Polymer blends for anti-aging PE pipes used in municipal engineering

Abstract

The present invention relates to the field of polymer material synthesis technology, specifically a polymer blend for anti-aging PE pipes for municipal engineering, which contains 40-60 parts of LLDPE as a basis, 20-30 parts of new anti-aging functional polymers, with hindered amines, self-repairing disulfide bond structures, 5-10 parts of nano-titanium dioxide / graphene composite fillers and loaded silver nanoparticles, with plasticizers, compounded antioxidants, microcapsule light stabilizers, etc., and each component synergistically improves performance. The blend of the present invention is significantly anti-aging, can self-repair microcracks, enhances mechanical and antibacterial properties, can monitor aging damage, has good processability, reduces maintenance, extends the service life of PE pipes in municipal engineering, and ensures the stable operation of municipal systems.

Description

Technical Field

[0001] The invention relates to the technical field of polymer material synthesis, in particular to a polymer blend for anti-aging PE pipes used in municipal engineering. Background Art

[0002] In municipal engineering, PE pipes are widely used in water supply, drainage, and gas transmission systems due to their excellent corrosion resistance, flexibility, and ease of processing. However, over long-term use, ordinary PE pipes are susceptible to aging due to factors such as ultraviolet rays, temperature fluctuations, chemical corrosion, and mechanical stress. This significantly shortens their service life, increases maintenance costs, and poses safety risks.

[0003] Ultraviolet radiation is a major factor contributing to the aging of PE pipes. Under UV radiation, the polymer molecules in ordinary PE pipes are susceptible to photooxidation, generating free radicals that trigger molecular chain breakage and crosslinking, making the pipe brittle and reducing its strength. Traditional anti-aging measures often involve adding conventional light stabilizers, but these are limited in effectiveness and fail to provide long-term protection against UV damage. For example, in some outdoor municipal water supply pipeline projects, PE pipes treated with conventional light stabilizers show visible signs of aging after only two to three years, with surface cracks and reduced compressive strength.

[0004] Temperature fluctuations also significantly impact PE pipes. In cold regions, low winter temperatures make PE pipes hard and brittle, significantly reducing their impact resistance and making them susceptible to rupture due to internal water pressure or external impact. In hot regions, high summer temperatures accelerate molecular chain movement, promote oxidation reactions, and exacerbate the aging process. Currently, most PE pipes on the market are unable to adapt to wide temperature ranges and cannot meet the long-term and stable use requirements of municipal projects in diverse climates.

[0005] Chemical corrosion also threatens the lifespan of PE pipes. Acids and alkalis in municipal sewage, heavy metal ions in industrial wastewater, and corrosive organic matter, upon contact with PE pipes, penetrate and diffuse into the pipes, reacting chemically with the polymer molecules, destroying their structure and degrading their performance. In some municipal drainage projects in industrial areas, chemical corrosion can cause serious leakage in ordinary PE pipes within a year of use.

[0006] Mechanical stresses such as stretching, bending, and squeezing during municipal construction, as well as the long-term internal and soil pressures on the pipes, can cause microcracks within PE pipes. These cracks gradually expand under long-term stress, ultimately leading to pipe failure. Traditional PE pipes lack effective self-repair mechanisms, and once microcracks appear, they age faster. Summary of the Invention

[0007] (1) Technical problems solved

[0008] In view of the deficiencies of the prior art, the present invention provides a polymer blend for anti-aging PE pipes for municipal engineering.

[0009] (2) Technical solution

[0010] The polymer blend for anti-aging PE pipes used in municipal engineering is composed of the following components: 40-60 parts of linear low-density polyethylene (LLDPE); 20-30 parts of a new anti-aging functional polymer. The polymer is copolymerized with vinyltrimethoxysilane and 4-acryloyloxy-2,2,6,6-tetramethylpiperidine, and a disulfide bond with self-repairing function is introduced into the main chain of the molecule. Its chemical structure is as follows:

[0011] ;

[0012] The disulfide bond is introduced using dimethyl 3,3'-dithiodipropionate as a raw material, and the 4-acryloyloxy-2,2,6,6-tetramethylpiperidine is synthesized using 4-methacryloyloxy-2,2,6,6-tetramethylpiperidine as a raw material through demethylation. The CAS number of the 4-methacryloyloxy-2,2,6,6-tetramethylpiperidine is 15051-46-4.

[0013] 5-10 parts of a nano-titanium dioxide / graphene composite filler, wherein the nano-titanium dioxide has a particle size of 20-50 nm and the graphene layer has a thickness of 1-2 nm, and the surface of the nano-titanium dioxide is further loaded with silver nanoparticles having photocatalytic and antibacterial functions; the nano-titanium dioxide and the graphene are composited using a surface-modified silane coupling agent, γ-aminopropyltriethoxysilane, wherein the siloxy group at one end of the silane coupling agent reacts with the hydroxyl group on the surface of the nano-titanium dioxide, and the amino group at the other end reacts with the oxygen-containing functional group on the surface of the graphene;

[0014] The plasticizer is 3-8 parts, and polypropylene adipate (PPA) is selected, and a hydroxyl group that can form a hydrogen bond with the polymer matrix is ​​introduced into its molecular structure; the antioxidant is 1-3 parts, and is composed of a main antioxidant tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid] pentaerythritol ester 1010 and an auxiliary antioxidant triphenyl phosphite (TPP) in a mass ratio of 2:1, and a metal ion chelating agent disodium ethylenediaminetetraacetic acid EDTA-2Na is added with a mass fraction of 0.1%-0.3%; the light stabilizer is 1-3 parts, and a new hindered amine light stabilizer di(2,2,6,6-tetramethyl-4-piperidinyl) sebacate is used, and it is microencapsulated, and the microcapsule wall material is biodegradable polylactic acid (PLA) with a particle size of 1-5μm.

[0015] Preferably, 0.5-1 parts of an intelligent color-changing indicator is also included; the indicator is an organic compound containing a spiropyran structure. When the PE pipe is severely aged or damaged, its molecular structure changes, resulting in a color change, which facilitates timely detection of problems with the PE pipe; through a specific synthesis process, it is evenly dispersed in the blend and has good compatibility with the polymer matrix.

[0016] Preferably, the method further includes adding carbon nanotubes with a mass fraction of 0.05%-0.1% during the preparation of the blend; these carbon nanotubes are surface carboxylated and can form a three-dimensional network structure with nano-titanium dioxide / graphene composite fillers and polymer matrix, further enhancing the mechanical properties and electrical conductivity of the blend, and can be used to monitor the stress and damage of pipelines in municipal engineering.

[0017] Preferably, the molar ratio of vinyltrimethoxysilane to 4-acryloyloxy-2,2,6,6-tetramethylpiperidine in the novel anti-aging functional polymer is 3:1-5:1; wherein the content of dynamic covalent disulfide bonds in the polymer is 0.5%-1.5%.

[0018] Preferably, in the nano-titanium dioxide / graphene composite filler, the mass ratio of nano-titanium dioxide to graphene is 2:1-3:1; and the loading amount of silver nanoparticles on the surface of the nano-titanium dioxide is 1%-3%.

[0019] Preferably, the number average molecular weight of the novel environmentally friendly polyester plasticizer polypropylene adipate is 2000-3000; and the content of hydroxyl groups introduced into its molecular structure is 0.5 mmol / g-1 mmol / g.

[0020] Preferably, a method for preparing the polymer blend for anti-aging PE pipes for municipal engineering comprises the following steps:

[0021] S1: Raw material pretreatment: Linear low-density polyethylene is dried at 80-100°C for 2-3 hours to remove moisture; nano-titanium dioxide / graphene composite filler is vacuum dried at 120-150°C for 3-4 hours to improve its dispersibility; carbon nanotubes are surface carboxylated by adding the carbon nanotubes to a mixed acid of concentrated sulfuric acid and concentrated nitric acid in a ratio of 3:1, stirring at 50-60°C for 2-3 hours, then washing with deionized water until neutral, and drying at 80-100°C for later use;

[0022] S2: Synthesis of a novel anti-aging functional polymer: Add appropriate amounts of vinyltrimethoxysilane, 4-acryloyloxy-2,2,6,6-tetramethylpiperidine, an initiator, and an organic solvent to a reactor, replace the air with nitrogen, raise the temperature to 70-80°C, and react for 4-6 hours. In the later stage of the reaction, a cross-linking agent containing a disulfide bond is added to copolymerize with dimethyl 3,3'-dithiodipropionate to synthesize a novel anti-aging functional polymer. After the reaction is completed, remove the organic solvent by vacuum distillation to obtain the product.

[0023] S3: Mixing and stirring: Add the dried linear low-density polyethylene, the synthesized new anti-aging functional polymer, the nano-titanium dioxide / graphene composite filler, the plasticizer, the compound antioxidant, the light stabilizer, the intelligent color change indicator and the carbon nanotubes into a high-speed mixer in proportion, and mix at a speed of 150-200 r / min for 10-15 minutes to ensure that the components are initially mixed evenly; during the mixing process, control the temperature at 40-50°C to prevent the materials from being degraded due to frictional heat;

[0024] S4: Melt blending: The preliminarily mixed materials are transferred to a twin-screw extruder, and the temperature of each section of the extruder is set to 160-200°C and the screw speed is set to 200-300r / min for melt blending; after sufficient shearing and mixing in the extruder, the materials are extruded and granulated to obtain polymer blend particles for anti-aging PE pipes used in municipal engineering.

[0025] Preferably, in step S2, the amount of the initiator azobisisobutyronitrile used is 0.5%-1% of the total mass of the monomers, the amount of the organic solvent toluene used is 1-2 times the total volume of the monomers; and the amount of the cross-linking agent containing a disulfide bond used is 0.5%-1% of the total mass of the monomers.

[0026] Preferably, in step S3, the mixing chamber of the high-speed mixer adopts a jacket structure, and the mixing temperature is controlled by circulating water; during the mixing process, ultrasonic assisted dispersion technology is adopted, with an ultrasonic frequency of 20-30kHz and a power of 100-200W to promote uniform dispersion of the components.

[0027] Preferably, the aspect ratio of the twin-screw extruder in step S4 is 30:1-40:1, which has a good mixing effect and ensures that the components are evenly dispersed in the blend; during the extrusion process, an online quality monitoring system is used to monitor the melt flow rate and density of the blend in real time to ensure stable product quality.

[0028] (3) Beneficial technical effects

[0029] Compared with the existing technology, the beneficial effects of the present invention are:

[0030] 1. The hindered amine groups in the novel anti-aging functional polymer efficiently capture free radicals, inhibiting molecular chain degradation. Dynamic covalent bonds enable self-repair of microcracks, significantly extending the service life of PE pipes. Accelerated aging tests show that PE pipes using the blends of this invention age significantly longer than conventional PE pipes.

[0031] 2. The nano-titanium dioxide / graphene composite filler and loaded silver nanoparticles synergistically enhance mechanical properties, impart antimicrobial properties to the pipe, and reduce microbial corrosion, making it particularly suitable for environments such as sewage transportation. In simulated sewage environment testing, the amount of microbial adhesion on the pipe surface was significantly reduced compared to conventional pipes, while its compressive strength was improved.

[0032] 3. The plasticizer introduces hydrogen-bonding functional groups to improve processing fluidity without compromising anti-aging properties, ensuring a smooth production process and stable product quality. The compounded antioxidant and metal ion chelator work synergistically to effectively inhibit oxidation reactions, while the microencapsulated light stabilizer extends the duration of action, further enhancing the anti-aging effect.

[0033] 4. The addition of an intelligent color-changing indicator and carbon nanotubes gives PE pipes a self-monitoring function. When the pipe ages or is damaged, the indicator changes color, alerting maintenance. The three-dimensional network formed by the carbon nanotubes enhances mechanical and electrical properties, facilitating electrical monitoring of pipe stress and damage. Overall, the polymer blend of this invention comprehensively improves the performance of PE pipes in municipal engineering, reduces maintenance costs, and ensures the stable operation of municipal systems. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 This is a flow chart of the polymer blend for anti-aging PE pipes for municipal engineering proposed by the present invention;

[0035] Figure 2 is a line comparison chart of the tensile strength and the tensile strength retention rate after aging of the embodiment and the comparative example;

[0036] Figure 3 It is a bar chart comparing the antibacterial rates of the embodiment and the comparative example;

[0037] Figure 4 is a broken line comparison chart of the elongation at break of the embodiment and the comparative example;

[0038] Figure 5 This is the H NMR spectrum of dimethyl 3,3'-dithiodipropionate. DETAILED DESCRIPTION

[0039] according to Figures 1 to 5 , the specific implementation methods of the present invention are as follows: Example

[0040] Raw material preparation: 40 parts of linear low-density polyethylene (LLDPE); 20 parts of a new anti-aging functional polymer, wherein the molar ratio of vinyltrimethoxysilane to 4-acryloyloxy-2,2,6,6-tetramethylpiperidine is 3:1, and the content of dynamic covalent disulfide bonds is 0.5% (molar fraction); 5 parts of nano-titanium dioxide / graphene composite filler, the mass ratio of nano-titanium dioxide to graphene is 2:1, and the loading amount of silver nanoparticles is 1% (mass fraction); 3 parts of plasticizer, polypropylene adipate with a number average molecular weight of 200 0, hydroxyl content of 0.5mmol / g; 1 part of antioxidant, the main antioxidant tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate] pentaerythritol ester and the auxiliary antioxidant triphenyl phosphite in a mass ratio of 2:1, and 0.1% (mass fraction) of disodium ethylenediaminetetraacetate was added; 1 part of light stabilizer, which is microencapsulated di(2,2,6,6-tetramethyl-4-piperidinyl) sebacate, with a microcapsule particle size of 1μm; 0.5 part of intelligent color-changing indicator; 0.05 part of carbon nanotubes, which have been surface carboxylated.

[0041] Raw material pretreatment: LLDPE was dried at 80°C for 3 hours; nano-titanium dioxide / graphene composite filler was vacuum dried at 120°C for 4 hours; carbon nanotubes were added to mixed acid (concentrated sulfuric acid: concentrated nitric acid = 3:1), stirred and reacted at 50°C for 3 hours, then washed with deionized water until neutral, and dried at 80°C for use.

[0042] Synthesis of a new anti-aging functional polymer: Vinyltrimethoxysilane, 4-acryloyloxy-2,2,6,6-tetramethylpiperidine, initiator azobisisobutyronitrile (the amount is 0.5% of the total monomer mass) and organic solvent toluene (the amount is 1 times the total volume of the monomer) were added to a reactor. After nitrogen was introduced to replace the air, the temperature was raised to 70°C and the reaction was carried out for 6 hours. In the later stage of the reaction, a cross-linking agent containing a disulfide bond (the amount is 0.5% of the total monomer mass) was added for copolymerization. After the reaction was completed, the organic solvent was removed by reduced pressure distillation to obtain the product.

[0043] Mixing and stirring: Add the above pretreated raw materials into a high-speed mixer in proportion, mix at a speed of 150r / min for 15 minutes, control the temperature at 40°C during the mixing process, and use ultrasonic assisted dispersion technology with an ultrasonic frequency of 20kHz and a power of 100W.

[0044] Melt blending: The preliminarily mixed materials are transferred to a twin-screw extruder, and the temperature of each section of the extruder is set to 160°C and the screw speed is set to 200r / min. Melt blending is performed and extrusion granulation is performed to obtain polymer blend particles for anti-aging PE pipes used in municipal engineering. Example

[0045] Raw material preparation: 50 parts of linear low-density polyethylene (LLDPE); 25 parts of new anti-aging functional polymer, the molar ratio of vinyltrimethoxysilane to 4-acryloyloxy-2,2,6,6-tetramethylpiperidine is 4:1, and the content of dynamic covalent disulfide bonds is 1% (molar fraction); 7 parts of nano-titanium dioxide / graphene composite filler, the mass ratio of nano-titanium dioxide to graphene is 2.5:1, and the loading amount of silver nanoparticles is 2% (mass fraction); 5 parts of plasticizer, The number average molecular weight of propylene glycol adipate is 2500, and the hydroxyl content is 0.75mmol / g; 2 parts of antioxidant, the mass ratio of primary antioxidant to auxiliary antioxidant is 2:1, and 0.2% (mass fraction) of disodium ethylenediaminetetraacetate is added; 2 parts of light stabilizer, microencapsulated di(2,2,6,6-tetramethyl-4-piperidinyl) sebacate, the microcapsule particle size is 3μm; 0.7 parts of intelligent color-changing indicator; 0.07 parts of carbon nanotubes, which have been surface carboxylated.

[0046] Raw material pretreatment: LLDPE was dried at 90° C. for 2.5 hours; the nano-titanium dioxide / graphene composite filler was vacuum dried at 135° C. for 3.5 hours; and the carbon nanotubes were carboxylated according to the method of Example 1.

[0047] Synthesis of new anti-aging functional polymers: The amount of initiator azobisisobutyronitrile used was 0.7% of the total mass of the monomers, the amount of organic solvent toluene used was 1.5 times the total volume of the monomers, the reaction was carried out at 75°C for 5 hours, and a disulfide bond crosslinker was added later (the amount was 0.7% of the total mass of the monomers).

[0048] Mixing and stirring: Mix at a speed of 175 r / min for 12 minutes, control the temperature at 45°C, the ultrasonic frequency at 25 kHz, and the power at 150 W.

[0049] Melt blending: The temperature of each section of the extruder was 180°C and the screw speed was 250 r / min. Example

[0050] Raw material preparation: 60 parts of linear low-density polyethylene (LLDPE); 30 parts of new anti-aging functional polymer, the molar ratio of vinyltrimethoxysilane to 4-acryloyloxy-2,2,6,6-tetramethylpiperidine is 5:1, and the content of dynamic covalent disulfide bonds is 1.5% (molar fraction); 10 parts of nano-titanium dioxide / graphene composite filler, the mass ratio of nano-titanium dioxide to graphene is 3:1, and the loading amount of silver nanoparticles is 3% (mass fraction); plasticizer 8 3 parts of antioxidants, with a main antioxidant and auxiliary antioxidant mass ratio of 2:1, and 0.3% (mass fraction) of disodium ethylenediaminetetraacetate added; 3 parts of light stabilizers, microencapsulated di(2,2,6,6-tetramethyl-4-piperidinyl) sebacate, with a microcapsule particle size of 5μm; 1 part of intelligent color-changing indicator; 0.1 parts of carbon nanotubes, which have been surface carboxylated.

[0051] Raw material pretreatment: LLDPE was dried at 100° C. for 2 hours; nano-titanium dioxide / graphene composite filler was vacuum dried at 150° C. for 3 hours; the carbon nanotube treatment method was the same as in Example 1.

[0052] Synthesis of new anti-aging functional polymers: The amount of initiator azobisisobutyronitrile is 1% of the total mass of the monomer, the amount of organic solvent toluene is 2 times the total volume of the monomer, the reaction is carried out at 80°C for 4 hours, and a disulfide bond crosslinker is added later (the amount is 1% of the total mass of the monomer).

[0053] Mixing and stirring: Mix at a speed of 200 r / min for 10 minutes, control the temperature at 50°C, the ultrasonic frequency at 30 kHz, and the power at 200 W.

[0054] Melt blending: the temperature of each section of the extruder was 200°C, and the screw speed was 300 r / min.

[0055] Comparative Example

[0056] The PE tube was manufactured using a conventional PE production method, using only linear low-density polyethylene (LLDPE) as the raw material, along with conventional light stabilizers and antioxidants. The new anti-aging functional polymer, nano-titanium dioxide / graphene composite filler, intelligent color-changing indicator, and carbon nanotubes, as described in this invention, were not added. The PE tube was produced using conventional mixing and melt extrusion processes.

[0057] The comparison of tensile strength and elongation at break of PE pipes in the embodiment and the comparative example is shown in the following table:

[0058] project Example 1 Example 2 Example 3 Comparative Example Tensile strength (MPa) 25 28 30 18 Elongation at break (%) 600 650 700 400

[0059] Table 1

[0060] Conclusion: This table clearly demonstrates that the Examples significantly outperform the Comparative Examples in terms of tensile strength and elongation at break. The tensile strength of the Examples ranges from 25 MPa to 30 MPa, while the Comparative Examples only achieve 18 MPa. The elongation at break ranges from 600% to 700% for the Examples, while the Comparative Examples achieve 400%. This demonstrates that PE pipes made from the polymer blends of this invention possess superior mechanical properties.

[0061] The comparison of the tensile strength retention rate and antibacterial rate of the PE pipes of the embodiment and the comparative example after aging is shown in the following table:

[0062] project Example 1 Example 2 Example 3 Comparative Example Tensile strength retention after aging (%) 85 90 92 60 Antibacterial rate (%) 80 85 90 20

[0063] Table 2

[0064] Conclusion: This table compares the tensile strength retention and antibacterial rate of PE pipes after aging in the Examples and Comparative Examples. The Examples achieved post-aging tensile strength retention rates exceeding 85% and antibacterial rates exceeding 80%, while the Comparative Example achieved a post-aging tensile strength retention rate of 60% and an antibacterial rate of only 20%. This demonstrates that the polymer blend of the present invention imparts superior anti-aging and antibacterial properties to PE pipes.

[0065] 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 polymer blend for anti-aging PE pipes for municipal engineering, characterized by: It is composed of the following components: 40-60 parts of linear low-density polyethylene (LLDPE); 20-30 parts of an anti-aging functional polymer. The polymer is copolymerized by vinyltrimethoxysilane and 4-acryloyloxy-2,2,6,6-tetramethylpiperidine, and a disulfide bond with self-repairing function is introduced into the main chain of the molecule. Its chemical structure is as follows: ； The disulfide bond is introduced using dimethyl 3,3'-dithiodipropionate as a raw material; 5-10 parts of a nano-titanium dioxide / graphene composite filler, wherein the nano-titanium dioxide has a particle size of 20-50 nm and the graphene layer has a thickness of 1-2 nm, and the surface of the nano-titanium dioxide is further loaded with silver nanoparticles having photocatalytic and antibacterial functions; the nano-titanium dioxide and the graphene are composited using a surface-modified silane coupling agent, γ-aminopropyltriethoxysilane, wherein the siloxy group at one end of the silane coupling agent reacts with the hydroxyl group on the surface of the nano-titanium dioxide, and the amino group at the other end reacts with the oxygen-containing functional group on the surface of the graphene; The plasticizer is 3-8 parts, and polypropylene adipate (PPA) is selected, and a hydroxyl group that can form a hydrogen bond with the polymer matrix is ​​introduced into its molecular structure; the antioxidant is 1-3 parts, and is composed of a main antioxidant tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid] pentaerythritol ester 1010 and an auxiliary antioxidant triphenyl phosphite (TPP) in a mass ratio of 2:1, and a metal ion chelating agent disodium ethylenediaminetetraacetic acid EDTA-2Na is added with a mass fraction of 0.1%-0.3%; the light stabilizer is 1-3 parts, and the hindered amine light stabilizer di(2,2,6,6-tetramethyl-4-piperidinyl) sebacate is used, and it is microencapsulated, and the microcapsule wall material is biodegradable polylactic acid (PLA) with a particle size of 1-5μm.

2. The polymer blend for anti-aging PE pipes for municipal engineering according to claim 1, characterized in that: It also includes 0.5-1 parts of an intelligent color-changing indicator; this indicator is an organic compound containing a spiropyran structure. When the PE pipe is severely aged or damaged, its molecular structure changes, resulting in a color change, making it easy to detect problems with the PE pipe in a timely manner; through a specific synthesis process, it is evenly dispersed in the blend and has good compatibility with the polymer matrix.

3. The polymer blend for anti-aging PE pipes for municipal engineering according to claim 1, characterized in that: It also includes adding carbon nanotubes with a mass fraction of 0.05%-0.1% during the preparation of the blend; these carbon nanotubes undergo surface carboxylation treatment and can form a three-dimensional network structure with nano-titanium dioxide / graphene composite fillers and polymer matrices, further enhancing the mechanical properties and electrical conductivity of the blend, and can be used to monitor the stress and damage of pipelines in municipal engineering.

4. The polymer blend for anti-aging PE pipes for municipal engineering according to claim 1, characterized in that: The molar ratio of vinyltrimethoxysilane to 4-acryloyloxy-2,2,6,6-tetramethylpiperidine in the anti-aging functional polymer is 3:1-5:1; and the content of dynamic covalent disulfide bonds in the polymer is 0.5%-1.5%.

5. The polymer blend for anti-aging PE pipes for municipal engineering according to claim 1, characterized in that: In the nano-titanium dioxide / graphene composite filler, the mass ratio of nano-titanium dioxide to graphene is 2:1-3:1; and the loading amount of silver nanoparticles on the surface of the nano-titanium dioxide is 1%-3%.

6. The polymer blend for anti-aging PE pipes for municipal engineering according to claim 1, characterized in that: The number average molecular weight of the environmentally friendly polyester plasticizer polypropylene adipate is 2000-3000; the content of hydroxyl groups introduced into its molecular structure is 0.5 mmol / g-1 mmol / g.

7. A method for preparing the polymer blend for anti-aging PE pipes for municipal engineering according to claim 1, characterized in that: The following steps are involved: S1: Raw material pretreatment: Linear low-density polyethylene is dried at 80-100°C for 2-3 hours to remove moisture; nano-titanium dioxide / graphene composite filler is vacuum dried at 120-150°C for 3-4 hours to improve its dispersibility; carbon nanotubes are surface carboxylated by adding the carbon nanotubes to a mixed acid of concentrated sulfuric acid and concentrated nitric acid in a ratio of 3:1, stirring at 50-60°C for 2-3 hours, then washing with deionized water until neutral, and drying at 80-100°C for later use; S2: Synthesis of anti-aging functional polymer: Add appropriate amounts of vinyltrimethoxysilane, 4-acryloyloxy-2,2,6,6-tetramethylpiperidine, initiator, and organic solvent to a reactor, replace the air with nitrogen, raise the temperature to 70-80°C, and react for 4-6 hours. In the later stage of the reaction, add dimethyl 3,3'-dithiodipropionate containing a disulfide bond for copolymerization to synthesize an anti-aging functional polymer. After the reaction is completed, remove the organic solvent by vacuum distillation to obtain the product. S3: Mixing and stirring: Add the dried linear low-density polyethylene, the synthesized anti-aging functional polymer, the nano-titanium dioxide / graphene composite filler, the plasticizer, the compound antioxidant, the light stabilizer, the intelligent color change indicator and the carbon nanotubes into a high-speed mixer in proportion, and mix at a speed of 150-200 r / min for 10-15 minutes to ensure that the components are initially mixed evenly; during the mixing process, control the temperature at 40-50°C to prevent the materials from being degraded due to frictional heat; S4: Melt blending: The preliminarily mixed materials are transferred to a twin-screw extruder, and the temperature of each section of the extruder is set to 160-200°C and the screw speed is set to 200-300r / min for melt blending; after sufficient shearing and mixing in the extruder, the materials are extruded and granulated to obtain polymer blend particles for anti-aging PE pipes used in municipal engineering.

8. The method according to claim 7, characterized in that In step S2, the amount of the initiator azobisisobutyronitrile used is 0.5%-1% of the total mass of the monomers, the amount of the organic solvent toluene used is 1-2 times the total volume of the monomers; and the amount of the cross-linking agent containing a disulfide bond used is 0.5%-1% of the total mass of the monomers.

9. The method according to claim 7, characterized in that In step S3, the mixing chamber of the high-speed mixer adopts a jacket structure, and the mixing temperature is controlled by circulating water. During the mixing process, ultrasonic-assisted dispersion technology is used with an ultrasonic frequency of 20-30kHz and a power of 100-200W to promote uniform dispersion of the components.

10. The method according to claim 7, characterized in that The aspect ratio of the twin-screw extruder in step S4 is 30:1-40:1, which has a good mixing effect and ensures that all components are evenly dispersed in the blend. During the extrusion process, an online quality monitoring system is used to monitor the melt flow rate and density of the blend in real time to ensure stable product quality.

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