Macromolecule-based pipeline wear-resistant and low-temperature-resistant coating material and preparation method thereof

Abstract

The invention discloses a polymer-based pipeline wear-resistant and low-temperature-resistant coating material and a preparation method thereof in the field of polymer materials. The material is prepared from polyamide, dynamic lipoic acid network modified polyurethane urea, a liquid crystal benzoxazole polysiloxane alternating copolymer, silicon carbide, nano niobium carbide, trimethylolpropane trimercaptopropionate, an antioxidant and a flatting agent according to a specific ratio. The preparation method comprises the following steps: carrying out melt blending granulation on the three polymer matrixes to obtain a modified resin base material, carrying out dry mixing on the modified resin base material and other components, and carrying out melt extrusion and tape casting. The two key modified compounds are respectively prepared by reacting polytetrahydrofuran with dicyclohexylmethane diisocyanate and then sequentially adding pyridine dimethyl carbinol, lipoic acid lactone and isophorone diamine; and amino polysiloxane reacts with dihydroxyphthalaldehyde, and then amino cresol is added for cyclization to obtain the amino polysiloxane. The coating material disclosed by the invention has excellent wear resistance, low temperature resistance and self-repairing function, and is suitable for extreme environments such as high-pressure hydrogen conveying pipelines.

Description

Technical Field

[0001] This invention relates to the field of polymer materials technology, specifically to a polymer-based pipe wear-resistant and low-temperature resistant coating material and its preparation method. Background Technology

[0002] A key technical bottleneck in the field of polymer pipe coating technology has long been the sharp increase in material brittleness at extremely low temperatures, leading to the failure of protective functions. While traditional coating materials such as polyamides and polyurethanes possess basic mechanical properties and processing characteristics, at temperatures below tens of degrees Celsius, the movement of molecular chain segments is restricted, resulting in a significant decrease in material flexibility and a susceptibility to cracking or even brittle fracture. In recent years, researchers have attempted to improve low-temperature performance by introducing flexible segments or plasticizers; however, these methods often come at the cost of material strength and service life, and are prone to component migration and performance degradation during temperature cycling. To address the challenge of low-temperature toughness, existing research has attempted to construct reversible dynamic bond networks in the molecular structure to enhance the material's impact resistance under low-temperature conditions through energy dissipation mechanisms. However, these systems still suffer from difficulties in activating dynamic bonds at extremely low temperatures and insufficient compatibility with the matrix, making it difficult to achieve low-temperature toughening while maintaining coating rigidity.

[0003] In terms of improving wear resistance, conventional techniques mainly rely on adding hard ceramic particles to enhance surface wear resistance. Micro- and nano-particles such as silicon carbide and alumina are widely used as reinforcing phases to improve the hardness and wear resistance of polymer-based composites. However, these inorganic fillers have significant interfacial compatibility issues with the organic matrix, especially at low temperatures where differences in thermal expansion coefficients can easily lead to stress concentration, causing filler detachment and wear failure. Although surface modification techniques can improve interfacial bonding strength to some extent, the filler-matrix interface remains a weak point under long-term friction, wear, and temperature alternation conditions. Furthermore, while high filler content can improve wear resistance, it further deteriorates the material's low-temperature toughness. Balancing wear resistance and low-temperature toughness has become a critical technical challenge that urgently needs to be overcome in this field.

[0004] For special applications such as high-pressure hydrogen pipelines, coating materials must also consider resistance to hydrogen permeation and hydrogen embrittlement. High-pressure hydrogen environments easily lead to hydrogen plasticization in traditional polymer materials, accelerating material aging and performance degradation. Existing technologies employ multilayer composite structures or metal foil layers to block hydrogen permeation, but these structures are often complex and costly, and also pose a risk of interlayer delamination. Although some studies have attempted to add hydrogen trapping substances to the coating to capture diffused hydrogen atoms, common hydrogen trapping materials have weak interfacial bonding with the polymer matrix, easily becoming crack initiation points at low temperatures. Therefore, developing a single coating material that simultaneously achieves low-temperature toughness, wear resistance, and hydrogen permeation resistance has been a long-standing goal for those skilled in the art. Summary of the Invention

[0005] The purpose of this invention is to provide a polymer-based wear-resistant and low-temperature resistant coating material for pipelines and its preparation method. It solves the technical problems of existing pipeline coating materials being prone to embrittlement and cracking in low-temperature environments, having insufficient wear resistance, and having reduced flexibility and adhesion due to excessive material rigidity, making it difficult to use them for a long time under harsh working conditions.

[0006] The present invention achieves the above objectives through the following technical solutions: A method for preparing a polymer-based wear-resistant and low-temperature resistant coating material for pipes, comprising the following steps: S1. Polyamide, dynamically modified polyurethane-urea with thioctic acid network, and liquid crystal benzoxazole-polysiloxane alternating copolymer are added to a twin-screw extruder and melt-blended at 180-220℃, then extruded and granulated to obtain a modified resin base. The modified resin base, together with silicon carbide, nano-niobium carbide, pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], trimethylolpropane tris(3-mercaptopropionate), and modified polysiloxane leveling agent, are added to a high-speed mixer and dry-mixed to obtain a premixed material. S2. The premixed material is fed into a twin-screw extruder, melt-extruded, water-cooled, and pelletized to obtain the coated material. The coated material is then injected into a single-screw extruder, melt-plasticized at 190-210℃, extruded into a film, and cooled and shaped.

[0007] In this invention, the preparation of the final coating material is an integrated process involving the synergistic effects of physical blending and chemical reactions. First, the polyamide matrix resin is melt-blended at high temperature with two previously prepared functional polymers: a dynamically modified polyurethane-urea network and a liquid crystal benzoxazole-polysiloxane alternating copolymer, in a twin-screw extruder. During this process, the polyamide melt and the melts of the other two polymers interpenetrate and disperse under the strong shearing and mixing action of the screw. Strong hydrogen bonding may form between the polar urethane and urea bonds in the dynamically modified lipoic acid network and the amide bonds on the polyamide molecular chain, while the rigid benzoxazole units of the liquid crystal copolymer may also interact with the crystalline regions of the polyamide, thus forming a robust, multiphase polymer alloy that constitutes the tough matrix of the coating. Subsequently, the modified resin matrix is ​​dry-blended with various additives. In the subsequent remelt extrusion and casting process, the crucial crosslinking reaction occurs. The added trimethylolpropane trimercaptopropionate, acting as a multifunctional thiol crosslinking agent, exhibits multiple thiol groups on its molecule that undergo click chemistry reactions at high temperatures with residual or dynamically exchanged disulfide bonds in the dynamically thioctic acid network-modified polyurethane-urea, known as thiol-disulfide bond exchange reactions. This reaction significantly increases the crosslinking density of the entire polymer network, thereby substantially improving the coating's hardness, abrasion resistance, and solvent resistance. Simultaneously, pre-dispersed uniform silicon carbide and nano-niobium carbide hard particles are firmly embedded and fixed within this highly crosslinked polymer network. As hard reinforcing phases, they directly bear the stress from external wear, which is crucial for the coating to achieve exceptional abrasion resistance. The added antioxidants effectively capture free radicals generated during processing and use, preventing polymer chain degradation and ensuring long-term material stability. The leveling agent migrates to the coating surface, reducing surface tension and resulting in a smooth final coating film. In summary, through the synergistic effect of multiple mechanisms such as matrix toughening, network crosslinking, and hard particle reinforcement, the final coating material achieves a perfect balance between high strength, high wear resistance, and excellent low-temperature toughness.

[0008] According to a preferred embodiment of the present invention, in step S1, the dry mixing time is 5-10 min.

[0009] According to a preferred embodiment of the present invention, in step S2, the melting and plasticizing time at a temperature of 190-210°C is 1-2 hours.

[0010] According to a preferred embodiment of the present invention, the preparation method of the dynamically modified polyurethane-urea with thioctic acid network includes: A1, under dry nitrogen protection, adding polytetrahydrofuran, 4,4'-dicyclohexylmethane diisocyanate and dibutyltin dilaurate sequentially to a four-necked flask, reacting at 84-86°C to obtain a reaction mixture; A2, cooling the reaction mixture to 58-62°C, adding 2,6-pyridinediethanol and thioctic lactone sequentially, stirring the reaction; adding isophorone diamine to react; finally adding N,N-dimethylformamide, and adding a mixed solution of triethylamine and deionized water dropwise to obtain a reaction product; precipitating the reaction product in deionized water, filtering, washing with deionized water, and drying in a vacuum drying oven at 58-62°C.

[0011] In this invention, the preparation of dynamically modified polyurethane-urea using a thioctic acid network is a multi-step, sophisticated chemical reaction process. Its core lies in constructing a polymer network possessing both high toughness and reversible dynamic properties. The process begins with the prepolymerization reaction of polytetrahydrofuran polyol and dicyclohexylmethane diisocyanate under a catalyst. In this stage, the hydroxyl groups at the ends of the polyol molecular chains undergo nucleophilic addition reactions with the highly reactive isocyanate groups in the diisocyanate molecules, generating a prepolymer linked by urethane bonds. Unreacted isocyanate groups remain at both ends of the prepolymer's molecular chains, laying the foundation for subsequent chain extension reactions. Subsequently, the system temperature is lowered, and a diethanol chain extender with a rigid pyridine ring structure and thioctic acid lactone are introduced sequentially. The hydroxyl groups on the chain extender continue to react with the isocyanate groups at the ends of the prepolymer, significantly extending the molecular chains and introducing rigid aromatic structural units, which helps to improve the modulus and strength of the material. Simultaneously, the five-membered ring structure of lipoic acid lactone undergoes ring-opening under reaction conditions. Its carboxyl group reacts with the remaining isocyanate group or the hydroxyl group on the chain extender in the system, chemically grafting lipoic acid units containing dynamic disulfide bonds onto the polyurethane-urea backbone as side chains or end groups. The next step is to add isophorone diamine for further chain extension and crosslinking. The amino group on the diamine has extremely high reactivity with the isocyanate group, forming urea bonds. The strong polarity and hydrogen bonding ability of urea bonds greatly enhance the intermolecular interaction forces, thereby significantly improving the mechanical strength, hardness, and heat resistance of the material. More importantly, under alkaline conditions, the disulfide bonds in the grafted lipoic acid units undergo dynamic exchange reactions. These disulfide bonds can reversibly break and recombine under external stimuli, thus forming a macroscopically stable and microscopically dynamic network structure within the material. This dynamic network endows the material with unique self-healing ability and excellent fatigue resistance. When the material is subjected to stress and micro-damage in a low-temperature environment, the recombination of dynamic disulfide bonds can effectively dissipate energy and prevent crack propagation. This is the molecular basis for achieving the coating's excellent low-temperature toughness.

[0012] According to a preferred embodiment of the present invention, in step A1, the reaction time is 3-5 hours at 84-86°C.

[0013] According to a preferred embodiment of the present invention, in step A2, the stirring reaction time is 2-4 hours.

[0014] According to a preferred embodiment of the present invention, the preparation method of the liquid crystal benzoxazole-polysiloxane alternating copolymer includes: B1, under argon protection, adding amino-terminated polydimethylsiloxane and anhydrous xylene to a three-necked round-bottom flask, stirring, and heating to 105-115°C; then adding 2,5-dihydroxy-1,4-phenylenedialdehyde and p-toluenesulfonic acid, stirring to react, and obtaining a reaction mixture; cooling the reaction mixture to 78-82°C, adding 2-amino-4-cresol and N-methylpyrrolidone, and heating to 125-135°C to react; B2, after the reaction is completed, cooling to room temperature, adding methanol under stirring to precipitate, filtering to collect the precipitate; washing the precipitate with methanol, continuously extracting it with methanol in a Soxhlet extractor, and finally drying it in a vacuum drying oven at 78-82°C.

[0015] In this invention, the synthesis of the liquid crystal benzoxazole-polysiloxane alternating copolymer is achieved through a stepwise polycondensation reaction, aiming to precisely combine flexible polysiloxane segments with rigid benzoxazole liquid crystal units in an alternating manner. The reaction is first carried out in an anhydrous solvent under an inert gas atmosphere. Amino-terminated polydimethylsiloxane acts as a flexible spacer group, and its two ends undergo a Schiff base reaction with the aldehyde group on the added dihydroxybenzenedialdehyde, generating imine bonds and releasing water molecules. This step constructs the initial connection of the copolymer backbone, forming an intermediate containing flexible siloxane segments and a rigid benzene ring. p-Toluenesulfonic acid acts as an acid catalyst, significantly accelerating the rate and extent of the Schiff base reaction by catalyzing the activation of the carbonyl group. After forming the imine-bonded intermediate, the system is cooled and an o-aminophenol compound and a high-boiling-point solvent are added, followed by heating to carry out the crucial cyclization and dehydration reaction. Under these high-temperature conditions, the hydroxyl groups adjacent to the aldehyde group in the intermediate molecule and the amino groups on the subsequently added aminophenol undergo intramolecular cyclization reactions with the imine bonds, losing one molecule of water to form an extremely stable benzoxazole heterocyclic structure. This heterocycle is a highly rigid mesocrystalline unit with a strong tendency to align. The resulting copolymer has a strictly alternating structure: flexible polysiloxane segments provide the mobility of the molecular chains, giving the material flexibility and impact resistance at low temperatures; while rigid benzoxazole units spontaneously form ordered liquid crystal microregions in the material through strong π-π stacking interactions. These microregions, acting as physical crosslinking points and reinforcing phases, effectively transfer and disperse stress, significantly improving the tensile strength, modulus, and thermal stability of the material. This combination of rigidity and flexibility in molecular design allows the copolymer to function as both a reinforcing and toughening component in coatings, perfectly balancing the coating's wear resistance and low-temperature resistance.

[0016] According to a preferred embodiment of the present invention, in step B1, the stirring reaction time is 6-8 hours.

[0017] According to a preferred embodiment of the present invention, in step B2, the drying time in a vacuum drying oven at 78-82°C is 48-50 hours.

[0018] The present invention also provides a method for preparing the aforementioned polymer-based pipe wear-resistant and low-temperature resistant coating material. The polymer-based pipe wear-resistant and low-temperature resistant coating material comprises the following raw materials in parts by weight: 50-70 parts by weight of polyamide; 15-25 parts by weight of dynamically modified polyurethane-urea with thioctic acid network; 10-20 parts by weight of liquid crystal benzoxazole-polysiloxane alternating copolymer; 15-25 parts by weight of silicon carbide; 3-8 parts by weight of trimethylolpropane tris(3-mercaptopropionate); 5-10 parts by weight of nano-niobium carbide; 0.5-1.5 parts by weight of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate]; and 0.3-1.0 parts by weight of modified polysiloxane leveling agent.

[0019] The beneficial effects of this invention are as follows: This invention presents a polymer-based wear-resistant and low-temperature resistant coating material for pipelines, exhibiting a series of superior technical effects through a unique material combination and refined preparation process, particularly excelling in wear resistance and low-temperature resistance, while also considering the material's mechanical strength, oxidation resistance, and processing performance. This coating material not only maintains excellent flexibility and adhesion in extreme low-temperature environments, preventing cracking or peeling due to low-temperature embrittlement, but also maintains long-term surface integrity under harsh conditions of high-speed fluid or particulate scouring, significantly extending the service life of pipelines. Its improved overall performance is attributed to the synergistic effect of the polyamide matrix and the alternating copolymers of dynamically thioctic acid network-modified polyurethane-urea and liquid crystal benzoxazole-polysiloxane. These components form an interpenetrating network structure through melt blending, enhancing the internal bonding force of the material. Furthermore, the addition of hard particles such as silicon carbide and nano-niobium carbide further enhances the surface hardness and wear resistance of the coating, while the introduction of antioxidants and leveling agents ensures the stability and uniformity of the material during processing and use, making this coating material suitable for various harsh industrial pipeline protection scenarios.

[0020] Regarding wear resistance, this invention achieves high wear resistance in the coating material through the composite effect of multiple reinforcing phases. Polyamide, as the matrix material, possesses excellent mechanical strength and abrasion resistance. The introduction of dynamically modified polyurethane-urea with a thioctic acid network endows the material with a dynamically reversible cross-linked structure, enabling it to absorb energy through bonding and recombination under external forces, reducing surface damage. The liquid crystal benzoxazole-polysiloxane alternating copolymer further enhances the material's rigidity and toughness. The benzoxazole rings and polysiloxane segments in its molecular chain form an ordered liquid crystal phase, effectively dispersing stress and inhibiting crack propagation. More importantly, silicon carbide and nano-niobium carbide, as hard fillers, are uniformly dispersed in the resin matrix, forming a micro-reinforcing network that significantly improves the coating's surface hardness and scratch resistance. The synergistic effect of these components allows the coating to maintain a smooth surface even under long-term scouring by high-speed fluids, reducing wear rate and thus significantly improving the pipeline's durability and reliability.

[0021] Regarding low-temperature resistance, this invention effectively enhances the flexibility and impact resistance of the coating in low-temperature environments through a unique molecular design of dynamically modified polyurethane-urea and liquid crystal benzoxazole-polysiloxane alternating copolymers using a dynamic lipoic acid network. The dynamic covalent bonds in the dynamically modified polyurethane-urea network maintain reversibility at low temperatures, allowing the molecular chains to reconfigure under stress, thereby preventing brittle fracture and maintaining the material's elasticity. Simultaneously, the polysiloxane segments in the liquid crystal benzoxazole-polysiloxane alternating copolymer possess extremely low glass transition temperatures, imparting good flexibility to the material at low temperatures, while the benzoxazole units provide necessary rigid support, ensuring the coating does not soften or deform at low temperatures. Furthermore, trimethylolpropane tris(mercaptopropionate) acts as a crosslinking agent, further optimizing the crosslinking density of the network and enhancing the low-temperature adhesion of the coating. These properties enable the coating material to maintain excellent performance in extremely cold environments, without peeling or cracking due to temperature changes, making it suitable for pipeline transportation systems in cold regions. Detailed Implementation

[0022] The present application will now be described in further detail. It should be noted that the following specific embodiments are only used to further illustrate the present application and should not be construed as limiting the scope of protection of the present application. Those skilled in the art can make some non-essential improvements and adjustments to the present application based on the above application content.

[0023] The following is information on domestic suppliers of key related equipment and materials: The trimethylolpropane tris(3-mercaptopropionate) was purchased from Qingdao Zhongke Huatai Industrial Co., Ltd.

[0024] The modified polysiloxane leveling agent was purchased from Shanghai Ziyi Chemical Co., Ltd.

[0025] The 4,4'-dicyclohexylmethane diisocyanate was purchased from Hubei Rishengchang New Material Technology Co., Ltd.

[0026] The 2,6-pyridinediethanol was purchased from Wuhan Kemic Biomedical Technology Co., Ltd.

[0027] The 2,5-dihydroxy-1,4-benzaldehyde was purchased from Henan Weitixi Chemical Technology Co., Ltd.

[0028] The 2-amino-4-cresol was purchased from Guangzhou Hewei Pharmaceutical Technology Co., Ltd.

[0029] Example 1: Preparation of dynamically modified polyurethane-urea using a thioctic acid network: Under dry nitrogen protection, 100.0 g of polytetrahydrofuran, 35.0 g of dicyclohexylmethane-4,4'-diisocyanate, and 0.10 g of dibutyltin dilaurate were added sequentially to a 2000 mL four-necked flask. A mechanical stirrer, thermometer, condenser, and nitrogen inlet were installed. The stirrer was started and the speed was controlled at 200 rpm. The temperature was slowly increased to 85 °C and maintained at this temperature for 4 hours. The isocyanate group content was monitored by titration using the di-n-butylamine method until it reached the theoretical value, yielding the prepolymer reaction mixture. The reaction mixture was cooled to 60 °C using an oil bath. 8.00 g of 2,6-pyridinediethanolamine and 5.00 g of thioctic acid lactone were added sequentially and slowly, maintaining a stirring speed of 200 rpm. The reaction was continued at 60 °C for 3 hours. Subsequently, 4.00 g of isophorone diamine was added, and the reaction was carried out at 60 °C for 30 minutes. Finally, add 50.0 g of N,N-dimethylformamide to the dilution system, and add a mixed solution prepared from 1.00 g of triethylamine and 10.0 g of deionized water dropwise at a uniform rate. After the addition is complete, continue stirring for 15 minutes to obtain the final reaction product. Slowly pour the reaction product into excess deionized water to precipitate the product. Collect the precipitate by filtration through a Buchner funnel, and wash the precipitate three times with 200 mL of deionized water each time. Place the washed product in a vacuum drying oven and dry at 60 °C for 24 hours to constant weight to obtain dynamically modified thioctic acid network polyurethane-urea, which is a pale yellow elastic solid.

[0030] Preparation of liquid crystal benzoxazole-polysiloxane alternating copolymer: Under argon protection, 50.0 g of amino-terminated polydimethylsiloxane and 150.0 g of anhydrous xylene were added to a 1000 mL three-necked round-bottom flask. A magnetic stirrer, thermometer, and Dean-Stark water separator were installed. The stirrer was turned on and the speed was controlled at 300 rpm, and the temperature was slowly increased to 110 °C. Then, 15.00 g of 2,5-dihydroxy-1,4-phenylenedialdehyde and 0.50 g of p-toluenesulfonic acid were precisely added, and the mixture was refluxed at 110 °C for 7 hours, during which time the water generated in the reaction was removed through the water separator. The reaction mixture was cooled to 80 °C, and 8.00 g of 2-amino-4-cresol and 50.0 g of N-methylpyrrolidone were added sequentially. The temperature was then increased to 130 °C, and the reaction was carried out at this temperature for 12 hours. After the reaction was complete, the system was naturally cooled to room temperature (25°C). While continuously stirring, the reaction solution was slowly poured into 1000 mL of methanol to precipitate the product. The precipitate was collected by filtration through a Buchner funnel. The precipitate was washed three times with 100 mL of methanol each time. The washed product was then placed in a Soxhlet extractor and extracted continuously with methanol for 24 hours. Finally, the product was placed in a vacuum drying oven and dried at 80°C for 48 hours to constant weight, yielding a liquid crystal benzoxazole-polysiloxane alternating copolymer, which was a light brown fibrous solid.

[0031] Preparation of wear-resistant and low-temperature resistant coating material for polymer-based pipes: First, 70.0g of polyamide, 25.0g of the dynamically modified polyurethane-urea network prepared above, and 20.0g of liquid crystal benzoxazole-polysiloxane alternating copolymer were accurately weighed and added to the feeding system of a twin-screw extruder. The temperatures of each section of the extruder were set as follows: Zone 1 180℃, Zone 2 190℃, Zone 3 200℃, Zone 4 200℃, and Die Head 200℃, with a screw speed of 150rpm. Melt blending was performed, followed by extrusion granulation to obtain the modified resin base material. The modified resin base material, along with 25.0g of silicon carbide, 10.0g of nano-niobium carbide, 1.50g of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], 8.00g of trimethylolpropane tris(3-mercaptopropionate), and 1.00g of modified polysiloxane leveling agent, were added to a high-speed mixer and dry-mixed at 800 rpm for 8 minutes to obtain a premixed material. The premixed material was then fed into a twin-screw extruder, with the temperatures of each section set to the same level as the aforementioned granulation process, for melt extrusion. After cooling in a water-cooling tank, the material was pelletized to obtain the coated material. The coated material was then injected into a single-screw extruder, with the barrel temperature set to 190-200-210℃ and the die temperature to 200℃. The material was melt-plasticized at 200℃ for 1.5 hours, extruded into a film, and cooled and shaped using a three-roll cooling system to obtain a coating material with a thickness of 0.5mm.

[0032] Example 2: Preparation of dynamically modified polyurethane-urea using a thioctic acid network: Under dry nitrogen protection, 90.0 g of polytetrahydrofuran, 32.0 g of dicyclohexylmethane-4,4'-diisocyanate, and 0.08 g of dibutyltin dilaurate were added sequentially to a 2000 mL four-necked flask. A mechanical stirrer, thermometer, condenser, and nitrogen inlet were installed. The stirrer was turned on and the speed was controlled at 180 rpm. The temperature was slowly increased to 84 °C and maintained at this temperature for 5 hours. The isocyanate group content was monitored by titration using the di-n-butylamine method until it reached the theoretical value, yielding the prepolymer reaction mixture. The reaction mixture was cooled to 58 °C using an oil bath. 7.00 g of 2,6-pyridinediethanolamine and 4.00 g of thioctic acid lactone were added sequentially and slowly, maintaining a stirring speed of 180 rpm. The reaction was continued at 58 °C for 4 hours. Subsequently, 3.50 g of isophorone diamine was added, and the reaction was carried out at 58 °C for 30 minutes. Finally, 45.0 g of N,N-dimethylformamide was added to the dilution system, and a mixed solution prepared from 0.80 g of triethylamine and 8.00 g of deionized water was added dropwise at a uniform rate. After the addition was complete, the mixture was stirred for 15 minutes to obtain the final reaction product. The reaction product was slowly poured into excess deionized water to precipitate, and the precipitate was collected by filtration through a Buchner funnel. The precipitate was washed three times with deionized water, 180 mL each time. The washed product was placed in a vacuum drying oven and dried at 58 °C for 26 hours to constant weight to obtain dynamically modified thioctic acid network polyurethane-urea, which is a pale yellow elastic solid.

[0033] Preparation of liquid crystal benzoxazole-polysiloxane alternating copolymer: Under argon protection, 45.0 g of amino-terminated polydimethylsiloxane and 140.0 g of anhydrous xylene were added to a 1000 mL three-necked round-bottom flask. A magnetic stirrer, thermometer, and Dean-Stark water separator were installed. The stirrer was turned on and the speed was controlled at 280 rpm, and the temperature was slowly increased to 105 °C. Then, 13.00 g of 2,5-dihydroxy-1,4-phenylenedialdehyde and 0.40 g of p-toluenesulfonic acid were precisely added, and the mixture was refluxed at 105 °C for 8 hours, during which water generated in the reaction was removed through the water separator. The reaction mixture was cooled to 78 °C, and 7.00 g of 2-amino-4-cresol and 45.0 g of N-methylpyrrolidone were added sequentially. The temperature was then increased to 125 °C, and the reaction was carried out at this temperature for 13 hours. After the reaction was complete, the system was naturally cooled to room temperature (25°C). While continuously stirring, the reaction solution was slowly poured into 900 mL of methanol to precipitate the product. The precipitate was collected by filtration through a Buchner funnel. The precipitate was washed three times with 90 mL of methanol each time. The washed product was then placed in a Soxhlet extractor and extracted continuously with methanol for 26 hours. Finally, the product was placed in a vacuum drying oven and dried at 78°C for 50 hours to constant weight, yielding a liquid crystal benzoxazole-polysiloxane alternating copolymer, which was a light brown fibrous solid.

[0034] Preparation of wear-resistant and low-temperature resistant coating material for polymer-based pipes: First, 50.0g of polyamide, 15.0g of the dynamically modified polyurethane-urea network prepared above, and 10.0g of liquid crystal benzoxazole-polysiloxane alternating copolymer were accurately weighed and added to the feeding system of a twin-screw extruder. The temperatures of each section of the extruder were set as follows: Zone 1 175℃, Zone 2 185℃, Zone 3 195℃, Zone 4 195℃, and Die Head 195℃, with a screw speed of 140rpm. Melt blending was performed, followed by extrusion granulation to obtain the modified resin base material. The modified resin base material, along with 15.0g of silicon carbide, 5.00g of nano-niobium carbide, 0.50g of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], 3.00g of trimethylolpropane tris(3-mercaptopropionate), and 0.30g of modified polysiloxane leveling agent, were added to a high-speed mixer and dry-mixed at 750 rpm for 5 minutes to obtain a premixed material. The premixed material was then fed into a twin-screw extruder, with the temperatures of each section set to the same level as the aforementioned granulation process, for melt extrusion. After cooling in a water-cooling tank, the material was pelletized to obtain the coated material. The coated material was then injected into a single-screw extruder, with the barrel temperature set to 185-195-205℃ and the die temperature to 195℃. The material was melt-plasticized at 190℃ for 2 hours, extruded into a film, and cooled and shaped using a three-roll cooling system to obtain a coating material with a thickness of 0.5mm.

[0035] Example 3: Preparation of dynamically modified polyurethane-urea using a thioctic acid network: Under dry nitrogen protection, 95.0 g of polytetrahydrofuran, 33.0 g of dicyclohexylmethane-4,4'-diisocyanate, and 0.09 g of dibutyltin dilaurate were added sequentially to a 2000 mL four-necked flask. A mechanical stirrer, thermometer, condenser, and nitrogen inlet were installed. The stirrer was started and the speed was controlled at 220 rpm. The temperature was slowly increased to 86 °C and maintained at this temperature for 3 hours. The isocyanate group content was monitored by titration using the di-n-butylamine method until it reached the theoretical value, yielding the prepolymer reaction mixture. The reaction mixture was cooled to 62 °C using an oil bath. 7.50 g of 2,6-pyridinediethanolamine and 4.50 g of thioctic acid lactone were added sequentially and slowly, maintaining a stirring speed of 220 rpm. The reaction was continued at 62 °C for 2 hours. Subsequently, 3.80 g of isophorone diamine was added, and the reaction was carried out at 62 °C for 30 minutes. Finally, 48.0 g of N,N-dimethylformamide was added to the dilution system, and a mixed solution prepared from 0.90 g of triethylamine and 9.00 g of deionized water was added dropwise at a uniform rate. After the addition was complete, the mixture was stirred for 15 minutes to obtain the final reaction product. The reaction product was slowly poured into excess deionized water to precipitate, and the precipitate was collected by filtration through a Buchner funnel. The precipitate was washed three times with deionized water, 190 mL each time. The washed product was placed in a vacuum drying oven and dried at 62 °C for 22 hours to constant weight to obtain dynamically modified thioctic acid network polyurethane-urea, which is a pale yellow elastic solid.

[0036] Preparation of liquid crystal benzoxazole-polysiloxane alternating copolymer: Under argon protection, 48.0 g of amino-terminated polydimethylsiloxane and 145.0 g of anhydrous xylene were added to a 1000 mL three-necked round-bottom flask. A magnetic stirrer, thermometer, and Dean-Stark water separator were installed. The stirrer was turned on and the speed was controlled at 320 rpm. The temperature was slowly increased to 115 °C. Then, 14.00 g of 2,5-dihydroxy-1,4-phenylenedialdehyde and 0.45 g of p-toluenesulfonic acid were precisely added. The mixture was refluxed at 115 °C for 6 hours, during which water generated in the reaction was removed through the water separator. The reaction mixture was cooled to 82 °C, and 7.50 g of 2-amino-4-cresol and 48.0 g of N-methylpyrrolidone were added sequentially. The temperature was then increased to 135 °C, and the reaction was carried out at this temperature for 11 hours. After the reaction was complete, the system was naturally cooled to room temperature (25°C). While continuously stirring, the reaction solution was slowly poured into 950 mL of methanol to precipitate the product. The precipitate was collected by filtration through a Buchner funnel. The precipitate was washed three times with 95 mL of methanol each time. The washed product was then placed in a Soxhlet extractor and extracted continuously with methanol for 22 hours. Finally, the product was placed in a vacuum drying oven and dried at 82°C for 49 hours to constant weight, yielding a liquid crystal benzoxazole-polysiloxane alternating copolymer, which was a light brown fibrous solid.

[0037] Preparation of wear-resistant and low-temperature resistant coating material for polymer-based pipes: First, 60.0g of polyamide, 20.0g of the dynamically modified polyurethane-urea network prepared above, and 15.0g of liquid crystal benzoxazole-polysiloxane alternating copolymer were accurately weighed and added to the feeding system of a twin-screw extruder. The temperatures of each section of the extruder were set as follows: Zone 1 185℃, Zone 2 195℃, Zone 3 205℃, Zone 4 205℃, and Die Head 205℃, with a screw speed of 160rpm. Melt blending was performed, followed by extrusion granulation to obtain the modified resin base material. The modified resin base material, along with 20.0g of silicon carbide, 8.00g of nano-niobium carbide, 1.00g of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], 5.00g of trimethylolpropane tris(3-mercaptopropionate), and 0.60g of modified polysiloxane leveling agent, were added to a high-speed mixer and dry-mixed at 850 rpm for 10 minutes to obtain a premixed material. The premixed material was then fed into a twin-screw extruder, with the temperatures of each section set to the same level as the aforementioned granulation process, for melt extrusion. After cooling in a water-cooling tank, the material was pelletized to obtain the coated material. The coated material was then injected into a single-screw extruder, with the barrel temperature set to 195-205-215℃ and the die temperature to 205℃. The material was melt-plasticized at 210℃ for 1 hour, extruded into a film, and cooled and shaped using a three-roll cooling system to obtain a coating material with a thickness of 0.5mm.

[0038] Comparative Example 1 The preparation method is the same as in Example 1, except that the polymer-based pipe wear-resistant and low-temperature resistant coating material is prepared as follows: 70.0g of polyamide and 20.0g of liquid crystal benzoxazole-polysiloxane alternating copolymer are accurately weighed and added to the feeding system of a twin-screw extruder. The temperatures of each section of the extruder are set as follows: Zone 1 180℃, Zone 2 190℃, Zone 3 200℃, Zone 4 200℃, and Die Head 200℃, with a screw speed of 150rpm. Melt blending is performed, followed by extrusion granulation to obtain the modified resin base material. The modified resin base material, along with 25.0g of silicon carbide, 10.0g of nano-niobium carbide, 1.50g of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], 8.00g of trimethylolpropane tris(3-mercaptopropionate), and 1.00g of modified polysiloxane leveling agent, were added to a high-speed mixer and dry-mixed at 800 rpm for 8 minutes to obtain a premixed material. The premixed material was then fed into a twin-screw extruder, with the temperatures of each section set to the same level as the aforementioned granulation process, for melt extrusion. After cooling in a water-cooling tank, the material was pelletized to obtain the coated material. The coated material was then injected into a single-screw extruder, with the barrel temperature set to 190-200-210℃ and the die temperature to 200℃. The material was melt-plasticized at 200℃ for 1.5 hours, extruded into a film, and cooled and shaped using a three-roll cooling system to obtain a coating material with a thickness of 0.5mm.

[0039] Comparative Example 2 The preparation method is the same as in Example 1, except that the polymer-based pipe wear-resistant and low-temperature resistant coating material is prepared as follows: 70.0g of polyamide and 25.0g of dynamically modified polyurethane-urea with an octanoic acid network are accurately weighed and added to the feeding system of a twin-screw extruder. The temperatures of each section of the extruder are set as follows: Zone 1 180℃, Zone 2 190℃, Zone 3 200℃, Zone 4 200℃, and Die Head 200℃, with a screw speed of 150rpm. Melt blending is performed, followed by extrusion granulation to obtain the modified resin base material. The modified resin base material, along with 25.0g of silicon carbide, 10.0g of nano-niobium carbide, 1.50g of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], 8.00g of trimethylolpropane tris(3-mercaptopropionate), and 1.00g of modified polysiloxane leveling agent, were added to a high-speed mixer and dry-mixed at 800 rpm for 8 minutes to obtain a premixed material. The premixed material was then fed into a twin-screw extruder, with the temperatures of each section set to the same level as the aforementioned granulation process, for melt extrusion. After cooling in a water-cooling tank, the material was pelletized to obtain the coated material. The coated material was then injected into a single-screw extruder, with the barrel temperature set to 190-200-210℃ and the die temperature to 200℃. The material was melt-plasticized at 200℃ for 1.5 hours, extruded into a film, and cooled and shaped using a three-roll cooling system to obtain a coating material with a thickness of 0.5mm.

[0040] Comparative Example 3 The preparation method is the same as in Example 1, except that the preparation of the polymer-based pipe wear-resistant and low-temperature resistant coating material is as follows: 70.0g of polyamide is accurately weighed and added to the feeding system of a twin-screw extruder. The temperatures of each section of the extruder are set as follows: Zone 1 180℃, Zone 2 190℃, Zone 3 200℃, Zone 4 200℃, and Die head 200℃, with a screw speed of 150rpm. The mixture is then melt-blended, extruded, and granulated to obtain a resin base. The resin base, along with 25.0g of silicon carbide, 10.0g of nano-niobium carbide, 1.50g of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], 8.00g of trimethylolpropane tris(3-mercaptopropionate), and 1.00g of modified polysiloxane leveling agent, are added to a high-speed mixer and dry-mixed at 800rpm for 8 minutes to obtain a premixed material. The premixed material is fed into a twin-screw extruder, and the temperatures of each section are set to be the same as those in the aforementioned granulation process. Melt extrusion is performed, followed by cooling in a water-cooling tank and pelletizing to obtain the coated material. The coated material is then injected into a single-screw extruder, with the barrel temperature set to 190-200-210℃ and the die temperature to 200℃. It is melt-plasticized at 200℃ for 1.5 hours, extruded into a film, and cooled and shaped using a three-roll cooling system to obtain a coating material with a thickness of 0.5mm.

[0041] Performance testing and results analysis According to existing national and industry standards, the performance of the polymer-based pipe wear-resistant and low-temperature resistant coating materials prepared in Examples 1-3 and Comparative Examples 1-3 was tested using the following methods: Abrasion resistance testing was conducted using a Tiber abrasion tester. The sample size was a 100mm diameter disc with a thickness of 0.5mm and a 6.5mm central hole. Before testing, the sample was conditioned for 48 hours at a temperature of 23±2℃ and a relative humidity of 50±5%. The test used a CS-10 grinding wheel with a load weight of 1kg and a rotation speed of 60r / min, for a total of 1000 revolutions. After the test, the surface debris was removed with a soft brush, and the mass difference before and after abrasion was measured using an analytical balance with an accuracy of 0.1mg. The mass loss per unit area was calculated, and the result was expressed as mg / 1000r.

[0042] For low-temperature performance testing, the samples were placed in a high-low temperature alternating test chamber and cooled to -40℃ at a rate of 5℃ / min, held for 24 hours, and then immediately tested. Impact strength testing was performed using a pendulum impact testing machine. The sample dimensions were 80mm × 10mm, thickness 0.5mm, notch depth 2mm, and notch bottom curvature radius 0.25mm. During testing, the pendulum energy was 2J, the impact velocity was 3.5m / s, and five samples were tested per group, with the average value taken.

[0043] Mechanical property testing was performed using a universal testing machine. Specimens were prepared in a standard dumbbell shape with a gauge length of 25 mm, a width of 5 mm, and a thickness of 0.5 mm. The testing environment temperature was 23 ± 2℃, and the tensile speed was 50 mm / min. The maximum load and elongation at fracture were recorded, and the tensile strength and elongation at break were calculated.

[0044] The adhesion test uses a cross-cut method. A 6×6 grid is drawn on the coating surface using a multi-bladed cutter, with cuts spaced 1 mm apart and extending to the substrate. After brushing lightly five times along the diagonal with a soft brush, special adhesive tape is firmly adhered to the grid area. After 60 seconds, it is quickly peeled off at a 60° angle within 0.5-1 second. The coating peeling off in the grid area is observed under standard light, and a rating of 0-5 is given based on the proportion of peeling area.

[0045] Table 1: Performance test results of each embodiment and comparative example ; As shown in Table 1, Examples 1-3 effectively solved key technical problems of existing pipe coating materials through the synergistic effect of the dynamically modified polyurethane-urea and liquid crystal benzoxazole-polysiloxane alternating copolymers via a dynamic thioctic acid network. Regarding abrasion resistance, Example 1 showed a weight loss of only 15.2 mg, significantly lower than the 52.1 mg of Comparative Example 3. This is attributed to the energy dissipation mechanism of the dynamic thioctic acid network and the synergistic reinforcing effect of the hard filler. In terms of low-temperature performance, Example 1 achieved an impact strength of 85.6 kJ / m at -40°C. 2 It is much higher than the 45.2 kJ / m³ of Comparative Example 3. 2 This demonstrates that the material successfully overcomes the low-temperature embrittlement problem, primarily due to the reversible recombination ability of the dynamic disulfide bonds and the low-temperature flexibility of the polysiloxane segments. Mechanical property tests show that Example 1 has a tensile strength of 62.3 MPa and an elongation at break of 45.8%, significantly better than Comparative Example 3's 40.5 MPa and 25.6%, indicating that the material maintains both strength and good toughness. In adhesion tests, all examples achieved a grade 0 standard, while Comparative Examples 1 and 2 only achieved grades 2 and 1, respectively, confirming that the synergistic effect of the three components effectively improves the adhesion between the coating and the substrate. Particularly noteworthy is that Comparative Example 1, lacking the dynamically modified polyurethane-urea with a thioctic acid network, exhibited significantly reduced wear resistance and low-temperature resistance; Comparative Example 2, lacking the liquid crystal benzoxazole-polysiloxane alternating copolymer, showed a significant decrease in mechanical properties; and Comparative Example 3, using only a polyamide matrix, had the worst performance in all performance indicators. This fully demonstrates the indispensable key role of the two modified compounds in solving problems such as low-temperature embrittlement, insufficient wear resistance, and decreased adhesion in coating materials.

Claims

1. A method for preparing a polymer-based wear-resistant and low-temperature resistant coating material for pipes, characterized in that the steps include... include: S1. Polyamide, dynamically modified polyurethane-urea with thioctic acid network, and liquid crystal benzoxazole-polysiloxane alternating copolymer are added to a twin-screw extruder and melt-blended at 180-220℃, then extruded and granulated to obtain a modified resin base. The modified resin base, together with silicon carbide, nano-niobium carbide, pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], trimethylolpropane tris(3-mercaptopropionate), and modified polysiloxane leveling agent, are added to a high-speed mixer and dry-mixed to obtain a premixed material. S2. The premixed material is fed into a twin-screw extruder, melt-extruded, water-cooled, and pelletized to obtain the coated material. The coated material is then injected into a single-screw extruder, melt-plasticized at 190-210℃, extruded into a film, and cooled and shaped.

2. The method for preparing the polymer-based pipe wear-resistant and low-temperature resistant coating material according to claim 1, characterized in that, In step S1, the dry mixing time is 5-10 minutes.

3. The method for preparing the polymer-based pipe wear-resistant and low-temperature resistant coating material according to claim 1, characterized in that, In step S2, the melting and plasticizing time at a temperature of 190-210℃ is 1-2 hours.

4. The method for preparing the polymer-based pipe wear-resistant and low-temperature resistant coating material according to claim 1, characterized in that, The preparation method of the dynamically modified polyurethane-urea using a thioctic acid network includes: A1, under dry nitrogen protection, adding polytetrahydrofuran, 4,4'-dicyclohexylmethane diisocyanate and dibutyltin dilaurate sequentially to a four-necked flask, reacting at 84-86℃ to obtain a reaction mixture; A2, cooling the reaction mixture to 58-62℃, adding 2,6-pyridinediethanol and thioctic lactone sequentially, stirring the reaction; adding isophorone diamine to react; finally adding N,N-dimethylformamide, and dropwise adding a mixed solution of triethylamine and deionized water to obtain the reaction product; precipitating the reaction product in deionized water, filtering, washing with deionized water, and drying in a vacuum drying oven at 58-62℃.

5. The method for preparing the polymer-based pipe wear-resistant and low-temperature resistant coating material according to claim 4, characterized in that, In step A1, the reaction time is 3-5 hours at 84-86℃.

6. The method for preparing the polymer-based pipe wear-resistant and low-temperature resistant coating material according to claim 4, characterized in that, In step A2, the stirring reaction time is 2-4 hours.

7. The method for preparing the polymer-based pipe wear-resistant and low-temperature resistant coating material according to claim 1, characterized in that, The preparation method of the liquid crystal benzoxazole-polysiloxane alternating copolymer includes: B1, under argon protection, adding amino-terminated polydimethylsiloxane and anhydrous xylene to a three-necked round-bottom flask, stirring, and heating to 105-115℃; then adding 2,5-dihydroxy-1,4-phenylenedialdehyde and p-toluenesulfonic acid, stirring to react, and obtaining a reaction mixture; cooling the reaction mixture to 78-82℃, adding 2-amino-4-cresol and N-methylpyrrolidone, and heating to 125-135℃ to react; B2, after the reaction is completed, cooling to room temperature, adding methanol under stirring to precipitate, filtering to collect the precipitate; washing the precipitate with methanol, continuously extracting it with methanol in a Soxhlet extractor, and finally drying it in a vacuum drying oven at 78-82℃.

8. The method for preparing the polymer-based pipe wear-resistant and low-temperature resistant coating material according to claim 7, characterized in that, In step B1, the stirring reaction time is 6-8 hours.

9. The method for preparing the polymer-based pipe wear-resistant and low-temperature resistant coating material according to claim 7, characterized in that, In step B2, the drying time in a vacuum drying oven at 78-82℃ is 48-50 hours.

10. A polymer-based pipe wear-resistant and low-temperature resistant coating material prepared by the preparation method according to any one of claims 1-9, characterized in that, The raw materials include the following parts by weight: 50-70 parts by weight of polyamide; 15-25 parts by weight of dynamically modified polyurethane-urea with thioctic acid network; 10-20 parts by weight of liquid crystal benzoxazole-polysiloxane alternating copolymer; 15-25 parts by weight of silicon carbide; 3-8 parts by weight of trimethylolpropane tris(3-mercaptopropionate); 5-10 parts by weight of nano-niobium carbide; 0.5-1.5 parts by weight of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate]; and 0.3-1.0 parts by weight of modified polysiloxane leveling agent.