A high-performance buried pipe and its preparation method

Abstract

The present invention relates to a high-performance buried pipe and a preparation method thereof, wherein the high-performance buried pipe comprises, from the inside out, a modified cross-linked polyethylene layer, a first modified hot-melt adhesive layer, an aluminum alloy layer, a second modified hot-melt adhesive layer, and a modified polyethylene layer. The first modified hot-melt adhesive layer and the second modified hot-melt adhesive layer are both made of polyethylene hot-melt adhesive doped with β-C3N4, the modified cross-linked polyethylene layer is made of cross-linked polyethylene doped with g-C3N4 composite glassy carbon, and the modified polyethylene layer is made of polyethylene doped with g-C3N4 composite glassy carbon. The high-performance buried pipe of the present invention has high strength, and the inner and outer walls are not easily corroded, the inner wall can remain smooth for a long time, the fluid resistance is small, the thermal conductivity is good, and the heat exchange efficiency is higher. The present invention solves the defects caused by doping g-C3N4 and glassy carbon alone by g-C3N4 composite glassy carbon. The g-C3N4 composite glassy carbon can be evenly dispersed inside the polyethylene and the cross-linked polyethylene, thereby improving the performance of the pipe.

Description

Technical Field

[0001] The invention relates to a high-performance buried pipe and a preparation method thereof, belonging to the technical field of ground source heat pumps. Background Art

[0002] The ground source heat pump system uses underground soil, groundwater or surface water as energy for heating, cooling or hot water production. Its working principle is similar to that of refrigerant cycle air conditioning, but the difference is that the heat and cold sources it uses are groundwater or ground sources.

[0003] At present, the materials of buried pipes used in ground source heat pumps are usually:

[0004] 1) PVC pipes

[0005] PVC pipes are the most commonly used buried pipe material in ground source heat pumps. They are cheap, durable, resistant to aging, and not easy to deform, but their service life is relatively short, generally 15-20 years.

[0006] 2) PE pipes

[0007] PE pipes have high corrosion resistance, pressure resistance and low temperature resistance, and their service life is generally more than 25 years.

[0008] 3) Aluminum-plastic composite pipes

[0009] Aluminum-plastic composite pipe is a new type of pipe that has high acid and alkali corrosion resistance, pressure resistance and high temperature resistance. It also has good thermal insulation and heat preservation properties, and its service life is more than 30 years.

[0010] Therefore, for underground pipes with high strength and corrosion resistance requirements, aluminum-plastic composite pipes are usually selected. The basic structure of aluminum-plastic composite pipes is five layers, namely plastic, hot melt adhesive, aluminum alloy, hot melt adhesive, and plastic from the inside out. However, existing aluminum-plastic composite pipes have the following defects:

[0011] The aluminum alloy sandwiched in the middle of the aluminum-plastic composite pipe is usually an aluminum foil layer or an aluminum strip layer. It is very thin but has a certain rigidity. If it is excessively deformed due to excessive external force during installation or use, or if it is subjected to severe underground water and soil impact, it will easily damage the aluminum foil layer or aluminum strip layer or crack it. In severe cases, it will cause water seepage and leakage in the pipeline.

[0012] Based on this, the present invention is proposed. Summary of the Invention

[0013] In view of the shortcomings of the existing technology, the present invention provides a high-performance buried pipe and a preparation method thereof. The specific technical solution is as follows:

[0014] A high-performance buried pipe, comprising, from the inside out, a modified cross-linked polyethylene layer, a first modified hot-melt adhesive layer, an aluminum alloy layer, a second modified hot-melt adhesive layer, and a modified polyethylene layer;

[0015] The first modified hot melt adhesive layer and the second modified hot melt adhesive layer are both made of polyethylene hot melt adhesive doped with β-C3N4, and the mass fraction of β-C3N4 in the polyethylene hot melt adhesive doped with β-C3N4 is 1.6% to 1.9%;

[0016] The modified cross-linked polyethylene layer is made of cross-linked polyethylene doped with g-C3N4 composite glassy carbon, and the mass fraction of the g-C3N4 composite glassy carbon doped in the cross-linked polyethylene doped with g-C3N4 composite glassy carbon is 7.5% to 9.5%;

[0017] The modified polyethylene layer is made of polyethylene doped with g-C3N4 composite glassy carbon, and the mass fraction of the g-C3N4 composite glassy carbon in the polyethylene doped with g-C3N4 composite glassy carbon is 5% to 6%.

[0018] As a further improvement, the mass fraction of the modified cross-linked polyethylene layer in the high-performance buried pipe is 20% to 25%, the mass fraction of the first modified hot-melt adhesive layer in the high-performance buried pipe is 3% to 5%, the mass fraction of the aluminum alloy layer in the high-performance buried pipe is 8% to 12%, and the mass fraction of the second modified hot-melt adhesive layer in the high-performance buried pipe is 3% to 5%.

[0019] As a further improvement, the mass fraction of the modified cross-linked polyethylene layer in the high-performance buried pipe is 21%, the mass fraction of the first modified hot-melt adhesive layer in the high-performance buried pipe is 3.5%, the mass fraction of the aluminum alloy layer in the high-performance buried pipe is 10%, the mass fraction of the second modified hot-melt adhesive layer in the high-performance buried pipe is 3.5%, and the mass fraction of the modified polyethylene layer in the high-performance buried pipe is 62%.

[0020] As a further improvement, the mass fraction of the modified cross-linked polyethylene layer in the high-performance buried pipe is 20%, the mass fraction of the first modified hot-melt adhesive layer in the high-performance buried pipe is 5%, the mass fraction of the aluminum alloy layer in the high-performance buried pipe is 12%, the mass fraction of the second modified hot-melt adhesive layer in the high-performance buried pipe is 5%, and the mass fraction of the modified polyethylene layer in the high-performance buried pipe is 58%.

[0021] As a further improvement, the mass fraction of the modified cross-linked polyethylene layer in the high-performance buried pipe is 25%, the mass fraction of the first modified hot-melt adhesive layer in the high-performance buried pipe is 3%, the mass fraction of the aluminum alloy layer in the high-performance buried pipe is 8%, the mass fraction of the second modified hot-melt adhesive layer in the high-performance buried pipe is 3%, and the mass fraction of the modified polyethylene layer in the high-performance buried pipe is 61%.

[0022] As a further improvement, the preparation method of the g-C3N4 composite glassy carbon comprises the following steps:

[0023] Pour glassy carbon, g-C3N4 powder and ethanol into a container and mix them, then place the container in an ultrasonic cleaner for ultrasonic dispersion in water, the power of the ultrasonic cleaner is 1250W, the molar ratio of glassy carbon to g-C3N4 powder in the container is 0.15:1, the particle size of the glassy carbon is less than or equal to 5μm, ultrasonicate for 1 to 2h, then place the container in a vacuum drying oven for drying, the drying temperature is 79 to 85°C, and after drying, the g-C3N4 composite glassy carbon is obtained.

[0024] As a further improvement, the method for preparing the high-performance buried pipe comprises the following steps:

[0025] The high-performance buried pipe is prepared by using an aluminum-plastic composite pipe extruder;

[0026] The modified cross-linked polyethylene layer is made by extruding cross-linked polyethylene doped with g-C3N4 composite glassy carbon as a raw material;

[0027] A first modified hot melt adhesive layer is extruded on the outer wall of the modified cross-linked polyethylene layer using polyethylene hot melt adhesive doped with β-C3N4 as a raw material to obtain a binary composite pipe unit;

[0028] Wrapping an aluminum alloy strip on the outer wall of a binary composite tube unit to obtain a ternary composite tube unit, wherein the aluminum alloy layer is made of the aluminum alloy strip;

[0029] A second modified hot melt adhesive layer is extruded on the outer wall of the ternary composite pipe unit using polyethylene hot melt adhesive doped with β-C3N4 as a raw material to obtain a quaternary composite pipe unit;

[0030] A modified polyethylene layer is extruded on the outer wall of a quaternary composite tube unit using polyethylene doped with g-C3N4 composite glassy carbon as a raw material;

[0031] After extrusion, the high-performance buried pipe is obtained after water cooling.

[0032] Beneficial effects of the present invention:

[0033] 1. The high-performance buried pipe of the present invention has high strength, the inner and outer walls are not easily corroded, the inner wall can remain smooth for a long time, the fluid resistance is small, the thermal conductivity is good, and the heat exchange efficiency is higher.

[0034] 2. The present invention solves the defects caused by doping g-C3N4 and glassy carbon separately by g-C3N4 composite glassy carbon. The g-C3N4 composite glassy carbon can be evenly dispersed inside polyethylene and cross-linked polyethylene, thereby improving the performance of the pipe.

[0035] 3. When the high-performance buried pipe of the present invention is buried deep underground, its impact resistance and pressure resistance and anti-seepage properties are effectively improved, which is particularly suitable for geothermal collection areas in deeper layers and with harsh geological environments. DETAILED DESCRIPTION

[0036] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0037] Example 1

[0038] The high-performance buried pipe comprises, from the inside out, a modified cross-linked polyethylene layer, a first modified hot-melt adhesive layer, an aluminum alloy layer, a second modified hot-melt adhesive layer, and a modified polyethylene layer;

[0039] The first modified hot melt adhesive layer and the second modified hot melt adhesive layer are both made of polyethylene hot melt adhesive doped with β-C3N4, and the mass fraction of β-C3N4 in the polyethylene hot melt adhesive doped with β-C3N4 is 1.6%;

[0040] The modified cross-linked polyethylene layer is made of cross-linked polyethylene doped with g-C3N4 composite glassy carbon, and the mass fraction of the g-C3N4 composite glassy carbon doped in the cross-linked polyethylene doped with g-C3N4 composite glassy carbon is 7.5%;

[0041] The modified polyethylene layer is made of polyethylene doped with g-C3N4 composite glassy carbon, and the mass fraction of the g-C3N4 composite glassy carbon doped in the polyethylene doped with g-C3N4 composite glassy carbon is 5%.

[0042] Among them, the mass fraction of the modified cross-linked polyethylene layer in the high-performance buried pipe is 21%, the mass fraction of the first modified hot melt adhesive layer in the high-performance buried pipe is 3.5%, the mass fraction of the aluminum alloy layer in the high-performance buried pipe is 10%, the mass fraction of the second modified hot melt adhesive layer in the high-performance buried pipe is 3.5%, and the mass fraction of the modified polyethylene layer in the high-performance buried pipe is 62%.

[0043] The preparation method of the g-C3N4 composite glassy carbon comprises the following steps:

[0044] Pour glassy carbon, g-C3N4 powder and ethanol into a container and mix them, then place the container in an ultrasonic cleaner for ultrasonic dispersion in water, the power of the ultrasonic cleaner is 1250W, the molar ratio of glassy carbon to g-C3N4 powder in the container is 0.15:1, the particle size of the glassy carbon is less than or equal to 5μm, ultrasonicate for 1h, then place the container in a vacuum drying oven for drying, the drying temperature is 79-80°C, and the g-C3N4 composite glassy carbon is obtained after drying.

[0045] The method for preparing the high-performance buried pipe comprises the following steps:

[0046] The high-performance buried pipe is prepared by using an aluminum-plastic composite pipe extruder;

[0047] The modified cross-linked polyethylene layer is made by extruding cross-linked polyethylene doped with g-C3N4 composite glassy carbon as a raw material;

[0048] A first modified hot melt adhesive layer is extruded on the outer wall of the modified cross-linked polyethylene layer using polyethylene hot melt adhesive doped with β-C3N4 as a raw material to obtain a binary composite pipe unit;

[0049] Wrapping an aluminum alloy strip on the outer wall of a binary composite tube unit to obtain a ternary composite tube unit, wherein the aluminum alloy layer is made of the aluminum alloy strip;

[0050] A second modified hot melt adhesive layer is extruded on the outer wall of the ternary composite pipe unit using polyethylene hot melt adhesive doped with β-C3N4 as a raw material to obtain a quaternary composite pipe unit;

[0051] A modified polyethylene layer is extruded on the outer wall of a quaternary composite tube unit using polyethylene doped with g-C3N4 composite glassy carbon as a raw material;

[0052] After extrusion, the high-performance buried pipe is obtained after water cooling.

[0053] Example 2

[0054] The high-performance buried pipe comprises, from the inside out, a modified cross-linked polyethylene layer, a first modified hot-melt adhesive layer, an aluminum alloy layer, a second modified hot-melt adhesive layer, and a modified polyethylene layer;

[0055] The first modified hot melt adhesive layer and the second modified hot melt adhesive layer are both made of polyethylene hot melt adhesive doped with β-C3N4, and the mass fraction of β-C3N4 in the polyethylene hot melt adhesive doped with β-C3N4 is 1.8%;

[0056] The modified cross-linked polyethylene layer is made of cross-linked polyethylene doped with g-C3N4 composite glassy carbon, and the mass fraction of the g-C3N4 composite glassy carbon doped in the cross-linked polyethylene doped with g-C3N4 composite glassy carbon is 8%;

[0057] The modified polyethylene layer is made of polyethylene doped with g-C3N4 composite glassy carbon, and the mass fraction of the g-C3N4 composite glassy carbon in the polyethylene doped with g-C3N4 composite glassy carbon is 5.5%.

[0058] Among them, the mass fraction of the modified cross-linked polyethylene layer in the high-performance buried pipe is 20%, the mass fraction of the first modified hot melt adhesive layer in the high-performance buried pipe is 5%, the mass fraction of the aluminum alloy layer in the high-performance buried pipe is 12%, the mass fraction of the second modified hot melt adhesive layer in the high-performance buried pipe is 5%, and the mass fraction of the modified polyethylene layer in the high-performance buried pipe is 58%.

[0059] The preparation method of the g-C3N4 composite glassy carbon comprises the following steps:

[0060] Pour glassy carbon, g-C3N4 powder and ethanol into a container and mix them, then place the container in an ultrasonic cleaner for ultrasonic dispersion in water, the power of the ultrasonic cleaner is 1250W, the molar ratio of glassy carbon to g-C3N4 powder in the container is 0.15:1, the particle size of the glassy carbon is less than or equal to 5μm, ultrasonicate for 2h, then place the container in a vacuum drying oven for drying, the drying temperature is 80-82°C, and the g-C3N4 composite glassy carbon is obtained after drying.

[0061] The method for preparing the high-performance buried pipe comprises the following steps:

[0062] The high-performance buried pipe is prepared by using an aluminum-plastic composite pipe extruder;

[0063] The modified cross-linked polyethylene layer is made by extruding cross-linked polyethylene doped with g-C3N4 composite glassy carbon as a raw material;

[0064] A first modified hot melt adhesive layer is extruded on the outer wall of the modified cross-linked polyethylene layer using polyethylene hot melt adhesive doped with β-C3N4 as a raw material to obtain a binary composite pipe unit;

[0065] Wrapping an aluminum alloy strip on the outer wall of a binary composite tube unit to obtain a ternary composite tube unit, wherein the aluminum alloy layer is made of the aluminum alloy strip;

[0066] A second modified hot melt adhesive layer is extruded on the outer wall of the ternary composite pipe unit using polyethylene hot melt adhesive doped with β-C3N4 as a raw material to obtain a quaternary composite pipe unit;

[0067] A modified polyethylene layer is extruded on the outer wall of a quaternary composite tube unit using polyethylene doped with g-C3N4 composite glassy carbon as a raw material;

[0068] After extrusion, the high-performance buried pipe is obtained after water cooling.

[0069] Example 3

[0070] The high-performance buried pipe comprises, from the inside out, a modified cross-linked polyethylene layer, a first modified hot-melt adhesive layer, an aluminum alloy layer, a second modified hot-melt adhesive layer, and a modified polyethylene layer;

[0071] The first modified hot melt adhesive layer and the second modified hot melt adhesive layer are both made of polyethylene hot melt adhesive doped with β-C3N4, and the mass fraction of β-C3N4 in the polyethylene hot melt adhesive doped with β-C3N4 is 1.9%;

[0072] The modified cross-linked polyethylene layer is made of cross-linked polyethylene doped with g-C3N4 composite glassy carbon, and the mass fraction of the g-C3N4 composite glassy carbon doped in the cross-linked polyethylene doped with g-C3N4 composite glassy carbon is 9.5%;

[0073] The modified polyethylene layer is made of polyethylene doped with g-C3N4 composite glassy carbon, and the mass fraction of the g-C3N4 composite glassy carbon doped in the polyethylene doped with g-C3N4 composite glassy carbon is 6%.

[0074] Among them, the mass fraction of the modified cross-linked polyethylene layer in the high-performance buried pipe is 25%, the mass fraction of the first modified hot melt adhesive layer in the high-performance buried pipe is 3%, the mass fraction of the aluminum alloy layer in the high-performance buried pipe is 8%, the mass fraction of the second modified hot melt adhesive layer in the high-performance buried pipe is 3%, and the mass fraction of the modified polyethylene layer in the high-performance buried pipe is 61%.

[0075] The preparation method of the g-C3N4 composite glassy carbon comprises the following steps:

[0076] Pour glassy carbon, g-C3N4 powder and ethanol into a container and mix them, then place the container in an ultrasonic cleaner for ultrasonic dispersion in water, the power of the ultrasonic cleaner is 1250W, the molar ratio of glassy carbon to g-C3N4 powder in the container is 0.15:1, the particle size of the glassy carbon is less than or equal to 5μm, ultrasonicate for 2h, then place the container in a vacuum drying oven for drying, the drying temperature is 83-85°C, and the g-C3N4 composite glassy carbon is obtained after drying.

[0077] The method for preparing the high-performance buried pipe comprises the following steps:

[0078] The high-performance buried pipe is prepared by using an aluminum-plastic composite pipe extruder;

[0079] The modified cross-linked polyethylene layer is made by extruding cross-linked polyethylene doped with g-C3N4 composite glassy carbon as a raw material;

[0080] A first modified hot melt adhesive layer is extruded on the outer wall of the modified cross-linked polyethylene layer using polyethylene hot melt adhesive doped with β-C3N4 as a raw material to obtain a binary composite pipe unit;

[0081] Wrapping an aluminum alloy strip on the outer wall of a binary composite tube unit to obtain a ternary composite tube unit, wherein the aluminum alloy layer is made of the aluminum alloy strip;

[0082] A second modified hot melt adhesive layer is extruded on the outer wall of the ternary composite pipe unit using polyethylene hot melt adhesive doped with β-C3N4 as a raw material to obtain a quaternary composite pipe unit;

[0083] A modified polyethylene layer is extruded on the outer wall of a quaternary composite tube unit using polyethylene doped with g-C3N4 composite glassy carbon as a raw material;

[0084] After extrusion, the high-performance buried pipe is obtained after water cooling.

[0085] Comparative Example 1

[0086] The high-performance buried pipe comprises, from the inside out, a cross-linked polyethylene layer, a first hot-melt adhesive layer, an aluminum alloy layer, a second hot-melt adhesive layer, and a polyethylene layer;

[0087] The first hot melt adhesive layer and the second hot melt adhesive layer are both made of polyethylene hot melt adhesive;

[0088] The cross-linked polyethylene layer is made of cross-linked polyethylene;

[0089] The polyethylene layer is made of polyethylene.

[0090] Among them, the mass fraction of the cross-linked polyethylene layer in the high-performance buried pipe is 21%, the mass fraction of the first hot melt adhesive layer in the high-performance buried pipe is 3.5%, the mass fraction of the aluminum alloy layer in the high-performance buried pipe is 10%, the mass fraction of the second hot melt adhesive layer in the high-performance buried pipe is 3.5%, and the mass fraction of the polyethylene layer in the high-performance buried pipe is 62%.

[0091] The method for preparing the high-performance buried pipe comprises the following steps:

[0092] The high-performance buried pipe is prepared by using an aluminum-plastic composite pipe extruder;

[0093] The cross-linked polyethylene layer is made by extrusion using cross-linked polyethylene as raw material;

[0094] A first hot melt adhesive layer is extruded on the outer wall of the cross-linked polyethylene layer using polyethylene hot melt adhesive as a raw material to obtain a binary composite pipe unit;

[0095] Wrapping an aluminum alloy strip on the outer wall of a binary composite tube unit to obtain a ternary composite tube unit, wherein the aluminum alloy layer is made of the aluminum alloy strip;

[0096] A second hot melt adhesive layer is extruded on the outer wall of the ternary composite pipe unit using polyethylene hot melt adhesive as raw material to obtain a quaternary composite pipe unit;

[0097] Using polyethylene as raw material, a polyethylene layer is extruded on the outer wall of the quaternary composite pipe unit;

[0098] After extrusion, the high-performance buried pipe is obtained after water cooling.

[0099] Comparative Example 2

[0100] The difference between this example and Example 1 is that in this example, the first modified hot melt adhesive layer and the second modified hot melt adhesive layer are both made of polyethylene hot melt adhesive doped with g-C3N4, and the mass fraction of β-C3N4 in the polyethylene hot melt adhesive doped with g-C3N4 is 1.6%; the rest are the same.

[0101] Comparative Example 3

[0102] The difference between this example and Example 1 is that the modified cross-linked polyethylene layer is made of cross-linked polyethylene doped with g-C3N4 and glassy carbon, g-C3N4 and glassy carbon are not compounded, but are directly mixed with the cross-linked polyethylene raw material, the molar ratio of glassy carbon to g-C3N4 powder is 0.15:1, and the rest are the same.

[0103] Comparative Example 4

[0104] The difference between this example and Example 1 is that the modified cross-linked polyethylene layer is made of cross-linked polyethylene doped with β-C3N4 and glassy carbon, β-C3N4 and glassy carbon cannot be compounded, and are directly mixed with the cross-linked polyethylene raw material, and the molar ratio of glassy carbon to β-C3N4 powder is 0.15:1. The rest are the same.

[0105] Comparative Example 5

[0106] The difference between this example and Example 1 is that the modified polyethylene layer is made of polyethylene doped with g-C3N4 and glassy carbon, g-C3N4 and glassy carbon are not compounded, but directly mixed with the polyethylene raw material, and the molar ratio of glassy carbon to g-C3N4 powder is 0.15:1. The rest are the same.

[0107] Comparative Example 6

[0108] The difference between this example and Example 1 is that the glassy carbon in Example 1 is completely replaced by graphene, and the rest are the same.

[0109] Comparative Example 7

[0110] The difference between this example and Example 1 is that the modified cross-linked polyethylene layer is made of cross-linked polyethylene doped with g-C3N4 composite glassy carbon, and the mass fraction of the g-C3N4 composite glassy carbon doped in the cross-linked polyethylene doped with g-C3N4 composite glassy carbon is 9.5%; the rest are the same.

[0111] Comparative Example 8

[0112] The difference between this example and Example 1 is that the modified polyethylene layer is made of polyethylene doped with g-C3N4 composite glassy carbon, and the mass fraction of the g-C3N4 composite glassy carbon doped in the polyethylene doped with g-C3N4 composite glassy carbon is 7%.

[0113] Performance Characterization Test of High-Performance Buried Pipe

[0114] The high-performance buried pipes corresponding to Example 1 and Comparative Examples 1 to 8 were sampled to obtain sample pipes of the same specifications.

[0115] 1. Measure the hydrostatic strength ring stress at 95°C / 1000h for polyethylene (PE) pipes for water supply according to GB-T-13663-2000.

[0116] 2. Compression resistance and anti-seepage

[0117] 2.1. Perform the first pressure test on the sample tube. The water pressure in the sample tube is 0.6 MPa. Maintain the pressure for 15 minutes and check for leaks.

[0118] 2.2. The sample tube is flattened radially under a press with a flattening ratio of 25% (e.g., if the outer diameter of the sample tube is 36 mm, the minimum outer diameter of the sample tube after flattening is 27 mm). The flattened sample tube is then returned to its original shape under normal pressure. This constitutes one flattening operation. After repeating the flattening operation 1000 times, the sample tube is subjected to a second pressure test. The water pressure in the sample tube is 0.6 MPa and the pressure is maintained for 15 minutes to check for leaks. If there is a leak, the water leaked during the 15-minute period is collected and weighed. The total weight of the leaked water can reflect the anti-seepage performance of the sample tube after the high-frequency flattening test. The results are shown in Table 1.

[0119] Table 1

[0120] 95℃ / 1000h Hydrostatic Strength Ring Stress First pressure test Second pressure test Example 1 3.57MPa No leakage No leakage Comparative Example 1 3.02MPa No leakage The total weight of leaked water is 3.5kg Comparative Example 2 3.09MPa No leakage The total weight of leaked water is 2.1kg Comparative Example 3 2.89MPa No leakage The total weight of leaked water is 4.7kg Comparative Example 4 2.83MPa No leakage The total weight of leaked water is 5.5kg Comparative Example 5 2.51MPa No leakage The total weight of leaked water is 4.3kg Comparative Example 6 3.50MPa No leakage The total weight of leaked water is 1.2kg Comparative Example 7 3.53MPa No leakage The total weight of leaked water is 0.8kg Comparative Example 8 3.55MPa No leakage No leakage

[0121] It can be seen from Table 1 and Comparative Example 2 that in polyethylene hot melt adhesive, the sole doping of lightweight g-C3N4 is very likely to lead to uneven mixing. Although it does not help to improve the impact resistance (95°C / 1000h hydrostatic strength ring stress), it will significantly affect its compressive and anti-seepage properties. During multiple extrusion deformation processes, it is very easy to cause micro-cracks in the pipe, resulting in leakage.

[0122] It can be seen from Table 1 and Comparative Example 3 that if g-C3N4 and glassy carbon are doped separately in the inner tube (modified cross-linked polyethylene layer), due to the hard nature and the uneven distribution of the doped hard particles (fillers), it will lead to a decrease in impact resistance and compressive and anti-permeability properties.

[0123] It can be seen from Table 1 and Comparative Example 4 that if the inner tube (modified cross-linked polyethylene layer) is doped with β-C3N4 and glassy carbon with higher hardness alone, due to its hard nature and the uneven distribution of the doped hard particles (fillers), it will lead to a decrease in impact resistance and compressive and anti-permeability properties.

[0124] It can be seen from Table 1 and Comparative Example 5 that if lightweight g-C3N4 and glassy carbon are doped alone in the outer tube (modified polyethylene layer), the doped particles (fillers) are unevenly distributed due to their hard nature and the difficulty of uniform dispersion of g-C3N4, which will lead to a decrease in impact resistance and pressure resistance and impermeability, and will have a greater impact on impact resistance.

[0125] As shown in Table 1 and Comparative Example 6, g-C3N4 composited with graphene has little effect on the strength of polyethylene and cross-linked polyethylene, resulting in little change in impact resistance. However, its improvement in toughness is not as good as that of glassy carbon, resulting in a decrease in both compressive and anti-permeability properties.

[0126] It can be seen from Table 1 and Comparative Example 7 that if the content of g-C3N4 composite glassy carbon in the inner tube (modified cross-linked polyethylene layer) is too large, the impact resistance will not change much, but will lead to a decrease in both compressive and anti-permeability properties.

[0127] It can be seen from Table 1 and Comparative Example 8 that if the content of g-C3N4 composite glassy carbon in the outer tube (modified polyethylene layer) is too large, the impact resistance and the compressive and anti-permeability properties will not change much.

[0128] In the above embodiment, the polyethylene hot melt adhesive doped with β-C3N4 can be prepared by mixing β-C3N4 powder into polyethylene hot melt adhesive raw material; the cross-linked polyethylene doped with g-C3N4 composite glassy carbon can be prepared by mixing g-C3N4 composite glassy carbon into cross-linked polyethylene raw material. The polyethylene doped with g-C3N4 composite glassy carbon can be prepared by mixing g-C3N4 composite glassy carbon into polyethylene raw material.

[0129] Polyethylene hot melt adhesive was purchased from Kangkai Renewable Resources Recycling Co., Ltd., Congtai District, Handan City.

[0130] In the present invention, g-C3N4 composite glassy carbon is used to solve the defects caused by doping g-C3N4 and glassy carbon alone. The g-C3N4 composite glassy carbon can be evenly dispersed in polyethylene and cross-linked polyethylene, thereby improving the performance of the pipe.

[0131] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A high-performance buried pipe, characterized in that: From the inside out, it includes a modified cross-linked polyethylene layer, a first modified hot melt adhesive layer, an aluminum alloy layer, a second modified hot melt adhesive layer, and a modified polyethylene layer. The first modified hot melt adhesive layer and the second modified hot melt adhesive layer are both made of polyethylene hot melt adhesive doped with β-C3N4, and the mass fraction of β-C3N4 in the polyethylene hot melt adhesive doped with β-C3N4 is 1.6% to 1.9%; The modified cross-linked polyethylene layer is made of cross-linked polyethylene doped with g-C3N4 composite glassy carbon, and the mass fraction of the g-C3N4 composite glassy carbon doped in the cross-linked polyethylene doped with g-C3N4 composite glassy carbon is 7.5% to 9.5%; The modified polyethylene layer is made of polyethylene doped with g-C3N4 composite glassy carbon, and the mass fraction of the g-C3N4 composite glassy carbon in the polyethylene doped with g-C3N4 composite glassy carbon is 5% to 6%; The preparation method of the g-C3N4 composite glassy carbon comprises the following steps: Pour glassy carbon, g-C3N4 powder and ethanol into a container and mix them, then place the container in an ultrasonic cleaner with water for ultrasonic dispersion, the power of the ultrasonic cleaner is 1250W, the molar ratio of glassy carbon to g-C3N4 powder in the container is 0.15:1, the particle size of the glassy carbon is less than or equal to 5μm, ultrasonicate for 1~2h, then place the container in a vacuum drying oven for drying, the drying temperature is 79~85℃, and after drying, the g-C3N4 composite glassy carbon is obtained.

2. The high-performance buried pipe according to claim 1, characterized in that: The mass fraction of the modified cross-linked polyethylene layer in the high-performance buried pipe is 20%~25%, the mass fraction of the first modified hot-melt adhesive layer in the high-performance buried pipe is 3%~5%, the mass fraction of the aluminum alloy layer in the high-performance buried pipe is 8%~12%, and the mass fraction of the second modified hot-melt adhesive layer in the high-performance buried pipe is 3%~5%.

3. The high-performance buried pipe according to claim 2, characterized in that: The mass fraction of the modified cross-linked polyethylene layer in the high-performance buried pipe is 21%, the mass fraction of the first modified hot-melt adhesive layer in the high-performance buried pipe is 3.5%, the mass fraction of the aluminum alloy layer in the high-performance buried pipe is 10%, the mass fraction of the second modified hot-melt adhesive layer in the high-performance buried pipe is 3.5%, and the mass fraction of the modified polyethylene layer in the high-performance buried pipe is 62%.

4. The high-performance buried pipe according to claim 2, characterized in that: The mass fraction of the modified cross-linked polyethylene layer in the high-performance buried pipe is 20%, the mass fraction of the first modified hot-melt adhesive layer in the high-performance buried pipe is 5%, the mass fraction of the aluminum alloy layer in the high-performance buried pipe is 12%, the mass fraction of the second modified hot-melt adhesive layer in the high-performance buried pipe is 5%, and the mass fraction of the modified polyethylene layer in the high-performance buried pipe is 58%.

5. The high-performance buried pipe according to claim 2, characterized in that: The mass fraction of the modified cross-linked polyethylene layer in the high-performance buried pipe is 25%, the mass fraction of the first modified hot-melt adhesive layer in the high-performance buried pipe is 3%, the mass fraction of the aluminum alloy layer in the high-performance buried pipe is 8%, the mass fraction of the second modified hot-melt adhesive layer in the high-performance buried pipe is 3%, and the mass fraction of the modified polyethylene layer in the high-performance buried pipe is 61%.

6. A method for preparing a high-performance buried pipe according to any one of claims 1 to 5, characterized in that: The following steps are involved: The high-performance buried pipe is prepared by using an aluminum-plastic composite pipe extruder; The modified cross-linked polyethylene layer is made by extruding cross-linked polyethylene doped with g-C3N4 composite glassy carbon as a raw material; A first modified hot melt adhesive layer is extruded on the outer wall of the modified cross-linked polyethylene layer using polyethylene hot melt adhesive doped with β-C3N4 as a raw material to obtain a binary composite pipe unit; Wrapping an aluminum alloy strip on the outer wall of a binary composite tube unit to obtain a ternary composite tube unit, wherein the aluminum alloy layer is made of the aluminum alloy strip; A second modified hot melt adhesive layer is extruded on the outer wall of the ternary composite pipe unit using polyethylene hot melt adhesive doped with β-C3N4 as a raw material to obtain a quaternary composite pipe unit; A modified polyethylene layer is extruded on the outer wall of a quaternary composite tube unit using polyethylene doped with g-C3N4 composite glassy carbon as a raw material; After extrusion is completed and water-cooled, the high-performance buried pipe is obtained.