A kind of inner wall super-hydrophobic PPR pipeline based on salvinia natans bionics and its preparation method

Abstract

This invention relates to the field of pipeline technology and provides a biomimetic PPR pipe with an inner wall of superhydrophobicity based on *Sophora japonica* and its preparation method. The pipe includes an outer layer, a middle layer, and an inner layer. The inner layer is a superhydrophobic functional layer with a biomimetic hierarchical micro / nano structure, comprising a micron-sized radial villous substrate and nano-sized waxy crystals covering it. This invention utilizes the unique hierarchical micro / nano structure on the surface of *Sophora japonica* to form a stable gas-liquid interface on the inner wall of the pipe, achieving long-lasting superhydrophobic performance. The biomimetic structure of *Sophora japonica* inhibits microbial contamination through a dual mechanism of physical repulsion and mechanical destruction. Furthermore, the biomimetic structure of *Sophora japonica* significantly improves pipeline efficiency through gas layer drag reduction and surface topology design.

Description

Technical Field

[0001] This invention belongs to the field of pipeline technology, and in particular relates to a superhydrophobic PPR pipeline with an inner wall based on the biomimetic model of Sophora japonica and its preparation method. Background Technology

[0002] Superhydrophobic surface technology has broad application prospects in the pipeline field, effectively solving problems such as scaling, microbial growth, and high fluid resistance. The surface of the *Aquilaria sinensis* plant exhibits extremely stable and excellent superhydrophobic properties due to its unique hierarchical micro / nano structure of "micron-scale radial hairs-nano-scale waxy crystals." This perfectly compensates for the shortcomings of existing technologies, such as "lack of precise biomimetic structures and difficulty in balancing stability and efficiency," providing an ideal biomimetic model for pipeline inner wall modification.

[0003] Currently, the main methods for constructing superhydrophobic surfaces or micro / nano structures on the inner walls of PPR and other plastic pipes include: 1. Plasma treatment combined with low surface energy material grafting. Although this method can improve hydrophobicity, the resulting coating usually lacks precise biomimetic micro / nano structures. Furthermore, plasma treatment equipment is expensive, and it is difficult to uniformly treat the inner wall of pipes, especially long pipes. The bonding force between the modified layer and the substrate is limited, and it is prone to failure under dynamic water flow.

[0004] 2. Laser etching combined with low surface energy coating. This method can construct microstructures, but it is difficult to efficiently and cost-effectively replicate the complex multi-level composite structures of plants like *Sophora japonica*. Furthermore, ultrafast laser equipment is expensive and has low processing efficiency.

[0005] Therefore, there is an urgent need in this field for a method that can combine the biomimetic structure of Sophora japonica with the PPR pipe manufacturing process to achieve efficient, stable and large-scale preparation of superhydrophobic properties for the inner wall of pipes. Summary of the Invention

[0006] This invention provides a superhydrophobic PPR pipe with an inner wall based on the biomimetic design of Sophora japonica and its preparation method, aiming to solve the above-mentioned problems.

[0007] This invention is achieved as follows: a superhydrophobic PPR pipe with an inner wall based on the biomimetic structure of *Sophora japonica*, comprising an outer layer, a middle layer, and an inner layer. The inner layer is a superhydrophobic functional layer with a biomimetic hierarchical micro / nano structure of *Sophora japonica*, comprising a micron-sized radial villous substrate and nano-sized waxy crystals covering it, formed by any of the following methods: (a) (Direction 1) Co-extrusion method: Hydrophobic scale inhibitory masterbatch self-assembles to form a biomimetic structure during the melting process; (b) (Direction 2) Spraying method: Spray a biomimetic solution onto the inner wall and then cure it; (c) (Direction 3) Chemical etching method: forming micro-nano topology by etching the inner wall with an etchant.

[0008] Preferably, the outer layer raw material comprises the following components by weight: 100 parts PPR resin and 2-5 parts coloring masterbatch. The coloring masterbatch comprises the following components: 1-5 wt% pigment, 10-60 wt% titanium dioxide, 0.5-1 wt% antioxidant (preferably hindered phenolic antioxidant or hindered phenol / phosphite composite antioxidant, specifically antioxidant 1010, antioxidant 168, or the two compounded in a 1:1 mass ratio), 1-5 wt% dispersant (preferably fatty acid amide dispersant or low molecular weight wax dispersant, specifically ethylene bis-stearamide (EBS), glyceryl monostearate (GMS), or polyethylene wax (molecular weight 1000-5000)), and the balance being PP / PE carrier.

[0009] Preferably, the intermediate layer raw material comprises the following components by weight: 100 parts PPR resin, 2-5 parts coloring masterbatch, 0.1-0.5 parts β nucleating agent (preferably TMB-5, CaCO3-based β nucleating agent) and 3-8 parts elastomer, wherein the elastomer is a polyolefin elastomer (POE) or a rubber (such as EPDM rubber with 50% ethylene content).

[0010] Preferably, when the inner layer is a co-extruded layer, the inner layer contains the following raw materials in parts by weight: 100 parts of PPR resin, 2-5 parts of coloring masterbatch, 2-4 parts of antibacterial agent (such as composite nano silver antibacterial agent, silver ion antibacterial agent, nano ZnO, etc.), and 3-8 parts of hydrophobic scale inhibitor masterbatch.

[0011] Preferably, when the inner layer is a spray coating, the biomimetic solution contains the following raw materials in parts by weight: 20-30 parts of hydrophobic scale inhibitor masterbatch nanoparticles (particle size D50=1-5μm), 6-10 parts of fluorinated polyurethane, 60-70 parts of anhydrous ethanol, and 2-4 parts of antibacterial agents (such as composite nano silver antibacterial agents, silver ion antibacterial agents, nano ZnO, etc.).

[0012] Preferably, when the inner layer is a chemically etched layer, the inner layer contains the following raw materials in parts by weight: 90 parts of PPR resin, 2-5 parts of coloring masterbatch, 2-4 parts of antibacterial agent (such as composite nano-silver antibacterial agent, silver ion antibacterial agent, nano-ZnO, etc.), and 2-4 parts of acid-responsive masterbatch, wherein the acid-responsive masterbatch contains 30-50 wt% calcium carbonate microparticles, which form a micro-pit array with a depth of 10-20 μm after etching.

[0013] Preferably, the hydrophobic scale inhibitor masterbatch is formed by blending and granulating a nano-inorganic material co-encapsulated with organofluorosilicone / magnesium / silicon carbide with a plastic carrier.

[0014] Specifically, the preparation steps of the hydrophobic scale inhibitor masterbatch are as follows: (1) Take nano-silica (particle size 50-100nm), soak it in 1wt% perfluorooctyltriethoxysilane (organofluorosilicone) ethanol solution at 70℃ for 2h to complete the first coating; (2) Add 0.5wt% magnesium nitrate aqueous solution, stir at 50℃ for 1h to complete magnesium element encapsulation; (3) Add 0.3wt% methyltrimethoxysilane (silicon carbide), react at 60℃ for 1.5h, and dry to obtain composite nanomaterials; (4) The composite nanomaterial and PP carrier (melt index 3g / 10min) are mixed at a weight ratio of 1:4 and granulated at 190℃ to obtain hydrophobic scale inhibitor masterbatch.

[0015] Preferably, the surface of the nanoscale waxy crystals has silica or silicon carbide nanocrystals vertically grown on it, with a diameter of 20-50 nm, a length of 1-5 μm, and a density of 10. 5 -10 6 root / mm 2 .

[0016] Specifically, the steps of the nanocrystal growth method are as follows: Whisker precursor treatment: Silica or silicon carbide nanocrystals (20-50 nm in diameter and 1-5 μm in length) are surface-modified with a silane coupling agent (KH-550) to give them amino active sites.

[0017] Orientation and fixation: Direction 1 / 3: After co-extrusion / etching, the tube is immersed in a whisker dispersion solution, and the whiskers are vertically anchored on the surface of nano-wax crystals by electrostatic adsorption and ultrasonic assistance. Option 2: Directly mix modified whiskers into the spraying solution, and the whiskers will be vertically aligned due to thermophoretic force during gradient curing.

[0018] Preferably, the surface of the nanocrystals is grafted with a pH-responsive block copolymer brush, which is composed of hydrophilic polyacrylic acid segments and hydrophobic perfluorooctyl ethyl acrylate segments; when the ambient pH is <6, the copolymer brush contracts to release magnesium ions; when the pH is >7, the copolymer brush expands to enhance hydrophobic properties.

[0019] Specifically, the steps of the method for grafting pH-responsive block copolymers onto the surface of the nanocrystals are as follows: Initiator modification: Nanocrystalline whiskers are immersed in a toluene solution containing ATRP initiator (α-bromoisobutyryl bromide) and reacted at 55-65℃ for 2 hours to graft bromine groups onto the surface.

[0020] RAFT aggregation: Under nitrogen protection, surface-modified nanocrystals of silane coupling agent are added to a monomer solution: by weight, acrylic acid (AA) 18-22 parts, perfluorooctyl ethyl acrylate (FA) 27-33 parts, solvent (toluene / acetone = 1:1) 200 parts, and RAFT reagent (such as tert-butyl dithiobenzoate) 0.4-0.6 parts. The reaction is carried out at 65-75℃ for 6 hours to form a polyacrylic acid-b-perfluorooctyl ethyl acrylate (PAA-b-PFA) block copolymer brush.

[0021] Ion loading: Whiskers are immersed in a 4-6% magnesium acetate solution, where PAA segments adsorb Mg. 2+ Dry and store for later use.

[0022] The present invention also provides a method for preparing the above-mentioned biomimetic PPR pipe with an inner wall of Sophora japonica, wherein when the inner layer is a blended extrusion layer, the method includes the following steps: (1) Prepare three layers of raw materials according to the specified proportions: (2) The three layers of raw materials are added to a co-extrusion equipment for melt co-extrusion: Three-layer co-extrusion temperature: outer / middle layer 180-220℃, inner layer 200-240℃; Inner layer shear rate: 1000-2000s -1 A cooling gradient of 20-40℃ / min enables the superhydrophobic masterbatch to self-assemble in a directional manner during the cooling process, forming a hierarchical structure of micron-sized hairs and nano-wax crystals. (3) The pipe is immersed in the whisker dispersion solution, and the whiskers are vertically anchored on the surface of the nano-wax crystals by electrostatic adsorption and ultrasonic assistance: The whisker dispersion formulation is as follows: Solvent: Deionized water + 0.5-1 wt% sodium dodecyl sulfate (SDS); pH adjustment: 8-10 (adjusted with ammonia or NaOH); Nanocrystal concentration: 0.5-3 wt%; Electrostatic adsorption: Apply DC voltage of 50-100V for 5-10 minutes, with an electrode spacing of 10-20cm; Auxiliary methods: Ultrasonic vibration (power 100-200W, time 5-10min) to promote vertical orientation; (4) Dry and cure at 80-100℃.

[0023] This invention also provides a method for preparing the above-mentioned biomimetic superhydrophobic PPR pipe with inner wall based on Sophora japonica, wherein when the inner layer is a sprayed coating, the method includes the following steps: (1) Preparation of double-layer tube blank: co-extrusion of outer layer and middle layer; (2) Inner wall pretreatment: Plasma activation or chemical roughening treatment is performed on the inner wall of the double-layer tube blank (e.g., nitrogen plasma is introduced, pressure is 0.1-0.5MPa, distance between nozzle and inner wall is 5-10cm, power is 200W, time is 30s). (3) Add nano whiskers to a biomimetic solution (1-5wt%) to obtain a mixture, and spray the mixture onto the inner wall: spraying pressure 0.2-0.4MPa, film thickness controlled 150±10μm; (4) Curing by temperature gradient: First stage: Keep warm at 75-85℃ for 3-5 minutes to allow nanoparticles to self-assemble into a micron-sized radial villous substrate; Second stage: Heat to 145-155℃ at 5℃ / min and hold for 2-3 min to induce the precipitation of nano-wax crystals on the surface of the hair; (5) Ultraviolet curing (using UV irradiation, wavelength 365nm, intensity 500mJ / cm) 2 (Cross-linked adhesive) for shaping.

[0024] This invention also provides a method for preparing the above-mentioned biomimetic superhydrophobic PPR pipe with inner wall based on Sophora japonica, wherein when the inner layer is a chemically etched layer, the method includes the following steps: (1) Preparation of three-layer co-extruded pipes; (2) Injecting an etchant into the inner layer: The etchant is a weak acid solution (such as 5-10% oxalic acid solution), and the etching time is 5-15 minutes to form a micron-level pit array on the inner wall; (3) Deposition of nano-hydrophobic materials: Organic fluorine-silicon nanoparticles (such as those impregnated with perfluorooctyltriethoxysilane ethanol solution, 0.5-1.5wt%) are loaded into the pits to construct a nanoscale wax crystal covering layer; (4) Immerse the tube in the whisker dispersion, apply a DC voltage of 50-100V, and use ultrasonic assistance (100-200W, 5-10min) to fix the whiskers vertically in the micron-sized pits. (5) Dry and cure at 80-100℃.

[0025] Compared with the prior art, the embodiments of this application have the following main advantages: 1. Highly efficient and stable superhydrophobic performance: The unique hierarchical micro-nano structure on the surface of Sophora japonica can form a stable gas-liquid interface on the inner wall of the pipe, achieving long-lasting superhydrophobic performance.

[0026] 2. The biomimetic structure of Sophora japonica significantly improves pipeline efficiency through air layer drag reduction and surface topology design.

[0027] 3. Based on the hierarchical structure of Sophora japonica, a vertical array of nano-whiskers is added to form a three-level gradient topology of "micron-nano wax crystal-nano whiskers". The nano-whiskers are interspersed between the wax crystals, and the mechanical interlocking improves the adhesion of the coating or the bonding force of the masterbatch. The whisker tips generate a local high voltage electric field, which enhances the physical sterilization efficiency (disrupts the cell membrane potential). The three-level structure works together to reduce the damage of water flow shear force to the air film and improves the dynamic hydrophobic stability.

[0028] 4. A pH-responsive copolymer brush is modified on the surface of nano-wax crystals. In a neutral / alkaline environment (pH>7), the copolymer brush expands, exposing the nano-wax crystals and enhancing hydrophobicity. When microorganisms produce acid through metabolism (pH<6), the copolymer brush curls up, releasing pre-loaded magnesium ions, which promotes the transformation of dirt crystals and kills bacteria. The copolymer brush covers the surface of the nano-whiskers, forming a "structure-chemistry" dual-level antifouling mechanism. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of the structure of a superhydrophobic PPR pipe with an inner wall based on the biomimetic design of Sophora japonica provided by the present invention.

[0030] Figure 2 This invention provides a flowchart of the preparation process of a superhydrophobic PPR pipe with an inner wall based on the biomimetic plant *Sophora japonica* using a co-extrusion method.

[0031] Figure 3 This invention provides a flow chart of a superhydrophobic PPR pipe with an inner wall based on the biomimetic design of Sophora japonica, using a spraying method.

[0032] Figure 4 This invention provides a flowchart of the preparation process of a superhydrophobic PPR pipe with an inner wall based on the biomimetic plant *Sophora japonica* using a chemical etching method.

[0033] Figure label annotations: 1. Outer layer; 2. Middle layer; 3. Inner layer. Detailed Implementation

[0034] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs; the terminology used herein in the specification of the application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application; the terms "comprising" and "having," and any variations thereof, in the specification, claims, and foregoing drawings of this application are intended to cover non-exclusive inclusion. The terms "first," "second," etc., in the specification, claims, or foregoing drawings of this application are used to distinguish different objects, not to describe a particular order.

[0035] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0036] Example 1 This invention provides a superhydrophobic PPR pipe with an inner wall based on the biomimetic design of *Lysimachia foenum-graecum*, such as... Figure 1 and Figure 2 As shown, it includes: Outer layer 1: 100 parts PPR resin and 2 parts coloring masterbatch, wherein the coloring masterbatch contains the following components: 1 wt% pigment, 10 wt% titanium dioxide, 0.5 wt% antioxidant, 1 wt% dispersant, and the balance is PP / PE carrier; Intermediate layer 2: 100 parts PPR resin, 2 parts coloring masterbatch, 0.1 parts β nucleating agent and 3 parts elastomer, wherein the elastomer is a polyolefin elastomer (POE) or a rubber body; Inner layer 3: 100 parts PPR resin, 2 parts coloring masterbatch, 2 parts antibacterial agent (preferably composite nano silver antibacterial agent), and 3 parts hydrophobic scale inhibitor masterbatch. The hydrophobic scale inhibitor masterbatch is made by blending and granulating nano-inorganic materials co-encapsulated with organofluorosilicone / magnesium / carbon silicon with a plastic carrier. The inner layer 3 is a superhydrophobic functional layer with a biomimetic hierarchical micro / nano structure, comprising a micron-sized radial villous substrate and nanoscale waxy crystals covering it. Silica or silicon carbide nanocrystals are vertically grown on the surface of the nanoscale waxy crystals, with a diameter of 20-50 nm, a length of 1-5 μm, and a density of 102. 5 -10 6 root / mm 2 The nanocrystal whisker surface-grafted pH-responsive block copolymer brush is composed of hydrophilic polyacrylic acid segments and hydrophobic perfluorooctyl ethyl acrylate segments; when the ambient pH < 6, the copolymer brush contracts to release magnesium ions; when the pH > 7, the copolymer brush expands to enhance hydrophobic properties; the preparation method of the biomimetic inner wall superhydrophobic PPR pipe based on Sophora japonica includes the following steps: (1) Prepare three layers of raw materials according to the specified proportions: (2) The three layers of raw materials are added to a co-extrusion equipment for melt co-extrusion: Three-layer co-extrusion temperature: outer layer 1 / middle layer 200℃, inner layer 220℃; Inner layer 3 shear rate: 1500s -1 A cooling gradient of 30℃ / min was applied to induce the superhydrophobic masterbatch to self-assemble in a directional manner during the cooling process, forming a hierarchical structure of micron-sized hairs and nano-wax crystals. (3) The pipe is immersed in the whisker dispersion solution, and the whiskers are vertically anchored on the surface of the nano-wax crystals by electrostatic adsorption and ultrasonic assistance: (3.1) Preparation of nanocrystals (3.1.1) First, modify the surface of silicon dioxide or silicon carbide nanocrystals (diameter 20-50nm, length 1-5μm) with silane coupling agent (KH-550) to give them amino active sites; (3.1.2) The nano whiskers were immersed in a toluene solution containing ATRP initiator (α-bromoisobutyryl bromide) and reacted at 60°C for 2 h to graft bromine groups onto the surface; (3.1.3) Under nitrogen protection, the surface-modified nanocrystals of the silane coupling agent were added to the monomer solution: by weight, 20 parts of acrylic acid (AA), 30 parts of perfluorooctyl ethyl acrylate (FA), 200 parts of solvent (toluene / acetone = 1:1), and 0.5 parts of RAFT reagent. (3.1.4) React at 65-75℃ for 6 hours to form a polyacrylic acid-b-perfluorooctyl ethyl acrylate (PAA-b-PFA) block copolymer brush; (3.1.5) The whiskers were immersed in a 5% magnesium acetate solution, and the PAA segments adsorbed Mg. 2+ Dry and store for later use; (3.2) Preparation of whisker dispersion Solvent: Deionized water + 0.75 wt% sodium dodecyl sulfate (SDS); pH adjustment: 9 (adjusted with ammonia or NaOH); Nanocrystal concentration: 1.75 wt%; (3.3) Immerse the tube in the whisker dispersion and electrostatically adsorb: apply a DC voltage of 75V for 7.5min and an electrode spacing of 15cm; auxiliary means: ultrasonic vibration (power 150W, time 7.5min) to promote vertical orientation; (4) Dry and cure at 90℃.

[0037] Example 2 The difference between this embodiment and Embodiment 1 is that: Outer layer 1: 100 parts PPR resin, 3.5 parts coloring masterbatch, wherein the coloring masterbatch contains the following components: 3 wt% pigment, 35 wt% titanium dioxide, 0.75 wt% antioxidant, 3 wt% dispersant, and the balance is PP / PE carrier; Intermediate layer 2: 100 parts PPR resin, 3.5 parts coloring masterbatch, 0.3 parts β nucleating agent and 5.5 parts elastomer, wherein the elastomer is a polyolefin elastomer (POE) or a rubber body; Inner layer 3: 100 parts PPR resin, 3.5 parts coloring masterbatch, 3 parts antibacterial agent (preferably composite nano silver antibacterial agent), and 5.5 parts hydrophobic scale inhibitor masterbatch.

[0038] Example 3 The difference between this embodiment and Embodiment 1 is that: Outer layer 1: 100 parts PPR resin and 5 parts coloring masterbatch, wherein the coloring masterbatch contains the following components: 5 wt% pigment, 60 wt% titanium dioxide, 1 wt% antioxidant, 5 wt% dispersant, and the balance is PP / PE carrier; Intermediate layer 2: 100 parts PPR resin, 5 parts coloring masterbatch, 0.5 parts β nucleating agent and 8 parts elastomer, wherein the elastomer is a polyolefin elastomer (POE) or a rubber body; Inner layer 3: 100 parts PPR resin, 5 parts coloring masterbatch, 4 parts antibacterial agent (preferably composite nano silver antibacterial agent), and 8 parts hydrophobic scale inhibitor masterbatch.

[0039] Example 4 This invention provides a superhydrophobic PPR pipe with an inner wall based on the biomimetic design of *Lysimachia foenum-graecum*, such as... Figure 1 and Figure 3 As shown, it includes: Outer layer 1: 100 parts PPR resin and 2 parts coloring masterbatch, wherein the coloring masterbatch contains the following components: 1 wt% pigment, 10 wt% titanium dioxide, 0.5 wt% antioxidant, 1 wt% dispersant, and the balance is PP / PE carrier; Intermediate layer 2: 100 parts PPR resin, 2 parts coloring masterbatch, 0.1 parts β nucleating agent and 3 parts elastomer, wherein the elastomer is a polyolefin elastomer (POE) or a rubber body; Inner layer 3: formed by curing after spraying a biomimetic solution onto the inner wall. The biomimetic solution contains the following raw materials in parts by weight: 20 parts of hydrophobic scale inhibitor masterbatch nanoparticles (particle size D50=1-5μm), 6 parts of fluorinated polyurethane, 60 parts of anhydrous ethanol, and 2 parts of antibacterial agent (preferably composite nano-silver antibacterial agent). The hydrophobic scale inhibitor masterbatch is made by blending and granulating nano-inorganic materials co-encapsulated with organic fluorosilicone / magnesium / carbon silicon with a plastic carrier. The inner layer 3 is a superhydrophobic functional layer with a biomimetic hierarchical micro / nano structure, comprising a micron-sized radial villous substrate and nanoscale waxy crystals covering it. Silica or silicon carbide nanocrystals are vertically grown on the surface of the nanoscale waxy crystals, with a diameter of 20-50 nm, a length of 1-5 μm, and a density of 102. 5 -10 6 root / mm 2The nanocrystal whisker surface-grafted pH-responsive block copolymer brush is composed of hydrophilic polyacrylic acid segments and hydrophobic perfluorooctyl ethyl acrylate segments; when the ambient pH < 6, the copolymer brush contracts to release magnesium ions; when the pH > 7, the copolymer brush expands to enhance hydrophobic properties; the preparation method of the biomimetic inner wall superhydrophobic PPR pipe based on Sophora japonica includes the following steps: (1) Preparation of double-layer tube blank: co-extrusion of outer layer 1 and intermediate layer 2; (2) Inner wall pretreatment: Plasma activation or chemical roughening treatment is performed on the inner wall of the double-layer tube blank (e.g., nitrogen plasma is introduced, power 200W, time 30s). (3) Add nano whiskers to a biomimetic solution (2.5wt%) to obtain a mixture, and spray the mixture onto the inner wall: spraying pressure 0.3MPa, film thickness controlled 150±10μm; (4) Curing by temperature gradient: First stage: Hold at 80℃ for 4 minutes to allow nanoparticles to self-assemble into a micron-sized radial villous substrate; Second stage: Heat to 150℃ at 5℃ / min and hold for 2.5min to induce the precipitation of nano-wax crystals on the surface of the hair; (5) Ultraviolet curing (using UV irradiation, wavelength 365nm, intensity 500mJ / cm) 2 (Cross-linked adhesive) is used to shape and form a biomimetic inner wall.

[0040] Example 5 The difference between this embodiment and embodiment 4 is that: Outer layer 1: 100 parts PPR resin, 3.5 parts coloring masterbatch, wherein the coloring masterbatch contains the following components: 3 wt% pigment, 35 wt% titanium dioxide, 0.75 wt% antioxidant, 3 wt% dispersant, and the balance is PP / PE carrier; Intermediate layer 2: 100 parts PPR resin, 3.5 parts coloring masterbatch, 0.3 parts β nucleating agent and 5.5 parts elastomer, wherein the elastomer is a polyolefin elastomer (POE) or a rubber body; Inner layer 3: formed by curing after spraying a biomimetic solution onto the inner wall. The biomimetic solution contains the following raw materials in parts by weight: 25 parts of hydrophobic scale inhibitor masterbatch nanoparticles (particle size D50=1-5μm), 8 parts of fluorinated polyurethane, 65 parts of anhydrous ethanol, and 3 parts of antibacterial agent (preferably composite nano silver antibacterial agent).

[0041] Example 6 The difference between this embodiment and embodiment 4 is that: Outer layer 1: 100 parts PPR resin and 5 parts coloring masterbatch, wherein the coloring masterbatch contains the following components: 5 wt% pigment, 60 wt% titanium dioxide, 1 wt% antioxidant, 5 wt% dispersant, and the balance is PP / PE carrier; Intermediate layer 2: 100 parts PPR resin, 5 parts coloring masterbatch, 0.1 parts β nucleating agent and 8 parts elastomer, wherein the elastomer is a polyolefin elastomer (POE) or a rubber body; Inner layer 3: formed by curing after spraying a biomimetic solution onto the inner wall. The biomimetic solution contains the following raw materials in parts by weight: 30 parts of hydrophobic scale inhibitory masterbatch nanoparticles (particle size D50=1-5μm), 10 parts of fluorinated polyurethane, 70 parts of anhydrous ethanol, and 4 parts of antibacterial agent (preferably composite nano silver antibacterial agent).

[0042] Example 7 This invention provides a superhydrophobic PPR pipe with an inner wall based on the biomimetic design of *Lysimachia foenum-graecum*, such as... Figure 1 and Figure 4 As shown, it includes: Outer layer 1: 100 parts PPR resin and 2 parts coloring masterbatch, wherein the coloring masterbatch contains the following components: 1 wt% pigment, 10 wt% titanium dioxide, 0.5 wt% antioxidant, 1 wt% dispersant, and the balance is PP / PE carrier; Intermediate layer 2: 100 parts PPR resin, 2 parts coloring masterbatch, 0.1 parts β nucleating agent and 3 parts elastomer, wherein the elastomer is a polyolefin elastomer (POE) or a rubber body; Inner layer 3: formed by chemical etching, consisting of 90 parts PPR resin, 2 parts coloring masterbatch, 2 parts antibacterial agent (preferably composite nano-silver antibacterial agent), and 2 parts acid-responsive masterbatch. The acid-responsive masterbatch contains 30-50 wt% calcium carbonate microparticles, and after etching, it forms a micro-pit array with a depth of 10-20 μm.

[0043] The inner layer 3 is a superhydrophobic functional layer with a biomimetic hierarchical micro / nano structure, comprising a micron-sized radial villous substrate and nanoscale waxy crystals covering it. Silica or silicon carbide nanocrystals are vertically grown on the surface of the nanoscale waxy crystals, with a diameter of 20-50 nm, a length of 1-5 μm, and a density of 102. 5 -10 6 root / mm 2 The nanocrystal whisker surface-grafted pH-responsive block copolymer brush is composed of hydrophilic polyacrylic acid segments and hydrophobic perfluorooctyl ethyl acrylate segments; when the ambient pH < 6, the copolymer brush contracts to release magnesium ions; when the pH > 7, the copolymer brush expands to enhance hydrophobic properties; the preparation method of the biomimetic inner wall superhydrophobic PPR pipe based on Sophora japonica includes the following steps: (1) Preparation of three-layer co-extruded pipes; (2) Injecting an etchant into the inner layer 3: The etchant is a weak acid solution (such as 7.5% oxalic acid solution), the etching time is 10 min, and the inner wall is etched to form a micron-level pit array; (3) Deposition of nano-hydrophobic materials: Loading organic fluorine-silicon nanoparticles (such as impregnated with perfluorooctyltriethoxysilane ethanol solution, 1wt%) into the pits to construct a nanoscale wax crystal covering layer; (4) Immerse the tube in the whisker dispersion, apply a 75V DC voltage, and use ultrasonic assistance (150W, 7.5min) to fix the whiskers vertically in the micron-sized pits. (4.1) Preparation of nanocrystals (4.1.1) First, modify the surface of silicon dioxide or silicon carbide nanocrystals (diameter 20-50nm, length 1-5μm) with silane coupling agent (KH-550) to give them amino active sites; (4.1.2) The nano whiskers were immersed in a toluene solution containing ATRP initiator (α-bromoisobutyryl bromide) and reacted at 60°C for 2 h to graft bromine groups onto the surface; (4.1.3) Under nitrogen protection, the surface-modified nanocrystals of the silane coupling agent were added to the monomer solution: by weight, 20 parts of acrylic acid (AA), 30 parts of perfluorooctyl ethyl acrylate (FA), 200 parts of solvent (toluene / acetone = 1:1), and 0.5 parts of RAFT reagent. (4.1.4) React at 65-75℃ for 6 hours to form a polyacrylic acid-b-perfluorooctyl ethyl acrylate (PAA-b-PFA) block copolymer brush; (4.1.5) The whiskers were immersed in a 5% magnesium acetate solution, and the PAA segments adsorbed Mg. 2+ Dry and store for later use; (4.2) Preparation of whisker dispersion Solvent: Deionized water + 0.75 wt% sodium dodecyl sulfate (SDS); pH adjustment: 9 (adjusted with ammonia or NaOH); Nanocrystal concentration: 1.75 wt%; (4.3) Immerse the tube in the whisker dispersion and electrostatically adsorb: apply a DC voltage of 75V for 7.5min and an electrode spacing of 15cm; auxiliary means: ultrasonic vibration (power 150W, time 7.5min) to promote vertical orientation. (5) A hierarchical micro-nano biomimetic structure was obtained by drying and curing at 90℃.

[0044] Example 8 The difference between this embodiment and embodiment 7 is that: Outer layer 1: 100 parts PPR resin, 3.5 parts coloring masterbatch, wherein the coloring masterbatch contains the following components: 3 wt% pigment, 35 wt% titanium dioxide, 0.75 wt% antioxidant, 3 wt% dispersant, and the balance is PP / PE carrier; Intermediate layer 2: 100 parts PPR resin, 3.5 parts coloring masterbatch, 0.3 parts β nucleating agent and 5.5 parts elastomer, wherein the elastomer is a polyolefin elastomer (POE) or a rubber body; Inner layer 3: formed by chemical etching, comprising 90 parts PPR resin, 3.5 parts coloring masterbatch, 3 parts antibacterial agent (preferably composite nano-silver antibacterial agent), and 3 parts acid-responsive masterbatch, wherein the acid-responsive masterbatch contains 30-50 wt% calcium carbonate microparticles, and after etching, forms a micro-pit array with a depth of 10-20 μm.

[0045] Example 9 The difference between this embodiment and embodiment 7 is that: Outer layer 1: 100 parts PPR resin and 5 parts coloring masterbatch, wherein the coloring masterbatch contains the following components: 5 wt% pigment, 60 wt% titanium dioxide, 1 wt% antioxidant, 5 wt% dispersant, and the balance is PP / PE carrier; Intermediate layer 2: 100 parts PPR resin, 5 parts coloring masterbatch, 0.5 parts β nucleating agent and 8 parts elastomer, wherein the elastomer is a polyolefin elastomer (POE) or a rubber body; Inner layer 3: formed by chemical etching, consisting of 90 parts PPR resin, 5 parts coloring masterbatch, 4 parts antibacterial agent (preferably composite nano-silver antibacterial agent), and 4 parts acid-responsive masterbatch. The acid-responsive masterbatch contains 30-50 wt% calcium carbonate microparticles, and after etching, it forms a micro-pit array with a depth of 10-20 μm.

[0046] Comparative examples are designed for the three technical directions (blending extrusion, spraying, and chemical etching) and existing technologies, as shown in Table 1: Table 1 The following key performance indicators were selected for testing: Static water contact angle (°): GB / T 30693-2014, measures superhydrophobic performance. The larger the value, the better the hydrophobic effect (superhydrophobicity usually requires >150°).

[0047] Roll-off angle (°): GB / T 30693-2014, measures the fluidity of a liquid on a surface. The smaller the value, the stronger the anti-adhesion (excellent superhydrophobic surfaces are usually <10°).

[0048] Escherichia coli inhibition rate (%): ISO 22196, bacterial concentration 10 5CFU / mL, after 24 hours of contact, the antibacterial performance was evaluated; the higher the value, the better the effect of inhibiting microbial contamination.

[0049] Staphylococcus aureus inhibition rate (%): ISO 22196, bacterial concentration 10 5 CFU / mL, after 24 hours of contact, the antibacterial performance was evaluated; the higher the value, the better the effect of inhibiting microbial contamination.

[0050] Antibacterial durability test: The sample was soaked in a distilled water bath at (50±2)℃ for 16 hours and then subjected to an antibacterial test.

[0051] Scale inhibition rate: ISO 2170, hard water (300ppm Ca) 2+ After 30 days of circulation, scale formation was measured: Following the test, the pipe sample was immersed in a 5% citric acid solution (60℃) for 10 minutes to remove scale from the inner wall. The stripping solution was rinsed with deionized water and the volume was adjusted to 100 mL. The Ca content was determined by EDTA titration. 2+ Concentration, calculate the scale mass on the inner wall (m=Ca) 2+ Concentration × constant volume × molar mass of calcium carbonate / Ca 2+ Molar mass), scale inhibition rate (%) = (1 − scale amount of experimental group / scale amount of blank PPR pipe) × 100.

[0052] Flow velocity improvement rate (%): GB / T 18940, DN25 pipe, flow velocity 1.5m / s, the percentage increase in water flow velocity compared to commercially available ordinary PPR pipes. The higher the value, the better the pipe efficiency.

[0053] Contact angle (°) after 1000h aging: to assess long-term effectiveness; the higher the value, the better the stability of hydrophobic properties.

[0054] The performance test data of the examples and comparative examples are shown in Table 2 below: Table 2 This invention comprehensively improves the hydrophobic, antibacterial, anti-scaling, and high-efficiency transport performance of PPR pipes through biomimetic structure of Sophora japonica, nano-whisker reinforcement, and pH-responsive design.

[0055] It should be noted that, for the sake of simplicity, the foregoing embodiments are all described as a series of actions. However, those skilled in the art should understand that the present invention is not limited to the described order of actions, as some steps may be performed in other orders or simultaneously according to the present invention. Furthermore, those skilled in the art should also understand that the embodiments described in the specification are preferred embodiments, and the actions and modules involved are not necessarily essential to the present invention.

[0056] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit the scope of protection of the invention. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on these embodiments, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

Claims

1. A superhydrophobic PPR pipe with an inner wall based on the biomimetic design of *Lysimachia foenum-graecum*, characterized in that, It comprises an outer layer, a middle layer, and an inner layer. The inner layer is a superhydrophobic functional layer with a biomimetic hierarchical micro / nano structure, including a micrometer-scale radial villous substrate and nanometer-scale waxy crystals covering it, and is formed by any of the following methods: (a) Blending extrusion method: Hydrophobic scale inhibitory masterbatch self-assembles to form a biomimetic structure during the melting process; (b) Spraying method: The biomimetic solution is sprayed onto the inner wall and then cured; (c) Chemical etching method: forming micro-nano topology by etching the inner wall with an etchant; The surface of the nanoscale waxy crystals has vertically grown silica or silicon carbide nanocrystals, with a diameter of 20-50 nm, a length of 1-5 μm, and a density of 10. 5 -10 6 root / mm 2 ; The nanocrystal whisker surface is grafted with a pH-responsive block copolymer brush, which is composed of hydrophilic polyacrylic acid segments and hydrophobic perfluorooctyl ethyl acrylate segments. When the ambient pH is less than 6, the copolymer brush contracts to release magnesium ions; when the pH is greater than 7, the copolymer brush expands to enhance hydrophobic properties.

2. The PPR pipe with a superhydrophobic inner wall based on the biomimetic design of *Lysimachia christinae* as described in claim 1, characterized in that... The outer layer raw material comprises the following components by weight: 100 parts of PPR resin and 2-5 parts of coloring masterbatch. The coloring masterbatch comprises the following components: 1-5 wt% pigment, 10-60 wt% titanium dioxide, 0.5-1 wt% antioxidant, 1-5 wt% dispersant, and the balance being PP / PE carrier.

3. The PPR pipe with a superhydrophobic inner wall based on the biomimetic design of *Lysimachia christinae* as described in claim 1, characterized in that... The intermediate layer raw material comprises the following components by weight: 100 parts PPR resin, 2-5 parts coloring masterbatch, 0.1-0.5 parts β nucleating agent, and 3-8 parts elastomer, wherein the elastomer is a polyolefin elastomer or a rubber.

4. The PPR pipe with a superhydrophobic inner wall based on the biomimetic design of *Lysimachia christinae* as described in claim 1, characterized in that... When the inner layer is a co-extruded layer, the inner layer contains the following raw materials in parts by weight: 100 parts of PPR resin, 2-5 parts of coloring masterbatch, 2-4 parts of antibacterial agent, and 3-8 parts of hydrophobic scale inhibitory masterbatch. When the inner layer is a spray coating, the biomimetic solution contains the following raw materials in parts by weight: 20-30 parts of hydrophobic scale inhibitor masterbatch nanoparticles, 6-10 parts of fluorinated polyurethane, 60-70 parts of anhydrous ethanol, and 2-4 parts of antibacterial agent. When the inner layer is a chemically etched layer, the inner layer contains the following raw materials in parts by weight: 90 parts of PPR resin, 2-5 parts of coloring masterbatch, 2-4 parts of antibacterial agent, and 2-4 parts of acid-responsive masterbatch. The acid-responsive masterbatch contains 30-50 wt% calcium carbonate microparticles, which form a micro-pit array with a depth of 10-20 μm after etching.

5. The PPR pipe with a superhydrophobic inner wall based on the biomimetic design of *Lysimachia foenum-graecum* as described in claim 4, characterized in that... The hydrophobic scale inhibitor masterbatch is made by blending and granulating nano-inorganic materials co-encapsulated with organofluorosilicone / magnesium / silicon carbide with a plastic carrier.

6. The method for preparing a superhydrophobic PPR pipe with an inner wall based on biomimetic *Lysimachia foenum-graecum* as described in claim 1, characterized in that, When the inner layer is a blended extrusion layer, the following steps are included: (1) Prepare three layers of raw materials according to the specified proportions: (2) The three layers of raw materials are added to a co-extrusion equipment for melt co-extrusion: Three-layer co-extrusion temperature: outer / middle layer 180-220℃, inner layer 200-240℃; Inner layer shear rate: 1000-2000s -1 Cooling gradient 20-40℃ / min; (3) Immerse the pipe in the whisker dispersion liquid, and use electrostatic adsorption and ultrasonic assistance to vertically anchor the whiskers on the surface of the nano wax crystals. (4) Dry and cure at 80-100℃.

7. The method for preparing a superhydrophobic PPR pipe with an inner wall based on biomimetic *Lysimachia foenum-graecum* as described in claim 1, characterized in that, When the inner layer is a sprayed coating, the following steps are included: (1) Preparation of double-layer tube blank: co-extrusion of outer layer and middle layer; (2) Inner wall pretreatment: Plasma activation or chemical roughening treatment is performed on the inner wall of the double-layer tube blank; (3) Add nano whiskers to a biomimetic solution to obtain a mixture, and spray the mixture onto the inner wall: spraying pressure 0.2-0.4MPa, film thickness controlled 150±10μm; (4) Curing by temperature gradient: First stage: Keep warm at 75-85℃ for 3-5 minutes to allow nanoparticles to self-assemble into a micron-sized radial villous substrate; Second stage: Heat to 145-155℃ at 5℃ / min and hold for 2-3 min to induce the precipitation of nano-wax crystals on the surface of the hair; (5) UV curing and shaping.

8. The method for preparing a superhydrophobic PPR pipe with an inner wall based on biomimetic *Lysimachia foenum-graecum* as described in claim 1, characterized in that, When the inner layer is a chemically etched layer, the following steps are included: (1) Preparation of three-layer co-extruded pipes; (2) Injecting an etchant into the inner layer: The etchant is a weak acid solution, and the etching time is 5-15 min, forming a micron-level pit array on the inner wall; (3) Deposition of nano-hydrophobic materials: Organic fluorine-silicon nanoparticles are loaded in the pits to construct a nanoscale wax crystal covering layer; (4) Immerse the pipe in the whisker dispersion solution and fix the whiskers vertically in the micron-sized pits by electrostatic adsorption and ultrasonic assistance. (5) Dry and cure at 80-100℃.

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