CN110951142B

CN110951142B - High-thermal-conductivity radiation crosslinked polyethylene pipe and preparation method and application thereof

Info

Publication number: CN110951142B
Application number: CN201911275007.3A
Authority: CN
Inventors: 霍伟智; 孔令光; 赵照; 孔德敬; 王清
Original assignee: FSPG Hi Tech Co Ltd
Current assignee: FSPG Hi Tech Co Ltd
Priority date: 2019-12-12
Filing date: 2019-12-12
Publication date: 2022-07-01
Anticipated expiration: 2039-12-12
Also published as: CN110951142A

Abstract

The invention provides a high-thermal-conductivity radiation crosslinked polyethylene pipe and a preparation method and application thereof, and relates to the technical field of high polymer materials. The high-thermal-conductivity radiation crosslinked polyethylene pipe provided by the invention is prepared from the following raw materials in parts by weight: 100 parts of polyethylene, 5-180 parts of graphite, 0.1-40 parts of boron nitride, 5-90 parts of thermoplastic elastomer and 0.2-108 parts of additive; the additive comprises: 0.05-9 parts of coupling agent, 0.05-90 parts of diluent, 0-6 parts of crosslinking sensitizer and 0.1-3 parts of antioxidant. The crosslinked polyethylene pipe prepared by the method through the process steps of activating granulation, pipe extrusion, radiation crosslinking and the like has the characteristics of high heat conduction, hydraulic pressure resistance, acid corrosion resistance, wide service temperature and the like, and can be applied to a building floor heating system, a ground source heat pump system, a chemical shell-and-tube heat exchanger and the like.

Description

High-thermal-conductivity radiation crosslinked polyethylene pipe and preparation method and application thereof

Technical Field

The invention relates to the technical field of high polymer materials, in particular to a high-thermal-conductivity radiation crosslinked polyethylene pipe and a preparation method and application thereof.

Background

Polyethylene is a recyclable, nontoxic and odorless nonpolar thermoplastic resin, and the pipe manufactured by using the polyethylene has the outstanding advantages of hydraulic pressure resistance, corrosion resistance, safety, sanitation and the like, and is widely applied to the fields of civil water supply and heating and industrial water supply heat exchange. However, the thermal conductivity of polyethylene is only 0.44W/(m ∙ K), which is less than one percent of steel, and thus, the heat exchange efficiency of the pipe is severely limited, and the efficient utilization of heat energy resources is difficult to realize. Therefore, the manufacture of the high thermal conductivity polyethylene pipe is one of the research focuses of engineers.

Chinese patent application CN109677069A discloses a multilayer composite high-thermal-conductivity irradiation cross-linked floor heating pipe, which comprises a scale inhibiting layer, a heat conducting layer and an apparent layer from inside to outside in sequence, wherein the heat conducting layer comprises the following components: polyethylene, a stabilizer, aluminum oxide, a toughening agent, a plasticizer, a lubricant, a coupling agent and a sensitizing agent. The multilayer pipe has the advantages of high heat conductivity coefficient, high surface quality, difficult scaling and no need of adhesive bonding. However, the use of alumina as the heat conductive material in the multilayer pipe causes a decrease in the acid etching resistance of the pipe. In addition, the inner layer and the outer layer of the multilayer pipe are not made of heat conducting materials, so that the heat resistance is high, and the total heat transfer resistance depends on the part with high heat resistance, so that the total heat conductivity coefficient of the product is not greatly improved.

Chinese patent application CN109354751A discloses a heat-conducting, insulating, anti-sticking and anti-thermal aging heat shrinkable tube, which comprises the following materials: the prepared pipe has the advantages of high thermal conductivity and high dielectric strength, and can be used for outer insulation protection of electronic cables. However, the use of activated calcined kaolin as an insulating filler in the material results in a decrease in the hydraulic resistance of the pipe, and is not suitable for use in fluid transport pipes requiring hydraulic resistance.

Chinese patent CN103524859B provides a graphite-containing heat-conducting polyethylene master batch, a preparation method and a composition thereof. The graphite-containing heat-conducting polyethylene master batch is composed of (by weight) 100 parts of polyethylene powder, 60-300 parts of graphite, 0.3-15 parts of coupling agent, 0.3-300 parts of diluent and 0.01-5 parts of antioxidant, and has excellent heat-conducting property. However, the invention uses a large amount of graphite for filling modification, which leads to increased brittleness of the pipe, and other modification aids are not added to improve the impact resistance and environmental stress cracking resistance, so that the pipe is easy to crack at low temperature.

Therefore, the heat-conducting polyethylene pipe prepared by the prior art has the problems of poor acid corrosion resistance, low hydraulic resistance, low temperature brittleness and the like, and is not suitable for severe application scenes of conveying acid pressurized fluid and the like at wide use temperature.

Disclosure of Invention

Aiming at the problems and the defects, the invention provides a high-thermal-conductivity radiation crosslinked polyethylene pipe which has the remarkable characteristics of high thermal conductivity, hydraulic pressure resistance, acid corrosion resistance and wide service temperature.

The invention provides a high-thermal-conductivity radiation crosslinked polyethylene pipe which is prepared from the following raw materials in parts by weight:

100 parts of polyethylene, namely 100 parts of polyethylene,

5-180 parts of graphite,

0.1 to 40 parts of boron nitride,

5 to 90 parts of a thermoplastic elastomer,

0.2-108 parts of an additive;

the additive comprises:

0.05 to 9 parts of a coupling agent,

0.05 to 90 parts of a diluent,

0 to 6 parts of a crosslinking sensitizer,

0.1-3 parts of antioxidant.

The high-thermal-conductivity radiation crosslinked polyethylene pipe has the advantages of low-cost and easily-obtained raw materials, natural acid corrosion resistance, effective improvement of brittleness of the pipe at low temperature by adding the thermoplastic elastomer, obvious improvement of stability of the pipe at high temperature by radiation crosslinking, high thermal conductivity, hydraulic pressure resistance, acid corrosion resistance and wide use temperature, and is suitable for conveying high-pressure fluid media and acidic fluid media.

In one embodiment, the high thermal conductivity radiation crosslinked polyethylene pipe comprises the following raw materials in parts by weight:

100 parts of polyethylene, namely 100 parts of polyethylene,

10-150 parts of graphite,

1 to 30 parts of boron nitride,

10-75 parts of a thermoplastic elastomer,

1.5-28.5 parts of an additive;

the additive comprises:

0.1 to 7.5 parts of a coupling agent,

0.2 to 15 parts of a diluent,

1 to 4 parts of a crosslinking sensitizer,

0.2-2 parts of antioxidant.

In one embodiment, the polyethylene has a 190 ℃/2.16 kg melt index of 0.05 to 3 g/10min and a density of 0.910 to 0.970 g/cm³The polyethylene of (1). Preferably, the polyethylene has a 190 ℃/2.16 kg melt index of 0.10 to 1.5 g/10min and a density of 0.925 to 0.960 g/cm³。

In one embodiment, the graphite is selected from one or more of natural graphite, colloidal graphite and expandable graphite, and the particle size of the graphite is 2-250 μm. Preferably, the particle size of the graphite is 10 to 50 μm.

In one embodiment, the boron nitride is hexagonal boron nitride with a particle size of 0.5-100 μm. Preferably, the particle size of the boron nitride is 1 to 25 μm. The boron nitride which is the same as the graphite crystal system is selected, so that heat can be stably transferred between the same crystal lattices through phonons, the interface barrier between the two is weakened, and the heat transfer rate is improved; the small-sized boron nitride can be inserted into a gap formed when the graphite is stacked, so that the two can be in continuous and close contact, and the heat-conducting property of the material is further improved.

In one embodiment, the ratio of the particle size of boron nitride to that of graphite is 1 (5-20). Graphite with large grain size and boron nitride with small grain size are selected as heat conducting materials, the two materials have similar crystal systems but different grain sizes, so that the two materials are mutually interpenetrated and stacked, a complex heat conducting network can be constructed in a polyethylene base material, and the heat conducting performance of the materials is remarkably improved.

In one embodiment, the thermoplastic elastomer is selected from ethylene-vinyl acetate copolymer and/or polyolefin elastomer. The polyolefin elastomer may be an ethylene-propylene copolymer, an ethylene-butene copolymer, an ethylene-hexene copolymer, an ethylene-octene copolymer, or the like. Preferably, the thermoplastic elastomer may be selected from a combination of ethylene-vinyl acetate copolymer and ethylene-octene copolymer.

In one embodiment, the coupling agent is selected from one of a silane coupling agent, a titanate coupling agent or an aluminum-titanium composite coupling agent.

In one embodiment, the diluent is selected from industrial white oil and/or absolute ethyl alcohol.

In one embodiment, the cross-linking sensitizer is an acrylate sensitizer and/or a methacrylate sensitizer. Preferably, the crosslinking sensitizer may be one or more selected from the group consisting of diethylene glycol diacrylate, trimethylolpropane trimethacrylate, and trimethylolpropane triacrylate.

In one embodiment, the antioxidant is selected from phenolic antioxidants and/or phosphite antioxidants. Preferably, the antioxidant can be selected from one or more than two of 1010, 754, 168 and 1178.

In addition, the invention also provides a preparation method of the high-thermal-conductivity radiation crosslinked polyethylene pipe, which comprises the following steps:

A. preparing modified master batch: firstly, heating and premixing graphite and boron nitride, adding a coupling agent and a diluent, and then continuously mixing to obtain activated powder; then adding the thermoplastic elastomer, part of polyethylene and the rest of additives into the activated powder, mixing, extruding and granulating to obtain modified master batch;

B. extruding the heat-conducting pipe: mixing the modified master batch and the rest polyethylene, then performing melt extrusion, and performing vacuum sizing, cooling sizing, traction and winding to obtain a heat-conducting pipe;

C. radiation crosslinking of the pipe: and (3) carrying out radiation crosslinking modification on the heat-conducting pipe to obtain the high-heat-conductivity radiation crosslinked polyethylene pipe.

In one embodiment, the step a specifically includes:

stirring and mixing graphite and boron nitride at 50-100 ℃ for 3-5 min, adding a coupling agent diluted by a diluent, and continuously mixing for 5-10 min to obtain activated powder; and then adding the thermoplastic elastomer, part of polyethylene and the rest of additives into the activated powder, mixing for 5-20 min, adding the mixed raw materials into a double-screw extruder, and extruding and granulating at 160-260 ℃ to obtain the modified master batch. Preferably, the part of polyethylene is 10% to 90% of the total amount of polyethylene. The double-screw extruder belongs to continuous mixing equipment, and has the advantages of good mixing effect, strong exhaust capacity, narrow residence time distribution, accurate material temperature control and the like compared with a single-screw extruder and an intermittent banburying-granulating machine.

In one embodiment, the step B specifically includes:

and mixing the modified master batch with the rest polyethylene, performing melt extrusion at 160-240 ℃, performing vacuum sizing and cooling sizing, and then pulling and rolling at the speed of 10-50 m/min to obtain the heat-conducting pipe.

In one embodiment, the step C specifically includes:

carrying out radiation crosslinking modification on the polyethylene pipe by using an electron accelerator or a cobalt source irradiation device, wherein the radiation energy is 2.0-3.5 MeV, the radiation beam current is 5-50 mA, and the radiation absorption dose of the pipe per unit mass is 30-180 kGy, so as to obtain the high-thermal-conductivity radiation crosslinked polyethylene pipe. Preferably, the radiation energy is 2.6-3.1 MeV, the radiation beam current is 10-40 mA, and the radiation absorption dose of the unit mass pipe is 80-150 kGy. The radiation crosslinking modification can enable the interior of the material to form a tighter crosslinking network, obviously improve the stability of the pipe at high temperature, and further improve the thermal conductivity coefficient of the material while improving the mechanical property of the material.

In addition, the invention also provides application of the high-thermal-conductivity radiation crosslinked polyethylene pipe in fluid transportation.

Compared with the prior art, the invention has the following beneficial effects:

according to the high-thermal-conductivity radiation crosslinked polyethylene pipe, the large-particle-size graphite and the small-particle-size boron nitride are compounded to serve as heat conduction materials, and the heat conduction coefficient can be improved to 0.55-1.45W/(m ∙ K) from 0.44W/(m ∙ K) of pure polyethylene by combining the modification effect of a radiation crosslinking technology; because the raw materials are natural and resistant to acid corrosion, the product still has no leakage and no fracture after being soaked in acid liquor with the pH =4.0 for 24 hours in hydrostatic pressure test, and the high requirement of the PE-X pipe for fluid transportation is met; the brittleness of the product at low temperature can be effectively improved by adding the thermoplastic elastomer, the stability of the product at high temperature can be obviously improved by radiation crosslinking, and the stability test time of the product at 10 ℃ and 110 ℃ is more than 8760 h.

In conclusion, the crosslinked polyethylene pipe manufactured by the method has the remarkable advantages of low cost, easy processing, high heat conduction, hydraulic pressure resistance, acid corrosion resistance, wide use temperature and the like, and can be widely applied to the fields of building floor heating systems, ground source heat pump systems, chemical shell-and-tube heat exchangers and the like.

Drawings

FIG. 1 is a process flow diagram of the preparation process in the example;

FIG. 2 is a flow chart of the preparation of modified master batch in the example;

FIG. 3 is a flow chart of extruding a thermally conductive tubing in an embodiment;

FIG. 4 is a flow chart of the radiation crosslinking of the pipe in the examples.

Detailed Description

To facilitate an understanding of the invention, a more complete description of the invention will be given below in terms of preferred embodiments. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.

In order to facilitate the understanding of the technical solutions of the present invention by the respective properties of the comparative examples and comparative examples, the dimensions of the pipe products of the following examples and comparative examples are unified intod _n16 S3.2。

Example 1

A high-thermal-conductivity radiation crosslinked polyethylene pipe is prepared by the following method (as shown in figure 1):

1) preparation of modified masterbatch (as shown in fig. 2):

surface activation: adding 48 parts of 25-micron expandable graphite and 2 parts of 5-micron boron nitride into a high-speed mixer, and stirring for 5 min at the temperature of 60-70 ℃; diluting 1.5 parts of silane coupling agent KH-550 with 3 parts of industrial white oil, adding into the powder, and continuously stirring for 8 min;

mixing and granulating: 50 parts of high-density polyethylene 5502, 15 parts of thermoplastic elastomer (10 parts of ethylene-vinyl acetate copolymer and 5 parts of ethylene-propylene copolymer), 2 parts of crosslinking sensitizer diethylene glycol diacrylate and 0.5 part of antioxidant (0.3 part of 1010 and 0.2 part of 168) are added into the powder after surface activation, and the powder is stirred at high speed for 12 min. And then adding the mixed raw materials into a double-screw extruder for extrusion granulation to obtain the modified master batch. The temperature profile of the twin-screw extruder was set as shown in table 1 below:

TABLE 1 temperature distribution of twin-screw extruder

Barrel 1

Barrel 2

Barrel 3

Barrel 4

Barrel 5

Barrel 6

Barrel 7

Die head

80℃

150℃

180℃

200℃

210℃

220℃

210℃

2) Extrusion of thermally conductive tubing (as shown in fig. 3):

and (3) mixing the modified master batch obtained in the step (a) and 50 parts of high-density polyethylene 5502, adding the mixture into a pipe extruder for melt extrusion, and carrying out vacuum sizing, cooling sizing, traction and rolling to obtain the heat-conducting pipe. The traction speed is controlled at 20 m/min. The temperature profile of the pipe extruder was set as shown in table 2 below:

TABLE 2 temperature profile of pipe extruder

Barrel 1

Barrel 2

Barrel 3

Barrel 4

Adapter

Filter screen

Die head 1

Die head 2

75℃

190℃

195℃

200℃

205℃

200℃

3) Radiation crosslinking of tubing (as shown in figure 4):

and (3) carrying out radiation crosslinking modification on the heat-conducting pipe obtained in the previous step by using a high-energy electron accelerator to finally obtain the high-heat-conductivity radiation crosslinked polyethylene pipe. The radiation energy is 2.8 MeV, the radiation beam current is 40 mA, and the radiation absorption dose of the unit mass pipe is 120 kGy.

Example 2

A high-thermal-conductivity radiation crosslinked polyethylene pipe is prepared by the following steps:

1) preparing modified master batch:

surface activation: adding 16 parts of 45-micron natural graphite and 4 parts of 20-micron boron nitride into a high-speed mixer, and stirring for 3 min at 55-65 ℃; diluting 1 part of titanate coupling agent TTS by 3 parts of absolute ethyl alcohol, adding the diluted solution into the powder, and continuously stirring for 7 min;

mixing and granulating: 20 parts of medium density polyethylene DX800, 5 parts of thermoplastic elastomer (2 parts of ethylene-vinyl acetate copolymer and 3 parts of ethylene-octene copolymer), 2.5 parts of cross-linking sensitizer trimethylolpropane trimethacrylate and 0.5 part of antioxidant (0.3 part of 1010 and 0.2 part of 1178) are added into the powder after surface activation, and stirred at high speed for 10 min. The same as in example 1.

2) Extruding the heat-conducting pipe:

the modified master batch obtained in the previous step and 80 parts of medium density polyethylene DX800 are mixed and added into a pipe extruder for melt extrusion, and the process is the same as that of example 1.

3) Radiation crosslinking of the pipe:

the same as in example 1.

Example 3

A high-thermal-conductivity radiation cross-linked polyethylene pipe is prepared by the following steps:

1) preparing modified master batch:

surface activation: adding 100 parts of 15-micron colloidal graphite and 25 parts of 2-micron boron nitride into a high-speed mixer, and stirring for 5 min at 70-80 ℃; diluting 5 parts of aluminum-titanium composite coupling agent HY-133 with 10 parts of industrial white oil, adding into the powder, and continuously stirring for 10 min;

mixing and granulating: 40 parts of medium density polyethylene SP980, 45 parts of thermoplastic elastomer (35 parts of ethylene-vinyl acetate copolymer and 10 parts of ethylene-butylene copolymer), 3 parts of crosslinking sensitizer trimethylolpropane triacrylate and 1 part of antioxidant (0.7 part 754 and 0.3 part 168) were added to the surface-activated powder, and stirred at high speed for 15 min. The same as in example 1.

2) Extruding the heat-conducting pipe:

the modified master batch obtained in the above step and 60 parts of medium density polyethylene SP980 were mixed and added to a pipe extruder to be melt-extruded, as in example 1.

3) Radiation crosslinking of the pipe:

the same as in example 1.

Example 4

The difference between the high-thermal-conductivity radiation crosslinked polyethylene pipe and the example 1 is that the dosage of the ethylene-propylene copolymer in the step 1) is increased from 5 parts to 40 parts, the dosage of the high-density polyethylene 5502 is correspondingly reduced from 50 parts to 15 parts, the granulation extrusion temperature is reduced by 10 ℃, and the extrusion temperature of the pipe in the step 2) is reduced by 5 ℃.

Example 5

A high thermal conductivity radiation crosslinked polyethylene pipe, which is different from example 1 in that no crosslinking sensitizer is added in step 1), and the radiation absorption dose in step 3) is increased to 135 kGy.

Comparative example 1

A polyethylene pipe differs from example 1 in that this comparative example does not have step 1), i.e., all raw materials are mixed and directly fed into a pipe extruder for melt extrusion. The same as in example 1.

During actual production, the melt is unstable after being extruded from a neck mold of a pipe extruder, the pipe wall is frequently cracked after entering a vacuum sizing sleeve, the melt cannot be cooled and molded to produce a heat-conducting pipe, and the radiation crosslinking step and the performance test cannot be carried out.

Comparative example 2

A polyethylene pipe differing from example 1 in that no thermoplastic elastomer was added in step 1) of this comparative example.

Comparative example 3

A polyethylene pipe differs from example 1 in that this comparative example does not have step 3), i.e., the heat conductive pipe is not modified by radiation crosslinking.

Comparative example 4

A polyethylene pipe differing from example 1 in that this comparative example replaces the boron nitride in step 1) with alumina of the same weight part and particle size.

Experimental example 1

The pipes of examples 1 to 5 and comparative examples 1 to 4 were tested for the degree of crosslinking and stability in a high-temperature hydrostatic pressure state according to the GB/T18992.2, and the test results are shown in Table 3.

TABLE 3 Cross-linking degree, thermal conductivity and high and low temperature stability test results of the pipes

Experimental example 2

Hydrostatic resistance tests for the pipes of examples 1-5 and comparative examples 1-4 were carried out according to the provisions of GB/T18992.2, and the results are shown in Table 4.

TABLE 4 hydrostatic resistance test results for tubing

Experimental example 3

The pipes of examples 1 to 5 and comparative examples 1 to 4 were subjected to hydrostatic pressure resistance test after being soaked in acid solution with pH =4.0 for 24 hours, and the hydrostatic pressure resistance test was carried out according to the regulations of GB/T18992.2, and the test results are shown in Table 5.

Table 5 hydrostatic pressure resistance test results of pipe material after pH =4.0 acid etching for 24 h

The test results of the experimental examples 1-3 show that the thermal conductivity of the embodiment of the invention can be improved from 0.44W/(m ∙ K) of pure polyethylene to 0.60-1.35W/(m ∙ K); the pipe has no leakage and no fracture under all 5 test conditions of the hydrostatic pressure resistant project in GB/T18992.2; after being soaked in acid liquor with pH =4.0 for 24 hours, the hydrostatic pressure resistance test is repeated, and no leakage or fracture is generated; the test time of the stability at high temperature (110 ℃, hydrostatic stress of 2.5 MPa) and low temperature (10 ℃, hydrostatic stress of 10 MPa) is more than 8760 h. In conclusion, the radiation crosslinked polyethylene pipe has the characteristics of high heat conduction, hydraulic pressure resistance, acid corrosion resistance, wide service temperature and the like.

Various technical features of the above embodiments may be combined arbitrarily, and for brevity, all possible combinations of the technical features in the above embodiments are not described. The combination of these features should be considered as being within the scope of the present specification as long as there is no contradiction therebetween.

The above-mentioned embodiments only express several embodiments of the present invention, and the description thereof is more specific and detailed, but not construed as limiting the scope of the invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the inventive concept, which falls within the scope of the present invention. Therefore, the protection scope of the present patent shall be subject to the appended claims.

Claims

1. The high-thermal-conductivity radiation crosslinked polyethylene pipe is characterized by being prepared from the following raw materials in parts by weight:

100 parts of polyethylene, namely 100 parts of polyethylene,

10-150 parts of graphite,

1 to 30 parts of boron nitride,

10-75 parts of a thermoplastic elastomer,

1.5-28.5 parts of an additive;

the additive comprises:

0.1 to 7.5 parts of a coupling agent,

0.2 to 15 parts of a diluent,

1 to 4 parts of a crosslinking sensitizer,

0.2-2 parts of an antioxidant;

the graphite is one or more of natural graphite, colloidal graphite and expandable graphite, and the particle size of the graphite is 10-50 mu m; the boron nitride is hexagonal boron nitride with the grain diameter of 1-25 μm; the particle size ratio of boron nitride to graphite is 1: (5-20);

the thermoplastic elastomer is ethylene-vinyl acetate copolymer and/or polyolefin elastomer;

the preparation method of the high-thermal-conductivity radiation crosslinked polyethylene pipe comprises the following steps:

C. radiation crosslinking of the pipe: carrying out radiation crosslinking modification on the polyethylene pipe by using an electron accelerator or a cobalt source irradiation device, wherein the radiation energy is 2.0-3.5 MeV, the radiation beam current is 5-50 mA, and the absorption dose of the pipe per unit mass to radiation is 30-180 kGy, so as to obtain the high-thermal-conductivity radiation crosslinked polyethylene pipe.

2. The high thermal conductivity radiation crosslinked polyethylene pipe according to claim 1, wherein said polyethylene has a 190 ℃/2.16 kg melt index of 0.05 to 3 g/10min and a density of 0.910 to 0.970 g/cm³。

3. The high thermal conductivity radiation crosslinked polyethylene pipe according to any one of claims 1 to 2, wherein the coupling agent is selected from one of a silane coupling agent, a titanate coupling agent or an aluminum titanium composite coupling agent; the diluent is industrial white oil and/or absolute ethyl alcohol; the crosslinking sensitizer is an acrylate sensitizer and/or a methacrylate sensitizer; the antioxidant is selected from phenolic antioxidant and/or phosphite antioxidant.

4. The high thermal conductivity radiation crosslinked polyethylene pipe according to claim 1, wherein the step a is specifically: mixing graphite and boron nitride at 50-100 ℃ for 3-5 min, adding a coupling agent diluted by a diluent, and continuously mixing for 5-10 min to obtain activated powder; then adding the thermoplastic elastomer, part of polyethylene and the rest of additives into the activated powder, mixing for 5-20 min, adding the mixed raw materials into a double-screw extruder, and extruding and granulating at 160-260 ℃ to obtain modified master batches;

the step B specifically comprises the following steps: and mixing the modified master batch with the rest polyethylene, performing melt extrusion at 160-240 ℃, performing vacuum sizing and cooling sizing, and then pulling and rolling at the speed of 10-50 m/min to obtain the heat-conducting pipe.

5. Use of the high thermal conductivity radiation crosslinked polyethylene pipe according to any one of claims 1 to 4 in fluid transport.