Anti-microbial adhesion surface treatment process for PP-RCT marine pipeline

Abstract

The invention relates to the technical field of pipeline surface treatment, in particular to an antimicrobial adhesion surface treatment process for a PP-RCT marine pipeline, which comprises the following steps: pipeline pretreatment: sequentially performing deionized water flushing, drying, alkali washing, neutral flushing and secondary drying on the PP-RCT marine pipeline; plasma treatment: placing the pretreated pipeline in plasma treatment equipment, vacuumizing, introducing argon, and carrying out plasma treatment under specific power and time; antibacterial agent loading is conducted, specifically, the pipeline subjected to plasma treatment is soaked in an antibacterial agent solution containing nano-silver particles, chitosan and polyethylene glycol-polycaprolactone segmented copolymer, and antibacterial agent loading is completed after adsorption, washing and drying are conducted; and surface graft polymerization: putting the pipeline loaded with the antibacterial agent into a graft monomer solution containing dimethylaminoethyl methacrylate, acrylic acid and an initiator, carrying out graft polymerization reaction by adopting a step-by-step heating mode under the protection of nitrogen, and washing and drying to finish the treatment.

Description

Technical Field

[0001] The present invention relates to the technical field of pipeline surface treatment, in particular to an anti-microbial adhesion surface treatment process for PP-RCT marine pipelines. Background Art

[0002] PP-RCT pipes, or highly crystalline, impact-resistant random copolymer polypropylene pipes, are increasingly used in marine applications due to their excellent chemical resistance, high strength-to-weight ratio, superior fatigue resistance, and favorable processing properties. However, the marine environment is complex, and seawater is rich in a variety of microorganisms. Over long-term use, PP-RCT pipes are susceptible to microbial attachment, forming biofilms. This microbial attachment not only affects the pipe's water delivery efficiency and increases energy consumption, but can also lead to corrosion, shortening its service life and compromising the safe operation of the vessel.

[0003] Currently, there are a variety of treatment methods for preventing microbial adhesion in pipelines. Some methods achieve antimicrobial effects by adding antimicrobial agents to the pipeline material. However, this approach may have problems such as antimicrobial migration and dissolution, resulting in poor durability of the antimicrobial effect and potential harm to the environment. Other surface treatment technologies, such as physical coating, can reduce microbial adhesion to a certain extent, but the adhesion and durability of the coating need to be improved. Under the long-term erosion and vibration of the marine environment, the coating easily falls off and loses its antimicrobial adhesion function. Therefore, the development of an efficient, long-lasting, and environmentally friendly PP-RCT marine pipeline antimicrobial adhesion surface treatment process is of great practical significance. Summary of the Invention

[0004] The present invention aims to provide an antimicrobial surface treatment process for PP-RCT marine pipes. The PP-RCT marine pipes treated by this process can significantly reduce the adhesion of microorganisms and have good antimicrobial properties, while ensuring that the original performance of the pipes is not affected. The treatment process is simple and environmentally friendly, and the treated surface has good durability.

[0005] To achieve the above object, the present invention provides the following technical solution: a surface treatment process for antimicrobial adhesion of PP-RCT marine pipes, comprising the following steps:

[0006] S1: Pipeline pretreatment: The PP-RCT marine pipeline is sequentially rinsed with deionized water, dried, alkaline washed, neutral rinsed and dried again;

[0007] S2: Plasma treatment: The pre-treated pipe is placed in a plasma treatment device, evacuated and then introduced with argon gas, and plasma treatment is performed at a specific power and time;

[0008] S3: Antimicrobial loading: The plasma-treated pipes were immersed in an antimicrobial solution containing nanosilver particles, chitosan, and polyethylene glycol-polycaprolactone block copolymer (PEG-PCL). The antimicrobial loading was completed after adsorption, rinsing, and drying.

[0009] S4: Surface grafting polymerization: The pipe loaded with the antibacterial agent is placed in a grafting monomer solution containing dimethylaminoethyl methacrylate (DMAEMA), acrylic acid (AA) and initiator. The grafting polymerization reaction is carried out in a step-by-step heating method under nitrogen protection. The treatment is completed after rinsing and drying.

[0010] Preferably, in the pipeline pretreatment, the drying temperature is 60-80°C, the first drying time is 2-4 hours, and the second drying time is 1-2 hours; the alkali washing adopts a sodium hydroxide solution with a concentration of 5-10%, and soaks at 40-60°C for 15-30 minutes.

[0011] Preferably, during the plasma treatment, the device is evacuated to a pressure of 1-5 Pa, and after argon is introduced, the pressure in the device is stabilized at 10-30 Pa, the plasma power is 100-300 W, and the treatment time is 5-15 minutes.

[0012] Preferably, in the antibacterial solution, the mass ratio of nanosilver particles to chitosan is 1:5-10, and the particle size of the nanosilver particles is 20-50 nm; the solvent of the antibacterial solution is an acetic acid solution with a mass fraction of 2-5%, and the mass fraction of polyethylene glycol-polycaprolactone block copolymer (PEG-PCL) in the antibacterial solution is 0.5-1%.

[0013] Preferably, in the antimicrobial agent loading, the immersion temperature of the pipe in the antimicrobial agent solution is room temperature, the immersion time is 2-4 hours, the drying temperature is 40-60° C., and the drying time is 1-2 hours.

[0014] Preferably, in the grafting monomer solution, the molar ratio of dimethylaminoethyl methacrylate (DMAEMA) to acrylic acid is 3-5:1, and the solution concentration is 10-20%; the initiator is potassium persulfate, and its addition amount is 0.5-1% of the total weight of the monomers.

[0015] Preferably, the step-by-step heating method of the surface graft polymerization is: first react at 60-65°C for 1-2 hours, then react at 70-75°C for 1-2 hours, and finally react at 75-80°C for 1-2 hours; the drying temperature is 60-80°C, and the drying time is 2-4 hours.

[0016] Preferably, the antibacterial agent solution is prepared by ultrasonic dispersion for 30-60 minutes; and the graft polymerization reaction is carried out in a constant temperature water bath.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] 1. The antimicrobial surface treatment process for PP-RCT marine pipelines uses plasma treatment to introduce a large number of active groups onto the pipeline surface, improving the loading stability of the antimicrobial agent and enabling nanosilver particles and chitosan to adhere evenly and firmly to the surface. Nanosilver, with its broad-spectrum antimicrobial properties, can destroy microbial cell membranes and inhibit their enzyme activity, while chitosan interferes with microbial metabolism through cationic adsorption. The killing rate of common microorganisms in the marine environment, such as Escherichia coli, Staphylococcus aureus, Pseudomonas aeruginosa, and algae, suggests that the polymer brush layer formed by surface graft polymerization has a steric hindrance effect, which can physically block the initial attachment of microorganisms and reduce the possibility of biofilm formation.

[0019] 2. The antimicrobial surface treatment process of the PP-RCT marine pipe uses nano-silver particles with a particle size of 20-50nm, excellent biocompatibility, and a loading of only 0.01-0.05g / m 2 , far below environmental standards. Chitosan, a natural polysaccharide, is biodegradable and will not accumulate in the marine environment. The entire treatment process eliminates the use of toxic and hazardous chemicals such as formaldehyde and heavy metals. Simply neutralizing the wastewater allows it to meet discharge standards, avoiding secondary pollution to the ship's ecology and the marine environment. The treated pipes release no toxic substances during use, meeting the International Maritime Organization's (IMO) environmental requirements for marine materials.

[0020] 3. This antimicrobial surface treatment process for PP-RCT marine pipelines controls the concentration and time of the alkaline wash during pipeline pretreatment within a reasonable range, removing only micron-level surface contaminants and a weak boundary layer without damaging the pipeline matrix. Both plasma treatment and graft polymerization reactions are performed under mild conditions, avoiding damage to the PP-RCT material structure caused by high temperature and high pressure. The post-treatment changes in tensile strength, flexural strength, and impact toughness of the treated pipelines are less than 5% compared to pre-treatment levels, meeting the mechanical property requirements for marine pipelines (GB / T19472.2-2019). Key properties such as the pipeline's chemical corrosion resistance and thermal conductivity remain stable, ensuring its safety and reliability when transporting media such as seawater and fuel oil. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0022] Figure 1 This is a schematic diagram of the surface microstructure of the PP-RCT marine pipeline after treatment according to the present invention. DETAILED DESCRIPTION

[0023] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0024] See also Figure 1 The present invention provides a technical solution: a surface treatment process for antimicrobial adhesion of PP-RCT marine pipes, comprising the following steps:

[0025] S1: Pipeline preprocessing:

[0026] Rinse the PP-RCT marine pipe with deionized water to remove dust, oil and other impurities on the surface, then dry it in an oven at 60-80°C for 2-4 hours. Place the dried pipe in a 5-10% sodium hydroxide solution at 40-60°C for 15-30 minutes for alkaline washing to remove organic pollutants on the pipe surface and roughen the surface to enhance the adhesion of the subsequent treatment layer to the pipe substrate. After alkaline washing, rinse the pipe with plenty of deionized water until the pH value of the rinse water is neutral, and then dry it again in an oven at 60-80°C for 1-2 hours.

[0027] S2: Plasma treatment:

[0028] The pretreated PP-RCT pipe is placed in a plasma treatment device, evacuated to a pressure of 1-5 Pa, and argon is introduced as a working gas to stabilize the pressure in the device at 10-30 Pa. The plasma power is set to 100-300 W, and the treatment time is 5-15 minutes. Through plasma treatment, active groups are introduced on the surface of the pipe to further improve the surface activity;

[0029] S3: Antimicrobial loading:

[0030] Adding nanosilver particles and chitosan in a mass ratio of 1:5-10 to a 2-5% mass fraction acetic acid solution, and ultrasonically dispersing for 30-60 minutes to uniformly disperse the nanosilver particles and chitosan in the solution to obtain an antibacterial agent solution, wherein the particle size of the nanosilver particles is 20-50 nm;

[0031] S4: Construction of antibacterial agent slow-release system: 0.5-1% mass fraction of polyethylene glycol-poly (caprolactone) block copolymer (PEG-PCL) is added to the antibacterial agent solution, which is uniformly mixed into the antibacterial agent solution by ultrasonic dispersion. The copolymer has temperature responsiveness, and its molecular chain structure changes within the temperature range of the marine pipeline. When microorganisms begin to adhere and secrete metabolites to raise the local microenvironment temperature, the structure of PEG-PCL promotes the slow release of the antibacterial agent, realizes the on-demand release of the antibacterial agent, and prolongs the antibacterial duration;

[0032] S5: The pipeline treated by plasma is soaked in the above antibacterial agent solution containing PEG-PCL for 2-4 hours at room temperature, so that the antibacterial agent is fully adsorbed on the surface of the pipeline. Then the pipeline is taken out and the surface is gently rinsed with deionized water to remove the unadsorbed antibacterial agent. Then the pipeline is dried in an oven at 40-60℃ for 1-2 hours.

[0033] S6: Surface graft polymerization:

[0034] Preparation of graft monomer solution: dimethylaminoethyl methacrylate (DMAEMA) and acrylic acid (AA) are added to deionized water in a molar ratio of 3-5:1 to prepare a graft monomer solution with a concentration of 10-20%, and 0.5-1% of initiator potassium persulfate is added thereto and stirred uniformly.

[0035] S7: Gradient graft polymerization control: during the graft polymerization process, the reaction is carried out in a stepwise heating manner. First, the temperature is raised to 60-65℃ for 1-2 hours to make the monomer initially graft on the surface of the pipeline to form a thin layer. Then the temperature is raised to 70-75℃ for 1-2 hours to promote further grafting of the monomer and increase the thickness of the polymer brush layer. Finally, the temperature is raised to 75-80℃ for 1-2 hours to make the surface grafted polymer chain segments more regularly arranged. Through this gradient heating method, a gradient structure polymer brush layer is formed from the surface of the pipeline to the outer layer, with gradually decreasing crosslinking density and gradually increasing hydrophilicity.

[0036] S8: The pipeline loaded with antibacterial agent is placed in the graft monomer solution and reacted in a constant temperature water bath under nitrogen protection for 3-6 hours according to the above gradient heating method, so that the monomer grafts on the surface of the pipeline to form a polymer brush layer with antibacterial and antifouling properties. After the reaction is completed, the pipeline is taken out and rinsed with a large amount of deionized water to remove the unreacted monomer and polymer on the surface. Then the pipeline is dried in an oven at 60-80℃ for 2-4 hours.

[0037] Example 1

[0038] Pipeline pretreatment:

[0039] The PP-RCT marine pipe was rinsed with deionized water and then dried in an oven at 60 °C for 4 h.

[0040] Prepare a 5% sodium hydroxide solution and soak the dried pipes in it at 40°C for 30 minutes for alkaline cleaning. After alkaline cleaning, rinse the pipes with plenty of deionized water until the pH of the rinse water is neutral, then dry them in a 60°C oven for 2 hours.

[0041] Plasma treatment:

[0042] Place the pretreated PP-RCT pipe in the plasma treatment equipment and evacuate to a pressure of 1 Pa. Introduce argon gas to stabilize the pressure in the equipment at 10 Pa, set the plasma power to 100 W, and the treatment time to 15 minutes.

[0043] Antimicrobial Loading:

[0044] 0.1 g of silver nanoparticles (particle size 20-50 nm) and 0.5 g of chitosan were weighed and added to 100 mL of 2% acetic acid solution, and then 0.5 g of polyethylene glycol-polycaprolactone block copolymer (PEG-PCL) was added and ultrasonically dispersed for 60 minutes to obtain an antibacterial agent solution.

[0045] The plasma-treated pipes were immersed in the antimicrobial solution at room temperature for 4 hours, then taken out and gently rinsed with deionized water, and then dried in an oven at 40°C for 2 hours.

[0046] Surface graft polymerization:

[0047] 15 g of dimethylaminoethyl methacrylate (DMAEMA) and 3 g of acrylic acid (AA) were weighed and added to 100 mL of deionized water, and then 0.15 g of potassium persulfate was added and stirred evenly to prepare a grafting monomer solution.

[0048] The antimicrobial-loaded pipe was placed in the grafted monomer solution and, under nitrogen, reacted in a 60°C water bath for two hours. The temperature was then raised to 70°C for two hours, and finally to 75°C for two hours. After the reaction, the pipe was removed and rinsed with plenty of deionized water, then dried in a 60°C oven for four hours.

[0049] Example 2

[0050] Pipeline preprocessing:

[0051] The PP-RCT marine pipe was rinsed with deionized water and then dried in an oven at 80°C for 2 hours.

[0052] The pipes were alkaline cleaned with 10% sodium hydroxide solution at 60°C for 15 minutes. After alkaline cleaning, they were rinsed with deionized water until neutral and then dried in an oven at 80°C for 1 hour.

[0053] Plasma treatment:

[0054] Place the pipe into the plasma treatment equipment and evacuate it to a pressure of 5 Pa.

[0055] Argon gas was introduced to stabilize the pressure at 30 Pa, the plasma power was set to 300 W, and the treatment time was 5 minutes.

[0056] Antimicrobial Loading:

[0057] 0.1 g of silver nanoparticles and 1 g of chitosan were added to 100 mL of 5% acetic acid solution, and 1 g of polyethylene glycol-polycaprolactone block copolymer (PEG-PCL) was added, and ultrasonic dispersion was performed for 30 minutes to prepare an antibacterial agent solution.

[0058] The plasma-treated pipes were immersed in the antibacterial solution at room temperature for 2 hours, taken out, rinsed, and dried in an oven at 60°C for 1 hour.

[0059] Surface graft polymerization:

[0060] 20 g of dimethylaminoethyl methacrylate (DMAEMA) and 4 g of acrylic acid (AA) were dissolved in 100 mL of deionized water, and 0.24 g of potassium persulfate was added to prepare a grafting monomer solution.

[0061] Place the antimicrobial-loaded pipe in the grafting monomer solution. Under nitrogen protection, first react in a 65°C constant-temperature water bath for 1 hour, then raise the temperature to 75°C for 1 hour, and finally raise the temperature to 80°C for 1 hour. After the reaction, rinse the pipe and dry it in an 80°C oven for 2 hours.

[0062] Example 3

[0063] Pipeline preprocessing:

[0064] Rinse the PP-RCT marine pipe with deionized water and dry it in an oven at 70 °C for 3 h.

[0065] Use 8% sodium hydroxide solution to alkaline wash the pipeline at 50℃ for 20 minutes. After rinsing until neutral, dry it in an oven at 70℃ for 1.5 hours.

[0066] Plasma treatment:

[0067] Place the pipe into the plasma equipment and evacuate to 3 Pa.

[0068] Argon was introduced to bring the pressure to 20 Pa, the power was set to 200 W, and the treatment was carried out for 10 minutes.

[0069] Antimicrobial Loading:

[0070] 0.1 g of silver nanoparticles and 0.8 g of chitosan were added to 100 mL of 3% acetic acid solution, and 0.8 g of polyethylene glycol-polycaprolactone block copolymer (PEG-PCL) was added, and ultrasonic dispersion was performed for 45 minutes to obtain an antibacterial agent solution.

[0071] The plasma-treated pipes were immersed in the antimicrobial solution at room temperature for 3 hours, rinsed, and then dried in an oven at 50°C for 1.5 hours.

[0072] Surface graft polymerization:

[0073] 18 g of dimethylaminoethyl methacrylate (DMAEMA) and 3.6 g of acrylic acid (AA) were weighed, added to 100 mL of deionized water, and then added with 0.21 g of potassium persulfate to prepare a grafting monomer solution.

[0074] Place the antimicrobial-loaded pipe in the grafting monomer solution and, under nitrogen, react in a 62°C water bath for 1.5 hours. Then, heat to 72°C for 1.5 hours, and finally to 78°C for 1.5 hours. After the reaction, rinse and dry in a 70°C oven for 3 hours.

[0075] Comparative Example 1

[0076] A PP-RCT marine pipe without any surface treatment was used as comparative example 1, and a microbial attachment test was directly performed.

[0077] Comparative Example 2

[0078] Only the PP-RCT marine pipeline was subjected to the pipeline pretreatment step (same as the pipeline pretreatment in Example 1) and then the microbial attachment test was performed.

[0079] Comparative Example 3

[0080] The PP-RCT marine pipeline was subjected to pipeline pretreatment and plasma treatment (same as the corresponding steps in Example 1), but without the antimicrobial agent loading and surface graft polymerization steps, and then a microbial attachment test was performed.

[0081] Comparative Example 4

[0082] The original technical solution was used to treat the PP-RCT marine pipe, that is, the antibacterial agent solution did not contain PEG-PCL, and the surface graft polymerization was carried out at a constant temperature (60° C.) for 6 hours. The other steps were the same as in Example 1, and then relevant performance tests were performed.

[0083] Performance testing:

[0084] Microbial Adhesion Test: Pipe samples from Examples 1-3 and Comparative Examples 1-4 were placed in simulated seawater containing a mixture of Escherichia coli, Staphylococcus aureus, Pseudomonas aeruginosa, and marine algae. After immersion for 7 days, the samples were removed and the number of microorganisms adhering to the pipe surfaces was determined using plate counts and microscopic observation. The results are shown in the following table:

[0085] sample <![CDATA[微生物附着量(个 / cm 2 )]]> Comparative Example 1 <![CDATA[5.0×10 5 ]]> Comparative Example 2 <![CDATA[4.5×10 5 ]]> Comparative Example 3 <![CDATA[3.0×10 5 ]]> Example 1 8.0 x 10 5 ]] Example 2 7.0 x 10 5 ]]> Example 3 <![CDATA[7.5×10 5 ]]>

[0086] As can be seen from the data in the table, the amount of microbial attachment to the pipes treated with the surface treatment process after adding the innovative points of the present invention (Examples 1-3) is significantly lower than that of the untreated pipe (Comparative Example 1), the pipe only partially treated (Comparative Example 2, Comparative Example 3), and the pipe treated with the original technical solution (Comparative Example 4), indicating that the surface treatment process after adding the innovative points can more significantly reduce the attachment of microorganisms on the surface of PP-RCT marine pipes.

[0087] Antibacterial durability testing: Pipe samples from Example 1 and Comparative Example 4 were placed in simulated seawater and their antibacterial efficacy was regularly measured, recording the time it took for the efficacy to drop to 80% of its initial level. The results showed that Example 1 had an antibacterial durability of 5.5 years, while Comparative Example 4 had an antibacterial durability of 3 years, demonstrating that the construction of the sustained-release antibacterial system effectively extended the antibacterial durability.

[0088] Adhesion testing: Adhesion testing was conducted on the pipe surface coatings (polymer brush layers formed by graft polymerization) treated in Examples 1-3 using the crosshatch method. According to GB / T9286-1998, 100 1mm x 1mm squares were scratched on the pipe surface using a crosshatch cutter. The surface was then taped and quickly peeled off. The coating shedding within the gridded areas was observed, and the adhesion grade was assessed. The results showed that all Examples 1-3 achieved an adhesion grade of 0, indicating strong adhesion between the grafted polymer brush layers and the pipe substrate, meeting the requirements for use in marine environments.

[0089] Mechanical Properties: The tensile and flexural strengths of the PP-RCT marine pipes from Examples 1-3 were tested using a universal material testing machine before and after treatment. Sample preparation and testing were performed in accordance with relevant national standards. Each sample was tested five times, and the average value was calculated. The test results are shown in the following table:

[0090]

[0091] As can be seen from the data in the table, the tensile strength and flexural strength of the pipe treated with the surface treatment process of the present invention are both within 5% compared to those before treatment. This indicates that the surface treatment process does not significantly affect the mechanical properties of the PP-RCT pipe and can ensure the normal use of the pipe in a marine environment.

[0092] It should be noted that, in this document, relational terms such as first and second, etc., are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "comprises," "comprising," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or device comprising a series of elements includes not only those elements, but also other elements not explicitly listed, or elements inherent to such process, method, article, or device. In the absence of further limitations, an element defined by the phrase "comprising a..." does not exclude the presence of additional identical elements in the process, method, article, or device comprising the element.

[0093] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A process for treating PP-RCT marine pipes for preventing microbial adhesion, characterized in that: The following steps are involved: S1: Pipeline pretreatment: The PP-RCT marine pipeline is sequentially rinsed with deionized water, dried, alkaline washed, neutral rinsed and dried again; S2: Plasma treatment: The pre-treated pipe is placed in a plasma treatment device, evacuated and then introduced with argon gas, and plasma treatment is performed at a specific power and time; S3: Antimicrobial loading: The plasma-treated pipes were immersed in an antimicrobial solution containing nanosilver particles, chitosan, and polyethylene glycol-polycaprolactone block copolymer (PEG-PCL). The antimicrobial loading was completed after adsorption, rinsing, and drying. S4: Surface grafting polymerization: The pipe loaded with the antibacterial agent is placed in a grafting monomer solution containing dimethylaminoethyl methacrylate (DMAEMA), acrylic acid (AA) and initiator. The grafting polymerization reaction is carried out in a step-by-step heating method under nitrogen protection. The treatment is completed after rinsing and drying.

2. The antimicrobial surface treatment process for PP-RCT marine pipes according to claim 1, characterized in that: In the pipeline pretreatment, the drying temperature is 60-80° C., the first drying time is 2-4 hours, and the second drying time is 1-2 hours; the alkali washing adopts a sodium hydroxide solution with a concentration of 5-10%, and the immersion time is 15-30 minutes at 40-60° C.

3. The antimicrobial surface treatment process for PP-RCT marine pipes according to claim 1, characterized in that: During the plasma treatment, the device is evacuated to a pressure of 1-5 Pa, and after argon gas is introduced, the pressure in the device is stabilized at 10-30 Pa. The plasma power is 100-300 W, and the treatment time is 5-15 minutes.

4. The antimicrobial surface treatment process for PP-RCT marine pipes according to claim 1, characterized in that: In the antibacterial solution, the mass ratio of nanosilver particles to chitosan is 1:5-10, and the particle size of the nanosilver particles is 20-50 nm. The solvent of the antibacterial solution is an acetic acid solution with a mass fraction of 2-5%, and the mass fraction of polyethylene glycol-polycaprolactone block copolymer (PEG-PCL) in the antibacterial solution is 0.5-1%.

5. The antimicrobial surface treatment process for PP-RCT marine pipes according to claim 1, characterized in that: In the antimicrobial agent loading, the pipe is immersed in the antimicrobial agent solution at room temperature for 2-4 hours, and the drying temperature is 40-60° C. for 1-2 hours.

6. The antimicrobial surface treatment process for PP-RCT marine pipes according to claim 1, characterized in that: In the grafting monomer solution, the molar ratio of dimethylaminoethyl methacrylate (DMAEMA) to acrylic acid is 3-5:1, and the solution concentration is 10-20%. The initiator is potassium persulfate, and its addition amount is 0.5-1% of the total weight of the monomers.

7. The antimicrobial surface treatment process for PP-RCT marine pipes according to claim 1, characterized in that: The step-by-step heating method of the surface graft polymerization is: first react at 60-65°C for 1-2 hours, then react at 70-75°C for 1-2 hours, and finally react at 75-80°C for 1-2 hours; the drying temperature is 60-80°C, and the drying time is 2-4 hours.

8. The antimicrobial surface treatment process for PP-RCT marine pipes according to claim 1, characterized in that: The antibacterial agent solution is prepared by ultrasonic dispersion for 30-60 minutes; and the graft polymerization reaction is carried out in a constant temperature water bath.

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