CA1183297A - Inhibition of water-treeing in polyolefin electrical insulation - Google Patents
Inhibition of water-treeing in polyolefin electrical insulationInfo
- Publication number
- CA1183297A CA1183297A CA000379078A CA379078A CA1183297A CA 1183297 A CA1183297 A CA 1183297A CA 000379078 A CA000379078 A CA 000379078A CA 379078 A CA379078 A CA 379078A CA 1183297 A CA1183297 A CA 1183297A
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- Prior art keywords
- ethylene
- composition
- insulating material
- polyolefin
- electrical insulating
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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Abstract
POLYOLEFIN COMPOSITION FOR ELECTRICAL INSULATION
ABSTRACT OF THE DISCLOSURE
A polyolefin composition for electrical insulation which comprises polyolefin or crosslinked polyolefin and a small quantity of high-molecular weight polyethylene glycol. This composition is far less vulnerable to the deterioration that occurs as dendroid voids when employed as an electrical insulation of high-tension power cables which are operated under water.
The polyethylene glycol has more than 44 carbon atoms and is used in an amount from 0.3 to 10 wt% based on polyolefin.
ABSTRACT OF THE DISCLOSURE
A polyolefin composition for electrical insulation which comprises polyolefin or crosslinked polyolefin and a small quantity of high-molecular weight polyethylene glycol. This composition is far less vulnerable to the deterioration that occurs as dendroid voids when employed as an electrical insulation of high-tension power cables which are operated under water.
The polyethylene glycol has more than 44 carbon atoms and is used in an amount from 0.3 to 10 wt% based on polyolefin.
Description
_C GROUND_ F THE _NVENTION
This invention relates to a polyolefin composition for electrical insulation which is far less vulnerable to the deterioration of insulation that occurs as dendroid voids (referred to as "water trees" hereunder) in polyolefin or crosslinked polyolefin employed as an electrical insulation, particularly For high-tension power cables which are operated under water.
It has been known that water trees grow from voids and foreign mat-ters, such as metals, in electrical insulation made of polyolefin or cross-linked polyolefin composition when the insulation is subjected to a high voltage under water. In spite of continued efforts for improvement of the manufacturing process, the complete elimination of foreign matters and voids is still difficult to achieve.
As a means for preventing water trees, incorporation of a small quantity of strong electrolyte into polyolefin was proposed in Japanese Patent Publication No. 24938/1977. ~n the other hand, there is a strong theory that the preSence of metal ions is a cause of water trees.
The idea of adding a voltage stabilizer or alcohol to polyolefin .was proposed several times as a common countermeasure for water trees. For example, Japanese Patent Laid-open No. 16746/1978 teaches that the addition of monohydric higher alcohol having 6 to 24 carbon atoms is effect;ve, How-ever, such low-molecular weight alcohol is mobile through polyolefin mole-cules and blooms easily to the surface of the insulation as the power cable ge-ts hot, with the result being that the bloomed alcohol evaporates and the e~ect of the alcohol is soon lost. Furthermore, Japanese Patents Laid-open Nos. 119937/197~, 40547/1977, ~0553/1977~ and 40554/1977 describe sup-plementarily the incorporation of a polyhydric alcohol into an electric in-sulation which is rnade resistant by adding as an indispensable ingredient a voltage stabilizer such as ferrocene, dihydronaphthalene, dialkoxynaphtha-lene, phosphorane, and halogenated p-nitroaniline. These patents clairn that the dielectric strength is further improved by the addition of a polyhydric alcohol, but they treat the polyhydric alcohol as a mere additive similar -to dispersants, surfactants, unsaturated polymers, etc. However, the signifi-cance oF addiny a polyhydric alcohol is barely recognized in the examples, and the polyhydric alcohols rnentioned in these patents broadly vary in their molecular weight. What is given great importance in these patents is not water trees which readily occur in an insulation placed under water, but rather the conventional treeing that is attributable to high voltage alone, no-t associated with the presence of water.
Another countermeasure for water treeing disclosed in Japanese Patent Laid-open No. 145799/1977 covers the addition of a large quan-t-ity of inorganic filler. In this patent, the addition of inorganic filler together , ....... ...................................................................~
~ J 2 ~ ~
~L~3 ~
with diethylene glycol was practiced in some exarnples, However, the reason why it was added is not described. Examples without diethylene glycol were rather superior to examples with this substance. Japanese Patent Laid-open No. 3700/1978 discloses the incorporation of a water tree inhibitor. The example of this patent illustrates a composition to which polyethylene glycol distearate is added in small quantities. However, the effect of this substance as a water tree inhibitor is just as mediocre as the effect of a metal salt of stearic acid. This Laid-open patent enumerates fatty acid, fatty acid metal salt, fatty acid ester, etc. in the same category. This Fact suggests that fatty acid is an indispensable moi-ety which must have a group that can catch water readily. Such a group, however, is not identified in the specification, and, needless to say, nothing is mentioned about polyethylene glycol.
Japanese Patent Laid~open No~ 60346/1979 discloses a modifier which is very effective for a crosslinked polyethylene composition. Such a modi-fier should be a compound of less than 24 carbons containing in the molecule both a carboxyl group or its metal salt with a high affinity for foreign matters such as metals and a double bond that forms chemical bonding with the polyolefin.
After a series of experiments on the prevention of water treeing, it was concluded that, contrary to the conventional teachings, a small quanti-ty o-~ high-molecular weight polyethylene glycol is all that is required, ~nd no voltage stabilizer nor carboxylic acid or its salt is necessary. As pointed out before, the prior art teaches the use of ethylene glycol or di-ethylene glycol as an adjuvant For a voltage stabilizer. Other prior art discloses polyethylene glycol end-blocked by stearic acid as a water tree inhibitor. ~hat differentiates the present invention from the prior art is that the problem can be solved simply by adding a small quantity of high-molecular weight polyethylene glycol, which is one of the cheapest compounds, to polyolefin.
One of the above-mentioned items of prior art maintains that a poly-hydric alcohol is effective secondarily. In this prior art, however, poly-ethylene glycol is treated as the same category as monomeric ethylene gly-col, propylene glycol, butane diol, etc. and alicyclic and aromatic poly-hydruxyl compounds. In contrast with these teachings, the present invention discloses that only high-molecular weight polyethylene glycol is effective arld polypropylene glycol is not. Accordingly, it is believed that high-mol~cular weight polyethylene glycol is quite different in its functional mechanism from polyhydric alcohols which have hereto-fore been used second-arily in combination with a voltage stabilizer and the like.
SUMMARY OF THE INVENT~ON
This invention relates to a polyolefin composition for electrical insulatjon which comprises polyolefin or crosslinked polyolefin and a small quantity o~ high-rnolecular weight polyethylene glycol. This cornpo-sition is far less vulnerable to the deterioration that occurs as den-droid voids when employed as an electrical insulation of high-tension pow-er cables which are operated under water. The polyethylene glycol has more than 44 carbon atoms and is used in an amount of from 0.3 to 10 wt%, based on the polyolefin or crosslinked polyolefin.
RIEF 3ESCRIPTION OF THE DRA~INGS
Figure 1 is a view of the test specimen.
Figure 2 is an enlarged view of an inverted conical hole in the test specimen .
Figure 3 is a perspective view of the test apparatus.
Figure 4 is an enlarged view of a water tree in a test specimen.
DETAILED DESCRIPTION OF THE INVENTION
The composition according to this invention is especially effective For preventing water trees which appear in an insulation immersed in water when deterioration takes place under high-tension. ~Water trees are differ-ent frorn cornmon electric trees not only in appearance, but also in the fact that the former occur only when a high-tension is applied to an insulation llnder water.) The composition of this invention will find applications in electrical insulating rnaterials to be used under water. Such applications -include power cable insulation, insulating tape for cable splicing, and other electric and electronic parts which might be exposed to water or w~ter vapor.
We will discuss how water -trees are different from electric trees which have so Far been terrned simply trees , and chemical trees which occur under spec-ific environments. ~ater trees occur when an organic poly-meric insulating material like a polyolefin is subjected to an electric field under water for a long time. Water trees were named from their den-droid configuration they usually assume. Actually, they are fine cavities or voids, which look white when filled with water but which are almost in-visible when dry. Therefore, specimens should be boiled in water or dyed -ror observation of water trees. On the other hand,electric trees which are referred to conventionally as trees grow and propagate along the pllh o~ electric discharge, leaving carboni2ed resin therein. This is the reason why they usllally look black. Meanwhile, chemical trees stem From copper sulFide and copper oxide which are formed on a copper conductor by reaction of copper with hydrogen sulfide and other reactive gases which have diffused to copper conductor through the resin insulation. These ~ 3 ~
reaction products grow into black or reddish brown needle crystals that look like trees. Chemical trees are characterized by ~he fact that they occur even under tension-free conditions.
The polyolefin as used in this invention includes polyethylene, polypropylene, ethylene-propylene copolymers, polybutene, polyisobutylene, poly-4-methylpentene, copolymers thereof~ and crosslinked products ther-of. High-molecular weight polyethylene glycol means polyethylene glycol having more than 44 carbon atoms, preferably more than 80 carbon atoms.
The polyethylene glycol is incorporated in an amount of 0.3 to 10 % by weight, based on the polyolefin or crosslinked polyolefin. Under 0.3 %, no satisfactory effect is attained, particularly in the case where poly-ethylene glycol of relatively low molecular weight is employed. On the other hand, when over 10 % is used, some difficulties are encountered in achieving uniform compounding without slight discoloration in the result-ing composition, although the inexpensive polyethylene glycol has no eco-nomic limitation in the quantity to be added.
Whether or not the polyolefin is crosslinked does not matter in this invention, and the use of stabilizers~ inorganic fillers, and other additives is within the scope of this invention.
EXAMPLES
The polyolefin used as the major constituent of the composition as selected From low-density polyethylene and ethylene-vinyl acetate co-polymer which are most popular as electrical insulating materials. High-molecular weight polyethylene glycol which characterizes this invention was selectrd from a series ranging From 1,000 to 20,000 in the molecular weight. It was confirrned that the present invention can be practiced For polyolefin with or without crosslinking. The results obtained are $hown in Table 1. ~lso shown in Table 1~ for comparison, are the results of Comparative Examples that follow.
Comparative Example 1 employed no polyethylene glycol and water trees were observed at all the measuring points. In Comparative Example
This invention relates to a polyolefin composition for electrical insulation which is far less vulnerable to the deterioration of insulation that occurs as dendroid voids (referred to as "water trees" hereunder) in polyolefin or crosslinked polyolefin employed as an electrical insulation, particularly For high-tension power cables which are operated under water.
It has been known that water trees grow from voids and foreign mat-ters, such as metals, in electrical insulation made of polyolefin or cross-linked polyolefin composition when the insulation is subjected to a high voltage under water. In spite of continued efforts for improvement of the manufacturing process, the complete elimination of foreign matters and voids is still difficult to achieve.
As a means for preventing water trees, incorporation of a small quantity of strong electrolyte into polyolefin was proposed in Japanese Patent Publication No. 24938/1977. ~n the other hand, there is a strong theory that the preSence of metal ions is a cause of water trees.
The idea of adding a voltage stabilizer or alcohol to polyolefin .was proposed several times as a common countermeasure for water trees. For example, Japanese Patent Laid-open No. 16746/1978 teaches that the addition of monohydric higher alcohol having 6 to 24 carbon atoms is effect;ve, How-ever, such low-molecular weight alcohol is mobile through polyolefin mole-cules and blooms easily to the surface of the insulation as the power cable ge-ts hot, with the result being that the bloomed alcohol evaporates and the e~ect of the alcohol is soon lost. Furthermore, Japanese Patents Laid-open Nos. 119937/197~, 40547/1977, ~0553/1977~ and 40554/1977 describe sup-plementarily the incorporation of a polyhydric alcohol into an electric in-sulation which is rnade resistant by adding as an indispensable ingredient a voltage stabilizer such as ferrocene, dihydronaphthalene, dialkoxynaphtha-lene, phosphorane, and halogenated p-nitroaniline. These patents clairn that the dielectric strength is further improved by the addition of a polyhydric alcohol, but they treat the polyhydric alcohol as a mere additive similar -to dispersants, surfactants, unsaturated polymers, etc. However, the signifi-cance oF addiny a polyhydric alcohol is barely recognized in the examples, and the polyhydric alcohols rnentioned in these patents broadly vary in their molecular weight. What is given great importance in these patents is not water trees which readily occur in an insulation placed under water, but rather the conventional treeing that is attributable to high voltage alone, no-t associated with the presence of water.
Another countermeasure for water treeing disclosed in Japanese Patent Laid-open No. 145799/1977 covers the addition of a large quan-t-ity of inorganic filler. In this patent, the addition of inorganic filler together , ....... ...................................................................~
~ J 2 ~ ~
~L~3 ~
with diethylene glycol was practiced in some exarnples, However, the reason why it was added is not described. Examples without diethylene glycol were rather superior to examples with this substance. Japanese Patent Laid-open No. 3700/1978 discloses the incorporation of a water tree inhibitor. The example of this patent illustrates a composition to which polyethylene glycol distearate is added in small quantities. However, the effect of this substance as a water tree inhibitor is just as mediocre as the effect of a metal salt of stearic acid. This Laid-open patent enumerates fatty acid, fatty acid metal salt, fatty acid ester, etc. in the same category. This Fact suggests that fatty acid is an indispensable moi-ety which must have a group that can catch water readily. Such a group, however, is not identified in the specification, and, needless to say, nothing is mentioned about polyethylene glycol.
Japanese Patent Laid~open No~ 60346/1979 discloses a modifier which is very effective for a crosslinked polyethylene composition. Such a modi-fier should be a compound of less than 24 carbons containing in the molecule both a carboxyl group or its metal salt with a high affinity for foreign matters such as metals and a double bond that forms chemical bonding with the polyolefin.
After a series of experiments on the prevention of water treeing, it was concluded that, contrary to the conventional teachings, a small quanti-ty o-~ high-molecular weight polyethylene glycol is all that is required, ~nd no voltage stabilizer nor carboxylic acid or its salt is necessary. As pointed out before, the prior art teaches the use of ethylene glycol or di-ethylene glycol as an adjuvant For a voltage stabilizer. Other prior art discloses polyethylene glycol end-blocked by stearic acid as a water tree inhibitor. ~hat differentiates the present invention from the prior art is that the problem can be solved simply by adding a small quantity of high-molecular weight polyethylene glycol, which is one of the cheapest compounds, to polyolefin.
One of the above-mentioned items of prior art maintains that a poly-hydric alcohol is effective secondarily. In this prior art, however, poly-ethylene glycol is treated as the same category as monomeric ethylene gly-col, propylene glycol, butane diol, etc. and alicyclic and aromatic poly-hydruxyl compounds. In contrast with these teachings, the present invention discloses that only high-molecular weight polyethylene glycol is effective arld polypropylene glycol is not. Accordingly, it is believed that high-mol~cular weight polyethylene glycol is quite different in its functional mechanism from polyhydric alcohols which have hereto-fore been used second-arily in combination with a voltage stabilizer and the like.
SUMMARY OF THE INVENT~ON
This invention relates to a polyolefin composition for electrical insulatjon which comprises polyolefin or crosslinked polyolefin and a small quantity o~ high-rnolecular weight polyethylene glycol. This cornpo-sition is far less vulnerable to the deterioration that occurs as den-droid voids when employed as an electrical insulation of high-tension pow-er cables which are operated under water. The polyethylene glycol has more than 44 carbon atoms and is used in an amount of from 0.3 to 10 wt%, based on the polyolefin or crosslinked polyolefin.
RIEF 3ESCRIPTION OF THE DRA~INGS
Figure 1 is a view of the test specimen.
Figure 2 is an enlarged view of an inverted conical hole in the test specimen .
Figure 3 is a perspective view of the test apparatus.
Figure 4 is an enlarged view of a water tree in a test specimen.
DETAILED DESCRIPTION OF THE INVENTION
The composition according to this invention is especially effective For preventing water trees which appear in an insulation immersed in water when deterioration takes place under high-tension. ~Water trees are differ-ent frorn cornmon electric trees not only in appearance, but also in the fact that the former occur only when a high-tension is applied to an insulation llnder water.) The composition of this invention will find applications in electrical insulating rnaterials to be used under water. Such applications -include power cable insulation, insulating tape for cable splicing, and other electric and electronic parts which might be exposed to water or w~ter vapor.
We will discuss how water -trees are different from electric trees which have so Far been terrned simply trees , and chemical trees which occur under spec-ific environments. ~ater trees occur when an organic poly-meric insulating material like a polyolefin is subjected to an electric field under water for a long time. Water trees were named from their den-droid configuration they usually assume. Actually, they are fine cavities or voids, which look white when filled with water but which are almost in-visible when dry. Therefore, specimens should be boiled in water or dyed -ror observation of water trees. On the other hand,electric trees which are referred to conventionally as trees grow and propagate along the pllh o~ electric discharge, leaving carboni2ed resin therein. This is the reason why they usllally look black. Meanwhile, chemical trees stem From copper sulFide and copper oxide which are formed on a copper conductor by reaction of copper with hydrogen sulfide and other reactive gases which have diffused to copper conductor through the resin insulation. These ~ 3 ~
reaction products grow into black or reddish brown needle crystals that look like trees. Chemical trees are characterized by ~he fact that they occur even under tension-free conditions.
The polyolefin as used in this invention includes polyethylene, polypropylene, ethylene-propylene copolymers, polybutene, polyisobutylene, poly-4-methylpentene, copolymers thereof~ and crosslinked products ther-of. High-molecular weight polyethylene glycol means polyethylene glycol having more than 44 carbon atoms, preferably more than 80 carbon atoms.
The polyethylene glycol is incorporated in an amount of 0.3 to 10 % by weight, based on the polyolefin or crosslinked polyolefin. Under 0.3 %, no satisfactory effect is attained, particularly in the case where poly-ethylene glycol of relatively low molecular weight is employed. On the other hand, when over 10 % is used, some difficulties are encountered in achieving uniform compounding without slight discoloration in the result-ing composition, although the inexpensive polyethylene glycol has no eco-nomic limitation in the quantity to be added.
Whether or not the polyolefin is crosslinked does not matter in this invention, and the use of stabilizers~ inorganic fillers, and other additives is within the scope of this invention.
EXAMPLES
The polyolefin used as the major constituent of the composition as selected From low-density polyethylene and ethylene-vinyl acetate co-polymer which are most popular as electrical insulating materials. High-molecular weight polyethylene glycol which characterizes this invention was selectrd from a series ranging From 1,000 to 20,000 in the molecular weight. It was confirrned that the present invention can be practiced For polyolefin with or without crosslinking. The results obtained are $hown in Table 1. ~lso shown in Table 1~ for comparison, are the results of Comparative Examples that follow.
Comparative Example 1 employed no polyethylene glycol and water trees were observed at all the measuring points. In Comparative Example
2, 0.25 parts by weight of polyethylene glycol having a molecular weight of 1000 was incorporated into 100 parts by weight of polyethylene. Water trees were observed at 25 % of the measuring points.
In Example 1, the occurrence of water trees was reduced to zero by adding 0.5 parts by weight of polyethylene glycol having a moleclllar weight oP 1000 to 100 parts by weight of crosslinked polyethylene. Good resul-ts werr also obtained in Example 2, in which the major constituent was ther-rnoplastic polyethylene. Examples 3 to 6 were intended to determine how the molecular weight and quantity of polyethylene glycol affect the occur-rence of water trees. It was found that the higher the molecular weight ., 5 ;3~
andthe larger the quantity added, the better the results, although the effect levels off beyond 0.5 %, Tests methods employed in the Exarnples are as follows:
(1) Preparation of test specimens: Tray-shaped specimens, each having twelve inverted conical holes on the botton, were cornpression molded from polyolefin compositjons into which specified quantities of polyethylene glycol had been incorporated by kneading. The section and dimensions of the specimen are shown in Fig. 1. An enlarged view of an inverted conical hole and dimensions of the hole are shown in Fig. 2.
(2) Test apparatus: The tray-shaped specimen was filled with O.Ol N sod-ium chloride solution~ and the bottom of the specimen was placed in O.Ol N
sodium chloride solution. Voltage (as specified below) was applied to the saline solutions inside and outside the specimen through platinum wires.
The perspective view of the apparatus is shown in Fig. 2, wherein 1 is a transparent test vessel, 2 is a wire leading to high voltage power source,
In Example 1, the occurrence of water trees was reduced to zero by adding 0.5 parts by weight of polyethylene glycol having a moleclllar weight oP 1000 to 100 parts by weight of crosslinked polyethylene. Good resul-ts werr also obtained in Example 2, in which the major constituent was ther-rnoplastic polyethylene. Examples 3 to 6 were intended to determine how the molecular weight and quantity of polyethylene glycol affect the occur-rence of water trees. It was found that the higher the molecular weight ., 5 ;3~
andthe larger the quantity added, the better the results, although the effect levels off beyond 0.5 %, Tests methods employed in the Exarnples are as follows:
(1) Preparation of test specimens: Tray-shaped specimens, each having twelve inverted conical holes on the botton, were cornpression molded from polyolefin compositjons into which specified quantities of polyethylene glycol had been incorporated by kneading. The section and dimensions of the specimen are shown in Fig. 1. An enlarged view of an inverted conical hole and dimensions of the hole are shown in Fig. 2.
(2) Test apparatus: The tray-shaped specimen was filled with O.Ol N sod-ium chloride solution~ and the bottom of the specimen was placed in O.Ol N
sodium chloride solution. Voltage (as specified below) was applied to the saline solutions inside and outside the specimen through platinum wires.
The perspective view of the apparatus is shown in Fig. 2, wherein 1 is a transparent test vessel, 2 is a wire leading to high voltage power source,
3 is a polyethylene lid, 4 is a transparent container, 5 is a platinum wire electrode, 6 is a specimen, 7 is an earthing wire, and 8 is an electrolyte.
(3) Occurrence and observation of trees: The presence or absence of 2~ water trees that had grown from the apex of the inverted conical hole in the specirnen after application of an alternating voltage, 5 kV and 5 kHz, For ~8 hours, was examined and the lerlgth of the tree was measured using an optical microscope. In order to facilitate observation, the specimen was sliced into thin chips near the apex of the inverted conical hole along the conical axis, and the sliced chips were dyed by boiling in a methylene blue aqueous solution. Figure 4 schematically shows an enlarged Yiew of a water tree as represented by 9.
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(3) Occurrence and observation of trees: The presence or absence of 2~ water trees that had grown from the apex of the inverted conical hole in the specirnen after application of an alternating voltage, 5 kV and 5 kHz, For ~8 hours, was examined and the lerlgth of the tree was measured using an optical microscope. In order to facilitate observation, the specimen was sliced into thin chips near the apex of the inverted conical hole along the conical axis, and the sliced chips were dyed by boiling in a methylene blue aqueous solution. Figure 4 schematically shows an enlarged Yiew of a water tree as represented by 9.
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Claims (17)
1. An electrical insulation composition consisting essentially of an organic polymeric electrical insulating material selected from the group consisting of a homopolymer of ethylene, an ethylene-vinyl acetate copolymer and cross-linked products thereof, and a polyethylene glycol having more than 44 carbon atoms in an amount of from 0.3 to 10 percent by weight.
2. A composition as defined in claim 1 wherein the polyethylene glycol has more than 88 carbon atoms.
3. An electrical insulation composition consisting essentially of an organic polymeric electrical insulating material selected from the group consisting of a homopolymer of ethylene, an ethylene-vinyl acetate copolymer and cross-linked products thereof and a polyethylene glycol having a molecular weight of from 1,000 to 20,000 in an amount of from 0.3 to 10 percent by weight.
4. A composition as defined in claim 1 wherein the polyethylene glycol is present in an amount of from 0.5 to 1.0 percent by weight.
5. A composition as defined in claim 3 wherein the polyethylene glycol is present in an amount of from 0.5 to 1.0 percent by weight.
6. A composition as defined in claim 1 wherein the organic polymeric electrical insulating material is a homo-polymer of ethylene.
7. A composition as defined in claim 1 wherein the organic polymeric electrical insulating material is an ethylene-vinyl acetate copolymer.
8. A composition as defined in claim 4 wherein the organic polymeric electrical insulating material is a homopolymer of ethylene.
9. A composition as defined in claim 4 wherein the organic polymeric electrical insulating material is an ethylene-vinyl acetate copolymer.
10. A composition as defined in claim 3 wherein the organic polymeric electrical insulating material is a homo-polymer of ethylene.
11. A composition as defined in claim 3 wherein the organic polymeric electrical insulating material is an ethylene-vinyl acetate copolymer.
12. A composition as defined in claim 5 wherein the organic polymeric electrical insulating material is a homopolymer of ethylene.
13. A composition as defined in claim 5 wherein the organic polymeric electrical insulating material is an ethylene-vinyl acetate copolymer.
14. A composition as defined in claim 1 wherein the organic polymeric electrical insulating material is a cross-linked product of a homopolymer of ethylene or a crosslinked product of an ethylene-vinyl acetate copolymer.
15. A composition as defined in claim 3 wherein the organic polymeric electrical insulating material is a cross-linked product of a homopolymer of ethylene or a crosslinked product of an ethylene-vinyl acetate copolymer.
16. A composition as defined in claim 4 wherein the organic polymeric electrical insulating material is a cross-linked product of a homopolymer of ethylene or a crosslinked product of an ethylene-vinyl acetate copolymer.
17. A composition as defined in claim 5 wherein the organic polymeric electrical insulating material is a cross-linked product of a homopolymer of ethylene or a crosslinked product of an ethylene-vinyl acetate copolymer.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000379078A CA1183297A (en) | 1981-06-05 | 1981-06-05 | Inhibition of water-treeing in polyolefin electrical insulation |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000379078A CA1183297A (en) | 1981-06-05 | 1981-06-05 | Inhibition of water-treeing in polyolefin electrical insulation |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1183297A true CA1183297A (en) | 1985-02-26 |
Family
ID=4120150
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000379078A Expired CA1183297A (en) | 1981-06-05 | 1981-06-05 | Inhibition of water-treeing in polyolefin electrical insulation |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1183297A (en) |
-
1981
- 1981-06-05 CA CA000379078A patent/CA1183297A/en not_active Expired
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