A corrosion-resistant polytetrafluoroethylene compensator and its preparation method

Abstract

The application discloses a polytetrafluoroethylene compensator with good corrosion resistance and a preparation method thereof. The polytetrafluoroethylene compensator is composed of a bellows, a connecting pipe flange and an end flange located at two ends of the bellows. The bellows is composed of an inner lining layer and a base material layer, and the base material layer is stainless steel. In the application, first, isocyanate silane is used to graft the surface of nano-aluminum oxide, and active reaction groups are introduced. Then, the active groups are reacted with benzotriazole to give the function of corrosion inhibition and adhesion enhancement. Finally, the remaining active groups are reacted with alkali-activated hydroxylated polytetrafluoroethylene to coat a layer of chemical inert layer on the surface. The obtained core-shell structure functional filler is dispersed in epoxy resin to prepare a coating, which is coated on a stainless steel substrate and solidified to form a high-performance compensator with high hardness, strong adhesion, excellent corrosion resistance and weather resistance.

Description

Technical Field

[0001] This invention relates to the field of compensator technology, specifically to a polytetrafluoroethylene compensator with good corrosion resistance and its preparation method. Background Technology

[0002] Bellows compensators, as a key flexible connection element, are widely used in pipeline systems in petroleum, chemical, power, metallurgy, aerospace and other fields. They are used to absorb and compensate for axial, lateral and angular displacements of pipelines caused by thermal expansion and contraction, mechanical vibration, etc., playing an important role in protecting the safe and stable operation of pipeline systems. Traditional bellows compensators mostly use stainless steel as the base material, and achieve good flexibility and compensation capacity through the bellows structure design.

[0003] However, in petrochemical and chemical industries, compensators are subjected to harsh conditions of high temperature, high pressure, and high-frequency vibration year-round, and are in long-term contact with highly corrosive chemical media (such as strong acids, strong alkalis, organic solvents, and wet chlorine). Although stainless steel substrates have a certain degree of corrosion resistance, they are still highly susceptible to pitting corrosion, intergranular corrosion, and stress corrosion cracking in the aforementioned complex and harsh working environments. This can lead to premature failure and leakage of the compensator, causing serious safety accidents and economic losses.

[0004] To improve the corrosion resistance of compensators, polytetrafluoroethylene (PTFE) compensators were developed. PTFE, known as the "king of plastics," possesses extremely excellent chemical stability and corrosion resistance, resisting the erosion of almost all chemical media, thus becoming an ideal material for manufacturing highly corrosion-resistant compensators. Existing PTFE compensators mainly come in two structural forms: one is a pure PTFE bellows, and the other is a composite structure with a stainless steel frame and an inner PTFE film or sheet lining.

[0005] However, PTFE compensators also have significant technical drawbacks. While pure PTFE bellows have excellent corrosion resistance, they have low mechanical strength and poor compressive strength, making them unsuitable for high-pressure conditions. In composite PTFE compensators, the bond between the PTFE lining and the stainless steel substrate relies mainly on mechanical assembly, resulting in weak bonding. Under temperature cycling and pressure fluctuations, problems such as lining detachment and damage can easily occur.

[0006] In recent years, functional coatings containing polytetrafluoroethylene (PTFE) have seen rapid development. These coatings typically use epoxy resins, polyurethanes, or similar materials as a matrix, adding PTFE micropowder as a functional filler, attempting to combine the adhesion of the resin matrix with the corrosion resistance of PTFE.

[0007] CN101654582A A rust-proof and corrosion-resistant coating comprising the following raw materials in the following weight ratio: epoxy resin: 40~50%, curing agent ethylenediamine: 30~40%, and polytetrafluoroethylene powder with a particle size of 100~500 nanometers: 20~30%.

[0008] However, due to its extremely low surface energy and strong chemical inertness, PTFE exhibits very poor compatibility with conventional resin matrices. Direct physical blending makes it difficult to achieve uniform dispersion, and the weak interfacial bonding leads to a decline in the mechanical properties of the coating, and even defects such as phase separation. Furthermore, how to further enhance the adhesion between the coating and the metal substrate, and endow the coating with more comprehensive protective functions, remains a significant challenge in this technical field.

[0009] Therefore, there is an urgent need for a new type of polytetrafluoroethylene (PTFE) compensator technology that can fully utilize the excellent corrosion resistance of PTFE and effectively solve key technical problems such as poor adhesion to the substrate and poor coating dispersibility, thereby achieving a high-performance, long-life, and highly reliable corrosion-resistant compensator product. Summary of the Invention

[0010] To address the shortcomings of existing technologies, the present invention aims to provide a polytetrafluoroethylene compensator with good corrosion resistance and its preparation method. By constructing a composite functional inner lining layer on the inner wall of its stainless steel substrate, the compensator possesses excellent chemical corrosion resistance, weather resistance, wear resistance, and strong adhesion to the substrate, thereby significantly improving its comprehensive protection capability and service life under harsh working conditions and achieving high reliability.

[0011] To achieve the above objectives, the present invention adopts the following technical solution:

[0012] A polytetrafluoroethylene compensator with good corrosion resistance, the compensator is composed of a bellows and connecting flanges and end flanges located at both ends of the bellows, the bellows is composed of an inner lining layer and a base material layer, the base material layer being stainless steel.

[0013] Preferably, the corrugated pipe is prepared by the following method steps:

[0014] (1) The nano-alumina was dried and dispersed in toluene and ultrasonically treated; 3-isocyanate propyltrimethoxysilane was added to deionized water for pre-hydrolysis to form a silanol intermediate; the silanol intermediate was then added dropwise to the nano-alumina suspension, triethylamine was added, the reaction was stirred, and the product was filtered, washed, and dried to obtain pretreated alumina.

[0015] Grafting onto alumina surface: First, 3-isocyanate propyltrimethoxysilane is pre-hydrolyzed in water, and its terminal methoxy group (-OCH3) is transformed into a more reactive silanol group (-Si-OH). Subsequently, these silanol groups undergo a dehydration condensation reaction with the hydroxyl groups (-Al-OH) on the nano-alumina surface under triethylamine catalysis to form a stable chemical bond (Al-O-Si), thereby firmly anchoring the silane molecule with the isocyanate functional group (-NCO) onto the alumina surface.

[0016] Preferably, in step (1), the ratio of nano-alumina, toluene, 3-isocyanate propyltrimethoxysilane, deionized water, and triethylamine is 10g: 120~150mL: 3~6g: 2~4mL: 0.4~1mL.

[0017] Preferably, in step (1), the ultrasonic treatment is performed for 10-30 min; the pre-hydrolysis is performed for 20-40 min; the stirring reaction is carried out at 65-80℃ for 5-8 h; and the product is washed with anhydrous acetone 2-4 times.

[0018] (2) Disperse the pretreated alumina in DMF, sonicate it, add benzotriazole under a nitrogen atmosphere, stir the reaction, filter, wash and dry the product to obtain the intermediate;

[0019] Surface functionalization: The active hydrogen (NH) on the benzotriazole molecule ring undergoes a nucleophilic addition reaction with some of the isocyanate groups (-NCO) on the pretreated alumina surface. This reaction consumes some of the -NCO groups, grafting the benzotriazole molecule onto the alumina surface, while retaining the remaining -NCO groups for subsequent steps.

[0020] Preferably, in step (2), the ratio of pretreated alumina, DMF and benzotriazole is 10g: 150~200mL: 1.2~2.4g.

[0021] Preferably, in step (2), the ultrasonic treatment is performed for 10 to 30 minutes; the stirring reaction conditions are 40 to 55°C for 3 to 6 hours.

[0022] (3) Add polytetrafluoroethylene powder to sodium hydroxide solution, stir and react, centrifuge, wash and dry the product to obtain hydroxylated polytetrafluoroethylene;

[0023] Surface activation of polytetrafluoroethylene (PTFE): The inert surface of polytetrafluoroethylene (PTFE) has extremely stable carbon-fluorine bonds (CF). Under high temperature and pressure, the strong alkali sodium hydroxide can break some of the CF bonds, causing fluoride ions to fall off. At the same time, hydroxyl ions (OH⁻) in the solution replace their positions, successfully introducing reactive hydroxyl groups (-OH) onto the PTFE surface, thereby "activating" the originally inert material surface.

[0024] Preferably, in step (3), the ratio of polytetrafluoroethylene powder to sodium hydroxide solution is 30g: 400~600mL; the concentration of sodium hydroxide solution is 4~6mmol / L; the stirring reaction conditions are 0.8~1.2MPa and 160~200℃ for 10~16h; the product is neutralized with dilute hydrochloric acid and then washed with deionized water until neutral.

[0025] (4) Disperse the intermediate in THF, add hydroxylated polytetrafluoroethylene, sonicate, stir the reaction under nitrogen atmosphere, centrifuge, wash and dry the product to obtain modified nano alumina.

[0026] The final composite material is formed by the classic carbamate reaction between the remaining isocyanate groups (-NCO) on the surface of the intermediate and the hydroxyl groups (-OH) on the surface of the hydroxylated polytetrafluoroethylene. Through this reaction, stable chemical bonds are formed between the alumina and polytetrafluoroethylene, ultimately grafting the nano-alumina particles and polytetrafluoroethylene together uniformly to form the target composite material.

[0027] Preferably, in step (4), the ratio of intermediate, THF and hydroxylated polytetrafluoroethylene is 10g: 300~500mL: 12~24g.

[0028] Preferably, in step (4), the ultrasonic treatment lasts for 1 to 2 hours; the stirring reaction conditions are 50 to 65°C for 10 to 16 hours.

[0029] (5) 10-16 parts of modified nano alumina are added to 30-45 parts of ethanol and 6-12 parts of deionized water and dispersed to obtain pre-dispersed alumina; 8-20 parts of curing agent, 0.4-1 parts of leveling agent, 1-3 parts of thickener, 1-3 parts of film-forming aid and 1-3 parts of defoamer are added to 100 parts of bisphenol A epoxy resin in sequence and stirred evenly to obtain resin base material; the pre-dispersed alumina is added to the resin base material and stirred evenly to obtain modified coating; the modified coating is applied evenly to the surface of the substrate layer by spraying or impregnation and cured to obtain inner lining layer; then the substrate stainless steel plate is hydraulically formed to obtain the corrugated pipe.

[0030] Preferably, in step (5), the curing conditions are pre-curing at 80~100℃ for 1~3h and complete curing at 120~140℃ for 1~3h.

[0031] Preferably, in step (5), the leveling agent is BYK-323, the thickener is BYK-410, the film-forming aid is diethanol ether, the defoamer is BYK-052, and the curing agent is aromatic amine curing agent T31.

[0032] 1. This invention provides a polytetrafluoroethylene (PTFE) compensator with excellent corrosion resistance. By preparing a special multifunctional inner lining layer on a stainless steel substrate, the overall performance of the compensator is significantly improved, especially in terms of corrosion resistance, weather resistance, and service life. The coating system of the inner lining layer is based on bisphenol A type epoxy resin and aromatic amine curing agent, providing excellent mechanical strength and basic adhesion. Simultaneously, modified nano-alumina is introduced as a core filler, enabling the inner lining layer to maintain high hardness and high wear resistance while synergistically achieving excellent chemical inertness, hydrophobicity, active corrosion inhibition, ultraviolet shielding ability, and super strong adhesion to the metal substrate. Finally, with the synergistic effect of various additives, a composite protective coating combining physical shielding and chemical inhibition, with a dense structure and highly synergistic performance, is constructed, thereby giving the compensator long-term reliable service capability under harsh operating conditions.

[0033] 2. This invention provides a method for preparing modified nano-alumina. First, isocyanate silane coupling agent pretreatment firmly anchors the organic layer onto the inorganic core through stable Al-O-Si chemical bonds, while simultaneously converting the alumina surface from hydrophilic to organic-philic. This solves the problem of easy agglomeration of nanoparticles in epoxy resin, ensuring uniform dispersion, which is the basis for forming a dense, defect-free coating. Second, the introduced benzotriazole functional layer not only absorbs ultraviolet light, improving the coating's weather resistance, but also coordinates with iron, chromium, and other metal ions on the stainless steel substrate surface, greatly enhancing the bonding and adhesion between the coating and the metal, and providing active corrosion inhibition when corrosion occurs. Finally, grafted polytetrafluoroethylene (PTFE) endows the coating with excellent chemical stability, hydrophobicity, salt spray resistance, and corrosion resistance, resulting in a qualitative leap in the comprehensive protective performance of the inner lining. Attached Figure Description

[0034] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly described below. It should be understood that the following drawings only show some schematic diagrams of certain embodiments of the present invention, and therefore should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0035] Figure 1 The polytetrafluoroethylene compensator prepared in Example 1 of this invention. Detailed Implementation

[0036] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. Of course, the specific embodiments described herein are only for explaining the invention and are not intended to limit the invention.

[0037] Unless otherwise specified, all chemical reagents and materials in this invention are purchased from the market or synthesized from raw materials purchased from the market.

[0038] The average particle size of the nano-alumina is 200nm. It was purchased from Anhui Zhonghang Nanotechnology Development Co., Ltd., model ZH-Al2O3200N.

[0039] The polytetrafluoroethylene powder has an average particle size of 0.1~10μm and was purchased from Daikin Industries, Japan, model L-2.

[0040] Bisphenol A type epoxy resin is E44 or E51.

[0041] A polytetrafluoroethylene (PTFE) compensator with good corrosion resistance, comprising a bellows and connecting flanges and end flanges located at both ends of the bellows, wherein the bellows consists of an inner lining layer and a base material layer, the base material layer being stainless steel; the bellows is prepared by the following method steps:

[0042] (1) 10g of nano alumina was dried and dispersed in 120-150mL of toluene and ultrasonically treated for 10-30min; 3-6g of 3-isocyanate propyltrimethoxysilane was added to 2-4mL of deionized water for pre-hydrolysis for 20-40min to form a silanol intermediate; then the silanol intermediate was added dropwise to the nano alumina suspension, 0.4-1mL of triethylamine was added, and the mixture was stirred at 65-80℃ for 5-8h. The product was filtered, washed 2-4 times with anhydrous acetone, and dried to obtain pretreated alumina.

[0043] (2) Disperse 10g of pretreated alumina into 150~200mL of DMF, sonicate for 10~30min, add 1.2~2.4g of benzotriazole under nitrogen atmosphere, stir and react at 40~55℃ for 3~6h, filter, wash and dry the product to obtain the intermediate;

[0044] (3) Add 30g of polytetrafluoroethylene powder to 400~600mL of 4~6mmol / L sodium hydroxide solution, stir and react at 0.8~1.2MPa and 160~200℃ for 10~16h, centrifuge the product, neutralize it with dilute hydrochloric acid, wash it with deionized water until neutral, and dry it to obtain hydroxylated polytetrafluoroethylene.

[0045] (4) Disperse 10g of intermediate into 300-500mL THF, add 12-24g of hydroxylated polytetrafluoroethylene, sonicate for 1-2h, stir and react for 10-16h in a nitrogen atmosphere at 50-65℃, centrifuge, wash and dry the product to obtain modified nano alumina.

[0046] (5) 10-16 parts of modified nano alumina are added to 30-45 parts of ethanol and 6-12 parts of deionized water and dispersed to obtain pre-dispersed alumina; 8-20 parts of curing agent, 0.4-1 parts of leveling agent, 1-3 parts of thickener, 1-3 parts of film-forming aid and 1-3 parts of defoamer are added to 100 parts of bisphenol A epoxy resin in sequence and stirred evenly to obtain resin base material; the pre-dispersed alumina is added to the resin base material and stirred evenly to obtain modified coating; the modified coating is applied evenly to the surface of the substrate layer by spraying or impregnation, pre-cured at 80-100℃ for 1-3 hours and fully cured at 120-140℃ for 1-3 hours to obtain inner lining layer, and then the substrate stainless steel plate is hydraulically formed to obtain the corrugated pipe.

[0047] The present invention will be further described below through specific embodiments. Example

[0048] A polytetrafluoroethylene (PTFE) compensator with good corrosion resistance, comprising a bellows and connecting flanges and end flanges located at both ends of the bellows, wherein the bellows consists of an inner lining layer and a base material layer, the base material layer being stainless steel; the bellows is prepared by the following method steps:

[0049] (1) 10g of nano alumina was dried and dispersed in 140mL of toluene and ultrasonically treated for 20min; 6g of 3-isocyanate propyltrimethoxysilane was added to 4mL of deionized water for pre-hydrolysis for 30min to form a silanol intermediate. The silanol intermediate was then added dropwise to the nano alumina suspension, 1mL of triethylamine was added, and the mixture was stirred at 80℃ for 5h. The product was filtered, washed three times with anhydrous acetone, and dried to obtain pretreated alumina.

[0050] (2) Disperse 10g of pretreated alumina into 180mL of DMF, sonicate for 20min, add 2.4g of benzotriazole under nitrogen atmosphere, stir and react at 55℃ for 3h, filter, wash and dry the product to obtain the intermediate;

[0051] (3) Add 30g of polytetrafluoroethylene powder to 500mL of 5mmol / L sodium hydroxide solution, stir and react at 1MPa and 200℃ for 10h, centrifuge the product, neutralize it with dilute hydrochloric acid, wash it with deionized water until neutral, and dry it to obtain hydroxylated polytetrafluoroethylene.

[0052] (4) Disperse 10g of intermediate into 400mL THF, add 24g of hydroxylated polytetrafluoroethylene, sonicate for 1.5h, stir and react for 10h under nitrogen atmosphere at 65℃, centrifuge, wash and dry the product to obtain modified nano alumina.

[0053] (5) 1600g of modified nano alumina was added to 4500g of ethanol and 1200g of deionized water and dispersed to obtain pre-dispersed alumina; 2000g of curing agent T31, 100g of leveling agent BYK-323, 300g of thickener BYK-410, 300g of film-forming aid diethanol ether, and 300g of defoamer BYK-052 were added to 10000g of bisphenol A epoxy resin in sequence and stirred evenly to obtain resin base material; the pre-dispersed alumina was added to the resin base material and stirred evenly to obtain modified coating; the modified coating was applied evenly to the surface of the substrate layer by impregnation method, pre-cured at 90℃ for 2h, and fully cured at 130℃ for 2h to obtain inner lining layer; then the substrate stainless steel plate was hydraulically formed to obtain the corrugated pipe.

[0054] The prepared polytetrafluoroethylene compensator is as follows Figure 1 As shown. Example

[0055] A polytetrafluoroethylene (PTFE) compensator with good corrosion resistance, comprising a bellows and connecting flanges and end flanges located at both ends of the bellows, wherein the bellows consists of an inner lining layer and a base material layer, the base material layer being stainless steel; the bellows is prepared by the following method steps:

[0056] (1) 10g of nano alumina was dried and dispersed in 140mL of toluene and ultrasonically treated for 20min; 5g of 3-isocyanate propyltrimethoxysilane was added to 3mL of deionized water for pre-hydrolysis for 30min to form a silanol intermediate. The silanol intermediate was then added dropwise to the nano alumina suspension, and 0.8mL of triethylamine was added. The mixture was stirred at 75℃ for 6h. The product was filtered, washed three times with anhydrous acetone, and dried to obtain pretreated alumina.

[0057] (2) Disperse 10g of pretreated alumina into 180mL of DMF, sonicate for 20min, add 2g of benzotriazole under nitrogen atmosphere, stir and react at 50℃ for 4h, filter, wash and dry the product to obtain the intermediate;

[0058] (3) Add 30g of polytetrafluoroethylene powder to 500mL of 5mmol / L sodium hydroxide solution, stir and react at 1MPa and 180℃ for 12h, centrifuge the product, neutralize it with dilute hydrochloric acid, wash it with deionized water until neutral, and dry it to obtain hydroxylated polytetrafluoroethylene.

[0059] (4) Disperse 10g of intermediate into 400mL THF, add 20g of hydroxylated polytetrafluoroethylene, sonicate for 1.5h, stir and react for 12h under nitrogen atmosphere at 60℃, centrifuge, wash and dry the product to obtain modified nano alumina.

[0060] (5) 1400g of modified nano alumina was added to 4000g of ethanol and 1000g of deionized water and dispersed to obtain pre-dispersed alumina; 1600g of curing agent T31, 80g of leveling agent BYK-323, 200g of thickener BYK-410, 200g of film-forming aid diethanol ether, and 200g of defoamer BYK-052 were added to 10000g of bisphenol A epoxy resin in sequence and stirred evenly to obtain resin base material; the pre-dispersed alumina was added to the resin base material and stirred evenly to obtain modified coating; the modified coating was applied evenly to the surface of the substrate layer by impregnation method, pre-cured at 90℃ for 2h, and fully cured at 130℃ for 2h to obtain inner lining layer; then the substrate stainless steel plate was hydraulically formed to obtain the corrugated pipe. Example

[0061] A polytetrafluoroethylene (PTFE) compensator with good corrosion resistance, comprising a bellows and connecting flanges and end flanges located at both ends of the bellows, wherein the bellows consists of an inner lining layer and a base material layer, the base material layer being stainless steel; the bellows is prepared by the following method steps:

[0062] (1) 10g of nano alumina was dried and dispersed in 140mL of toluene and ultrasonically treated for 20min; 4g of 3-isocyanate propyltrimethoxysilane was added to 3mL of deionized water for pre-hydrolysis for 30min to form a silanol intermediate. The silanol intermediate was then added dropwise to the nano alumina suspension, and 0.6mL of triethylamine was added. The mixture was stirred at 70℃ for 7h. The product was filtered, washed three times with anhydrous acetone, and dried to obtain pretreated alumina.

[0063] (2) Disperse 10g of pretreated alumina into 180mL of DMF, sonicate for 20min, add 1.6g of benzotriazole under nitrogen atmosphere, stir and react at 45℃ for 5h, filter, wash and dry the product to obtain the intermediate;

[0064] (3) Add 30g of polytetrafluoroethylene powder to 500mL of 5mmol / L sodium hydroxide solution, stir and react at 1MPa and 170℃ for 14h, centrifuge the product, neutralize it with dilute hydrochloric acid, wash it with deionized water until neutral, and dry it to obtain hydroxylated polytetrafluoroethylene.

[0065] (4) Disperse 10g of intermediate into 400mL THF, add 16g of hydroxylated polytetrafluoroethylene, sonicate for 1.5h, stir and react for 14h under nitrogen atmosphere at 55℃, centrifuge, wash and dry the product to obtain modified nano alumina.

[0066] (5) 1200g of modified nano alumina was added to 3500g of ethanol and 800g of deionized water and dispersed to obtain pre-dispersed alumina; 1200g of curing agent T31, 60g of leveling agent BYK-323, 200g of thickener BYK-410, 200g of film-forming aid diethanol ether, and 200g of defoamer BYK-052 were added to 10000g of bisphenol A epoxy resin in sequence and stirred evenly to obtain resin base material; the pre-dispersed alumina was added to the resin base material and stirred evenly to obtain modified coating; the modified coating was applied evenly to the surface of the substrate layer by impregnation method, pre-cured at 90℃ for 2h, and fully cured at 130℃ for 2h to obtain inner lining layer; then the substrate stainless steel plate was hydraulically formed to obtain the corrugated pipe. Example

[0067] A polytetrafluoroethylene (PTFE) compensator with good corrosion resistance, comprising a bellows and connecting flanges and end flanges located at both ends of the bellows, wherein the bellows consists of an inner lining layer and a base material layer, the base material layer being stainless steel; the bellows is prepared by the following method steps:

[0068] (1) 10g of nano alumina was dried and dispersed in 140mL of toluene and ultrasonically treated for 20min; 3g of 3-isocyanate propyltrimethoxysilane was added to 2mL of deionized water for pre-hydrolysis for 30min to form a silanol intermediate. The silanol intermediate was then added dropwise to the nano alumina suspension, and 0.4mL of triethylamine was added. The mixture was stirred at 65℃ for 8h. The product was filtered, washed three times with anhydrous acetone, and dried to obtain pretreated alumina.

[0069] (2) Disperse 10g of pretreated alumina into 180mL of DMF, sonicate for 20min, add 1.2g of benzotriazole under nitrogen atmosphere, stir at 40℃ for 6h, filter, wash and dry the product to obtain the intermediate;

[0070] (3) Add 30g of polytetrafluoroethylene powder to 500mL of 5mmol / L sodium hydroxide solution, stir and react at 1MPa and 160℃ for 16h, centrifuge the product, neutralize it with dilute hydrochloric acid, wash it with deionized water until neutral, and dry it to obtain hydroxylated polytetrafluoroethylene.

[0071] (4) Disperse 10g of intermediate into 400mL THF, add 12g of hydroxylated polytetrafluoroethylene, sonicate for 1.5h, stir and react for 16h under nitrogen atmosphere at 50℃, centrifuge, wash and dry the product to obtain modified nano alumina.

[0072] (5) 1000g of modified nano alumina was added to 3000g of ethanol and 600g of deionized water and dispersed to obtain pre-dispersed alumina; 800g of curing agent T31, 40g of leveling agent BYK-323, 100g of thickener BYK-410, 100g of film-forming aid diethanol ether, and 100g of defoamer BYK-052 were added to 10000g of bisphenol A epoxy resin in sequence and stirred evenly to obtain resin base material; the pre-dispersed alumina was added to the resin base material and stirred evenly to obtain modified coating; the modified coating was applied evenly to the surface of the substrate layer by impregnation method, pre-cured at 90℃ for 2h, and fully cured at 130℃ for 2h to obtain inner lining layer; then the substrate stainless steel plate was hydraulically formed to obtain the corrugated pipe.

[0073] A polytetrafluoroethylene (PTFE) compensator with good corrosion resistance, comprising a bellows and connecting flanges and end flanges located at both ends of the bellows, wherein the bellows consists of an inner lining layer and a base material layer, the base material layer being stainless steel; the bellows is prepared by the following method steps:

[0074] (1) 10g of nano alumina was dried and dispersed in 140mL of toluene and ultrasonically treated for 20min; 6g of 3-isocyanate propyltrimethoxysilane was added to 4mL of deionized water for pre-hydrolysis for 30min to form a silanol intermediate. The silanol intermediate was then added dropwise to the nano alumina suspension, 1mL of triethylamine was added, and the mixture was stirred at 80℃ for 5h. The product was filtered, washed three times with anhydrous acetone, and dried to obtain pretreated alumina.

[0075] (2) Disperse 10g of pretreated alumina into 180mL of DMF, sonicate for 20min, add 2.4g of benzotriazole under nitrogen atmosphere, stir and react at 55℃ for 3h, filter, wash and dry the product to obtain the intermediate;

[0076] (3) Add 30g of polytetrafluoroethylene powder to 500mL of 5mmol / L sodium hydroxide solution, stir and react at 1MPa and 200℃ for 10h, centrifuge the product, neutralize it with dilute hydrochloric acid, wash it with deionized water until neutral, and dry it to obtain hydroxylated polytetrafluoroethylene.

[0077] (4) 460g of intermediate and 1140g of hydroxylated polytetrafluoroethylene were added to 4500g of ethanol and 1200g of deionized water and dispersed to obtain pre-dispersed alumina; 2000g of curing agent T31, 100g of leveling agent BYK-323, 300g of thickener BYK-410, 300g of film-forming aid diethanol ether, and 300g of defoamer BYK-052 were added to 10000g of bisphenol A epoxy resin in sequence and stirred evenly to obtain resin base material; the pre-dispersed alumina was added to the resin base material and stirred evenly to obtain modified coating; the modified coating was applied evenly to the surface of the substrate layer by impregnation method, pre-cured at 90℃ for 2h, and fully cured at 130℃ for 2h to obtain inner lining layer; then the substrate stainless steel plate was hydraulically formed to obtain the corrugated pipe.

[0078] A polytetrafluoroethylene (PTFE) compensator with good corrosion resistance, comprising a bellows and connecting flanges and end flanges located at both ends of the bellows, wherein the bellows consists of an inner lining layer and a base material layer, the base material layer being stainless steel; the bellows is prepared by the following method steps:

[0079] (1) 10g of nano alumina was dried and dispersed in 140mL of toluene and ultrasonically treated for 20min; 6g of 3-isocyanate propyltrimethoxysilane was added to 4mL of deionized water for pre-hydrolysis for 30min to form a silanol intermediate. The silanol intermediate was then added dropwise to the nano alumina suspension, 1mL of triethylamine was added, and the mixture was stirred at 80℃ for 5h. The product was filtered, washed three times with anhydrous acetone, and dried to obtain pretreated alumina.

[0080] (2) 1290g of pretreated alumina and 310g of benzotriazole were added to 4500g of ethanol and 1200g of deionized water and dispersed to obtain pre-dispersed alumina; 2000g of curing agent T31, 100g of leveling agent BYK-323, 300g of thickener BYK-410, 300g of film-forming aid diethanol ether, and 300g of defoamer BYK-052 were added to 10000g of bisphenol A epoxy resin in sequence and stirred evenly to obtain resin base material; the pre-dispersed alumina was added to the resin base material and stirred evenly to obtain modified coating; the modified coating was applied evenly to the surface of the substrate layer by impregnation method, pre-cured at 90℃ for 2h, and fully cured at 130℃ for 2h to obtain inner lining layer; then the substrate stainless steel plate was hydraulically formed to obtain the corrugated pipe.

[0081] The modified coatings prepared in Examples 1-4 and Comparative Examples 1-2 were subjected to performance tests. Referring to GB / T 9286-2021 "Paints and Varnishes - Cross-cut Test", the coatings were sprayed onto a steel plate with dimensions of 100mm × 100mm × 1mm, with a coating thickness controlled at 100μm, and then cured. On the prepared coating surface, a cross-cut tester was used to penetrate the coating with uniform pressure, creating 10 × 10 1mm × 1mm squares. Then, 25mm wide 3M 600 tape was applied to the marked areas, pressing the tape firmly with a finger to ensure full contact with the coating. After 30 seconds, the tape was quickly peeled off at a 90° angle. The degree of coating peeling within the squares was observed, and the adhesion grade was divided into 0-5 levels. Grade 0 indicates no coating peeling and the best adhesion; Grade 5 indicates a peeling area greater than 65% and the worst adhesion. The results are shown in Table 1.

[0082] The abrasion resistance was tested according to the standard GB / T 1768-2006 "Determination of abrasion resistance of paints and varnishes - Rotary rubber wheel method", with a test value of 1 kg / 1000 r and a CS-17 wheel. The average value of 10 tests was recorded in Table 1.

[0083] Referring to GB / T 1865-2009 "Artificial Weathering and Artificial Radiation Exposure to Filtered Xenon Arc Radiation for Paints and Varnishes", the coating was sprayed onto a steel plate with dimensions of 150mm × 70mm × 1mm, with a coating thickness controlled at 100μm, and then cured. The sample was placed in a xenon arc lamp aging test chamber, with the irradiance set at 0.55W / (m²·nm) (340nm), black panel temperature at 65℃, relative humidity at 50%, and a test cycle of 1000h. The color difference ΔE before and after the test was measured using a colorimeter to evaluate the weather resistance. The results are shown in Table 1.

[0084] The corrosion resistance of the sample coating in chemical reagents was tested in accordance with GB 9274-1988 "Determination of resistance to liquid media for paints and varnishes". Four chemical reagents, namely 10% sulfuric acid, 10% sodium hydroxide, toluene, and methyl ethyl ketone, were selected as immersion media. After immersion for 240 hours, the coating was tested for leakage (i.e., whether the coating was damaged) and observed for phenomena such as loss of gloss, blistering, and peeling.

[0085] The corrosion resistance of the samples in neutral salt spray was tested in accordance with GB / T 1771-2007 "Determination of resistance to neutral salt spray of paints and varnishes". The instrument used was the Q-Fog circulating salt spray corrosion test chamber. The test conditions were: 5% sodium chloride solution as electrolyte, spray pressure of 8 psi, ambient temperature of 35℃. The sample was generally placed at a 15° angle in the salt spray chamber. After 240 hours, the blistering, rusting and other corrosion phenomena of the sample were recorded.

[0086] Table 1. Coating performance test results

[0087] Example 1 Example 2 Example 3 Example 4 Comparative Example 1 Comparative Example 2 Adhesion rating 0 0 0 0 1 0 Abrasion resistance (mg) 13.4 14.1 14.3 14.9 25.8 20.5 Weather resistance (ΔE) 1.2 1.3 1.4 1.6 2.4 2.1 Corrosion resistant (10% sulfuric acid) No change in appearance; adhesion level 0 No change in appearance; adhesion level 0 No change in appearance; adhesion level 0 No change in appearance; adhesion level 0 No change in appearance; adhesion level 0 Bubbling, turning white Corrosion resistant (10% sodium hydroxide) No change in appearance; adhesion level 0 No change in appearance; adhesion level 0 No change in appearance; adhesion level 0 No change in appearance; adhesion level 0 No change in appearance; adhesion level 0 Bubbling, turning white Corrosion resistant (toluene) No change in appearance; adhesion level 0 No change in appearance; adhesion level 0 No change in appearance; adhesion level 0 No change in appearance; adhesion level 0 Bubbling, turning white Cracking, bubbling, whitening, peeling Corrosion resistant (methyl ethyl ketone) No change in appearance; adhesion level 0 No change in appearance; adhesion level 0 No change in appearance; adhesion level 0 No change in appearance; adhesion level 0 Bubbling, turning white Cracking, bubbling, whitening, peeling Corrosion resistant (neutral salt spray) No change in appearance; adhesion level 0 No change in appearance; adhesion level 0 No change in appearance; adhesion level 0 No change in appearance; adhesion level 0 No change in appearance; adhesion level 0 Bubbling, turning white

[0088] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A polytetrafluoroethylene compensator having excellent corrosion resistance, characterized by comprising a polytetrafluoroethylene tube having a wall thickness of 0.1 to 0.3 mm. The compensator is composed of a bellows and end flanges at both ends of the bellows, the bellows is composed of an inner liner and a base material layer, and the base material layer is stainless steel; The bellows is prepared by the following method steps: (1) dispersing nano-alumina dried to remove moisture into toluene, and ultrasonic treatment; adding 3-isocyanate propyl trimethoxysilane into deionized water to pre-hydrolyze to form a silanol intermediate, and then adding the silanol intermediate into a nano-alumina suspension dropwise, adding triethylamine, stirring and reacting, filtering, washing and drying the product to obtain pre-treated alumina; (2) dispersing the pre-treated alumina into DMF, ultrasonic treatment, adding benzotriazole under a nitrogen atmosphere, stirring and reacting, filtering, washing and drying the product to obtain an intermediate; (3) adding polytetrafluoroethylene powder into a sodium hydroxide solution, stirring and reacting, centrifuging, washing and drying the product to obtain hydroxylated polytetrafluoroethylene; (4) dispersing the intermediate into THF, adding hydroxylated polytetrafluoroethylene, ultrasonic treatment, stirring and reacting under a nitrogen atmosphere, centrifuging, washing and drying the product to obtain modified nano-alumina; (5) taking mass as a measurement standard, dispersing 10-16 parts of modified nano-alumina into 30-45 parts of ethanol and 6-12 parts of deionized water to obtain pre-dispersed alumina; adding curing agent 8-20 parts, leveling agent 0.4-1 part, thickening agent 1-3 parts, film-forming aid 1-3 parts and defoaming agent 1-3 parts into 100 parts of bisphenol A type epoxy resin in sequence, stirring uniformly to obtain a resin base; adding the pre-dispersed alumina into the resin base, stirring uniformly to obtain modified paint; The modified paint is uniformly attached to the surface of the base material layer by spraying or dipping method, and the inner liner is obtained after curing, and then the base stainless steel plate is hydroformed to obtain the bellows.

2. The compensator of claim 1, wherein, In step (1), the amount ratio of nano-alumina, toluene, 3-isocyanate propyl trimethoxysilane, deionized water and triethylamine is 10g:120-150mL:3-6g:2-4mL:0.4-1mL.

3. The compensator of claim 1, wherein, In step (1), the ultrasonic treatment is 10-30min; the pre-hydrolysis is 20-40min; the stirring and reaction condition is stirring and reacting at 65-80℃ for 5-8h; the product is washed with anhydrous acetone for 2-4 times.

4. The compensator of claim 1, wherein, In step (2), the amount ratio of pre-treated alumina, DMF and benzotriazole is 10g:150-200mL:1.2-2.4g.

5. The compensator of claim 1, wherein, In step (2), the ultrasonic treatment is 10-30min; the stirring and reaction condition is stirring and reacting at 40-55℃ for 3-6h.

6. The compensator of claim 1, wherein, In step (3), the amount ratio of polytetrafluoroethylene powder and sodium hydroxide solution is 30g:400-600mL; the concentration of the sodium hydroxide solution is 4-6mmol / L; the stirring and reaction condition is stirring and reacting at 0.8-1.2MPa and 160-200℃ for 10-16h; the product is neutralized with dilute hydrochloric acid, and then washed with deionized water until neutral.

7. The compensator of claim 1, wherein, In step (4), the amount ratio of the intermediate, THF and hydroxylated polytetrafluoroethylene is 10g:300-500mL:12-24g.

8. The compensator of claim 1, wherein, In step (4), the ultrasonic treatment is for 1-2 h; the stirring reaction condition is stirring reaction at 50-65 °C for 10-16 h.

9. The compensator of claim 1, wherein, In step (5), the curing condition is pre-curing at 80-100 °C for 1-3 h and full curing at 120-140 °C for 1-3 h.

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