CN110804238B - Modified crosslinked polyethylene, preparation method thereof and cable - Google Patents
Modified crosslinked polyethylene, preparation method thereof and cable Download PDFInfo
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- CN110804238B CN110804238B CN201911074136.6A CN201911074136A CN110804238B CN 110804238 B CN110804238 B CN 110804238B CN 201911074136 A CN201911074136 A CN 201911074136A CN 110804238 B CN110804238 B CN 110804238B
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- 229920003020 cross-linked polyethylene Polymers 0.000 title claims abstract description 61
- 239000004703 cross-linked polyethylene Substances 0.000 title claims abstract description 61
- 238000002360 preparation method Methods 0.000 title claims abstract description 25
- GUJOJGAPFQRJSV-UHFFFAOYSA-N dialuminum;dioxosilane;oxygen(2-);hydrate Chemical compound O.[O-2].[O-2].[O-2].[Al+3].[Al+3].O=[Si]=O.O=[Si]=O.O=[Si]=O.O=[Si]=O GUJOJGAPFQRJSV-UHFFFAOYSA-N 0.000 claims abstract description 151
- 229910052901 montmorillonite Inorganic materials 0.000 claims abstract description 72
- -1 alkyl quaternary ammonium salt Chemical class 0.000 claims abstract description 38
- 238000002156 mixing Methods 0.000 claims abstract description 31
- 239000000203 mixture Substances 0.000 claims abstract description 23
- 125000000391 vinyl group Chemical group [H]C([*])=C([H])[H] 0.000 claims abstract description 15
- 229920002554 vinyl polymer Polymers 0.000 claims abstract description 15
- 239000004698 Polyethylene Substances 0.000 claims abstract description 14
- 229920000573 polyethylene Polymers 0.000 claims abstract description 14
- 239000003431 cross linking reagent Substances 0.000 claims abstract description 13
- 238000004132 cross linking Methods 0.000 claims abstract description 11
- 239000000155 melt Substances 0.000 claims abstract description 11
- 239000003963 antioxidant agent Substances 0.000 claims abstract description 10
- 230000003078 antioxidant effect Effects 0.000 claims abstract description 10
- 238000006243 chemical reaction Methods 0.000 claims abstract description 7
- 238000002844 melting Methods 0.000 claims abstract description 6
- 230000008018 melting Effects 0.000 claims abstract description 6
- 238000003682 fluorination reaction Methods 0.000 claims description 13
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 12
- 238000001035 drying Methods 0.000 claims description 10
- 238000003756 stirring Methods 0.000 claims description 10
- 238000000034 method Methods 0.000 claims description 9
- YCKRFDGAMUMZLT-UHFFFAOYSA-N Fluorine atom Chemical compound [F] YCKRFDGAMUMZLT-UHFFFAOYSA-N 0.000 claims description 8
- 229910052731 fluorine Inorganic materials 0.000 claims description 8
- 239000011737 fluorine Substances 0.000 claims description 8
- FWDBOZPQNFPOLF-UHFFFAOYSA-N ethenyl(triethoxy)silane Chemical compound CCO[Si](OCC)(OCC)C=C FWDBOZPQNFPOLF-UHFFFAOYSA-N 0.000 claims description 6
- XMNIXWIUMCBBBL-UHFFFAOYSA-N 2-(2-phenylpropan-2-ylperoxy)propan-2-ylbenzene Chemical group C=1C=CC=CC=1C(C)(C)OOC(C)(C)C1=CC=CC=C1 XMNIXWIUMCBBBL-UHFFFAOYSA-N 0.000 claims description 5
- NKSJNEHGWDZZQF-UHFFFAOYSA-N ethenyl(trimethoxy)silane Chemical compound CO[Si](OC)(OC)C=C NKSJNEHGWDZZQF-UHFFFAOYSA-N 0.000 claims description 3
- QGZKDVFQNNGYKY-UHFFFAOYSA-N Ammonia Chemical compound N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 claims description 2
- 238000004519 manufacturing process Methods 0.000 claims 2
- BLRPTPMANUNPDV-UHFFFAOYSA-N Silane Chemical compound [SiH4] BLRPTPMANUNPDV-UHFFFAOYSA-N 0.000 claims 1
- 125000005210 alkyl ammonium group Chemical group 0.000 claims 1
- 229910000077 silane Inorganic materials 0.000 claims 1
- 239000000463 material Substances 0.000 abstract description 15
- 239000007789 gas Substances 0.000 description 11
- 239000011259 mixed solution Substances 0.000 description 8
- 229920000642 polymer Polymers 0.000 description 8
- 239000008367 deionised water Substances 0.000 description 6
- 229910021641 deionized water Inorganic materials 0.000 description 6
- 238000000227 grinding Methods 0.000 description 6
- 239000010410 layer Substances 0.000 description 6
- 238000012360 testing method Methods 0.000 description 5
- 230000015572 biosynthetic process Effects 0.000 description 4
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- 240000005572 Syzygium cordatum Species 0.000 description 3
- 235000006650 Syzygium cordatum Nutrition 0.000 description 3
- 230000032683 aging Effects 0.000 description 3
- 230000004888 barrier function Effects 0.000 description 3
- 239000002131 composite material Substances 0.000 description 3
- 239000000412 dendrimer Substances 0.000 description 3
- 230000002209 hydrophobic effect Effects 0.000 description 3
- 230000002401 inhibitory effect Effects 0.000 description 3
- 230000000670 limiting effect Effects 0.000 description 3
- 229920001684 low density polyethylene Polymers 0.000 description 3
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- 150000002500 ions Chemical class 0.000 description 1
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- 238000011056 performance test Methods 0.000 description 1
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- 229910021647 smectite Inorganic materials 0.000 description 1
- 238000001179 sorption measurement Methods 0.000 description 1
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- 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
- C08K13/00—Use of mixtures of ingredients not covered by one single of the preceding main groups, each of these compounds being essential
- C08K13/06—Pretreated ingredients and ingredients covered by the main groups C08K3/00 - C08K7/00
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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
- C08K3/34—Silicon-containing compounds
- C08K3/346—Clay
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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
- C08K5/00—Use of organic ingredients
- C08K5/04—Oxygen-containing compounds
- C08K5/14—Peroxides
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- 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
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- C08K9/04—Ingredients treated with organic substances
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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
- C08K9/00—Use of pretreated ingredients
- C08K9/04—Ingredients treated with organic substances
- C08K9/06—Ingredients treated with organic substances with silicon-containing compounds
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
- H01B3/00—Insulators or insulating bodies characterised by the insulating materials; Selection of materials for their insulating or dielectric properties
- H01B3/18—Insulators or insulating bodies characterised by the insulating materials; Selection of materials for their insulating or dielectric properties mainly consisting of organic substances
- H01B3/30—Insulators or insulating bodies characterised by the insulating materials; Selection of materials for their insulating or dielectric properties mainly consisting of organic substances plastics; resins; waxes
- H01B3/44—Insulators or insulating bodies characterised by the insulating materials; Selection of materials for their insulating or dielectric properties mainly consisting of organic substances plastics; resins; waxes vinyl resins; acrylic resins
- H01B3/441—Insulators or insulating bodies characterised by the insulating materials; Selection of materials for their insulating or dielectric properties mainly consisting of organic substances plastics; resins; waxes vinyl resins; acrylic resins from alkenes
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- C08L2203/00—Applications
- C08L2203/20—Applications use in electrical or conductive gadgets
- C08L2203/202—Applications use in electrical or conductive gadgets use in electrical wires or wirecoating
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- C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
- C08L2312/00—Crosslinking
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Abstract
The invention relates to a modified cross-linked polyethylene, a preparation method thereof and a cable, wherein the preparation method of the modified cross-linked polyethylene comprises the following steps: providing montmorillonite; treating one part of montmorillonite with alkyl quaternary ammonium salt to obtain first modified montmorillonite; treating the other part of montmorillonite with vinyl trialkoxysilane to obtain second modified montmorillonite; taking the rest part of montmorillonite as third unmodified montmorillonite; melting and blending the first modified montmorillonite, the second modified montmorillonite, the third unmodified montmorillonite, polyethylene and an antioxidant to obtain a melt blend; and carrying out crosslinking reaction on the molten blend and a crosslinking agent to obtain the modified crosslinked polyethylene. The modified crosslinked polyethylene can improve the branch resistance of the material, so that the crosslinked polyethylene cable can be applied to higher voltage levels.
Description
Technical Field
The invention relates to the technical field of material preparation, in particular to modified cross-linked polyethylene, a preparation method thereof and a cable.
Background
At present, with the wide application of high-voltage crosslinked polyethylene cables, people pay more attention to the safe operation problem of the high-voltage cables. So far, the key problem for limiting the long-term operation of the high-voltage crosslinked polyethylene cable is that when the material is subjected to the action of an electric field for a long time, due to aging factors such as heat, mechanical force, environment and the like, aging forms such as partial discharge, water branches and the like exist in the material, and the aging forms are finally attributed to the electric branches. When an electric branch appears in the insulating material, the breakdown field intensity of the material is sharply reduced, the insulating property is reduced, finally, the polymer insulation is caused to have a breakdown point to cause the failure of the whole cable line, and when the cable breaks down once, not only manpower and material resources are wasted, but also huge economic loss is caused.
Disclosure of Invention
Based on the above, there is a need for a modified crosslinked polyethylene, a preparation method thereof and a cable. The modified crosslinked polyethylene can improve the branch resistance of the material, so that the crosslinked polyethylene cable can be applied to higher voltage levels.
A preparation method of modified crosslinked polyethylene comprises the following steps:
providing three parts of montmorillonite;
treating one part of montmorillonite with alkyl quaternary ammonium salt to obtain first modified montmorillonite;
treating the other part of montmorillonite with vinyl trialkoxysilane to obtain second modified montmorillonite;
taking the rest part of montmorillonite as third unmodified montmorillonite;
melting and blending the first modified montmorillonite, the second modified montmorillonite, the third unmodified montmorillonite, polyethylene and an antioxidant to obtain a molten blend;
and carrying out crosslinking reaction on the melt blend and a crosslinking agent to prepare the modified crosslinked polyethylene.
In one embodiment, after the step of melt blending, the step of crosslinking reaction further comprises the following steps:
subjecting the melt blend to a fluorination treatment.
In one embodiment, in the step of subjecting the molten blend to fluorination treatment, the molten blend is placed in a closed space containing fluorine gas, and the volume percentage of fluorine gas in the closed space is 1% to 5%.
In one embodiment, in the modified cross-linked polyethylene, by weight, the polyethylene is 100 parts, the first modified montmorillonite is 5-15 parts, the second modified montmorillonite is 5-15 parts, the third unmodified montmorillonite is 5-15 parts, the antioxidant is 2-3 parts, and the cross-linking agent is 3-5 parts.
In one embodiment, in the modified cross-linked polyethylene, the mass percentage of the third unmodified montmorillonite is 4.8% -5.2%.
In one embodiment, the step of treating one part of montmorillonite with alkyl quaternary ammonium salt to obtain the first modified montmorillonite comprises the following steps:
mixing montmorillonite, alkyl quaternary ammonium salt and water, ultrasonically stirring, and drying at 65-95 ℃ to prepare the first modified montmorillonite; and/or
The step of treating one part of montmorillonite with vinyl trialkoxysilane to obtain the second modified montmorillonite comprises the following steps:
mixing montmorillonite, vinyl trialkoxysilane and water, ultrasonically stirring, and drying at the temperature of 65-95 ℃ to prepare the second modified montmorillonite.
In one embodiment, the alkyl quaternary ammonium salt is selected from: one or more of octadecyl quaternary ammonium salt and hexadecyl quaternary ammonium salt; and/or
The vinyl trialkoxysilane is selected from the group consisting of: one or more of vinyltrimethoxysilane and vinyltriethoxysilane; and/or
The cross-linking agent is dicumyl peroxide.
In one embodiment, the melt blending step is performed by using a torque rheometer at a temperature of 140 ℃ to 160 ℃ and a rotation speed of 30rpm to 50rpm for 20 minutes to 30 minutes.
In one embodiment, in the step of the crosslinking reaction, the mixture is mixed in an open mill at a temperature of 100 ℃ to 120 ℃ for 5 minutes to 15 minutes.
The cable comprises an insulating layer, wherein the insulating layer comprises the modified crosslinked polyethylene prepared by the preparation method.
According to the preparation method of the modified crosslinked polyethylene, the alkyl quaternary ammonium salt and the vinyl trialkoxysilane are adopted to organically treat the montmorillonite, the hydrophobic property of the montmorillonite is improved, the compatibility between the montmorillonite and the polymer is further improved, meanwhile, the unmodified third unmodified montmorillonite is added, and under the synergistic effect of the montmorillonite, the montmorillonite and the polymer, the crosslinked polyethylene composite material with the net structure can be prepared through a melting intercalation method and a crosslinking method, so that the growth of electric tree branches can be effectively inhibited, the performances of impact resistance, fatigue resistance, size stability, gas barrier and the like of the modified crosslinked polyethylene can be effectively improved, and the comprehensive physical property and the processing property are effectively improved. In addition, the raw materials in the preparation method of the modified polyethylene are low in price and pollution-free, and the preparation method is suitable for industrial production and application.
Drawings
A in fig. 1 is a graph showing the test result of the hydrophilic angle of example 1, and b in fig. 1 is a graph showing the test result of the hydrophilic angle of example 2;
in FIG. 2, a is a structural diagram of an electrical dendron of the modified crosslinked polyethylene of example 1 at a positive direct current short-circuit voltage of 14kV for 300 min; b represents the electrical dendrogram of unmodified crosslinked polyethylene at a positive direct current short-circuit voltage of 14kV for 300 min.
Detailed Description
In order that the invention may be more fully understood, a more particular description of the invention will now be rendered by reference to specific embodiments thereof that are illustrated in the appended drawings. 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 in the description of the invention herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items.
The invention provides a preparation method of modified cross-linked polyethylene, which comprises the following steps:
s101: providing three parts of montmorillonite; treating one part of montmorillonite with alkyl quaternary ammonium salt to obtain first modified montmorillonite; treating the other part of montmorillonite with vinyl trialkoxysilane to obtain second modified montmorillonite; and taking the rest part of montmorillonite as third unmodified montmorillonite.
The montmorillonite in the invention is nano montmorillonite which is obtained by peeling, purifying, refining and the like of smectite clay, the average value of the thickness of a wafer is less than 25nm, and the content of the montmorillonite is more than 95%. Because of its strong dispersivity, when montmorillonite is used as additive to be added into high-molecular material, the properties of impact resistance, fatigue resistance, size stability and gas barrier are greatly improved, and the comprehensive physical property and processing property are raised.
In the use process of the montmorillonite, because the interlayer spacing and the hydrophilic property of the montmorillonite are limited, polymers are difficult to enter a montmorillonite layer, so that the inventor conducts organic treatment on the montmorillonite, and the hydrophilic layer in the montmorillonite layer is changed into a hydrophobic layer by utilizing the structural properties (including charge property, ion adsorption and exchange property, expansibility and the like) of the montmorillonite, so that the compatibility between the montmorillonite and the polymers is improved, specifically: one part of montmorillonite is treated by alkyl quaternary ammonium salt to improve the compatibility of the montmorillonite and the polymer, and the other part of montmorillonite is treated by vinyl trialkoxysilane to improve the expansibility of the montmorillonite.
Furthermore, in the modified cross-linked polyethylene, the mass percentage of the first modified montmorillonite is 4-5%, and the mass ratio of the second modified montmorillonite is 4-5%, so that the prepared modified cross-linked polyethylene has excellent compatibility and higher expansibility, and is further beneficial to modification of the cross-linked polyethylene.
Further, in the modified cross-linked polyethylene, the mass percentage of the third unmodified montmorillonite is 0.8-1.2%. Furthermore, in the modified cross-linked polyethylene, the mass percentage of the third unmodified montmorillonite is 1%.
The inventor of the invention finds in research that when the content of the untreated montmorillonite (i.e. the third unmodified montmorillonite) is 0.8-1.2% of the composite material, a tiny net structure exists, the net structure has an inhibition effect on the growth of electric tree branches, and the branch resistance of the modified cross-linked polyethylene is better.
Further, the step of treating one part of montmorillonite with alkyl quaternary ammonium salt to obtain the first modified montmorillonite comprises the following steps:
mixing montmorillonite, alkyl quaternary ammonium salt and deionized water, ultrasonically stirring, and drying at 65-95 deg.C to obtain the first modified montmorillonite. Among them, the alkyl quaternary ammonium salt is preferably: one or more of octadecyl quaternary ammonium salt and hexadecyl quaternary ammonium salt; more preferably octadecyl quaternary ammonium salt.
Further, the step of treating the other part of montmorillonite with vinyl trialkoxysilane to obtain the second modified montmorillonite comprises the following steps:
mixing montmorillonite, vinyl trialkoxysilane and deionized water, ultrasonically stirring, and drying at 65-95 ℃ to prepare the second modified montmorillonite. Among them, the vinyltrialkoxysilane is preferably: one or more of vinyltrimethoxysilane and vinyltriethoxysilane; more preferably vinyltriethoxysilane.
Further, the third unmodified montmorillonite is preferably ground so that the third unmodified montmorillonite can better permeate into the first modified montmorillonite and the second modified montmorillonite to form a fine mesh structure. In addition, the first modified montmorillonite, the second modified montmorillonite and the third unmodified montmorillonite can be subjected to ultrasonic blending and then subsequent steps are carried out, so that the materials can be fully mixed.
S102, melting and blending the first modified montmorillonite, the second modified montmorillonite, the third unmodified montmorillonite, the polyethylene and the antioxidant to obtain a melt blend.
In step S102, a torque rheometer can be used for melt blending, preferably at a temperature of 140 ℃ to 160 ℃ and a rotation speed of 30rpm to 50rpm for 20 minutes to 30 minutes.
In one embodiment, in the modified cross-linked polyethylene, by weight, 100 parts of polyethylene, 5-15 parts of first modified montmorillonite, 5-15 parts of second modified montmorillonite, 5-15 parts of third unmodified montmorillonite, 2-3 parts of antioxidant and 3-5 parts of cross-linking agent.
In one embodiment, in the modified cross-linked polyethylene, by weight, 100 parts of polyethylene, 10 parts of first modified montmorillonite, 10 parts of second modified montmorillonite, 10 parts of third unmodified montmorillonite, 2-3 parts of antioxidant and 4 parts of cross-linking agent are used.
Further, preferably the polyethylene is a low density polyethylene.
S103: the melt blend is subjected to a fluorination treatment.
It is understood that step S103 may be omitted. Preferably, the melt blend is fluorinated and then subjected to subsequent steps, the melt blend is fluorinated, so that fluorinated groups are generated on the surface of the polyethylene, the hydrophobicity of the surface is improved by the fluorinated groups on the surface of the polyethylene, the growth of water tree branches can be inhibited, and the formation of electric tree branches is inhibited, so that the modified cross-linked polyethylene has obvious advantages compared with the hydrophobicity, the water tree branch growth and the electric tree branch growth in the traditional scheme.
In step S103, the molten blend may be put into a closed space containing fluorine gas for fluorination treatment, preferably, the volume percentage of fluorine gas in the closed space is 1% to 5%, more preferably 3%. Among them, the gas in the closed space is preferably an inert gas.
The fluorination treatment time can be adjusted according to actual conditions, and is preferably treated for 6 to 9 hours under the condition that the volume percentage of the fluorine gas is 3 percent.
S104: and carrying out crosslinking reaction on the molten blend and a crosslinking agent to obtain the modified crosslinked polyethylene.
Among them, the kind of the crosslinking agent is not particularly limited, and dicumyl peroxide is preferably used, which is advantageous for forming a modified crosslinked polyethylene with a network structure to inhibit the growth of electrical tree branches.
According to the preparation method of the modified crosslinked polyethylene, the alkyl quaternary ammonium salt and the vinyl trialkoxysilane are adopted to organically treat the montmorillonite, the hydrophobic property of the montmorillonite is improved, the compatibility between the montmorillonite and the polymer is further improved, meanwhile, the unmodified third unmodified montmorillonite is added, and under the synergistic effect of the montmorillonite, the montmorillonite and the polymer, the crosslinked polyethylene composite material with the net structure can be prepared through a melting intercalation method and a crosslinking method, so that the growth of electric tree branches can be effectively inhibited, the performances of impact resistance, fatigue resistance, size stability, gas barrier and the like of the modified crosslinked polyethylene can be effectively improved, and the comprehensive physical property and the processing property are effectively improved. In addition, the raw materials in the preparation method of the modified polyethylene are low in price and pollution-free, and the preparation method is suitable for industrial production and application.
The invention also provides a cable which comprises the modified crosslinked polyethylene prepared by the preparation method.
The preparation method of the modified crosslinked polyethylene is as described above, and is not described herein again.
The modified crosslinked polyethylene prepared by the preparation method can effectively improve the branch resistance of the material, so that the crosslinked polyethylene cable can be applied to higher voltage levels.
The present invention will be described below with reference to specific examples.
Example 1
The raw material composition of this example is as described above;
the preparation method comprises the following steps:
step 1: the filler is organically treated, in the embodiment, the nano-montmorillonite is divided into three parts, and two parts of the nano-montmorillonite are organically treated, wherein the organic treatment method respectively comprises the following steps:
1) mixing the first part of montmorillonite with deionized water, adding octadecyl quaternary ammonium salt, and stirring the mixed solution by using an ultrasonic oscillator. And (3) placing the mixed solution in a vacuum oven, exhausting air, drying at the temperature of 80 ℃, grinding to obtain a first part of organically treated montmorillonite, and marking as first modified montmorillonite.
2) Mixing the second part of montmorillonite with deionized water, adding vinyltriethoxysilane, and stirring the mixed solution with an ultrasonic oscillator. And placing the mixed solution in a vacuum oven, exhausting air and drying, wherein the oven temperature is 80 ℃, and grinding to obtain a second part of organically treated montmorillonite, which is marked as second modified montmorillonite after the solution is dried.
3) Grinding the third part of montmorillonite to obtain third unmodified montmorillonite, and mixing with the first modified montmorillonite and the second modified montmorillonite in an ultrasonic oscillator.
Step 2: mixing materials (melt blending), and sequentially and respectively adding low-density polyethylene (18D), montmorillonite (a mixture of first modified montmorillonite, second modified montmorillonite and third unmodified montmorillonite) and an antioxidant into a torque rheometer, wherein the temperature of the torque rheometer is 150 ℃, the rotating speed is 40rpm, and the melt blending time is 25 minutes.
And step 3: fluorination crosslinking the material obtained after blending was treated for 8 hours under a closed gas condition with a volume fraction of 3% fluorine gas. After the treatment, the treated material and a crosslinking agent (dicumyl peroxide) are placed in an open mill at 110 ℃ for mixing for 7 minutes, and the modified crosslinked polyethylene of the embodiment 1 is obtained.
Example 2
The same as example 1 except that the fluorination treatment step was not included in this example.
The raw material composition of this example is as described above;
the preparation method comprises the following steps:
step 1: the filler is organically treated, in the embodiment, the nano-montmorillonite is divided into three parts, and two parts of the nano-montmorillonite are organically treated, wherein the organic treatment method respectively comprises the following steps:
1) mixing the first part of montmorillonite with deionized water, adding octadecyl quaternary ammonium salt, and stirring the mixed solution by using an ultrasonic oscillator. And (3) placing the mixed solution in a vacuum oven, exhausting air, drying at the temperature of 80 ℃, grinding to obtain a first part of organically treated montmorillonite, and marking as first modified montmorillonite.
2) Mixing the second part of montmorillonite with deionized water, adding vinyltriethoxysilane, and stirring the mixed solution with an ultrasonic oscillator. And placing the mixed solution in a vacuum oven, exhausting air and drying, wherein the oven temperature is 80 ℃, and grinding to obtain a second part of organically treated montmorillonite, which is marked as second modified montmorillonite after the solution is dried.
3) Grinding the third part of montmorillonite, marking as third unmodified montmorillonite, putting the third unmodified montmorillonite, the first modified montmorillonite and the second modified montmorillonite into a container, and uniformly mixing the first modified montmorillonite and the second modified montmorillonite in an ultrasonic oscillator.
Step 2: mixing materials (melt blending), and sequentially and respectively adding low-density polyethylene (18D), montmorillonite (a mixture of first modified montmorillonite, second modified montmorillonite and third unmodified montmorillonite) and an antioxidant into a torque rheometer, wherein the temperature of the torque rheometer is 150 ℃, the rotating speed is 40rpm, and the melt blending time is 25 minutes.
And 3, step 3: and (3) crosslinking, namely mixing the material obtained after blending and a crosslinking agent (dicumyl peroxide) in an open mill at 110 ℃ for 7 minutes to obtain the modified crosslinked polyethylene of the embodiment 2.
Performance testing
(1) Hydrophilic Angle test
The hydrophilicity angles of the modified crosslinked polyethylene are tested in examples 1 and 2 by measuring the contact angle of the GB/T30693-2014 plastic film with water, the test results are shown in FIG. 1, wherein a in FIG. 1 is the sample subjected to fluorination treatment in example 1, and b in FIG. 1 is the sample not subjected to fluorination treatment in example 2, and it can be seen from FIG. 1 that the hydrophobicity of the modified crosslinked polyethylene can be obviously increased by the fluorination treatment. It is demonstrated that the fluorination treatment can generate fluorinated groups on the polyethylene surface, thereby improving the hydrophobicity of the modified crosslinked polyethylene surface, inhibiting the growth of water tree and further inhibiting the formation of electric tree.
(2) Performance test for inhibiting electrical dendrite formation
The electrical dendron structure diagram of the modified cross-linked polyethylene of examples 1-2 is observed by a scanning electron microscope at a positive direct current short circuit voltage of 14kV for 300min, and the experiment result shows that the examples 1-2 can inhibit the formation of electrical dendrons in the cross-linked polyethylene, especially the example 1, by comparing the unmodified cross-linked polyethylene (which is basically the same as the example 1 except that montmorillonite is not added for modification). In FIG. 2, a is a direct current short circuit dendrogram of the modified crosslinked polyethylene of example 1, and b is a direct current short circuit dendrogram of the unmodified crosslinked polyethylene. As can be seen from a in fig. 2, the modified crosslinked polyethylene dendrons are shorter and do not significantly branch at the tip and have no tendency to form dendritic electrical dendrons compared to the unmodified crosslinked polyethylene. Therefore, the layered structure formed by the montmorillonite of various combinations inhibits the growth of the tree branches. As can be seen from b in fig. 2, the unmodified crosslinked polyethylene electrical dendron grows mainly along the needle tip, and has a bifurcation at the tip, with a tendency to form a branched electrical dendron.
The technical features of the embodiments described above may be arbitrarily combined, and for the sake of brevity, all possible combinations of the technical features in the embodiments described above are not described, but should be considered as being within the scope of the present specification as long as there is no contradiction between the combinations of the technical features.
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 (9)
1. A preparation method of modified crosslinked polyethylene is characterized by comprising the following steps:
providing three parts of montmorillonite;
treating one part of montmorillonite with alkyl quaternary ammonium salt to obtain first modified montmorillonite;
treating the other part of montmorillonite with vinyl trialkoxysilane to obtain second modified montmorillonite;
taking the rest part of montmorillonite as third unmodified montmorillonite;
melting and blending the first modified montmorillonite, the second modified montmorillonite, the third unmodified montmorillonite, polyethylene and an antioxidant to obtain a molten blend;
fluorinating the melt blend, and then carrying out crosslinking reaction with a crosslinking agent to prepare modified crosslinked polyethylene;
in the modified cross-linked polyethylene, by weight, the polyethylene is 100 parts, the first modified montmorillonite is 5-15 parts, the second modified montmorillonite is 5-15 parts, the third unmodified montmorillonite is 5-15 parts, the antioxidant is 2-3 parts, and the cross-linking agent is 3-5 parts.
2. The production method according to claim 1, wherein in the step of subjecting the molten blend to the fluorination treatment, the molten blend is subjected to the fluorination treatment in a closed space containing fluorine gas, and the percentage by volume of fluorine gas in the closed space is 1% to 5%.
3. The preparation method of claim 1, wherein the third unmodified montmorillonite is present in the modified cross-linked polyethylene in an amount of 4.8-5.2% by mass.
4. The preparation method according to any one of claims 1 to 3, wherein the step of treating one part of montmorillonite with alkyl quaternary ammonium salt to obtain the first modified montmorillonite comprises the following steps:
mixing montmorillonite, alkyl quaternary ammonium salt and water, ultrasonically stirring, and drying at 65-95 ℃ to prepare the first modified montmorillonite; and/or
The step of treating one part of montmorillonite with vinyl trialkoxysilane to obtain the second modified montmorillonite comprises the following steps:
mixing montmorillonite, vinyl trialkoxy silane and water, ultrasonically stirring, and drying at the temperature of 65-95 ℃ to prepare the second modified montmorillonite.
5. The method according to any one of claims 1 to 3, wherein the quaternary alkyl ammonium salt is selected from the group consisting of: one or more of octadecyl quaternary ammonium salt and hexadecyl quaternary ammonium salt; and/or
The vinyl trialkoxysilane is selected from the group consisting of: one or more of vinyltrimethoxysilane and vinyltriethoxysilane; and/or
The cross-linking agent is dicumyl peroxide.
6. The method according to any one of claims 1 to 3, wherein in the step of melt blending, a torque rheometer is used to melt blend the components at a temperature of 140 ℃ to 160 ℃ and a rotation speed of 30rpm to 50rpm for 20 minutes to 30 minutes.
7. The production method according to any one of claims 1 to 3, wherein the step of the crosslinking reaction is carried out in an open mill at a temperature of 100 ℃ to 120 ℃ for 5 minutes to 15 minutes.
8. A modified cross-linked polyethylene prepared by the preparation method of any one of claims 1 to 7.
9. A cable comprising an insulating layer comprising the modified crosslinked polyethylene of claim 8.
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