CN103467839A - Electric stress control heat shrink tube and manufacturing method thereof - Google Patents

Abstract

An electric stress control heat shrinkable tube, which is composed of the following components in parts by mass: 30-60 parts of ethylene-vinyl acetate copolymer (EVA); 40-60 parts of conductive carbon black masterbatch; 0-20 parts of propylene rubber (EPDM); 30-100 parts of high dielectric constant functional filler; 1-2 parts of cross-linking sensitizer; 1-3 parts of lubricant; 1-2 parts of antioxidant. The electrical stress control heat-shrinkable tube of the invention meets the requirements of environmental protection, has very good processing performance, mechanical and mechanical performance, and relatively stable electrical performance.

Description

A kind of electrical stress control heat-shrinkable tube and its preparation method

technical field

The invention relates to a heat-shrinkable tube and a preparation method thereof, in particular to an electric stress-controlled heat-shrinkable tube and a preparation method thereof.

Background technique

Electrical stress control is an extremely important part in the design of medium and high voltage cable accessories. Electric stress control is to control the electric field distribution and electric field intensity inside the cable accessories, that is, to take appropriate measures to make the electric field distribution and electric field intensity in the best state, thereby improving the reliability and service life of the cable accessories. Compared with cable terminals and intermediate joints containing stress cones, cable terminals and intermediate joints with stress tubes occupy less space and have low technical content, which is convenient for workers to construct on site, and has been developed rapidly.

Two standards refer to electrical stress control heat shrink tubing:

JB/T 7829-2006 Rated voltage 1kV (Um=1.2kV) to 35kV (Um=40.5kV) power cable heat shrinkable terminal

JB/T 7830-2006 Rated voltage 1kV (Um=1.2kV) to 10kV (Um=12kV) extruded insulation power cable heat shrinkable straight-through joint

It is required that the dielectric constant of the electric stress control heat shrinkable tube is not less than 20, and the volume resistivity is 10 ⁸ -10 ¹² Ω·cm, and the two technical requirements of stress control and volume resistance must be taken into account.

The stability of the electrical parameters of the electrical stress control material is also often affected by various factors. Operating in a long-term electric field, temperature, and external environment changes will cause the stress control material to age, and the volume resistivity of the stress control material after aging will occur. Great changes, the volume resistivity becomes larger, the stress control material becomes an insulating material, which cannot improve the electric field, the volume resistivity becomes smaller, the stress control material becomes a conductive material, and the cable fails. This is why heat-shrinkable cable accessories using stress-controlling materials to improve the electric field can only be used for medium-voltage power cable lines and why heat-shrinkable cable accessories often fail.

At present, many domestic and foreign cable accessories manufacturers produce electric stress control heat shrinkable tubes. The quality of foreign products is better, but the price is higher, and the domestic products are less stable and not environmentally friendly. For example, two national inventions with the application publication number CN 101701081 A titled "a heat-shrinkable stress control tube material" and the application publication number CN 101701085 A titled "a method for preparing a heat-shrinkable stress control tube material" The formula mentioned in the patent is 80-120 parts of polyethylene, 10-40 parts of chlorinated polyethylene, 30-90 parts of barium titanate, 5-50 parts of conductive carbon black, and 0.5-10 parts of lubricant. The tensile strength is 12MPa, the elongation at break is 360%, the volume resistivity is 10 ¹¹ Ω·cm, and the dielectric constant is 19; the application publication number is CN 102382380 A, and the name is "continuous heat-shrinkable stress control tube material and its preparation method" The national invention patent uses 20-40 parts of chlorinated polyethylene, 25-45 parts of thermoplastic elastomer, 10-20 parts of carbon black, 20-30 parts of barium titanate, etc. to prepare a dielectric constant greater than 15 and a volume resistivity greater than 10 ¹⁰ Ω·cm electrical stress control material; the formula mentioned in the national invention patent with application publication number CN 10313095 A and titled "Environmental Protection, Moisture-proof, High Dielectric Stress Control Sleeve Material and Its Stable and High-speed Manufacturing Method" is chlorinated rubber 25-45 parts, polyolefin 15-35 parts, carbon black 5-10 parts, piezoelectric material 15-30 parts, stabilizer 1-2 parts, etc. The four patents all use chlorinated polyethylene or chlorinated rubber. Compared with polyolefin, this material has a higher dielectric constant and lower volume resistivity, which is convenient for adjusting the electrical stress control material to the required range. However, in the process of processing and use, it is easy to dehydrochloride, and the thermal stability is not good enough; a large amount of carbon black is added to the formula to reduce the volume resistivity of the material, but the particle size of carbon black is small, and it is not easy to disperse evenly in the substrate, and It is easy to scatter during the production process, pollute the working environment, cause a short circuit in the electrical system of the processing equipment, and affect normal production.

Therefore, it is necessary to develop heat-shrinkable tube products with simple production process, excellent electrical properties and stable electrical stress control.

Contents of the invention

The technical problem to be solved by the present invention is to provide an electric stress control heat-shrinkable tube and a preparation method thereof, which meet environmental protection requirements, have very good processing performance, mechanical and mechanical properties, and relatively stable electrical properties.

In order to solve the above-mentioned technical problems, the present invention proposes the following technical solutions: an electric stress control heat-shrinkable tube, which consists of the following components in parts by mass:

Ethylene-vinyl acetate copolymer (EVA) 30-60 parts;

Conductive carbon black masterbatch 40-60 parts;

EPDM 0～20 parts;

High dielectric constant functional filler 30-100 parts;

Cross-linking sensitizer 1-2 parts;

Lubricant 1 to 3 parts;

Antioxidant 1-2 parts.

The above technical solution is further limited in that: the ethylene-vinyl acetate copolymer is preferably an ethylene-vinyl acetate copolymer with a mass content of vinyl acetate of 15% and a melt index of 1.5 g/10min.

A further limitation of the above technical solution is that: the conductive carbon black masterbatch is preferably a conductive carbon black masterbatch with a mass content of 30% conductive carbon black and a melt index of 2g/10min.

A further limitation of the above technical solution is that: the EPDM rubber is preferably EPDM rubber with a Mooney viscosity ML(1+4) (125° C.) of 40-45 MU.

The above technical solution is further limited in that: the high dielectric constant functional filler is preferably barium titanate porcelain powder with a weight content of 99.4% barium titanate, a particle size of 0.5-1.0 μm, and a dielectric constant ≥ 1800.

The above-mentioned technical scheme is further limited in that: the cross-linking sensitizer is preferably trimethylolpropane trimethacrylate (TMPTA), pentaerythritol tetraacrylate (PETEA), triallyl isocyanate (TAIC) One or a mixture of two or more of them.

The further limitation of the above-mentioned technical solution is that the lubricant is preferably one of zinc stearate (ZnSt), magnesium stearate (MgSt), n-butyl stearate (BS) or two or more of them mixture of species.

The further limitation of the above technical solution is: the antioxidant is preferably obtained by mixing thiobisphenol antioxidant and hindered phenol antioxidant according to the mass ratio (1-3): 1;

The thiobisphenol antioxidant is 4,4'-thiobis(6-tert-butyl-3-methylphenol) (antioxidant 300);

The hindered phenolic antioxidant is tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate] pentaerythritol ester (antioxidant 1010).

In order to solve the above-mentioned technical problems, the present invention proposes the following technical solutions: a preparation method for preparing the above-mentioned electric stress control heat-shrinkable tube, comprising the following steps:

Step 1: Preparation of Electrical Stress Control Heat Shrink Tube Pellets:

(1), 30-60 parts by mass of ethylene-vinyl acetate copolymer, 40-60 parts by mass of conductive carbon black masterbatch, 0-20 parts by mass of ethylene-propylene rubber, 1-3 parts by mass of lubricant and 1-2 parts by mass The mass parts antioxidant is put into the internal mixer for mixing, the internal mixing time is 2-4min, and the internal mixing temperature is 110-130°C;

(2) Then add 1-2 parts by mass of cross-linking sensitizer and 30-100 parts by mass of high dielectric constant functional filler and mix evenly. The mixing time is 4-8 minutes, the mixing temperature is 120-150°C, and the material is discharged , to get the mixture;

(3) Extrude the mixture through a twin-screw extruder at a temperature of 130-160°C, water-cool, ventilate and dry, and pelletize to obtain electric stress-controlled heat-shrinkable tube pellets;

Step 2: Extrusion of electric stress-controlled heat-shrinkable tube: extrude the pellets prepared in step 1 at a temperature of 120-150°C with an extruder, water-cool and roll;

Step 3: Irradiation of the electric stress-controlled heat-shrinkable tube: the electric-stress-controlled heat-shrinkable tube extruded in step 2 is irradiated and cross-linked by an electron accelerator, and the irradiation intensity is 6-10 Mrad;

Step 4: Expansion of the electrical stress-controlled heat-shrinkable tube: In step 3, the irradiated tube is expanded by 2-4 times at a temperature of 90-130°C, cooled and shaped, and cut to obtain the finished electrical-stress-controlled heat-shrinkable tube.

The above technical solution is further limited in that: the ethylene-vinyl acetate copolymer is an ethylene-vinyl acetate copolymer with a vinyl acetate mass content of 15% and a melt index of 1.5g/10min;

Described conductive carbon black masterbatch is that the mass content of conductive carbon black is 30%, and melt index is the conductive carbon black masterbatch of 2g/10min;

The EPDM rubber is preferably EPDM rubber with a Mooney viscosity ML (1+4) (125°C) of 40-45 MU;

The high dielectric constant functional filler is barium titanate porcelain powder with a weight content of 99.4% barium titanate, a particle size of 0.5-1.0 μm, and a dielectric constant ≥ 1800;

The crosslinking sensitizer is one of trimethylolpropane trimethacrylate, pentaerythritol tetraacrylate, triallyl isocyanate or a mixture of two or more thereof;

Described lubricant is one in zinc stearate, magnesium stearate, n-butyl stearate or the mixture of two or more thereof;

The antioxidant is obtained by mixing a thiobisphenol antioxidant and a hindered phenol antioxidant in a mass ratio (1-3): 1;

The thiobisphenol antioxidant is 4,4'-thiobis(6-tert-butyl-3-methylphenol);

The hindered phenolic antioxidant is tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate] pentaerythritol ester.

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

The electrical stress control heat-shrinkable tube of the present invention does not contain halogen, meets environmental protection requirements, and is added with an efficient anti-oxidation system. It has good thermal stability during processing and use, and has very good processing performance, mechanical properties, and electrical The performance is relatively stable, which can well ensure the overall safety of the cable accessories;

In the production process of the electrical stress control heat shrinkable tube of the present invention, conductive carbon black masterbatch is added to reduce the volume resistivity of the material, which is easy to disperse evenly on the substrate, and there is no conductive dust flying during the production process, and does not pollute the working environment and equipment , to ensure the smooth progress of production;

The electric stress control heat-shrinkable tube of the invention has simple preparation method, excellent mechanical properties, electrical properties and thermal aging properties, and is suitable for industrialized production.

Detailed ways

The invention discloses an electric stress control heat-shrinkable tube, which consists of the following components in parts by mass:

Ethylene-vinyl acetate copolymer (EVA) 30-60 parts;

Conductive carbon black masterbatch 40-60 parts;

EPDM 0～20 parts;

High dielectric constant functional filler 30-100 parts;

Cross-linking sensitizer 1-2 parts;

Lubricant 1 to 3 parts;

Antioxidant 1-2 parts.

The ethylene-vinyl acetate copolymer is preferably an ethylene-vinyl acetate copolymer with a mass content of vinyl acetate of 15% and a melt index of 1.5 g/10 min (ASTM D1238).

The conductive carbon black masterbatch is preferably a conductive carbon black masterbatch with a mass content of 30% conductive carbon black and a melt index of 2g/10min (ASTM D1238).

The EPDM rubber is preferably an EPDM rubber with a Mooney viscosity ML(1+4) (125° C.) of 40-45 MU.

The high dielectric constant functional filler is preferably barium titanate porcelain powder with a weight content of 99.4% barium titanate, a particle size of 0.5-1.0 μm, and a dielectric constant ≥ 1800.

The cross-linking sensitizer is preferably one of trimethylolpropane trimethacrylate (TMPTMA), pentaerythritol tetraacrylate (PETEA), triallyl isocyanate (TAIC) or two or more of them mixture of species.

The lubricant is preferably one of zinc stearate (ZnSt), magnesium stearate (MgSt), n-butyl stearate (BS) or a mixture of two or more thereof.

The antioxidant is preferably obtained by mixing a thiobisphenol antioxidant and a hindered phenol antioxidant in a mass ratio (1-3):1.

The thiobisphenol antioxidant is preferably 4,4'-thiobis(6-tert-butyl-3-methylphenol) (antioxidant 300).

The hindered phenolic antioxidant is preferably tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate] pentaerythritol (antioxidant 1010).

The preparation method of the electric stress control heat shrinkable tube comprises the following steps:

Step 1: Preparation of Electrical Stress Control Heat Shrink Tube Pellets:

(1), 30-60 parts by mass of ethylene-vinyl acetate copolymer, 40-60 parts by mass of conductive carbon black masterbatch, 0-20 parts by mass of ethylene-propylene rubber, 1-3 parts by mass of lubricant and 1-2 parts by mass The mass parts antioxidant is put into the internal mixer for mixing, the internal mixing time is 2-4min, and the internal mixing temperature is 110-130°C;

(2) Then add 1-2 parts by mass of cross-linking sensitizer and 30-100 parts by mass of high dielectric constant functional filler and mix evenly. The mixing time is 4-8 minutes, the mixing temperature is 120-150°C, and the material is discharged , to get the mixture;

(3) Extrude the mixture through a twin-screw extruder at a temperature of 130-160°C, water-cool, ventilate and dry, and pelletize to obtain electric stress-controlled heat-shrinkable tube pellets;

Step 2: Extrusion of electric stress-controlled heat-shrinkable tube: extrude the pellets prepared in step 1 at a temperature of 120-150°C with an extruder, water-cool and roll;

Step 3: Irradiation of the electric stress-controlled heat-shrinkable tube: the electric-stress-controlled heat-shrinkable tube extruded in step 2 is irradiated and cross-linked by an electron accelerator, and the irradiation intensity is 6-10 Mrad;

Step 4: Expansion of the electrical stress-controlled heat-shrinkable tube: In step 3, the irradiated tube is expanded by 2-4 times at a temperature of 90-130°C, cooled and shaped, and cut to obtain the finished electrical-stress-controlled heat-shrinkable tube.

the

Preparation Example 1

Step 1: Preparation of Electrical Stress Control Heat Shrink Tube Pellets:

① 60 parts by mass of ethylene-vinyl acetate copolymer, 40 parts by mass of conductive carbon black masterbatch, 1 part by mass of lubricant (specifically 1 part by mass of zinc stearate) and 1 part by mass of antioxidant (including 0.75 parts by mass Antioxidant 300 and 0.25 parts of antioxidant 1010) were put into the internal mixer for mixing, the internal mixing time was 2min, and the internal mixing temperature was 110°C;

② Then add 1 mass part of cross-linking sensitizer (specifically, 1 mass part of trimethylolpropane trimethacrylate (TMPTMA)) and 100 mass parts of high dielectric constant functional filler (specifically, 100 mass parts of titanic acid Barium) banburying evenly; banburying time 4min, banburying temperature 120 ℃, discharge, get the mixture;

③Extrude the mixture through a twin-screw extruder at a temperature of 130°C, water-cool, ventilate and dry, and pelletize to obtain electric stress-controlled heat-shrinkable tube pellets;

Step 2: Extrusion of electric stress-controlled heat-shrinkable tube: Extrude the pellets prepared in Step 1 at a temperature of 120°C with an extruder, water-cool and roll;

Step 3: Irradiation of the electric stress-controlled heat-shrinkable tube: the electric-stress-controlled heat-shrinkable tube extruded in step 2 is irradiated and cross-linked by an electron accelerator, and the irradiation intensity is 8 Mrad;

Step 4: Expansion of the electrical stress-controlled heat-shrinkable tube: In step 3, the irradiated tube is expanded by 2 times at a temperature of 100°C, cooled, shaped, and cut to obtain the finished electrical-stress-controlled heat-shrinkable tube.

The mechanical and mechanical performance test results of the electric stress control heat shrinkable tube of this embodiment are: tensile strength (test standard GB/T 1040) 12.6MPa, elongation at break 436%; electrical performance test results are: volume resistivity (test Standard GB/T 1410) 8.9*10 ¹¹ Ω·cm, dielectric constant (testing standard GB/T 1409) 23, dielectric loss 0.12.

the

Preparation Example 2

Step 1: Preparation of Electrical Stress Control Heat Shrink Tube Pellets:

① Mix 30 parts by mass of ethylene-vinyl acetate copolymer, 50 parts by mass of conductive carbon black masterbatch, 20 parts by mass of EPDM rubber, 2 parts by mass of lubricant (specifically take 2 parts by mass of magnesium stearate) and 2 parts by mass of magnesium stearate 1 part of antioxidant (including 1 part of antioxidant 300 and 1 part of antioxidant 1010) was put into the internal mixer for mixing, the mixing time was 3 minutes, and the mixing temperature was 120°C;

② Then add 1.5 parts by mass of cross-linking sensitizer (specifically, 1.5 parts by mass of pentaerythritol tetraacrylate (PETEA)) and 80 parts by mass of high dielectric constant functional filler (specifically, 80 parts by mass of barium titanate) and banbury evenly; The banburying time is 6min, the banburying temperature is 140°C, and the material is discharged to obtain the mixture;

③Extrude the mixture through a twin-screw extruder at a temperature of 150°C, water-cool, ventilate and dry, and pelletize to obtain electric stress-controlled heat-shrinkable tube pellets;

Step 2: Extrusion of electric stress-controlled heat-shrinkable tubing: Extrude the pellets prepared in Step 1 at a temperature of 140°C with an extruder, water-cool, and wind up;

Step 3: Irradiation of the electric stress-controlled heat-shrinkable tube: the electric-stress-controlled heat-shrinkable tube extruded in step 2 is irradiated and cross-linked by an electron accelerator, and the irradiation intensity is 6 Mrad;

Step 4: Expansion of the electric stress-controlled heat-shrinkable tube: Step 3. The irradiated tube is expanded by 3 times at a temperature of 120°C, cooled and shaped, and cut to obtain the finished electric-stress-controlled heat-shrinkable tube.

The test results of the mechanical and mechanical properties of the electrical stress-controlled heat-shrinkable tube in this embodiment are: tensile strength (test standard GB/T 1040) 12.9MPa, elongation at break 442%; electrical performance test results are: volume resistivity (test standard GB/T 1410) 3.2*10 ¹⁰ Ω·cm, the dielectric constant is (testing standard GB/T 1409) 32, and the dielectric loss is 0.19.

the

Preparation Example 3

Step 1: Preparation of Electrical Stress Control Heat Shrink Tube Pellets:

① 30 parts by mass of ethylene-vinyl acetate copolymer, 60 parts by mass of conductive carbon black masterbatch, 10 parts by mass of EPDM rubber, 3 parts by mass of lubricant (specifically 3 parts by mass of n-butyl stearate) and 1.5 parts by mass of antioxidant (including 1 part of antioxidant 300 and 0.5 part of antioxidant 1010) were put into the internal mixer for mixing, the mixing time was 4 minutes, and the mixing temperature was 130°C;

② Then add 1 mass part of cross-linking sensitizer (specifically 1 mass part of triallyl isocyanate (TAIC)) and 100 mass parts of high dielectric constant functional filler (specifically 100 mass parts of barium titanate) and banbury evenly ; The banburying time is 8min, the banburying temperature is 150°C, and the material is discharged to obtain the mixture;

③Extrude the mixture through a twin-screw extruder at a temperature of 160°C, water-cool, ventilate and dry, and pelletize to obtain electric stress-controlled heat-shrinkable tube pellets;

Step 2: Extrusion of electric stress-controlled heat-shrinkable tube: Extrude the pellets prepared in Step 1 at a temperature of 150°C with an extruder, water-cool, and wind up;

Step 3: Irradiation of the electric stress-controlled heat-shrinkable tube: the electric-stress-controlled heat-shrinkable tube extruded in step 2 is irradiated and cross-linked by an electron accelerator, and the irradiation intensity is 10 Mrad;

Step 4: Expansion of the electrical stress-controlled heat-shrinkable tube: Step 3. The irradiated tube expands 3 times at a temperature of 130°C, and after cooling, setting and cutting, the finished electrical stress-controlled heat-shrinkable tube is obtained.

The test results of the mechanical and mechanical properties of the electrical stress-controlled heat-shrinkable tube in this embodiment are: tensile strength (test standard GB/T 1040) 12.6 MPa, elongation at break 426%; electrical performance test results are: volume resistivity (test standard GB/T 1410) 5.9*10 ⁹ Ω·cm, dielectric constant (testing standard GB/T 1409) 42, dielectric loss 0.28.

the

Preparation Example 4

Step 1: Preparation of Electrical Stress Control Heat Shrink Tube Pellets:

① Mix 40 parts by mass of ethylene-vinyl acetate copolymer, 50 parts by mass of conductive carbon black masterbatch, 10 parts by mass of EPDM rubber, 2 parts by mass of lubricant (specifically 2 parts by mass of zinc stearate) and 2 parts by mass of zinc stearate 1 part of antioxidant (including 1.5 part of antioxidant 300 and 0.5 part of antioxidant 1010) was put into the internal mixer for mixing, the mixing time was 3 minutes, and the mixing temperature was 110°C;

② Then add 1 mass part of cross-linking sensitizer (specifically 1 mass part of triallyl isocyanate (TAIC)) and 30 mass parts of high dielectric constant functional filler (specifically 30 mass parts of barium titanate) and banbury evenly ; The banburying time is 6min, the banburying temperature is 130°C, and the material is discharged to obtain the mixture;

③Extrude the mixture through a twin-screw extruder at a temperature of 140°C, water-cool, ventilate and dry, and pelletize to obtain electric stress-controlled heat-shrinkable tube pellets;

Step 2: Extrusion of electric stress-controlled heat-shrinkable tube: Extrude the pellets prepared in Step 1 at a temperature of 130°C with an extruder, water-cool, and wind up;

Step 3: Irradiation of the electric stress-controlled heat-shrinkable tube: the electric-stress-controlled heat-shrinkable tube extruded in step 2 is irradiated and cross-linked by an electron accelerator, and the irradiation intensity is 10Mrad;

Step 4: Expansion of the electrical stress-controlled heat-shrinkable tube: Step 3. The irradiated tube expands 3 times at a temperature of 90°C, and after cooling, setting and cutting, the finished electrical stress-controlled heat-shrinkable tube is obtained.

The test results of the mechanical and mechanical properties of the electrical stress-controlled heat-shrinkable tube in this embodiment are: tensile strength (test standard GB/T 1040) 14.8 MPa, elongation at break 477%; electrical performance test results are: volume resistivity (test standard GB/T 1410) 3.7*10 ⁹ Ω·cm, dielectric constant (test standard GB/T 1409) 23, dielectric loss 0.18.

the

Preparation Example 5

Step 1: Preparation of Electrical Stress Control Heat Shrink Tube Pellets:

① Mix 50 parts by mass of ethylene-vinyl acetate copolymer, 45 parts by mass of conductive carbon black masterbatch, 5 parts by mass of EPDM rubber, 2 parts by mass of lubricant (specifically 2 parts by mass of magnesium stearate) and 2 parts by mass of 1 part of antioxidant (including 1 part of antioxidant 300 and 1 part of antioxidant 1010) was put into the internal mixer for mixing, the mixing time was 2 minutes, and the mixing temperature was 120°C;

② Then add 2 parts by mass of cross-linking sensitizer (specifically, 2 parts by mass of trimethylolpropane triacrylate (TMPTA)) and 50 parts by mass of high dielectric constant functional filler (specifically, 50 parts by mass of barium titanate) The banburying is uniform; the banburying time is 6 minutes, the banburying temperature is 140°C, and the material is discharged to obtain the mixture;

③Extrude the mixture through a twin-screw extruder at a temperature of 150°C, water-cool, ventilate and dry, and pelletize to obtain electric stress-controlled heat-shrinkable tube pellets;

Step 2: Extrusion of electric stress-controlled heat-shrinkable tubing: Extrude the pellets prepared in Step 1 at a temperature of 140°C with an extruder, water-cool, and wind up;

Step 3: Irradiation of the electric stress-controlled heat-shrinkable tube: the electric-stress-controlled heat-shrinkable tube extruded in step 2 is irradiated and cross-linked by an electron accelerator, and the irradiation intensity is 6 Mrad;

Step 4: Expansion of the electrical stress-controlled heat-shrinkable tube: In step 3, the irradiated tube is expanded by 4 times at a temperature of 110°C, cooled, shaped, and cut to obtain the finished electrical-stress-controlled heat-shrinkable tube.

The test results of the mechanical and mechanical properties of the electrical stress-controlled heat-shrinkable tube in this embodiment are: tensile strength (test standard GB/T 1040) 14.3MPa, elongation at break 469%; electrical performance test results are: volume resistivity (test standard GB/T 1410) 2.1*10 ¹¹ Ω·cm, the dielectric constant is (testing standard GB/T 1409) 26, and the dielectric loss is 0.13.

the

Preparation Example 6

Step 1: Preparation of Electrical Stress Control Heat Shrink Tube Pellets:

① 35 parts by mass of ethylene-vinyl acetate copolymer, 50 parts by mass of conductive carbon black masterbatch, 15 parts by mass of EPDM rubber, 3 parts by mass of lubricant (specifically, 3 parts by mass of n-butyl stearate) and 1.5 parts by mass of antioxidant (including 1 part of antioxidant 300 and 0.5 part of antioxidant 1010) were put into the internal mixer for mixing, the mixing time was 4 minutes, and the mixing temperature was 120°C;

② Then add 2 mass parts of cross-linking sensitizer (specifically 2 mass parts of pentaerythritol tetraacrylate (PETEA)) and 60 mass parts of high dielectric constant functional filler (specifically 60 mass parts of barium titanate) and banbury evenly; The banburying time is 6min, the banburying temperature is 140°C, and the material is discharged to obtain the mixture;

③Extrude the mixture through a twin-screw extruder at a temperature of 140°C, water-cool, ventilate and dry, and pelletize to obtain electric stress-controlled heat-shrinkable tube pellets;

Step 2: Extrusion of electric stress-controlled heat-shrinkable tube: Extrude the pellets prepared in Step 1 at a temperature of 130°C with an extruder, water-cool, and wind up;

Step 3: Irradiation of the electric stress-controlled heat-shrinkable tube: the electric-stress-controlled heat-shrinkable tube extruded in step 2 is irradiated and cross-linked by an electron accelerator, and the irradiation intensity is 8 Mrad;

Step 4: Expansion of the electric stress-controlled heat-shrinkable tube: Step 3. The irradiated tube is expanded by 3 times at a temperature of 120°C, cooled and shaped, and cut to obtain the finished electric-stress-controlled heat-shrinkable tube.

The test results of the mechanical and mechanical properties of the electric stress-controlled heat-shrinkable tube in this embodiment are: tensile strength (test standard GB/T 1040) 14.1MPa, elongation at break 463%; electrical performance test results are: volume resistivity (test standard GB/T 1410) 3.6*10 ¹⁰ Ω·cm, dielectric constant (testing standard GB/T 1409) 35, dielectric loss 0.24.

Claims (10)

1. An electric stress control heat-shrinkable tube, which is composed of the following components in parts by mass: Ethylene-vinyl acetate copolymer 30-60 parts; Conductive carbon black masterbatch 40-60 parts; EPDM 0～20 parts; High dielectric constant functional filler 30-100 parts; Cross-linking sensitizer 1 to 2 parts; Lubricant 1 to 3 parts; Antioxidant 1 to 2 parts. 2. The electric stress control heat-shrinkable tube according to claim 1, characterized in that: the ethylene-vinyl acetate copolymer has a vinyl acetate mass content of 15% and a melt index of 1.5g/10min Ethylene-vinyl acetate copolymer. 3. The electric stress control heat-shrinkable tube according to claim 1, characterized in that: the mass content of the conductive carbon black masterbatch is 30%, and the melt index is 2g/10min conductive carbon black Masterbatch. 4. The electric stress control heat shrinkable tube according to claim 1, characterized in that: the EPDM rubber is preferably EPDM with a Mooney viscosity ML (1+4) (125°C) of 40-45MU Propylene rubber. 5. The electric stress control heat-shrinkable tube according to claim 1, characterized in that: the high dielectric constant functional filler is barium titanate with a weight content of 99.4%, a particle size of 0.5-1.0 μm, and a dielectric constant of ≥1800 barium titanate porcelain powder. 6. The electric stress control heat-shrinkable tube according to claim 1, characterized in that: the cross-linking sensitizer is trimethylolpropane trimethacrylate, pentaerythritol tetraacrylate, triallyl isocyanate one of them or a mixture of two or more of them. 7. The electric stress control heat-shrinkable tube according to claim 1, characterized in that: the lubricant is one or two of zinc stearate, magnesium stearate, n-butyl stearate or a mixture of several. 8. The electrical stress control heat-shrinkable tube according to claim 1, characterized in that: the antioxidant is a thiobisphenol antioxidant and a hindered phenol antioxidant in a mass ratio (1-3) : 1 ratio obtained; The thiobisphenol antioxidant is 4,4'-thiobis(6-tert-butyl-3-methylphenol); The hindered phenolic antioxidant is tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate] pentaerythritol ester. 9. A preparation method for preparing the electric stress control heat-shrinkable tube as claimed in claim 1, characterized in that, the preparation method comprises the following steps: Step 1: Preparation of Electrical Stress Control Heat Shrink Tube Pellets: (1), 30-60 parts by mass of ethylene-vinyl acetate copolymer, 40-60 parts by mass of conductive carbon black masterbatch, 0-20 parts by mass of ethylene-propylene rubber, 1-3 parts by mass of lubricant and 1-2 parts by mass The mass parts antioxidant is put into the internal mixer for mixing, the internal mixing time is 2-4min, and the internal mixing temperature is 110-130°C; (2) Then add 1-2 parts by mass of cross-linking sensitizer and 30-100 parts by mass of high dielectric constant functional filler and mix evenly. The mixing time is 4-8 minutes, the mixing temperature is 120-150°C, and the material is discharged , to get the mixture; (3) Extrude the mixture through a twin-screw extruder at a temperature of 130-160°C, water-cool, ventilate and dry, and pelletize to obtain electric stress-controlled heat-shrinkable tube pellets; Step 2: Extrusion of electric stress-controlled heat-shrinkable tube: extrude the pellets prepared in step 1 at a temperature of 120-150°C with an extruder, water-cool and roll; Step 3: Irradiation of the electric stress-controlled heat-shrinkable tube: the electric-stress-controlled heat-shrinkable tube extruded in step 2 is irradiated and cross-linked by an electron accelerator, and the irradiation intensity is 6-10 Mrad; Step 4: Expansion of the electrical stress-controlled heat-shrinkable tube: In step 3, the irradiated tube is expanded by 2-4 times at a temperature of 90-130°C, cooled and shaped, and cut to obtain the finished electrical-stress-controlled heat-shrinkable tube. 10. the preparation method of electric stress control heat-shrinkable tube according to claim, is characterized in that, described ethylene-vinyl acetate copolymer is that the mass content of vinyl acetate is 15%, and melt index is 1.5g/ 10min of ethylene-vinyl acetate copolymer; Described conductive carbon black masterbatch is that the mass content of conductive carbon black is 30%, and melt index is the conductive carbon black masterbatch of 2g/10min; The EPDM rubber is preferably EPDM rubber with a Mooney viscosity ML (1+4) (125°C) of 40-45 MU; The high dielectric constant functional filler is barium titanate porcelain powder with a weight content of 99.4% barium titanate, a particle size of 0.5-1.0 μm, and a dielectric constant ≥ 1800; The crosslinking sensitizer is one of trimethylolpropane trimethacrylate, pentaerythritol tetraacrylate, triallyl isocyanate or a mixture of two or more thereof; Described lubricant is one in zinc stearate, magnesium stearate, n-butyl stearate or the mixture of two or more thereof; The antioxidant is obtained by mixing a thiobisphenol antioxidant and a hindered phenol antioxidant in a mass ratio (1-3): 1; The thiobisphenol antioxidant is 4,4'-thiobis(6-tert-butyl-3-methylphenol); The hindered phenolic antioxidant is tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate] pentaerythritol ester.