High-density polyethylene composite material for corrugated pipes and its preparation method

Abstract

This invention relates to the field of polymer compound composition technology, and more particularly to a high-density polyethylene composite material for corrugated pipes and its preparation method. The invention involves modifying graphene oxide and then hybridizing it with carboxylated carbon nanotubes to obtain a modified graphene-carbon nanotube hybrid. This hybrid is then compounded with grafted polyethylene to obtain modified polyethylene. After mixing with other additives, the polyethylene is extruded and granulated to obtain the composite material. The modified graphene-carbon nanotube hybrid reduces agglomeration, ensures interfacial bonding between graphene, carbon nanotubes, and the matrix, and significantly improves the mechanical properties and thermal stability of the composite material.

Description

Technical Field

[0001] This invention relates to the field of polymer composition technology, and more particularly to a high-density polyethylene composite material for corrugated pipes and its preparation method. Background Technology

[0002] Corrugated pipes are a new type of drainage plastic pipe made from high-density polyethylene (HDPE) with certain necessary additives, through extrusion molding. They have a corrugated outer layer and a smooth inner layer, and are mainly used for sewage and rainwater discharge from urban buildings. Permeable corrugated pipes are made by perforating grooves and wrapping the outside of the pipe with needle-punched geotextile. Based on the type, corrugated pipes can be divided into single-wall permeable corrugated pipes and double-wall permeable corrugated pipes. Currently, they can be made from virgin high-density polyethylene (HDPE) or by directly adding inorganic substances and waste plastics.

[0003] High-density polyethylene (HDPE), a common thermoplastic resin, is widely used in various fields such as packaging materials, automotive trim, pipes, and wires and cables due to its cost-effectiveness, good processability, strong moisture resistance, and excellent chemical stability. However, HDPE materials also have some limitations, such as a tendency to generate static electricity, relatively low tensile strength, and low thermal and electrical conductivity, which limit its application in certain specific fields. To overcome these limitations, researchers have significantly improved the mechanical properties, thermal stability, and flame retardant properties of HDPE composites through modification, such as adding fillers like carbon nanotubes, plant fibers, minerals, and polymers. For example, by adding fillers such as plant fibers, minerals, carbon nanotubes, and polymers to HDPE, the prepared composites showed significant improvements in tensile strength, flexural strength, and impact resistance. In addition, the application of flame retardants such as Si-PDA halogen-free flame retardants, focused piperazine phosphate (PAPP), and bio-based lignin can increase the thermal stability of the material and improve its flame retardant properties. These modification methods not only improve the performance of HDPE but also expand its application range, enabling it to better meet the needs of modern industry.

[0004] CN117603524A discloses a high-mechanical-performance high-density polyethylene composite material, its preparation method, and its applications, belonging to the technical field of modified polyethylene composite materials. This composite material uses high-density polyethylene and ethylene-octene copolymer as the matrix resin, and glass fibers of specific sizes, ultra-high molecular weight polyethylene fibers, and carbon nanotubes as composite reinforcing fillers to construct a three-dimensional network structure. While improving the impact toughness and weather resistance of high-density polyethylene, its mechanical strength is further enhanced, meeting the requirements for use in steel wire mesh reinforced plastic-polyethylene composite pipes under harsh environmental conditions.

[0005] CN102850628B relates to a polyethylene pipe using carbon nanotubes as a reinforcing phase, comprising the following components in parts by weight: 70-100 parts of high-density polyethylene; 1-10 parts of carbon nanotubes. The carbon nanotube-reinforced polyethylene pipe of this invention has the following characteristics: 1) excellent flexibility and formability; 2) the carbon nanotubes are uniformly distributed and oriented in the polyethylene matrix, firmly bonded to the matrix, and do not dissipate or lose due to friction, resulting in good durability; 3) it does not conflict with other additives, exhibits good synergy, and improves the antistatic properties, mechanical strength, and thermal aging properties of the composite material.

[0006] Carbon nanotube (CNT) modification is one of the effective ways to improve the properties of HDPE. The carbon in CNTs is mainly in the form of sp... 2 Predominantly hybridized with overlapping p orbitals, CNTs possess large delocalized π bonds and band structures, exhibiting significant conjugation effects, thus granting them excellent electrical properties. Furthermore, CNTs possess nanoscale dimensions and extremely high aspect ratios (100–1000). However, CNTs exhibit poor dispersibility in composite materials and weak interaction with the polymer matrix; therefore, addressing this deficiency has become a key research focus. Summary of the Invention

[0007] In view of the above-mentioned deficiencies of the prior art, the technical problem to be solved by the present invention is to provide a high-density polyethylene composite material for corrugated pipes and a method for preparing the same.

[0008] Polyethylene's applications are limited due to its low strength, hardness, and poor thermal stability. Inorganic materials such as carbon nanotubes have been used for blending and modification to improve various defects in polymers; however, the tendency of carbon nanotubes to agglomerate and their poor compatibility with polymers limit the performance improvement achieved by this modification. Therefore, this invention provides a modified graphene-carbon nanotube hybrid. This hybrid is obtained by modifying graphene oxide and then combining it with carbon nanotubes. The hybrid significantly increases compatibility with polyethylene, thereby inhibiting agglomeration. Furthermore, the hybrid can chemically bond with modified polyethylene, further improving its interfacial bonding with the polymer. The high strength, high hardness, and excellent thermal stability of carbon nanotubes and graphene themselves enhance the mechanical properties and thermal stability of the polyethylene composite. This invention uses proprietary recycled materials to prepare high-density polyethylene, achieving energy conservation, emission reduction, pollution reduction, and cost reduction.

[0009] To achieve the above objectives, the present invention provides a method for preparing high-density polyethylene composite material for corrugated pipes, comprising the following steps:

[0010] S1. Benzoyl peroxide is dissolved in white oil and added to high-density polyethylene. After stirring evenly, maleic anhydride is added and stirred evenly again. Grafted polyethylene is obtained by melt grafting and granulation.

[0011] S2. Add graphene oxide to water and heat to 40-50°C to disperse for 1-2 hours. Then add dicyclohexylcarbodiimide, 4-dimethylaminopyridine and 1,3-propanediamine. After ultrasonic dispersion, heat to 90-100°C and stir for 4-8 hours. Filter and wash the residue with N,N-dimethylformamide and dry to obtain modified graphene.

[0012] S3. Add carboxylated carbon nanotubes and modified graphene to water, disperse evenly, then add 2,3-diaminosuccinic acid, dicyclohexylcarbodiimide, and 4-dimethylaminopyridine. Heat to 50-70℃ and stir for 4-8 hours. After filtration and drying, obtain the modified graphene-carbon nanotube hybrid.

[0013] S4. Modified polyethylene is obtained by mixing modified graphene-carbon nanotube hybrid with grafted polyethylene and then kneading it. Modified polyethylene is then mixed with toughening agent, lubricant, antioxidant and UV inhibitor, and then extruded and granulated to obtain the final product.

[0014] Furthermore, the mass ratio of the high-density polyethylene to maleic anhydride, benzoyl peroxide, and white oil is 100:0.5-1:0.05-0.1:0.1-0.5.

[0015] Furthermore, in step S2, the mass ratio of graphene oxide to dicyclohexylcarbodiimide, 4-dimethylaminopyridine, and 1,3-propanediamine is 1:2-4:0.1-0.5:10-15.

[0016] Furthermore, in step S3, the mass ratio of carboxylated carbon nanotubes to modified graphene, 2,3-diaminosuccinic acid, dicyclohexylcarbodiimide, and 4-dimethylaminopyridine is 1:1~2:2~3:2~4:0.1~0.5.

[0017] Furthermore, the toughening agent is one of ethylene-octene copolymer and ethylene-propylene copolymer.

[0018] Furthermore, the lubricant is one of PE wax, EVA wax, calcium stearate, and ethylene distearate amine.

[0019] Furthermore, the antioxidant is one of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], octadecyl β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, tris-(2,4-di-tert-butylphenyl)phosphite, and dioctadecyl thiodipropionate.

[0020] Furthermore, the UV protectant is one of UV-327, UV-531, and UV-326.

[0021] Furthermore, the mass ratio of the grafted polyethylene to the modified graphene-carbon nanotube hybrid, toughening agent, lubricant, antioxidant, and UV stabilizer is 100:0.5~2:2~5:0.3~0.8:0.1~0.5:0.2~0.7.

[0022] The present invention also provides a high-density polyethylene composite material for corrugated pipes, which is prepared by the above method.

[0023] The beneficial effects of this invention are:

[0024] Compared with existing technologies, this invention modifies graphene oxide and then hybridizes it with carboxylated carbon nanotubes to obtain a modified graphene-carbon nanotube hybrid. This modified graphene-carbon nanotube hybrid is then compounded with grafted polyethylene to obtain modified polyethylene. Finally, after mixing with other additives, it is extruded and granulated to obtain the composite material. The modified graphene-carbon nanotube hybrid reduces agglomeration, ensures interfacial bonding between graphene, carbon nanotubes, and the matrix, and significantly improves the mechanical properties and thermal stability of the composite material. Detailed Implementation

[0025] High-density polyethylene (HDPE) is made by mixing three materials in a mass ratio of 35:55:10: small hollow plastic sheets, mainly used for plastic bottles for daily necessities; large hollow plastic sheets, mainly used for plastic buckets; and low-density polyethylene (LDPE) film recycled granules, mainly made from recycled industrial packaging film. The tensile strength is ≥20MPa.

[0026] Graphene oxide, particle size: 1–10 μm.

[0027] Carboxylated carbon nanotubes, length: 5-15 μm, model: KR-130, KERI Nano.

[0028] Ethylene-propylene copolymer, POE8010, Dow Chemical, USA.

[0029] UV-327, CAS No.: 3864-99-1, Foshan Jieheng New Materials.

[0030] Example 1

[0031] A method for preparing a high-density polyethylene composite material for corrugated pipes includes the following steps, in parts by weight:

[0032] S1. Dissolve 0.06 parts of benzoyl peroxide in 0.3 parts of white oil and add it to 100 parts of high-density polyethylene. Stir evenly and then add 0.8 parts of maleic anhydride. Continue to stir evenly and then obtain grafted polyethylene by melt grafting and granulation.

[0033] S2. Add 1 part of graphene oxide to 100 parts of water, heat to 45°C and disperse for 2 hours. Then add 3 parts of dicyclohexylcarbodiimide, 0.3 parts of 4-dimethylaminopyridine and 12 parts of 1,3-propanediamine. After ultrasonic dispersion, heat to 95°C and stir for 8 hours. Filter, wash the residue with N,N-dimethylformamide and dry to obtain modified graphene.

[0034] S3. Add 1 part of carboxylated carbon nanotubes and 1 part of modified graphene to 100 parts of water, disperse evenly, then add 2 parts of 2,3-diaminosuccinic acid, 4 parts of dicyclohexylcarbodiimide, and 0.4 parts of 4-dimethylaminopyridine. Heat to 60°C and stir for 8 hours. After filtration and drying, obtain the modified graphene-carbon nanotube hybrid.

[0035] S4. Mix 1.5 parts of modified graphene-carbon nanotube hybrid with 100 parts of grafted polyethylene and then knead to obtain modified polyethylene. Mix the modified polyethylene with 4 parts of ethylene-propylene copolymer, 0.5 parts of calcium stearate, 0.6 parts of dioctadecyl thiodipropionate and 0.6 parts of UV-327, and then extrude and granulate to obtain the final product.

[0036] Example 2

[0037] It is basically the same as Example 1, except that the weight of the modified graphene-carbon nanotube hybrid is 1 part.

[0038] Example 3

[0039] It is basically the same as Example 1, except that the weight of the modified graphene-carbon nanotube hybrid is 2 parts.

[0040] Compare with Example 1

[0041] A method for preparing a high-density polyethylene composite material for corrugated pipes includes the following steps, in parts by weight:

[0042] S1. Dissolve 0.06 parts of benzoyl peroxide in 0.3 parts of white oil and add it to 100 parts of high-density polyethylene. Stir evenly and then add 0.8 parts of maleic anhydride. Continue to stir evenly and then obtain grafted polyethylene by melt grafting and granulation.

[0043] S2. 1.5 parts of graphene oxide and 100 parts of grafted polyethylene are mixed and then kneaded to obtain modified polyethylene. The modified polyethylene is then mixed with 4 parts of ethylene-propylene copolymer, 0.5 parts of calcium stearate, 0.6 parts of dioctadecyl thiodipropionate and 0.6 parts of UV-327, and then extruded and granulated to obtain the final product.

[0044] Compare with Example 2

[0045] A method for preparing a high-density polyethylene composite material for corrugated pipes includes the following steps, in parts by weight:

[0046] S1. Dissolve 0.06 parts of benzoyl peroxide in 0.3 parts of white oil and add it to 100 parts of high-density polyethylene. Stir evenly and then add 0.8 parts of maleic anhydride. Continue to stir evenly and then obtain grafted polyethylene by melt grafting and granulation.

[0047] S2. 1.5 parts of carboxylated carbon nanotubes and 100 parts of grafted polyethylene are mixed and then kneaded to obtain modified polyethylene. The modified polyethylene is then mixed with 4 parts of ethylene-propylene copolymer, 0.5 parts of calcium stearate, 0.6 parts of dioctadecyl thiodipropionate and 0.6 parts of UV-327, and then extruded and granulated to obtain the final product.

[0048] Compare with Example 3

[0049] A method for preparing a high-density polyethylene composite material for corrugated pipes includes the following steps, in parts by weight:

[0050] S1. Dissolve 0.06 parts of benzoyl peroxide in 0.3 parts of white oil and add it to 100 parts of high-density polyethylene. Stir evenly and then add 0.8 parts of maleic anhydride. Continue to stir evenly and then obtain grafted polyethylene by melt grafting and granulation.

[0051] S2. Mix 100 parts of grafted polyethylene with 4 parts of ethylene-propylene copolymer, 0.5 parts of calcium stearate, 0.6 parts of dioctadecyl thiodipropionate and 0.6 parts of UV-327, and then granulate by extrusion.

[0052] Test Example 1

[0053] The composite materials in the examples and control examples were tested according to GB / T 1040.2-2022 "Determination of tensile properties of plastics - Part 2: Test conditions for molded and extruded plastics" and the methods therein. The tensile speed was 50 mm / min, and the tensile strength and elongation at break were recorded. The test was repeated 5 times and the average value was taken. The specific results are shown in Table 1.

[0054] Table 1. Test Results of Mechanical Properties of High-Density Polyethylene Composite Materials for Corrugated Pipes

[0055] Experimental protocol Tensile strength / MPa Elongation at break / % Example 1 28.53 600.12 Example 2 26.22 567.82 Example 3 24.15 550.24 Compare with Example 1 23.23 535.68 Compare with Example 2 23.86 540.26 Compare with Example 3 22.16 520.24

[0056] Test Example 2

[0057] The composite materials in the examples and control examples were tested according to the method in GB / T 19466.6-2009 "Differential Scanning Calorimetry (DSC) for Plastics - Part 6: Determination of Oxidation Induction Time (Isothermal OIT) and Oxidation Induction Temperature (Dynamic OIT)", and their oxidation induction time was recorded. The specific results are shown in Table 2.

[0058] Table 2. Thermal stability test results of high-density polyethylene composite materials for corrugated pipes.

[0059]

[0060]

[0061] As shown in Table 1, the addition of graphene oxide, carboxylated carbon nanotubes, or modified graphene-carbon nanotube hybrids significantly improved the tensile strength and elongation at break of the composite material. This is because carbon nanotubes and graphene have high aspect ratios and large surface areas, which helps them form an effective load transfer mechanism in the polymer matrix, improving the mechanical properties of the composite material. Furthermore, carbon fibers themselves possess high strength. Example 1 showed a better improvement in mechanical properties compared to Control Examples 1-2. This is likely because, compared to graphene oxide and carboxylated carbon nanotubes, the modified graphene-carbon nanotube hybrid not only inhibited the agglomeration of the raw materials themselves, but its covalent bonding also enhanced the interfacial bonding with polyethylene. Moreover, the mixing process allowed the modified graphene-carbon nanotube hybrid to covalently bond with the grafted polyethylene, further enhancing the interfacial bonding with polyethylene, thus resulting in the most significant improvement in mechanical properties. A comparison of Examples 1-3 shows that Example 1 exhibited the best mechanical properties, indicating that there is an optimal addition amount of the modified graphene-carbon nanotube hybrid.

[0062] GB / T 19466.6-2009, "Differential Scanning Calorimetry (DSC) for Plastics - Part 6: Determination of Oxidation Induction Time (Isothermal OIT) and Oxidation Induction Temperature (Dynamic OIT)," specifies the method for determining the OIT of polymeric materials using DSC, applicable to the evaluation of polyolefin materials and other plastics. Differential scanning calorimetry (DSC) is a thermal analysis technique that studies the thermal properties of materials by measuring the difference in heat flow between a sample and a reference. In the evaluation of the thermal stability of plastic materials, DSC can be used to determine the oxidation induction time (OIT), which includes the determination of isothermal OIT and dynamic OIT. Isothermal OIT is the time interval from the initial introduction of oxygen or air at a constant temperature until the sample undergoes an oxidation reaction. The determination of OIT is crucial for evaluating the heat and oxidation resistance of materials, as it reflects the stability of the material to the effects of heat and oxygen during storage, processing, and use. As can be seen from Table 2, the thermal stability of the examples was significantly improved compared to the control examples. The thermal stability of control examples 1-2 was also better than that of control example 3. This is because graphene and carbon nanotubes have extremely high thermal conductivity. Adding these materials to a matrix such as polyethylene can construct an efficient heat conduction network, thereby improving the heat transfer efficiency and thermal stability of the composite material. Compared to control examples 1-2, the modified graphene-carbon nanotube hybrid and grafted polyethylene undergo covalent bonding after mixing in the examples. This can inhibit the molecular chain movement of polyethylene when heated to a certain extent, thereby further improving the thermal stability.

[0063] The preferred embodiments of the present invention have been described in detail above. It should be understood that those skilled in the art can make numerous modifications and variations based on the concept of the present invention without creative effort. Therefore, all technical solutions that can be obtained by those skilled in the art based on the concept of the present invention through logical analysis, reasoning, or limited experimentation on the basis of existing technology should be within the scope of protection defined by the claims.

Claims

1. A method for preparing a high-density polyethylene composite material for corrugated pipes, characterized in that, Includes the following steps: S1. Benzoyl peroxide is dissolved in white oil and added to high-density polyethylene. After stirring evenly, maleic anhydride is added and stirred evenly again. Grafted polyethylene is obtained by melt grafting and granulation. The mass ratio of high-density polyethylene to maleic anhydride, benzoyl peroxide and white oil is 100:0.5~1:0.05~0.1:0.1~0.

5. S2. Add graphene oxide to water and heat to 40-50℃ to disperse for 1-2 hours. Then add dicyclohexylcarbodiimide, 4-dimethylaminopyridine and 1,3-propanediamine. The mass ratio of graphene oxide to dicyclohexylcarbodiimide, 4-dimethylaminopyridine and 1,3-propanediamine is 1:2-4:0.1-0.5:10-15. After ultrasonic dispersion, heat to 90-100℃ and stir for 4-8 hours. Filter, wash the residue with N,N-dimethylformamide and dry to obtain modified graphene. S3. Add carboxylated carbon nanotubes and modified graphene to water, disperse evenly, and then add 2,3-diaminosuccinic acid, dicyclohexylcarbodiimide, and 4-dimethylaminopyridine. The mass ratio of carboxylated carbon nanotubes to modified graphene, 2,3-diaminosuccinic acid, dicyclohexylcarbodiimide, and 4-dimethylaminopyridine is 1:1~2:2~3:2~4:0.1~0.

5. Heat to 50~70℃ and stir for 4~8 hours. After filtration and drying, the modified graphene-carbon nanotube hybrid is obtained. S4. Modified polyethylene is obtained by mixing modified graphene-carbon nanotube hybrid with grafted polyethylene and then kneading. Modified polyethylene is then mixed with toughening agent, lubricant, antioxidant and UV stabilizer and then extruded and granulated. The mass ratio of grafted polyethylene to modified graphene-carbon nanotube hybrid, toughening agent, lubricant, antioxidant and UV stabilizer is 100:0.5~2:2~5:0.3~0.8:0.1~0.5:0.2~0.

7.

2. The method for preparing high-density polyethylene composite material for corrugated pipes as described in claim 1, characterized in that, The toughening agent is one of ethylene-octene copolymer and ethylene-propylene copolymer.

3. The method for preparing high-density polyethylene composite material for corrugated pipes as described in claim 1, characterized in that, The lubricant is one of PE wax, EVA wax, calcium stearate, and ethylene distearate amine.

4. The method for preparing high-density polyethylene composite material for corrugated pipes as described in claim 1, characterized in that, The antioxidant is one of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], octadecyl β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, tris-(2,4-di-tert-butylphenyl)phosphite, and dioctadecyl thiodipropionate.

5. The method for preparing high-density polyethylene composite material for corrugated pipes as described in claim 1, characterized in that, The UV protectant is one of UV-327, UV-531, and UV-326.

6. A high-density polyethylene composite material for corrugated pipes, characterized in that, Prepared by the method described in any one of claims 1 to 5.

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