusions 1011 are integrally formed with the tube body 1, and their surfaces are covered with polytetrafluoroethylene propylene material.

[0154] The end of the pipe body 1 is provided with a flange 2. The flange 2 is made of the same basalt fiber reinforced unsaturated polyester resin as the reinforcing structural layer 102, and the surface of the flange 2 is covered with polytetrafluoroethylene propylene material.

[0155] II. Working Principle

[0156] 1. Acid and alkali resistance protection principle: The perfluoroethylene propylene material on the surface of the corrosion-resistant inner lining 101 and the flow guiding protrusion 1011 directly isolates the corrosive medium flowing through, preventing the inner wall of the pipe body 1 and the flow guiding protrusion 1011 from being corroded; the perfluoroethylene propylene coating on the surface of the flange 2 ensures the corrosion resistance of the connection parts.

[0157] 2. Airflow optimization and drag reduction principle: The guide protrusions 1011 on the inner wall of the tube body 1 are set along the axial direction, which can guide the airflow to flow along the axial direction, reduce the formation of vortices in the airflow in the tube body, reduce airflow resistance, and at the same time reduce the friction between the airflow and the inner wall of the tube body 1, thereby reducing the generation of frictional static electricity.

[0158] 3. Strength Support Principle: The reinforcing structural layer 102, formed by the composite of basalt fiber and unsaturated polyester resin, provides basic mechanical strength support for the pipe body 1; the flow guiding protrusion 1011 is integrally formed with the pipe body 1, which improves the local structural stability; the flange 2 is made of the same material as the reinforcing structural layer 102, ensuring the strength matching of the connection parts;

[0159] 4. Self-cleaning principle: The micro-nano composite structure formed by surface etching, combined with low surface energy fluorocarbon resin, reduces surface adhesion, making it difficult for pollutants to adhere and achieving self-cleaning.

[0160] III. Experimental Data

[0161] 1. Acid and alkali resistance test: The duct was immersed in a 25% nitric acid solution and a 20% sodium carbonate solution for 30 days. The duct body 1 and the guide protrusion 1011 showed no corrosion or damage and no leakage.

[0162] 2. Airflow resistance test: When airflow at a speed of 4 m / s is introduced into duct 1, the airflow resistance of duct 1 is tested to be 80 Pa, which is 35% lower than that of similar ducts without guide protrusions;

[0163] 3. Mechanical strength test: The circumferential compressive strength of pipe body 1 is 9MPa, and the axial tensile strength is 6MPa; the structure of flange 2 is stable when subjected to a pressure of 1.2MPa.

[0164] 4. Self-cleaning test: The hydrophobic self-cleaning outer layer 103 has a static water contact angle of 155° and a roll-off angle of 9°; when fly ash is evenly sprayed on the surface and blown by an airflow with a wind speed of 2m / s, the fly ash removal rate reaches 97%.

[0165] IV. Technical Effects

[0166] As can be seen from the above scheme, this embodiment effectively optimizes airflow distribution and reduces airflow resistance by setting an integrally formed guide protrusion 1011 on the inner wall of the pipe body 1. The airflow resistance is significantly reduced compared to the duct without a guide structure, thus improving ventilation efficiency. The corrosion-resistant inner lining layer 101 is made of polytetrafluoroethylene propylene material, which ensures the stable use of the duct in various corrosive media environments. The reinforcing structural layer 102 adopts a basalt fiber chopped strand mat layer structure, which achieves lightweighting of the pipe body 1 while ensuring the basic mechanical strength, making it easy to transport and install. The hydrophobic self-cleaning outer layer 103, with its etched micro-nano structure and fluorocarbon resin combination, has a good self-cleaning effect and a high fly ash removal rate. The overall scheme achieves a synergistic effect of acid and alkali resistance, low airflow resistance, self-cleaning, and lightweighting, making it suitable for the low-pressure, high-cleanliness corrosive media ventilation conditions in the pharmaceutical industry.

[0167] V. Preparation Method

[0168] 1. Preparation of corrosion-resistant inner liner 101 with flow-guiding protrusions 1011: Polytetrafluoroethylene propylene material is selected, and injection molding process is adopted. A mold with flow-guiding protrusions 1011 is used to form a corrosion-resistant inner liner 101 with a thickness of 0.8mm in one step, ensuring that the flow-guiding protrusions 1011 and the inner liner are integrally formed. The molding temperature is 290-300℃, and the mold is removed after cooling.

[0169] 2. Preparation of reinforcing structural layer 102: Basalt fiber chopped strand mat is cut to fit the size of the tube body 1. Corrosion-resistant unsaturated polyester resin is evenly coated on the outer surface of the corrosion-resistant inner lining layer 101. Basalt fiber chopped strand mat is laid and compacted using a vacuum-assisted molding process to remove air and ensure that the resin fully impregnates the fiber. Then, it is cured at room temperature for 8-9 hours to form a reinforcing structural layer 102 with a volume fraction of 35% and a thickness of 4mm.

[0170] 3. Preparation of hydrophobic self-cleaning outer layer 103: The outer surface of the reinforcing structure layer 103 is etched by plasma etching process to form a micro-nano rough structure. After etching, fluorocarbon resin is uniformly coated by spraying process with a thickness controlled at 0.2 mm. It is cured at room temperature for 3 hours to form hydrophobic self-cleaning outer layer 103.

[0171] 4. Preparation and assembly of flange 2: Flange 2 is prepared by basalt fiber and corrosion-resistant unsaturated polyester resin. After processing, it is coated with polytetrafluoroethylene propylene material and fixed to the end of the pipe body 1 by adhesive bonding. Bolts are used for reinforcement to complete the preparation of the overall air duct.

[0172] The above are merely preferred embodiments of the present invention and are not intended to limit the implementation methods and protection scope of the present invention. Those skilled in the art should recognize that any equivalent substitutions and obvious changes made based on the description and illustrations of the present invention should be included within the protection scope of the present invention.

Claims

1. A self-cleaning acid and alkali resistant composite air duct, comprising a duct body (1), characterized in that, The tube body (1) is a multi-layer composite structure, consisting of a corrosion-resistant inner lining layer (101), a reinforcing structural layer (102), and a hydrophobic self-cleaning outer layer (103) stacked sequentially from the inside to the outside. The corrosion-resistant inner lining (101) is the inner surface layer facing the flowing medium and is made of acid and alkali resistant polymer material; The hydrophobic self-cleaning outer layer (103) is an outer surface layer exposed to the external environment. Its surface has a micro-nano composite structure and is coated or blended with low surface energy materials, so that the static water contact angle of the outer surface layer is greater than 150° and the roll-off angle is less than 10°. The reinforcing structural layer (102) is composited between the corrosion-resistant inner lining layer (101) and the hydrophobic self-cleaning outer layer (103), providing mechanical strength support for the pipe body (1).

2. The self-cleaning acid and alkali resistant composite air duct according to claim 1, characterized in that, The corrosion-resistant inner lining (101) is made of at least one of polyvinylidene fluoride, polytetrafluoroethylene, perfluoroethylene propylene, or chlorinated polyvinyl chloride.

3. The self-cleaning acid and alkali resistant composite air duct according to claim 1, characterized in that, The reinforcing structural layer (102) is a fiber-reinforced composite material layer, which includes fibers and a matrix resin, wherein the fibers are glass fibers, carbon fibers or basalt fibers, and the matrix resin is a corrosion-resistant unsaturated polyester resin, vinyl ester resin or epoxy resin.

4. The self-cleaning acid and alkali resistant composite air duct according to claim 3, characterized in that, The reinforcing structural layer (102) is at least one of a continuous fiber winding layer, a fiber fabric lay-up, or a chopped fiber felt layer; the fiber winding angle of the continuous fiber winding layer is 30°-60°.

5. The self-cleaning acid and alkali resistant composite air duct according to claim 1, characterized in that, The micro-nano composite structure of the hydrophobic self-cleaning outer layer (103) is formed in situ on the surface of the reinforcing structure layer (102) by surface etching, template method or spraying nanoparticles; the low surface energy material is at least one of polydimethylsiloxane, perfluorooctyltriethoxysilane or fluorocarbon resin.

6. The self-cleaning acid and alkali resistant composite air duct according to claim 1, characterized in that, A conductive or electrostatic functional layer is further laminated on the inner surface of the corrosion-resistant lining layer (101). The material of the conductive or electrostatic functional layer is a conductive polymer material or a polymer composite material doped with conductive fillers. The conductive filler is at least one of carbon black, graphene, or metal nanoparticles. The surface resistivity of the conductive or electrostatic functional layer is 10⁻⁶. 3 Ω-10 9 Ω.

7. The self-cleaning acid and alkali resistant composite air duct according to claim 1, characterized in that, The pipe body (1) is provided with a flange (2) at its end, and the surface of the flange (2) is at least covered with the corrosion-resistant inner lining (101) material; the flange (2) is made of the same fiber-reinforced composite material as the reinforcing structural layer (102).

8. The self-cleaning acid and alkali resistant composite air duct according to claim 1, characterized in that, The corrosion-resistant inner lining (101) has a thickness of 0.5mm-3mm, the reinforcing structural layer (102) has a thickness of 2mm-10mm, and the hydrophobic self-cleaning outer layer (103) has a thickness of 0.1mm-0.8mm.

9. The self-cleaning acid and alkali resistant composite air duct according to claim 3, characterized in that, The volume fraction of fibers in the reinforcing structural layer (102) is 30%-60%.

10. The self-cleaning acid and alkali resistant composite air duct according to any one of claims 1-9, characterized in that, The inner wall of the tube (1) is provided with a plurality of flow guiding protrusions (1011) along the axial direction. The flow guiding protrusions (1011) are integrally formed with the tube (1) and their surfaces are covered with a corrosion-resistant inner lining layer (101) material.

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