CA1161589A - Electrical tree and water tree resistant polymer compositions - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE An unfilled polymeric, composition having improved electrical treeing and water treeing properties comprising a polymeric component and effective amounts of an organic compound, such as, a specially defined silane. These compositions are particularly useful as insulation for high voltage transmission and distribution cables.

Description

1 ELECTRICAL TREE AND WATER TREE R~SISTANT POLYM~R
COMPO~ITIONS

This invention relates to polymeric compositions 5 having increased resistance to electrical treeing and water treeing properties, said compositions being useful as insulation for electrical cables.
Polymeric compositions are well-known and are used extensively as insulation materials for wire and 10 cable. As an insulator, it is important that the composition have various physical and electrical pxoperties, such as resistance to mechanical cut through, stress crack resistance and dielectric failure. Recent publi-cations have indicated that water tree growth and electrical 15 tree growth in the insulation are particularly important problems since they are associated with, though not necessarily totally responsible for, dielectric failure.
An important application for an insulation material is in high voltage transmission and distribution 20 cable, especially in direct buried underground service and three types of trees have been observed in power cables, to wit, electrical trees, water trees and electro-- chemical trees. It is generally believed that electrical trees are generated by corona discharges causing fusion 25 and breakdown of the polymer, whereas water trees are usually observed in cables buried in wet locations and have a different appearance comparea to the electrical trees. The electrochemical trees are similar to the water trees but are characterized by the presence 30 of metal ions in the trees.

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1 U.S. Pa-tent No. 4,144,202 gran-ted to Ashcraft et al. relates to inhibiting the electrical breakdown of insulation by water treeing in dielectric materials based on ethylene polymers. This patent discusses 5 electrical failures which are due to treeing and explains the concept of treeing and some of the causes for treeing.
In general, as the polymeric composition breaks down the damage progresses through the insulator, or dielectric, in a path that loo~s something like a tree, Txeeing lO usually is a slow type failure and may take years to cause a failure in the insulation~ As disclosed in the patent, water treeing is inhibited in the ethylene polymer com-positions by employing therein certain organo silane compounds, In particular, the organo silane is a silane 15 con~aining an epoxy containing radical. Suitable polymers, adjuvants and processing procedures for preparing the composition are described in the patent U.S. Patent 4,206,260 to 20 E.J. McMahon relatesto insulation particularly suit~bl~
for high voltage power cable containing an effective amount of an alcohol of 6 to 24 carbon atoms which imparts ~ electrical tree growth resistance to the composition.
~his Patent , as in U,S, No. 4,144~202, supra, con-25 tain a discussion of the electrical treeing problem in polymer compositions and cite numerous patents attempting to overcome this problem, German Offenlegungsschrift 2,737,430 discloses that certain alkoxysilanes added to polyolefin insulation prevent water-tree formation. Several trimethoxy and triethoxy silanes are said to be useful, No alkoxyalkoxy ~6~

l silanes are taught or suggested as having both water treeing and electrical treeing inhibiting properties.
U.S. Patent No. 3,553,34~ granted to Betts, 5 British Patent No. l,2a8,256 granted to General Electric Company and British Patent No. 1,277,378 gxanted to General Electric Company relate to mineral filled polymer compositions useful as electrical wire and cable insulation The mineral filler is treated with an organosilane such lO as an alkyl alkoxysilane or a vinyl alkoxysilane to decrease the porosity of the composition. None of these patents teach or suggest that addition of an organosilane to an unfilled polymer composition will beneficially enhance the water -treeing and electrical treeins resistance of the 15 polymer com~osition.
Unfortunately~ however, the prior art has not provided an insulation composition having both increased resistance to water treeing and electrical treeing.
As noted in U.S. No~ 4,144,202, supra, intrinsic electric 20 breakdown, failure by corona~ electrical treeing and water treeing are different and the mechanisms for each are different and a different solution is required to effect - an improvement in a dielectric material for each mode of failure involved. Thus, the problem of providing a 25 single composition capable of resisting both electrical treeing and water treeing is a formidable one confronting the art, It has now been unexpectedly discovered that 30 polymeric compositions comprising an effective amount of

2 certain organic compound, such as a specially defined silane component, exhibit both enhanced resistance to water treeing and electrical treeing properties. The ~.~.6~

1 eomposition may also be cured using known techniques to provide a crosslinked composition having further improved properties for certain applications.
In general, the polymerie co~position comprises 5 per hundred par~s by weight polymer (phr) about 0,1 to 10 phr of a silane having the following formula A:
Rl R - Si - R2 - ' ~ 3 wherein R, Rl, R2 and R3 are eaeh independently selected from Cl to Cg alkyl, Cl to C8 alkoxy, Cl to C8 acyloxy, C6 to C18 aryloxy or substituted aryloxy, C6 to C18 15 aryl or substituted aryl, hydrogen, halogen, an epoxy containing radieal, C2 to C8 alkenyl, a nitrogen eontain-ing radical, a carboxy eontaining radieal, a mercapto eontaining radieal and an ether eontaining radical~ with the proviso that at least one, and preferably at least three, e.g.~ all of R, Rl, R2 and R3 be a group wherein the group contains at least one electron donating atom in the chain of the group and which is at a position other than the position ad~acent to the silicon atom.
The electron donating group may be, for example, oxygen, 25 nitrogen, sulphur and the like. Oxygen is preferred beeause of its demonstrated effeetiveness~ A highly preferred group has the electron donating atom separated from the silieon atom by three atoms~
A preferred eomposition comprises about 0.5 to 5 phr silane component, most preferably about 1 to

3 phr.

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l A particularly preferred unfilled polymeric composition comprises a homogeneous mixture of a polymeric component and an effective amount, as a water treeing and electrical treeing inhibitor, of an organic compound having 5 the following formula B;

R2 ~ 2 - Yl (-CnH2n) 2 6 (R3)a wherein Rl, R2 and R3 are the same or different and l n 2n~ Y2R6 r Cl to C8 alkyl, C1 to C8 alkoxy C
to C8 acyloxy, C6 to C18 aryloxy or substituted aryloxy, C6 to C18 aryl or substituted aryl, hydrogen, halogen 15 an epo~y containing radical, C2 to C8 alkenyl, a nitrogen containing radical, a carboxy containing radical, a mercapto containing radical or an ether containing radical;
R6 is Cl to C8 alkyl, Cl to C8 alkoxy, Cl to C8 acyloxy, C6 to Cl8 aryloxy or substituted aryloxy, C6 to C18 20 aryl or substituted aryl, hydrogen, halogen, an epoxy containing radical, C2 to C8 alkenyl, a nitrogen contain-ing radical, a carboxy containing radical, a mercapto containing radical or an ether containing radical;
. Yl and Y2 are the same or different and are 0, S or N~;
Z is Si, Sn, Ti, P or B
a is 0 or l; and n i5 l to 8.
This particularly preferred composition comprises 3 about 0.1 to lO parts (by weight) per hundred parts (phr) of polymer of the organic compound of formula B. An especially preferred composition comprises about 0.5 to 5 phr of organic compound component,-preferably about l to 3 phr, 5~

1 This invention is also directed to a method of stabilizing a polymeric insulated electrical conductor against water treeing and electrical treeing which comprises coating an electrical conductor ~ith an 5 insulating effective amount of a polymeric insulating composition, said composition comprising a homogeneous mixture of a polymeric component and an effective amount, as a water txeeing and electrical treeing inhibitor, of an organic compound having the following formula s:
Rl R2 - Z - Y1(CnH2n) Y2 6 (R3)a 15 wherein R1, R2 and R3 are the same or different and are Y1(CnH2n) Y2R6, Cl to C8 alkyl, Cl to C8 acyloxy~ C6 to C18 aryloxy or substituted aryloxy, C6 to Cl~ aryl or ~ahstituted aryl, hydrogen, halogen, an epoxy containing radical, C2 to C8 alkenyl, a nitrogen containing radical, 20 a carboxy containing radical, a mercapto containing radical or an ether containing radica~ R6 is Cl to C8 alkyl, Cl to C8 alkoxy, Cl to C8 acyloxy, C6 to C18 - aryloxy or substituted aryloxy, C6 to C18 aryl or substi-tuted aryl, hydrogen, halogen, an epoxy containing radical, 25 C2 to C8 alkenyl, a nitrogen containing radical,~a carboxy containing radical, a mercapto containing radical or an ether containing radical;
Yl an~ Y2 are the sa~e or different and are 0, S:or 3 a is 0 or 1; and~
n is 1 to 8, ~hereby said insulated electrical conductor exhibits water treeing and ~lectrical 1 treeing inhibition when exposed to an environment subject to water treeing and electrical treeing con-ditions.
The compositions of the invention find particular 5 utility in high voltage transmission and distribution cables but are useful in other electrical applications where a unique combination of enhanced water treeing and electrical treeing properties are needed.

In general, the polymers suitable for the practice of this invention include any normally solid synthetic organic polymeric thermoplastic resin, Included are polyolefins and copolymers thereofl vinyls, olefin-vinyl copolymers, olefin-allyl copolymers, poly-15 amides, acrylics, polystyrenes, cellulosics, polyesters and flurocarbons.
The polyolefins include normally solid polymers of olefins, particularly mono-alpha-olefins, which comprise from about two to about six carbon atoms, e.g., 20 polyethylene, polypropylene, polybutene, polyisobutylene, poly(4-methyl-pentene), and the like. Preferred poly-olefins are polyethylene and polypropylene. Polyethylene - is especially preferred~ An especially preferred poly-ethylene because of its demonstrated effectiveness is 25 termed NA 310*and is sold by National Distillers and Chemical Company.
Copolymers of ethylene, and other compounds interpolymerizable with ethylene such as butene-l, pentene-l, styrene and the like may be employed. In 30 general the ethylene will comprise about 50 to ~ 100 weight % ethylene.

* Trade Mark 1 Suitable vinyl polymers include polyvinyl chloride, polyvinyl acetate, vinyl chloride/vinyl acetate copolymers, polyvinyl alcohol and polyvinyl acetal.
Suitable olefin-vinyl copolymers include ethylene-5 vinyl acetate, ethylene-vinyl propionate, ethylene-vinyl isobutyrate, ethylene-vinyl alcohol, ethylene-methyl acrylate, ethylene-ethyl acrylate J ethylene-ethyl meth-acrylate, and the like. In general the ethylene consti-tutes at least about 25~ of the copolymer by weight.
Olefin-allyl copolymers include ethylene-allyl benzene, ethylene-allyl ether, ethylene-acrolein, and the like.
The silane employed in the polymeric compositions of the invention may be selected from one or more compounds 15 of the following formula A:
Rl R - Si - R2 wherein R, Rl, R2 and R3 are defined as hereina~ove in connection with formula A~
The organic compound employed in the particularly preferred unfilled polymeric compositions of the invention is 25 selected from one or more compounds of the following formula B:
Rl R2 ~ Z - Yl(CnH2n~ Y2 6 : 30 (R3)a Rl~ R2, R3, R6, Yl, Y2, Z, a and n are defined as hereinabove in connection with formula B~

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g 1 A number of R, Rl, R2 and R3 groups useful in connection with the present invention is shown in "Chemicals and Plastics Physical Properties. 1978-80" published by Union Carbide Company on page 43 Exemplary are chloro, methyl, ethyl, methoxy, ethoxy, phenyl,~hydrogen, chloropropyl, vinyl 2-methoxyethoxy, gamma-methacryloxy-propyl, beta-(3,~epoxycyclohexyl)-ethyl, gamma-glycidoxy-propyl, acetoxy, gamma-mercaptopropyl, gamma-aminopropyl, 10 bis-hydroxyethyl-gamma-amino-propyl, bis-acrylic acid gamma-amino-propyl, N-beta(aminoethyl~-gamma-amino-propyl, and methyl 12(gamma-trimethoxysilypropylamino~ethylamino]
3 propionate.
As noted hereinabove, at least one of the R, 15 Rl, R2 and R3 groups of formula A have an electron donating atom such as oxygen, nitrogen or sulphur atom in the chain of the groups. Preferably the electron donating atom is separated from the silicon atom by three atoms.
A preferred group has the following formula, (OR40R5) wherein R4 is Cl to C6 and R5 is a Cl to C8 alkyl, hydrogen, Cl to C8 alkoxy or C2 to C8 alkenyl. A particularly preferred group is 2 methoxyethoxy which has the formula, ( oC2~4CH3 ) 25 A preferred compound is sold under the name A--172*by Union Carbide Company and is chemically defined as vinyl-tris (2-methoxyethoxy) silane. Other R, Rl, R~ and R3 groups include gamma-methacryloxy-propyl, gamma-glycidoxy-propyl, gamma-aminopropyl, bis-hydroxy-ethyl-gamma-amino-30 propyl and N-béta(aminoethyl)-gamma-amino-propyl.
The Rl, R2 and R3 groups of formula B useful in connection with the present invention when Z is silicon, include examples of the groups discussed above * Trade Mark 5~3~

1 in connection with the Union Carbide Company publicaton, particularly when Yl(Cn~l2n) Y2R6 is an alkoxyalkoxy groups.
Among the useful silanes of formula B are gamma-meth-acryloxypropyl-tris(2-methoxyethoxy) silane, tetrakis-(2-methoxyethoxy) silane, methyl-tris (2-methoxyethoxy) silane, phenyl-tris(2 methoxyethoxy) silane, vinyl-tris (2-phenoxyethoxy) silane, vinyl-tris (2-methylthioethoxy) silane and vinyl-tris (2-methoxyethoxy) silane with the latter being particularly preferred. Replacing the silicon with such atoms as ~in, titanium, phosphorous or boron provides other useful compounds which find utility in the invention Thus, such compounds as tris (2-ethoxyethyl) phosphite, tris (2-n-butoxyethyl) phosphite, tetrakis (2 methoxyethoxy) titanium and the like may be employed 15 and are included with the scope of this invention.
Therefore, in the preferred organic compounds of formula ~, Rl, R2, and P~3 are each selected from Yl(CnH2n)~2R6, alkyl, alkoxy, acyloxy, aryl or alkenyl, R6 is alkyl or aryl, Yl and Y2 are o and Z is Si or P- Of eourse~when Z is Si, a is 20 1 and when Z is P, a is 0.
~ hen it is desired to use a polymerie composi-tiO}l whieh can be crosslinked, crosslinking can be accom-plished by any of the known proeedures sueh as ehemical means including peroxide eross-linking; by radiation using 25 eleetron aeeelerators, ~r-rays, high energy radiation, sueh as X-rays, mierowaves ete,; or by thermal erosslinking.
The basie proeedures for erosslinking polymers are ~:
extremely well known to the art and need not be described here in detail.
Conventional crosslinking agents sueh as organie peroxides may be suitably employed, Typieal organie peroxide.free radieal generators include dieumyl peroxide;
2,5-bis (tert.-butylperoxy)-2,5 dimethylhexane; di--t-butyl $~

1 peroxide benzoyl peroxide; J6, ~I bis(t-butyl peroxy) diisopropyl benzene and the like, as discussed in U.S.
Patent No. 3,287,312. The amount of organic peroxidel when employed, will range from about 0.5 to 5.0% by weight 5 based on the total weight of the composition, or about 0.5 to 10 phr, preferably 3 to 6 phr.
~ lhile the silanes and the organic compounds described hereinabove are useful for both thermoplastic and cured polymeric compositions, for compositions to 10 be cured it is preferred that one of the groups/ to wit, R, Rl, R2, or R3, be an organo functional group, e.g., a vinyl group, which group provides the composition with enhanced curing properties.
Minor amounts of other additives may also be 15 employed in conventional amounts to obtain the desired results, Conventional antioxidants such as the hindered phenols, polyquinolines and the like may be employed.
Other ingredients that may be included are plasticizers, dyes, pigments, heat and light stabilizers, antistatic 20 agents and the li~c~
The preferred compositions of this invention are unfilled polymer compositions~ The term 'unfilled" as applied to the - instant composition shall mean a composition which contains less than 10% of a conventional polymer filler. For certain 25 applications and to meet particular specifications the unfilled compositions herein may contain no filler. The compositions of this invention may contain, therefore, O to less than 10~ filler.
Accordingly, fillers, such as mineral fillers, may be employed to this limited extent in preparing the compositions of the 30invention, but in the particularly preferred embodiment and for certain uses, these compositions contain no fillers.

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1 The polymer compositions of this invention can be prepared by mixing the various ingredients When the organic compound and the polymeric component are mixed together to form the instant compositions, the organic 5 compound and poly~eric component are homogeneously dispersed in each other. The order of mixing and specific procedure employed are not critical except to the extent that from the time the peroxide is added, if employed, the temperature is less than about 130~C. in order to prevent premature 10 curing of the composition. This precaution, however, is conventional in the art.
The components may be mixed on a variety of apparatus including multi-roll mills, screw mills, continuous mixers, compounding extruders and Banbury*mixers.
After being extruded onto wire or cable, or other substrate, the crosslinkable compositions are vul-canized at elevated temperatures, e.g., above about 180C.
using conventional vulcanizing procedures.
In order to determine the utility and effective-20 ness of the polymeric compositions of the present inventionwith regard to its inhibiting effect on the water treeing and the electrical treeing thereof, the co~positions - were evaluated by the use of accelerated tests.
Electrical tree tests were performed using the 25 method similar to that in IEEE Conference Paper No. C73, 257-3 1973 by E.J. McMahon and J.R. Perkins. Strips of material approximately 1" wide were cut from a 1/4"
thick compression molded plaque~ The block was machined to give a strip having parallel edges 1" apart, The strip 3 was then cut into 1" square blosks. A blunt needle and a sharp needle were inserted into opposite parallel edges, at elevated temperatures, so that the points were 1/8"
* Trade Mark ~6~5~

l apart. Nee~le insertion and cooling of the sample was performed slowly to avoid inducing thermal or mechanical stresses in the specimen. The sharp needle has a tip diameter of about 0.0002" while the diameter of the blunt 5 needle is 0.002"~ Eight specimens were prepared and tested simultaneously for each composition~ ~he electrical tree test was performed by energizing the sharp needle at 15 XV using a frequency of 60 ~z; the blunt needle was connected to ground. The time required for lO each of the eight specimens to fail by tree ~rowth and subsequent electrical short was re~orded. The time required for 50~ of the samples to fail was employed to characterize the effectiveness of the tree retardant being evaluated.
The water tree test is performed using a procedure similar to that described in ~,S. Patent 4,1~4,202. A
;compression molded disc about 150 millimeters (mm.) in diameter having 24 conical depressions was prepared for each co~.position. The geometry of the disc and dimensions 20 of the depressions are substantially the same as shown in USP 4,144~202. The base of the disc is sprayed with silver paint which serves as the ground electrode. An acrylic tube 6" long is clamped to the upper face forming a test cell. About 150 ml, of 0.01 N sodium chloride 25 solution was poured into the cell and the air bubbles trapped on the surface of the sample were removed.
A platinum wire ring was then immersed in the electrolyte and connected to the electrical supply which provides ,5KV at a frequency of 3KHz. Samples were energized for 30 22 hours after~which time they were removed from the test cell and washed with distilled water. The ten central depressions were cut from the disc and stained to s~

1 make the water trees more visible, Thin sections were obtained with a microtome, which were then examined microscopically (at 200X) and the tree size measured.
Normally four discs were made for each sample so that the 5laverage tree size is calculated from forty individual measurements. In evaluating different tree re-tardants, the relative tree size was determined by comparing the average tree size obtained on a standard thermoplastic high voltage insulation material containing no tree lO~retardant additivesO
Various embodiments of the present invention will now be illustrated by reference to the following specific examples. It is to be understood, however, that such examples are presented for purposes of illustration only, 15land the present invention is in no way to be deemed as limited thereby. A11 parts and percentages are by weight and temperatures in degrees Fahrenheit unless otherwise noted.
I

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1 ~X~PL~ I
The compositions were prepared by milling a commercial grade of polyethylene (NA 310) and the treeing additive (2P6 by weight) on a 2-roll mill at about 5 300~F. for about 10 minutes to obtain a homoyeneous dis-persion, The crepe obtained was then used to prepare the samples for electric tree and water tree testing using the procedures described hereinabove. The test results are shown in Table 1. All the compositions have the same 10 formulation except for the "treeing" additive as noted in Table 1 and comprise a commercial grade of polyethylene having a Melt Index of about 0,20 to 0.35 g/10 min. and a density of about ,917 grams/cubic centimeter (g/cc).
The control sample does not contain a "treeing" additive.

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1 TABL~ I
Sample Treeing Additive Double Needle Water Tree No. Test Time to (Relative 50% Failure Tree Size) (minutes) , _ A Vinyl-tris- ~ 12,700 0,23 (2-methoxy-ethoxy) silane (no failures) B Gamma-glycid- 2,800 0.34 oxypropyl -tri-methoxysilane 1 Control 80 (No Additive) 2 Vinyl triethoxy 30 0.29 silane ... . _ _ .. _ 3 Beta-(3,4-epoxy- 620 0.34 cyclohexyl)-ethyl-trimethoxysilane . . _ _ .

4 Dodecanol 127 0.34 3o 1 The results clearly show the improvement in both water treeing and electrical treeing properties o~
formulations prepared in accordance with the present inven-tion. Thus, comparing Samples A and B, o~ the invention,

5 with Samples 1-~, which are outside the invention, the improvement is readily apparent. Comparing Sample A
with the control, Sample 1, shows the vast improvement in properties when vinyl-tris (2-methoxyethoxy) silane is employed. Similarly~ a comparison of Sample A wi-th Sample 10 2 shows the importance for utilizing a silane having an electron donor atom in the chain of the groups attached to the silicon atom. A comparison of Sample A with Sample B shows the advantage of employing three electron donating group radicals attached to the silicon atom.

In the same fashion as in Exam~le I, a number of organic compounds were evaluated as "treeing" additives.
In all instances the addi-tive was incorporated in the polyeth~lene at a concentration of 1.5%. The results of the electrical tree and water tree testing are shown in Table II.

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1 The silanes evaluated demonstrated a superiority in both water tree and electrical tree resistance for those silanes having alkoxyalkoxy substituents. (Samples

6, 9, 10, 14, 22 and 23). This can be seen by comparing inter alia the silane pairs of samples 6 and 7, 9 and 11 and 13 and 14. It also appears tha-t there is an optimum number of alkoxy alkoxy substituents - compare samples 6, 9 and 10. The effect of a vinyl substituent as compared to an alkyl or aryl substituent is evident from comparing samplés 6~ 9 and 22, The location of a particular substituent, viz, an aryl group, can influence the inhibi-tion properties of the organic compound as seen ~rom samples 22 and 23, Samples 24 and 25 show that organic phosphites are effective in both water and electrical tree inhibition.
while sample 26 shows similar effectiveness for an organic titanium compound.
While the invention has been directed principally to the use of silanes, it will be understood by those skilled 20 in the art that other compounds containi.ng a multivalent atom such as titanium, tin, phosphorous, and the like may be employed.

Claims (33)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A polymeric composition having enhanced resistance to water treeing and electrical treeing comprising a homogeneous mixture of a polymeric component and an effective amount, as a water treeing and an electrical treeing inhibitor, of an organic compound having the formula:
wherein R1, R2 and R3 are the same or different and are Y1(CnH2n) Y2R6, C1 to C8 alkyl, C1 to C8 alkoxy, C1 to C8 acyloxy, C6 to C18 aryloxy or substituted aryloxy, C6 to C18 aryl or substituted aryl, hydrogen, halogen, an epoxy containing radical, C2 to C8 alkenyl, a nitrogen containing radical, a carboxy containing radical, a mercapto containing radical or an ether containing radical; R6 is C1 to C8 alkyl, C1 to C8-alkoxy, C1 to C8 acyloxy, C6 to C18 aryloxy or substituted aryloxy, C6 to C18 aryl or substituted aryl, hydrogen, halogen, an epoxy containing radical, C2 to C8 alkenyl, a nitrogen containing radical, a carboxy containing radical, a mercapto con-taining radical or an ether containing radical;
Y1 and Y2 are the same or different and are O, S or NH;
Z is Si, Sn, Ti, P or B;
a is 0 or 1; and
1. Claim 1 (continued) n is 1 to 8 with the proviso that when Z is P, a is 0, Y1 and Y2 are each 0 and R1 and R2 are the same and are Y1 (CnH2n)Y2R6), and when Z is P, R6 is not hydrogen, said composition containing from 0 to 10% by weight of filler.
2. 2. A composition as in claim 1 wherein the polymer is polyethylene,
3. 3. A composition as in claim 1 wherein R1, R2 and R3 are each selected from Y1(CnH2n) Y2R6, alkyl, alkoxy, acyloxy, aryl or alkenyl, R6 is alkyl or aryl, and Y1 and Y2 are each 0.
4. 4. A composition as in claim 3 wherein Z is Si and a is 1.
5. 5. A composition as in claim 4 wherein R1 is vinyl, R2 and R3 are each Y1(CnH2n) Y2R6, R6 is methyl and n is 2.
6. 6. A composition as in claim 4 wherein R1 is methyl, R2 and R3 are each Y1(CnH2n) Y2R6, R6 is methyl and n is 2.
7. 7. A composition as in claim 4 wherein R1, R2 and R3 are each Y1(CnH2n) Y2R6, R6 is methyl and n is 2.
8. 8. A composition as in claim 4 wherein R1 is gamma-methacryloxypropyl, R2 and R3 are each Y1(CnH2n) Y2R6, R6 is methyl and n is 2.
9. 9. A composition as in claim 4 wherein R1 is phenyl, R2 and R3 are each Y1(CnH2n) Y2R6, R6 is methyl and n is 2.
10. 10. A composition as in claim 4 wherein R1 is vinyl, R2 and R3 are each Y1(CnH2n) Y2R6, R6 is phenyl and n is 2.
11. 11. A composition as in claim 1, wherein z is P, R6 is ethyl and n is 2.
12. 12. A composition as in claim 1, wherein Z is P, R6 is n-butyl and n is 2.
13. 13. A composition as in claim 3 wherein Z is Ti and a is 1.
14. 14. A composition as in claim 13 wherein R1, R2 and R3 are each Y1(CnH2n) Y2R6, R6 is methyl and n is 2.
    
    15. A method of stabilizing a polymeric insulated electrical conductor against water treeing and electrical tree-ing which comprises:
    coating an electrical conductor with an insulating effective amount of a polymeric insulating composition containing a homogeneous mixture of a polymeric component and an effective amount, as a water treeing and electrical treeing inhibitor, of an organic compound having the following formula:
    wherein R1, R2 and R3 are the same or different and are Y1(CnH2n) Y2R6, C1 to C8 alkyl, C1 to C8 alkoxy, C1 to C8 acyloxy, C6 to C18 aryloxy or substituted aryloxy, C6 to C18 aryl or substituted aryl, hydrogen, halogen, an epoxy containing radical, C2 to C8 alkenyl, a nitrogen containing radical, a carboxy containing radical, a mercapto containing radical or an ether containing radical;
    R6 is C1 to C8 alkyl, C1 to C8 alkoxy, C1 to C8 acyloxy, C6 to C18 aryloxy or substituted aryloxy, C6 to C18 aryl or substituted aryl, hydrogen, halogen, an epoxy containing radical, C2 to C8 alkenyl, a nitrogen containing radical, a carboxy containing radical, a mercapto containing radical or an ether containing radical:
    Y1 and Y2 are the same or different and are O, S or NH;
    Z is Si, Sn, Ti, P or B;
    a is 0 or 1; and
15. Claim 15 (continued) n is 1 to 8 with the provision that when Z is P1, a is O, Y1 and Y2 are each o and R1 and R2 are the same and are Y
    (CnH2n) Y2R6), and when Z is P, R6 is not hydrogen, the composition containing from 0 to 10% by weight of filler whereby said insulated electrical conductor exhibits water tree-ing and electrical treeing inhibition when exposed to an environ-ment subject to water treeing and electrical treeing conditions.
16. 16. A method as in claim 15 wherein the polymer is polyethylene.
17. 17. A method as in claim 15 wherein R1, R2 and R3 are each selected from Y1(CnH2n)Y2R6, alkyl, alkoxy, acyloxy, and aryl or alkenyl, R6 is alkyl or aryl, and Y1 and Y2 are each 0.
18. 18. A method as in claim 17 wherein Z is Si and a is y.
19. 19. A method as in claim 18 wherein R1 is vinyl, R2 and R3 are each Y1(CnH2n)Y2R6, R6 is methyl and n is 2.
20. 20. A method as in claim 18 wherein R1 is methyl, R2 and R3 are each Y1(CnH2n)Y2R6, R6 is methyl and n is 2.
21. 21. A method as in claim 18 wherein R1, R2 and R3 are each Y1(CnH2n)Y2R6, R6 is methyl and n is 2.
22. 22. A method as in claim 18 wherein R1 is gamma-methacryloxypropyl, R2 and R3 are each Y1(CnH2n)Y2R6, R6 is methyl and n is 2.
23. 23. A method as in claim 20 wherein R1 is phenyl, R2 and R3 are each Y1(CnH2n)Y2R6, R6 is methyl and n is 2.
24. 24. A method as in claim 20 wherein R1 is vinyl, R2 and R3 are each Y1(CnH2n)Y2R6, R6 is phenyl and n is 2.
25. 25. A method as in claim 19 wherein Z is P and a is 0.
26. 26. A method as in claim 25 wherein R6 is ethyl and n is 2.
27. 27. A method as in claim 25 wherein R1 and R2 are each Y1(CnH2n)Y2R6, R6 is n-butyl and n is 2.
28. 28. A method as in claim 17 wherein Z is Ti and a is 1.
29. 29. A method as in claim 28, wherein R1, R2 and R3 are each Y1(CnH2n)Y2R6, R6 is methyl and n is 2.
30. 30. A method in accordance with claims 15, 18 or 29, wherein the insulating composition is curable or cured.
31. 31. A method according to claims 15, 18 or 29, wherein the composition contains an effective amount of crosslinking agent, antioxidant, plasticizer, stabilier and/or antistatic agent.
32. 32. A method according to claim 15, 18 or 29, wherein the composition contains an effective amount of pigment or dye.
33. 33. An electrical conductor coated with the compositions of claims 1, 2 or 14.