CN118006071A - Semiconductive shielding material and preparation method thereof - Google Patents
Semiconductive shielding material and preparation method thereof Download PDFInfo
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- CN118006071A CN118006071A CN202410226207.4A CN202410226207A CN118006071A CN 118006071 A CN118006071 A CN 118006071A CN 202410226207 A CN202410226207 A CN 202410226207A CN 118006071 A CN118006071 A CN 118006071A
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- 239000000463 material Substances 0.000 title claims abstract description 82
- 238000002360 preparation method Methods 0.000 title claims abstract description 11
- 239000005038 ethylene vinyl acetate Substances 0.000 claims abstract description 60
- 229920001200 poly(ethylene-vinyl acetate) Polymers 0.000 claims abstract description 60
- 229920001684 low density polyethylene Polymers 0.000 claims abstract description 54
- 239000004702 low-density polyethylene Substances 0.000 claims abstract description 54
- FPYJFEHAWHCUMM-UHFFFAOYSA-N maleic anhydride Chemical compound O=C1OC(=O)C=C1 FPYJFEHAWHCUMM-UHFFFAOYSA-N 0.000 claims abstract description 32
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 claims abstract description 31
- 239000000203 mixture Substances 0.000 claims abstract description 23
- 239000000758 substrate Substances 0.000 claims abstract description 8
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- 238000004132 cross linking Methods 0.000 claims description 17
- 238000000748 compression moulding Methods 0.000 claims description 16
- 239000003431 cross linking reagent Substances 0.000 claims description 14
- 238000000034 method Methods 0.000 claims description 7
- -1 2, 4-di-t-butylcumene peroxide Chemical class 0.000 claims description 4
- XTXRWKRVRITETP-UHFFFAOYSA-N Vinyl acetate Chemical compound CC(=O)OC=C XTXRWKRVRITETP-UHFFFAOYSA-N 0.000 claims description 4
- XMNIXWIUMCBBBL-UHFFFAOYSA-N 2-(2-phenylpropan-2-ylperoxy)propan-2-ylbenzene Chemical compound C=1C=CC=CC=1C(C)(C)OOC(C)(C)C1=CC=CC=C1 XMNIXWIUMCBBBL-UHFFFAOYSA-N 0.000 claims description 3
- 238000004519 manufacturing process Methods 0.000 claims description 3
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- 229910052799 carbon Inorganic materials 0.000 description 2
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
- C08K3/00—Use of inorganic substances as compounding ingredients
- C08K3/02—Elements
- C08K3/04—Carbon
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
- C08K2201/00—Specific properties of additives
- C08K2201/001—Conductive additives
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
- C08L2201/00—Properties
- C08L2201/08—Stabilised against heat, light or radiation or oxydation
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Abstract
The application relates to a semiconductive shielding material and a preparation method thereof. A semiconductive shielding material comprising a polymeric substrate and conductive carbon black dispersed in the polymeric substrate; the polymeric substrate comprises the graft cross-linked product of a blend of ethylene vinyl acetate copolymer and low density polyethylene with maleic anhydride. The application provides a semiconductive shielding material, which has the advantages that the polarity of the material is greatly reduced due to the simultaneous existence of an ethylene-vinyl acetate copolymer with large polarity and a low-density polyethylene with low polarity, so that conductive carbon black can be more uniformly dispersed, the volume resistivity of the semiconductive shielding material is reduced, the conductivity of the material is improved, and meanwhile, maleic anhydride is introduced as a compatilizer, so that the ethylene-vinyl acetate copolymer and the low-density polyethylene are more uniform in mutual melting, and the mechanical property and the heat aging resistance of the material are also greatly improved on the premise of ensuring the stability of the electrical property of the semiconductive shielding material.
Description
Technical Field
The application relates to the technical field of electric materials, in particular to a semiconductive shielding material and a preparation method thereof.
Background
With the rapid development of economy and the continuous expansion of urban scale, large-capacity, long-distance and high-efficiency power transmission is becoming a main development direction nowadays. Compared with alternating current transmission, the direct current transmission has the advantages of low loss, low cost, high stability, convenient regulation and control and the like, so that the direct current transmission has great advantages in both economy and technology. Although the direct current transmission has certain defects, such as high manufacturing cost of the converter equipment, easy generation of harmonic waves and the like. However, due to the inherent advantages of direct current transmission, the direct current transmission has wide application in the aspects of high power, long-distance transmission, interconnection among high power systems and the like.
The high-voltage direct-current cable is used as core equipment of a high-voltage transmission system and is widely applied to long-distance and large-span transmission lines due to the advantages of low loss, high reliability, no maintenance and the like. The semi-conductive shielding layer can avoid the phenomenon of uneven surface electric field on the surface of the high-voltage insulated cable conductor caused by the reasons of unsmooth surface, air gaps, tip burrs and the like, and reduce the probability of the insulation developing to breakdown due to partial discharge, so that the semi-conductive shielding layer occupies an important position in the high-voltage insulated cable. The semiconductive shielding material for the cable is a composite semiconductive high-molecular material formed by taking a high-molecular polymer as a matrix and introducing a conductive filler into the matrix, wherein the matrix resin is generally polyolefin resin, and the main component of the conductive filler is carbon filler.
With the development of the high-voltage direct-current cable, the usage amount of the semiconductive shielding material used for the high-voltage direct-current cable is also increased. However, the materials produced by the current semiconductive shielding materials have poor performance levels such as conductivity, mechanical strength, thermal aging resistance and the like due to the imperfect formulation and processing technology system. Therefore, research on the technology of the semiconductive shielding material has a great pushing effect on the autonomous development of the power cable industry, and the autonomous development of the semiconductive shielding material for the high-voltage cable has great significance in terms of both social benefit and economic benefit.
Disclosure of Invention
Based on the above, the application provides a semiconductive shielding material which is beneficial to improving the conductivity, the mechanical property and the thermal aging resistance and a preparation method thereof.
The application provides a semiconductive shielding material, which comprises a polymer substrate and conductive carbon black dispersed in the polymer substrate;
The polymeric substrate comprises the graft cross-linked product of a blend of ethylene vinyl acetate copolymer and low density polyethylene with maleic anhydride.
In some embodiments, the ethylene-vinyl acetate copolymer has a vinyl acetate content of 16% -20%.
In some embodiments, the ethylene-vinyl acetate copolymer has a melt index of 2.2g/10min to 2.8g/10min.
In some embodiments, the low-density polyethylene has a melt index of 2g/10min to 3g/10min.
In some embodiments, the mass ratio of the ethylene-vinyl acetate copolymer to the low density polyethylene is 1 (0.66-1.5).
In some of these embodiments, the mass of the maleic anhydride is 1% -5% of the sum of the mass of the ethylene-vinyl acetate copolymer and the low density polyethylene.
In some embodiments, the mass of the conductive carbon black is 30% -50% of the sum of the mass of the ethylene-vinyl acetate copolymer and the low density polyethylene.
The application also provides a preparation method of the semiconductive shielding material in any embodiment, which comprises the following steps:
Melt blending the ethylene-vinyl acetate copolymer, the low density polyethylene, the conductive carbon black, and the maleic anhydride to form a melt blend; and
And (3) carrying out graft crosslinking reaction on the melt blend and compression molding to form the semiconductive shielding material.
In some of these embodiments, a cross-linking agent is also added during melt blending.
In some of these embodiments, the crosslinking agent comprises 2, 4-di-tert-butylcumene peroxide or dicumyl peroxide.
In some embodiments, the amount of the cross-linking agent added is 0.8% -1.2% of the sum of the mass of the ethylene-vinyl acetate copolymer and the low density polyethylene.
In some of these embodiments, the melt blending temperature is: 105-115 ℃.
In some of these embodiments, the melt blending is performed at a speed of: 45r/min to 55r/min.
In some embodiments, the grafting crosslinking reaction is performed and the compression molding is performed at a temperature of 175 ℃ to 185 ℃.
In some embodiments, the grafting crosslinking reaction is performed and the compression molding pressure is 13MPa to 18MPa.
The application provides a semiconductive shielding material, which comprises a polymer substrate and conductive carbon black dispersed in the polymer substrate, wherein the polymer substrate comprises a graft cross-linked product of a blend of ethylene-vinyl acetate copolymer and low density polyethylene and maleic anhydride. The polarity of the material is greatly reduced by the simultaneous existence of the ethylene-vinyl acetate copolymer and the low-density polyethylene, so that the conductive carbon black can be more uniformly dispersed, the volume resistivity of the semiconductive shielding material is reduced, the conductivity of the material is improved, and meanwhile, maleic anhydride is introduced as a compatilizer, so that the ethylene-vinyl acetate copolymer and the low-density polyethylene are more uniform in fusion, and the mechanical property and the thermal aging resistance of the material are also greatly improved on the premise of ensuring the stability of the electrical property of the semiconductive shielding material.
Drawings
FIG. 1 is a SEM cross-sectional scanning electron micrograph of the semiconductive shielding material of example 1 at 40K;
FIG. 2 is a SEM cross-sectional scanning electron micrograph of the semiconductive shielding material of example 1 at 2k times;
FIG. 3 is a graph showing the results of the measurement of the volume resistivity of the semiconductive shield materials of example 1, comparative example 1 and comparative example 2 with respect to the change of temperature;
FIG. 4 is a graph showing the tensile strength test results of the semiconductive shielding materials of examples 1 to 3 and comparative example 2;
FIG. 5 is a graph showing the results of the elongation at break test of the semiconductive shield materials of examples 1 to 3 and comparative example 2;
fig. 6 is a graph showing the results of the thermal elongation and the permanent set of the semiconductive shield materials of examples 1 to 3 and comparative example 2.
Detailed Description
In order that the application may be readily understood, a more complete description of the application will be rendered by reference to the embodiments that are illustrated below. This application 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 application belongs. The terminology used herein in the description of the application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. The term "and/or" as used herein includes any and all combinations of one or more of the associated listed items.
In the application, the technical characteristics described in an open mode comprise a closed technical scheme composed of the listed characteristics and also comprise an open technical scheme comprising the listed characteristics.
In the present application, references to "preferred", "better", "preferred" are merely descriptive of better embodiments or examples, and it is to be understood that no limitation of the scope of the application is thereby made.
In the present application, references to "further", "still further", "particularly" and the like are used for descriptive purposes and indicate that the application is not to be interpreted as limiting the scope of the application.
In the present application, reference to "optional", "optional" means either optional or not, i.e. means either one of two parallel schemes selected from "with" or "without". If multiple "alternatives" occur in a technical solution, if no particular description exists and there is no contradiction or mutual constraint, then each "alternative" is independent.
In the present application, a numerical range (i.e., a numerical range) is referred to, and optional numerical distributions are considered to be continuous within the numerical range and include two numerical endpoints (i.e., a minimum value and a maximum value) of the numerical range and each numerical value between the two numerical endpoints unless otherwise specified. Further, when a plurality of range description features or characteristics are provided, these ranges may be combined. In other words, unless otherwise indicated, the ranges disclosed herein are to be understood to include any and all subranges subsumed therein.
The application provides a semiconductive shielding material, which comprises a polymer substrate and conductive carbon black dispersed in the polymer substrate;
the polymeric substrate comprises the graft cross-linked product of a blend of an ethylene vinyl acetate copolymer and a low density polyethylene with maleic anhydride.
The semiconductive shielding material takes a high molecular polymer as a matrix, and conductive filler is introduced into the matrix to form a composite material, wherein the matrix resin is generally polyolefin resin, and the main component of the conductive filler is carbon filler. The semiconductive shielding layer occupies an important position in the high-voltage insulated cable, can avoid uneven surface electric field phenomenon caused by the reasons of unsmooth surface, air gap, tip burrs and the like of a conductor, and reduces the probability of the insulation developing to breakdown due to partial discharge.
The ethylene-vinyl acetate copolymer (EVA) belongs to polyolefin polymer, and has the advantages of low melting temperature, good fluidity, polar and halogen-free elements, compatibility with various polymers and mineral powder, easy realization of balance of mechanical and physical properties, electrical properties and processing properties, low price, full market supply and the like, and is a semiconductive shielding material of a high-voltage direct-current cable commonly used in the market. However, the ethylene-vinyl acetate copolymer itself has strong polarity, and conductive carbon black particles are unevenly dispersed therein, thereby affecting the conductive properties of the material. Therefore, the application introduces the blending and crosslinking of the low-density polyethylene (LDPE) and the ethylene-vinyl acetate copolymer, and the low-density polyethylene is a nonpolar high polymer, and the polarity of matrix resin can be greatly reduced by the two polymers, so that the conductive carbon black is distributed more uniformly in the system, thereby reducing the volume resistivity of the material and improving the conductivity. Further, because the ethylene-vinyl acetate copolymer is a strong polar polymer, and when the ethylene-vinyl acetate copolymer is blended with nonpolar low-density polyethylene, the compatibility is poor, and the interfacial condition is easy to occur, so that adverse effects can be caused on the material performance.
In some embodiments, the ethylene-vinyl acetate copolymer has a vinyl acetate content of 16% -20%
In some embodiments, the ethylene-vinyl acetate copolymer has a melt index of 2.2g/10min to 2.8g/10min.
In some embodiments, the low density polyethylene has a melt index of 2g/10min to 3g/10min.
In some embodiments, the mass ratio of the ethylene-vinyl acetate copolymer to the low density polyethylene is 1 (0.66-1.5). The ethylene-vinyl acetate copolymer and the low-density polyethylene are mixed according to the proper mass ratio, so that the polarities of the ethylene-vinyl acetate copolymer and the low-density polyethylene are fully coordinated, the conductive carbon black is dispersed more uniformly, and the volume resistivity of the material is reduced. It is understood that the mass ratio of ethylene-vinyl acetate copolymer to low density polyethylene may be, for example, but not limited to, 1:0.66, 1:0.8, 1:0.9, 1:1, 1:1.1, 1:1.2, 1:1.5, and the like. Preferably, the mass ratio of the ethylene-vinyl acetate copolymer to the low density polyethylene is 1:1.
In some of these embodiments, the mass of maleic anhydride is 1% -5% of the sum of the mass of the ethylene-vinyl acetate copolymer and the low density polyethylene. The introduction of maleic anhydride can improve the compatibility of the ethylene-vinyl acetate copolymer and the low-density polyethylene, reduce the generation of interface conditions, be favorable for improving the mechanical property and the thermal aging resistance of the material, and in the mass range, the maleic anhydride can be properly grafted with the polymer to improve the compatibility of the material. Further, if the amount of maleic anhydride is too high, a large amount of maleic anhydride will precipitate after cooling, and the improvement of the material performance cannot be promoted, resulting in waste of raw materials, so that the amount of maleic anhydride used is controlled to be within 5% of the sum of the mass of the ethylene-vinyl acetate copolymer and the mass of the low-density polyethylene. It will be appreciated that the mass of maleic anhydride may be, for example, but not limited to, 1%, 2%, 3%, 4%, 5% of the sum of the mass of ethylene-vinyl acetate copolymer and low density polyethylene. Etc. Preferably, the mass of maleic anhydride is 5% of the sum of the mass of the ethylene-vinyl acetate copolymer and the low density polyethylene.
In some of these embodiments, the mass of the conductive carbon black is 30% -50% of the sum of the mass of the ethylene-vinyl acetate copolymer and the low density polyethylene. The conductive carbon black with the above dosage can ensure that the dosage of the conductive particles is sufficient, the material has good conductive performance, and the conductive carbon black can be uniformly distributed in the material. It is understood that the mass of the conductive carbon black may be, for example, but not limited to, 30%, 31%, 32%, 40%, 50%, etc. of the sum of the mass of the ethylene-vinyl acetate copolymer and the low density polyethylene. Preferably, the mass of the conductive carbon black is 30% of the sum of the mass of the ethylene-vinyl acetate copolymer and the low density polyethylene.
The application also provides a preparation method of the semiconductive shielding material in any embodiment, which comprises the following steps:
Melt blending an ethylene-vinyl acetate copolymer, a low density polyethylene, conductive carbon black, and maleic anhydride to form a melt blend; and
The molten blend is subjected to a graft crosslinking reaction and compression molding to form a semiconductive shield material.
In some of these embodiments, a cross-linking agent is also added during melt blending.
In some of these embodiments, the crosslinking agent comprises 2, 4-di-tert-butylcumene peroxide or dicumyl peroxide.
In some embodiments, the amount of crosslinker added is 0.8% -1.2% of the sum of the mass of the ethylene-vinyl acetate copolymer and the low density polyethylene. The polymer in the system can be fully crosslinked and molded by adding the crosslinking agent with the dosage. It is understood that the amount of crosslinking agent added may be, for example, but not limited to, 0.8%, 0.9%, 1.0%, 1.1%, 1.2% of the sum of the mass of the ethylene-vinyl acetate copolymer and the low density polyethylene, and the like. Preferably, the crosslinking agent is added in an amount of 1.0% of the sum of the mass of the ethylene-vinyl acetate copolymer and the mass of the low-density polyethylene.
In some of these embodiments, the melt blending temperature is: 105-115 ℃. It is understood that the temperature of melt blending can be, for example, but not limited to, 105 ℃, 108 ℃, 110 ℃, 112 ℃, 115 ℃, and the like. Preferably, the temperature of melt blending is 110 ℃.
In some of these embodiments, the melt blending is performed at a speed of: 45r/min to 55r/min. It is understood that the rotational speed of the melt blending may be, for example, but not limited to, 45r/min, 48r/min, 50r/min, 53r/min, 55r/min, and the like. Preferably, the melt blending is carried out at a speed of 50r/min.
In some embodiments, the grafting crosslinking reaction is performed and the compression molding is performed at a temperature of 175 ℃ to 185 ℃. It is understood that the temperature at which the graft crosslinking reaction and compression molding are performed may be, for example, but not limited to 175 ℃, 178 ℃, 180 ℃, 182 ℃, 185 ℃, and the like. Preferably, the grafting crosslinking reaction is carried out and the compression molding is carried out at a temperature of 180 ℃.
In some embodiments, the grafting crosslinking reaction is performed and the compression molding pressure is 13MPa to 18MPa. It is understood that the pressure at which the graft crosslinking reaction is carried out and compression molding may be, for example, but not limited to, 13MPa, 14MPa, 15MPa, 18MPa, etc. Preferably, the grafting crosslinking reaction is carried out and the compression molding is carried out at a pressure of 15MPa.
The semiconductive shielding material provided by the application can be used as a material of a semiconductive shielding layer of a cable, and preferably can be used as a material of a semiconductive shielding layer of a high-voltage direct-current cable.
The present application will be described in further detail with reference to the following examples. The following embodiments are more specific, and it is understood that in other embodiments, this is not limiting. In the following examples, the instruments, reagents and materials involved, unless otherwise specified, are conventional instruments, reagents and materials already known in the art and are commercially available. The experimental methods, detection methods, and the like in the examples described below are conventional experimental methods and detection methods known in the prior art unless otherwise specified.
Wherein:
Ethylene-vinyl acetate copolymer derived from zeolitization 18J3, melt flow rate 2.6g/10min, vinyl acetate content 18%;
Low density polyethylene derived from zeolitization, melt flow rate 2.3g/10min;
Maleic anhydride, derived from microphone;
conductive carbon black derived from cabot VXC500;
2, 4-Di-tert-butylcumene peroxide, derived from Weng Jiang chemicals.
Example 1
A preparation method of a semiconductive shielding material comprises the following steps:
Uniformly shaking an ethylene-vinyl acetate copolymer and low-density polyethylene in the same container according to the mass ratio of 1:1, fully mixing, putting into an internal mixer, keeping the temperature of the internal mixer at 110 ℃, keeping the rotating speed at 50r/min, adding conductive carbon black for melt mixing for 5 minutes after 8 minutes, adding maleic anhydride for melt mixing for 5 minutes, and finally adding a crosslinking agent of 2, 4-di-tert-butyl cumyl peroxide for melt mixing for 3 minutes, and cooling to obtain a cooled melt blend. The mass of each of the conductive carbon black, the maleic anhydride and the 2, 4-di-tert-butyl cumyl peroxide is 30%, 5% and 1% of the sum of the mass of the ethylene-vinyl acetate copolymer and the mass of the low-density polyethylene respectively.
And (3) melting the cooled melt blend at 110 ℃ through a flat vulcanizing machine, and then carrying out graft crosslinking reaction and compression molding on the melt blend at 180 ℃ and 15MPa to obtain the semiconductive shielding material.
Example 2
The procedure is as in example 1, except that the mass of maleic anhydride is 1% of the sum of the mass of the ethylene-vinyl acetate copolymer and the mass of the low-density polyethylene, respectively.
Example 3
The procedure is as in example 1, except that the mass of maleic anhydride is 3% of the sum of the mass of the ethylene-vinyl acetate copolymer and the mass of the low-density polyethylene, respectively.
Comparative example 1
The procedure is substantially as in example 1, except that no low-density polyethylene and no maleic anhydride are added. Specifically:
A preparation method of a semiconductive shielding material comprises the following steps:
And (3) placing the ethylene-vinyl acetate copolymer in a container, shaking uniformly, placing the container into an internal mixer, keeping the temperature of the internal mixer at 110 ℃ and the rotating speed at 50r/min, adding conductive carbon black after 8 minutes for melt mixing for 5 minutes, adding a crosslinking agent of 2, 4-di-tert-butyl cumyl peroxide for melt mixing for 3 minutes, and cooling to obtain a cooled melt blend. The mass of the conductive carbon black and the mass of the 2, 4-di-tert-butyl cumyl peroxide are respectively 30% and 1% of the sum of the ethylene-vinyl acetate copolymer.
And (3) melting the cooled melt blend at 110 ℃ through a flat vulcanizing machine, and then crosslinking and compression molding the melt blend at 180 ℃ and 15MPa to obtain the semiconductive shielding material.
Comparative example 2
The procedure is substantially as in example 1, except that maleic anhydride is not added. Specifically:
A preparation method of a semiconductive shielding material comprises the following steps:
uniformly shaking an ethylene-vinyl acetate copolymer and low-density polyethylene in the same container according to the mass ratio of 1:1, fully mixing, putting into an internal mixer, keeping the temperature of the internal mixer at 110 ℃, keeping the rotating speed at 50r/min, adding conductive carbon black after 8 minutes for melt mixing for 5 minutes, adding a crosslinking agent of 2, 4-di-tert-butyl cumyl peroxide for melt mixing for 3 minutes, and cooling to obtain a cooled melt blend. The mass of each of the conductive carbon black and the 2, 4-di-tert-butyl cumyl peroxide is 30 percent and 1 percent of the sum of the mass of the ethylene-vinyl acetate copolymer and the mass of the low-density polyethylene respectively.
And (3) melting the cooled melt blend at 110 ℃ through a flat vulcanizing machine, and then crosslinking and compression molding the melt blend at 180 ℃ and 15MPa to obtain the semiconductive shielding material.
SEM section scanning is carried out on the semiconductive shielding material prepared in the embodiment 1, and scanning results are shown in fig. 1 and 2, and it can be seen that white particles in the drawing are conductive carbon black, the conductive carbon black is uniformly dispersed in a polymer matrix, and the ethylene-vinyl acetate copolymer has good compatibility with low-density polyethylene, and no obvious interface condition occurs.
The semiconductive shield materials prepared in example 1, comparative example 1 and comparative example 2 were tested for volume resistivity with temperature, and the higher the volume resistivity, the worse the dispersion effect of the conductive carbon black was, and the worse the conductivity was, and the test results are shown in fig. 3, and it can be seen that the volume resistivity of the semiconductive shield materials of example 1, comparative example 1 and comparative example 2 were increased and increased with temperature. Among them, the volume resistivity of example 1 and comparative example 2 is significantly lower than that of comparative example 1, demonstrating that the addition of low density polyethylene to the ethylene-vinyl acetate copolymer system can effectively reduce the polarity of the material, so that the conductive carbon black particles are more uniformly dispersed and have better conductive properties. Although example 1 had an increase in volume resistivity compared to comparative example 2, since example 1 incorporated maleic anhydride for grafting, the polarity of the grafted product was slightly increased, but the difference was not very significant, example 1 still had better conductivity.
The mechanical properties of the semiconductive shielding materials prepared in examples 1-3 and comparative example 2 are tested according to the mechanical industry standard GB/T1040.2-2006 of the people's republic of China, and the specific method comprises the following steps: and punching the test sample into a shape sample by adopting a No. II dumbbell knife, and then placing the shape sample on a stretcher for testing. The test results are shown in fig. 4 and 5.
Fig. 4 is a graph showing the tensile strength test results of the semiconductive shielding materials of examples 1 to 3 and comparative example 2, and it can be seen that the tensile strengths of examples 1 to 3 are significantly higher than that of comparative example 2, and that the tensile strengths of the semiconductive shielding materials are increased with the increase of the maleic anhydride content as compared with examples 1 to 3.
Fig. 5 is a graph showing the results of the elongation at break test of the semiconductive shielding materials of examples 1 to 3 and comparative example 2, and it can be seen that the elongation at break of examples 1 to 3 is significantly higher than that of comparative example 2, and that the elongation at break of the semiconductive shielding material increases with the increase of the maleic anhydride content as can be seen from the comparison of examples 1 to 3.
The thermal elongation and permanent deformation performance of the semiconductive shielding materials prepared in examples 1-3 and comparative example 2 are tested according to the mechanical industry standard GB/T2951.21-2008 of the people's republic of China, so that the thermal aging resistance of the materials is analyzed, and the lower the thermal elongation and the permanent deformation, the better the thermal aging resistance. The test results are shown in fig. 6.
Fig. 6 is a graph showing the results of the thermal elongation and the permanent deformation of the semiconductive shielding materials of examples 1 to 3 and comparative example 2, and it can be seen that the thermal elongation and the permanent deformation of examples 1 to 3 are significantly lower than those of comparative example 2, which means that the heat aging resistance of examples 1 to 3 is better, and it can be seen from the comparison of examples 1 to 3 that the heat aging resistance of the semiconductive shielding material is gradually improved with the increase of the maleic anhydride content.
As can be seen from the results of fig. 4 to 6, the semiconductive shielding material of embodiment 1 greatly increases the compatibility between the ethylene-vinyl acetate copolymer and the low-density polyethylene after the maleic anhydride is added, so that the blending of the two is more uniform, the adhesiveness is obviously improved, and the mechanical property and the thermal aging resistance of the semiconductive shielding material are obviously improved on the premise of ensuring good conductivity.
The technical features of the above-described embodiments may be arbitrarily combined, and all possible combinations of the technical features in the above-described embodiments are not described for brevity of description, however, as long as there is no contradiction between the combinations of the technical features, they should be considered as the scope of the description.
The above examples illustrate only a few embodiments of the application, which are described in detail and are not to be construed as limiting the scope of the application. It should be noted that it will be apparent to those skilled in the art that several variations and modifications can be made without departing from the spirit of the application, which are all within the scope of the application. Accordingly, the scope of protection of the present application is to be determined by the appended claims.
Claims (10)
1. A semiconductive shield composition comprising a polymeric substrate and conductive carbon black dispersed in the polymeric substrate;
The polymeric substrate comprises the graft cross-linked product of a blend of ethylene vinyl acetate copolymer and low density polyethylene with maleic anhydride.
2. The semiconductive shield composition of claim 1, wherein the ethylene-vinyl acetate copolymer has a vinyl acetate content of 16% -20%; and/or
The melt index of the ethylene-vinyl acetate copolymer is 2.2g/10 min-2.8 g/10min.
3. The semiconductive shielding material of claim 1, wherein the low density polyethylene has a melt index of 2g/10min to 3g/10min.
4. A semiconductive shielding material according to any one of claims 1 to 3, wherein the mass ratio of the ethylene-vinyl acetate copolymer and the low density polyethylene is 1 (0.66 to 1.5).
5. A semiconductive shielding material according to any one of claims 1-3, wherein the mass of maleic anhydride is 1-5% of the sum of the mass of the ethylene-vinyl acetate copolymer and the mass of the low density polyethylene.
6. A semiconductive shielding material according to any one of claims 1-3, wherein the mass of the conductive carbon black is 30-50% of the sum of the mass of the ethylene-vinyl acetate copolymer and the mass of the low density polyethylene.
7. A method for producing the semiconductive shield material according to any one of claims 1 to 6, comprising the steps of:
Melt blending the ethylene-vinyl acetate copolymer, the low density polyethylene, the conductive carbon black, and the maleic anhydride to form a melt blend; and
And (3) carrying out graft crosslinking reaction on the melt blend and compression molding to form the semiconductive shielding material.
8. The method of preparing a semiconductive shield according to claim 7, wherein a cross-linking agent is also added during melt blending.
9. The method for producing a semiconductive shield material according to claim 8, wherein the crosslinking agent comprises 2, 4-di-t-butylcumene peroxide or dicumyl peroxide; and/or
The addition amount of the cross-linking agent is 0.8% -1.2% of the sum of the mass of the ethylene-vinyl acetate copolymer and the mass of the low-density polyethylene.
10. The method for preparing a semiconductive shielding material according to any one of claims 7 to 9, wherein the preparation method satisfies one or more of the following conditions:
(1) The temperature of melt blending is: 105-115 ℃;
(2) The rotational speed of the melt blending is: 45 r/min-55 r/min;
(3) The temperature for grafting and crosslinking reaction and compression molding is 175-185 ℃;
(4) And carrying out graft crosslinking reaction and compression molding at 13-18 MPa.
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