Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
~31~3~
RAYC~IEM LIMITED - 1 -- RR339
Electrical Wire
This invention relates to electrical wires and
especially to wires that employ electrical insulation
based on aromatic polymers.
Electrical wire and cable that use aromatic
polymer insulation have been used for many years in
numerous applications. For example wires that employ
polyimide wraps or tapes usually bonded with fluoro-
polymer adhesive layers have been used extensively as
aircraft wirel for both civil and military applica-
tions. Other examples of aromatic insulation that have
been used for equipment wire or "hook-up" wirel air
frame wire and in wire harnesses include aromatic
polyether ketonesl polyether ether ketones, modified
polyphenylene oxidel and polyimide amides. Highly aro-
matic polymers have been used successfully in many
applications because they have a range of desirable
properties especially high strength and toughness/
abrasion resistancel temperature resistance, dielectric
strength and are often inherently highly flame-
retarded.
,~
:
,
, .
.. . .
7 3 ~
- 2 - RK339
The combination of these properties has enabled
wire and cable fabricated from these polymers to be
used in small lightweight constructions. Such
constructions have been used increasingly in both mili-
tary and civil applications due to the high density and
complexity of modern electrical systems.
However, these highly aromatic polymers suffer
from a major problem: they are particularly susceptible
to breakdown due to arcing~ A potential difference
between two conductors, or between a conductor in which
the insulation has been mechanically damaged, and
ground, can result in the formation of an arc between
the conductors or between the conductor and ground.
The high temperature of the arc causes the polymer to
degrade extremely rapidly and form an electrically con-
ductive carbonaceous deposit which can extend rapidly,
and lead to catastrophic failure in which many or all
of the wires in a bundle are destroyed. Arcing can
occur at very low voltages, for example 24~ d.c. or
lower, and since, unlike tracking, no electrolyte or
moisture is involved, it is a particularly hazardous
phenomenon. Arcs may also be struck by drawing apart
two conductors between which a current is passing as
described for example by J.M. Somerville "The Electric
Arc", Methuen 1959.
Another phenomenon that can be associated with
tracking and arcing is ~rosion. In this case insu-
lating material is removed by a Paporization process
originated by an electrical discharge without the for-
mation of electrically conductive deposits so that
failure of the insulation will not occur until complete
puncture of the insulation occurs.
.
. ' . ' '.' ' .
. . -. , .
. .
- 3 - 13 ~ RR339
According to the present invention there is pro-
vided an electrical wire which comprises an elongate
electrical conductor and electrical insulation that
comprises:
(a) an inner insulating layer which comprises a
polyamide or polyester having aliphatic moieties;
and
(b) an outer insulating layer which comprises an aro-
matic polymer.
The wire according to -the invention has the advan-
tage that it can combine the beneficial properties of
highly aromatic polymers, e.g. their good electrical
breakdown resistance, fire retardancy, temperature sta-
bility and mechanical toughness, with good arc-tracking
resistance. In addition, it is possible according to
the invention to employ polymers for the inner layer
that are relatively inexpensive and light in weight as
compared with fluorinated polymers that have been pro-
posed, and which have greater toughness, e.g. greater
resistance to cut-through and abrasion together with
reduced tendency to wrinkle as compared with polyole-
fins.
Preferably the polyamide or polyester forming the
inner layer has a carbonaceous char residue of not more
than 15%, more preferably not more than 10%, most pre-
ferably not more than 5%, especially not more than 2%
and most especially substantially zero. The char resi-
due of the polymer components in the electrical wire
according to the invention can be measured by the
.
.
- - - ~ .
~,. ' ' ' ' -
. ~ ~
. ~ -' '
~311 ~73~
~ 4 - RK339
method known as thermogravimetric analysis, or TGA, in
which a sample of the polymer is heated in nitrogen or
other inert atmosphere at a defined rate to a defined
temperature and the residual weight, which is composed
of char, is recorded. The char residue is simply the
quantity of this residual char expressed as a percen-
tage of the initial polymer after having taken into
account any non polymeric volatile or non-volatile com~
ponents. The char residue values quoted herein are
defined as having been measured at 850C. This will
normally be achieved by choosing a polyamide or
polyester that has a relatively low molar carbon to
hydrogen ratio. Preferably the polymer has a carbon to
hydrogen ratio of not more than 1.1, more preferably
not more than 1.0, especially not more than 0.75 and
most especially not more than 0.65.
It is possible for the polyester or polyamide to
include one or more aromatic moieties in addition to
its aliphatic moieties, and indeed a number of pre-
ferred polymers do so. However the polymer should have
sufficient aliphatic nature that the C:H ratio is not
too high. Preferred polyamides include the nylons,
e.g. nylon 46, nylon 6, nylon 7, nylon 66, nylon 610,
nylon 611, nylon 612, nylon 11, nylon 12 and nylon 1212
and aliphatic/aromatic polyamides, e.g. those based on
the condensation of an aromatic dicarboxylic acid and
an aliphatic diamene such as polyamides based on the
condensation of terephthalic acid with trimethylhexa-
methylene diamine (preferably containing a mixture of
2,2,4-and 2,4,4-trimethylhexamethylene diamine
isomers)/ polyamides formed from the condensation of
one or more bisaminomethylnorbornane isomers with one
_ 5 _ ~ 3 ~ RK33g
or more aliphatic, cycloaliphatic or aromatic
dicarboxylic acids e.g. terephthalic acid and
optionally including one or more amino acid or lactam
e.g. ~-caprolactam comonomers, polyamides based on
units derived from laurinlactam~ isophthalic acid and
bis-(4-amino-3-methylcyclohexyl) methane, polyamides
based on the condensation of 2,2-bis-(p-aminocyclo-
hexyl) propane with adipic and azeleic acids, and
polyamides based on the condensation of trans cyclo-
hexane-1,4-dicarboxylic acid with the trimethylhexa-
methylene diamine isomers mentioned above.
Other preferred aliphatic polymers include ~hose
based on polyether and polyamide blocks, especially the
so called a "polyether-ester amide block copolymers" of
repeating unit:
-C-A-C-O-B-O-
O O
wherein A represents a polyamide sequence of average
molecular weight in the range of from 300 to 15,000,
preferably from 800 to 5000; and B represents a linear
or branched polyoxyalkylene sequence of average molecu-
lar weight in the range of from 200 to 6000, preferably
from 400 to 3000.
Preferably the polyamide sequence is formed from
alpha,omega-aminocarboxylic acids, lactams or diamine/-
dicarboxylic acid combinations that include C4 to C14
carbon chains, and the polyoxyalkylene sequence is
based on ethylene glycol, propylene glycol and/or
tetramethylene glycol, and the polyoxyalkylene sequence
; ~
: . .
~ ' '.
'' . .,
'
-
~ 3~73~
- 6 - RK339
constitutes from 5 to 85%, especially from 10 to 50% o
the total block copolymer by weight. These polymers
and their preparation are described in UK Patent
Specifications Nos. 1,473,972, 1,532,930, 1,555,644,
2l005,283A and 2,011,450A.
The polyesters that are used in the inner layer
preferably include those based on a polyalkylene diol,
preferably having a least 3 carbon atoms, or a cyclo-
aliphatic diol and an aromatic dicarboxylic acid.
Preferred polyesters include polytetramethylene
terephthalate, and cycloaliphatic diol terephthalic
acid copolymers e.g. copolymers of terephthalate and
isophthalate units with 1,4-cyclohexanedimethyloxy
units. The polyesters can include polyether esters,
for example polyether polyester block copolymers having
long chain units of the general formula:
O O
-OGO-C-R-C-
and short-chain ester units of the formula
O O
Il 1~
-ODO-C-R-C-
in which G is a divalent radical remaining after
the removal o terminal hydroxyl groups from a
polyalkylene oxide) glycol, preferably a poly (C2
to C4 alkylene oxide) having a molecular weight of
about 600 to 6000; R is a divalent radical
remaining after removal of carboxyl groups from at
least one dicarboxylic acid having a molecular
. ,. ~ '
~ 3 ~ ~ 7 ~ RR339
weight of less than about 300; and D is a divalent
radical remaining after removal of hydroxyl groups
from at least one diol having a molecular weight
less than 250.
Preferred examples of such copolyesters are the
polyether ester polymers derived from terephthalic
acid, polytetramethylene ether glycol and
1,4-butane diol. These are random block copoly-
mers having crystalline hard blocks with the
repeating unit:
-(CH2)4-O-C ~ C-
and amorphous, elastomeric polytetramethylene
ether terephthalate soft blocks of repeating unit
O O
[O(CH2)4-~-O-C ~ C-
having a molecular weight of about 600 to 3000,
i.e. n = 6 to 40.
If desired the polyamide or polyester may be
blended with one or more other polymers. For example
polyamides may be used as blends with the polyesters,
polyolefins such as polyethylene, ethylene ethyl acry-
late copolymers or styrene/diene block copolymers, and
the polyesters may be used as blends with ionomers or
the above polymers referred to in connection with
polyamides.
- 8 ~ 3 ~ R~339
The preferred aromatic polymers which are used in
this invention are well known to those skilled in the
art, and reference may be made for example to U.S.
Patents Nos. 3,025,605, 3,306,874, 3,257,357,
3,354,129, 3,441,538, 3,442,538, 3,446,65~, 3,658,938,
3,677,921, 3,838,097, 3,847,867, 3,953,400, 3,956,240,
4,107,147, 4,108,837, 4,111,908, 4,175,175, 4,293,670,
4,320,224, and 3,446,654, British Patents Nos.
971,227, 1,369,210 and 1,599,106 and European Patent
Applications Nos. 170,065, 124,276 and 178,185. Such
polymers include polyketones, polyether ketones,
polyether ether ketones, polyether sulphones, polyether
ketone/sulphone copolymers, polyether imides and
polyphenylene oxides. Blends of different polymers can
be used. Preferred aromatic polymers are polymers with
a melting or softening point of at least 250C, par-
ticularly at least 300C and which may be crystalline
or amorphous. Softening points of amorphous polymers
may conveniently be measured by thermomechanical analy-
sis (TMA), in which case the softening point refers to
the temperature at which the probe has reached 60%
penetration.
The polymers may be wholly aromatic or they may
include one or more aliphatic moieties.
In one class of such polymers the polymex compri-
ses, and preferably consists essentially of, units of
the formula
-Ar-Q-
the units being the same or different,
- 9 - ~3~97~ R~339
wherein Ar represents an unsubstituted or substituted
divalent aromatic radical and Q represents -O-, -S-,
-SO2-, -CO-, -NH-CO- or -COO-, or Ar represents a tri-
valent radical and Q represents
~CO--
-N
CO--
each bond of the Q radical preferably being bonded
directly to an aromatic carbon atom.
One preferred class of polymer comprises the
polyphenylene oxides of the repeating unit
Rl
~
Rl
;
in which the groups Rl, which may be the same or dif-
ferent, each represents a hydrogen or halogen atom or a
hydrocarbon atom having no tertiary alpha carbon atom.
In another class of aromatic polymers the aromatic
polymer is a crystalline polyarylene ether comprising
recurring units of the formula
; -O-E-O-E'-
where E is the residue of a dihydric phenol and E' is
the residue of an aromatic compound having an electron
;~'
, ,,, ~,
:
.
- lo - ~ 31~ ~ 3 ~ RR339
withdrawing group in at least one of the posi~ions
ortho and ~ to the valence bonds, the E and E' radi-
cals being linked to the -O- radicals through aromatic
carbon atoms. In one preferred sub-class, E is a radi-
cal of the formula
2 )x~
(Y)y (Y')z
wherein R2 is a divalent radical; x is O or l; Y is a
radical selected from halogen atoms, alkyl radicals
containing 1 to 4 carbon atoms and alkoxy rad.icals con-
taining 1 to 4 carbon atoms; y is 0, 1, 2, 3 or 4; Y'
is a radical selected from halogen atoms, alkyl radi-
cals containing 1 to 4 carbon atoms and alkoxy radicals
containing 1 to 4 carbon atoms; z is 0, 1, 2, 3 or 4,
and E' is a radical of the formula
~R3 ~
wherein R3 iS a sulphone, carbonyl, vinyl, sulphoxide,
azo, saturated fluorocarbon, organic phosphine oxide or
ethylidene radical. In this class preferred poly-
sulphones are those in which y and z are 0, x is lj R3
is a sulphone radical and R2 is a radical of the for-
mula
",
~ 3 ~
- 11 - RK339
R4
--C--
R4
wherein each of R4 is independently selected from
hydrogen atoms; alkyl radicals containing 1 to 4 carbon
atoms which may be unsubstituted or substituted by one
or more halogen atorns; aryl, alkaryl and aralkyl radi-
cals containing 6 to lO carbon atoms which may be
unsubstituted or substituted by one or more halogen
atoms.
In another class of aromatic polymers, the polymer
is a polyether imide or polysulphone imide which
comprises recurring units of the formula
O O
-Q-Z \ ~ N-R6-N \ / Z-Q-Rs-
11 1~
O o
where Q is -O- or -S02-, Z is a trivalent aromatic
radical, Rs i5 a divalent aromatic radical and R6 is a
divalent organic radical. Preferably the aromatic
polymer has the general repeat unit:
,'
`
; ,, -
:: :
.
.:
7 3 ~
12 - RK339
O O
-N ~30-D-o~ N-R ' -
O O
in which D represents a group of the formula:
~ C ~ or _ ~ CH2 ~ , and
R' represents an arylene group.
Another class of polymers is the polyetherketones
that have repeating groups comprising aromatic ether
and aromatic ketone groups together with an imide,
amide, ester, benzoxazole or benzothiazole group.
Examples of such polymers are those having repeating
units of the formula:
~ O ~ R7 ~ O ~ CO- ~ CO-
where R7 represents an imide, amide or ester group.
Yet another class of aromatic polymer is thepolyarylates. Polyarylates that may be used include
those that are derived from dihydric phenols and at
least one aromatic dicarboxylic acid. Examples of such
polymers include those derived from a dihydric phenol
of the general formula
,
': ~ : . -
,
- 13 ~ 9 7 ~ ~ R~339
tY)b (Y)b
HO ~ R8 - ~ OH
in which the groups Y, which may be the same or dif-
ferent, each represent a hydrogen atom, a Cl to C4
alkyl group, or a chlorine or bromine atom; b is 0 or
an integer from 1 to 4; R8 represents a divalent
saturated or unsaturated hydrocarbon group, e.g. an
alkylene, alkylidine, cycloalkylene or cycloalkylidine
group, an oxygen or sulphur atom or a ~arbonyl or
sulphonyl group; and c is 0 or 1.
Preferred aromatic polymers consist essentially of
repeating units having one of the following formulae
( 1 ) 43~o~co_
(2) ~ O - ~ O ~ CO-
(3) ~ O ~ CO-
(4) CH3
4~o-
c~3
- ~
.
, .. , ' - :
,, : ' ; . :: '
- 14 - 131973~ RK339
(5)
~o~co~o~co~fo_~co
wherein each of x, m and n is O or 1, with n being O
when x is 1, p is an integer from 1 to 4, with m being
1 and x being O when p is greater than 1, e.g.,
~3 {3 3 ~co or
-O~CO~-O~CO~CO~,
(6) ~ O - ~ S02-
(7) CH3
~ 502 ~ o-
CH3
(8)
C ~ ~ N
O O
or
:'
- 15 - ~ 7 ~ 8 RR339
(9) CH3
O~I-~oCo~
CH3
in which units derived wholly from isophthalic acid or
terephthalic acid or a mixture of both are present.
Other polymers containing aromatic moieties e.g.
poly 1,12-dodecamethylene pyromellitimide or
1,13-tridecamethylene pyromellitimide, as described in
U.S. patent No. 3,551,200, may be used.
Blends of any two or more of the above polymers
may be employed as may copolymers based on any two or
more of these polymers. In addition, blends of any of
these aromatic polymers with aliphatic polymers, e.g.
the aliphatic polymers referred to herein may be used.
Many aromatic polymers that are used in the wire
insulation will have a char residue of at least 30%,
some polymers having a char residue of at least 40% and
even at least 50%. This does not mean to say that a
high char value is desired for its own sake, but simply
that good mechanical and physical properties of these
aromatic polymers including temperature stability and
fire retardancy, are usually associated with high char
res-dues. The preferred aromatic polymers will usually
have a molar C:H ratio of at least 1.0, preferably at
least 1.2, more preferably at least 1.3 and especially
at least 1.4. The toughest polymers such as the
polyaryl ether ketones, which are associated with high
char residues, Wi11 have C:H ratios greater than 1.5.
.
'
~3~7~8
16 27065-170
Although it ls posslble to employ the aromatlc polymer
ln the form of a blend wlth one or more aliphatlc polymers in
additlon to, or lnstead of, any other aromatlc polymers for
e~ample as describe~ ln our copendlng Canadlan appllcatlons Serlal
Nos. 571,477 and 571,478 entltled "Electrical Wire and Cable" and
entitled "Electrlcal Wlre", the outer layer will usually consist
solely of the aromatlc polymer as the polymeric component.
Preferably also, the wire insulatlon ls substantially
free oE halogens, since the presence of slgnlflcant quantltles of
halogens can cause corroslve and toxlc gases to be emltted when
the wire is sub~ected to a flre. Preferably the wire lnsulatlon
contains not more than 10% by welght halogens, more preferably not
more than 5~ by weight halogens and especlally substantlally no
halogens.
The wire insulation, or at least the lnner layer may be
cross-linked, for example, by exposure to high energy radiatlon.
Radlation cross-linking may be effected by exposure to
hlgh energy lrradlatlon such as an electron beam or gamma-rays.
Radlatlon dosages ln the range 20 to 800 kGy, preferably 20 to 500
Z0 kGy, e.g. 20 to Z00 kGy and partlcularly 40 to 120 kGy are ln
general approprlate dependlng on the characterlstics of the
polymer ln questlon. For the purposes of promotlng cross-linklng
durlng lrradlation, preferably from 0.2 to 15 welght per cent of a
prorad such as a polyfunctlonal vlnyl or allyl compound, for
e~ample,
L3~7~8
- 17 - RK339
triallyl cyanurate, triallyl isocyanurate (TAIC),
methylene bis acrylamide, metaphenylene diamine bis
maleimide or other crosslinking agents, for example as
described in U.S. patents Nos. 4,121,001 and 4,176,02~,
are incorporated into the composition prior to irra-
diation.
The insulation may include additional additives,
for example reinforcing or non-reinforcing fillers,
stabilisers such as ultra-violet stabilisers, antioxi-
dants r acid acceptors and anti-hydrolysis stabilisers,
pigments, processing aids such as plasticizers, haloge-
nated or non-halogenated flame retardants e.g. hydrated
metal oxides such as alumina trihydrate or magnesium
hydroxide, or decabromodiphenyl ether, fungicides and
the like.
In many cases the wire insulation will consist
solely of the polyamide/polyester inner layer and the
aromatic outer layer. However, if desired one or more
other layers may be present. For example an additional
inorganic arc-control layer may be provided directly on
the conductor, formed for example by deposition of an
inorganic material on the conductor. Such a layer
would enable the thickness of the inner insulating
layer to be reduced. Alternatively or in addition a
wet-tracking control layer, which will normally have a
low carbonaceous char residue e.g. not more than 15% by
weight and which may be formed, for example, from an
aliphatic polymer, may be provided on top of the aroma-
tic polymer in order to improve the resistance of the
insulation to wet tracking (the phenomenon of wet
tracking being described in our ~ur'opean patent appli-
'
~3~3~
18 270~5-170
cation No. 571,477 entitled "Electrlcal Wlre and Cable".
The wlres and cables according to the lnventlon may be
formed by conventlonal techniques. For example the polymers may
be blended with any additlonal components, ln a mixer, pelle~lsed,
and then extruded onto a wlre concluctor. Other, non-preferred,
wires may be formed by a tape-wrapplng method although it is
preferred for both the aromatic and the polyamlde/polyester layers
to be melt shapeable so that the wire insulatlon can be formed by
extruslon.
The wlres may be used individually as equlpment or
"hook-up" wlres, or alrframe wlres, or ln bundles and harnesses,
both ~acketted and un~ackettecl, and may be used ln multlconductor
cables. The wires, harnesses or cables may be unscreened or they
may be provlded wlth a screen to protect them from electromagnetlc
lnterference, as well known ln the art. In addition flat cables
may be formed uslng the insulatlon materlals according to the
lnventlon, elther employlng flat conductors or round conductors.
The inventlon wlll now be descrlbed by way of example
with reference to the accompanying drawlngs, in which:
Flgure 1 ls an lsometric vlew of a wlre in accordance
wlth the lnvention;
Flgure 2 ls a schematlc vlew of the test arrangement for
wet tracking; and
7 3 ~
- 19 - RK339
Figure 3 is a schematic view of the test arrange-
ment for dry arcing.
Referring initially to figure 1 of the accom-
panying drawings, an electrical wire comprises a con-
ductor 11 which may be solid or stranded as shown and
is optionally tinned. A 100 micrometre thick inner
layer 12 (primary insulation) formed from polybutylene
terephthalate or a butylene oxide-butylene terephtha-
late block copolymer is extruded onto the conductors
followed by a 100 micrometre thick layer 13 of poly-
etherketone, polyether ether ketone or a polyarylether-
imide. After the insulating layers have been extruded,
or even before layer 13 has been extruded, layer 12 may
be crosslinked by irradiating the wire with high energy
electrons to a dose of about 120 kGy.
The following Examples illustrate the invention.
In the Examples the following test procedure was used:
Dry Arc Test
This test is designed to simulate what happens
when a fault in a wire bundle causes arcing under dry
conditions. A graphite rod is used to initiate the arc
which causes thermal degradation of the insulation.
Continuation of the fault current can only occur
through the wire bundle under test due to shorting
across adjacent phases through a conductive char, or
direct conductor-conductor contact such as might occur
if the insulation is totally removed by the duration of
the arc.
. ~
, ~ ' -
:
~3~9~
- 20 - RK33~
Figure 1 shows the sample set-up. A wire bundle
21 is prepared from seven 10cm lengths 22 of 22AWG
tinned-copper or nickel-plated copper conductor coated
with a layer of the wire insulation under test. The
bundle 22 is arranged with 5iX wires around one central
wire and held together with tie wraps spaced about 5cm
apart. One of the outer wires is notched circumferen~
tially between the tie wraps to expose 0.5mm bare con-
ductor and one end of each wire is stripped to enable
connections to be made via insulating crocodile clips.
A rod 23 is provided which is made of a
spectrographically pure graphite, diameter 4.6mm, with
an impurity level not more than 20ppm. It is prepared
before each test by sharpening one end using a conven~
tional pencil sharpener of European design to give an
angle of 10 degrees off vertical with a tip diameter of
0.4~0.1mm. A 100g weight 24 is clamped onto the top of
the rod 23 to maintain contact during the arc ini-
tiation and also acts as a device to limit the depth of
penetration of the rod by restricting its downward tra-
vel. The rod passes through a PTFE bush which allows
it to slide freely up and down.
The arrangement of levers enables precise posi-
tioning of the rod 23 on the wire bundle 21 which is
held securely in place by means of a simple clamp 25
made of an electrically insulating resin and mounted on
a block 26 made of the same material.
The power source can be either:
a) a 3-phase 400~z 115/200V generator of at
, ~
~3~7~$
- 21 - RK339
least 5kVA capacity
b) a single phase 50Hz 115V transformer, at
least 3kV~ capacity
c) 2~V d.c. supplied by two 12V accumulators.
The fault current is detected by means of current
clamps surrounding the connecting leads and the voltage
at failure is measured using a 10:1 voltage probe. The
transducer signals are fed into a mul-ti-channel digital
storage oscilloscope where they can be displayed and
manipulated to obtain power curves (voltage x current)
and energy ~integration of power curve).
The wire bundle 21 is positioned in the clamp 25
so that the notched wire is uppermost. Adjacent wires
of the bundle are connected to different phases of the
supply through 7.5A aircraft type circuit breakers, and
the central wire is connected directly to neutral. In
the case of single phase or d.c. supplies, alternate
wires are connected to neutral or the negative ter-
minal, with the remaining wires, including the central
wire, connected through circuit breakers to live or the
postive terminal. The carbon rod is also connected to
neutral or the negative terminal and positioned so that
the point is in contact with the exposed conductor.
The gap between the lOOg weight and the PTFE bush is
adjusted to the diameter of the insulated wire under
test using a suitable spacer to limit the penetration
of the rod into the sample. A voltage probe is con-
nected across the damaged wire and the rod, and current
clamps positioned on each of the three phases, or on
the wires connected to the live side of the supply. A
protective screen is placed in front of the test set-up
,
:
.
,
~:
` ~ ,
~3 ~ ~7~
- 22 - RK339
and the power switched on. A material is deemed to
pass this test if:
a) no circuit breakers come out and the activity
i5 relatively non-eventful, or
b) there is no further activity on resetting the
breakers after a non-eventful test.
In addition, non-tracking materials will have
relatively few spikes in the current trace with a
correspondingly low total energy consumed. Tracking
materials, on the other hand, show many spikes usually
on all three phases, which are accompanied by violent
crepitation and large energy consumption.
The following wire constructions were prepared by
extruding onto 22 AWG nickel plated copper wire unless
otherwise stated using a 20mm Baughan extruder. In the
cases where a blend has been used, it has been prepared
using a Baker Perkins twin-screw extruder, and in all
cases the inner layer contained 5% TAIC and was cross-
linked by high energy electron irradiation to a dose of
120 kGy. Examples l to 5 were tested for dry tracking
with a 115 V 50 Hz, single phase power source, and the
results are given in Table I. Examples 6 to 12 were
tested using 115 V, 400 Hz three phase supply, and the
results are given in Table II.
In the Examples the following polymers were used:
Polyaryletheretherketone: A polymer having the repeat
unit of the formula:
,
.
: :
; :
7 ~ ~
- 23 - RK339
~-o~o~
Polyetherimide: A polymer having a repeat unit of
formula:
~O~C~O~ ~
CH ~ ~ N ~ N
Example 1
100 lum of an aromatic-aliphatic polyamide (polymer
formed from a mixture of 2,2,4- and 2,4,4-trimethyl-
hexamethylenediamine and terephthalic acid) was
extruded as the inner insulating layer with 100 ~m of
polyaryletheretherketone as the outer insulating layer.
Example 2
100 ~m of a blend of polytetramethylene terephtha-
i,
late, an ionomer resin (Surlyn 9090 from Dupont) and acrosslînking agent (Diacryl 101) in the ratio of
77.5 : 17.5 : 5 as the inner insulating layer with
100 um of polyaryletheretherketone as the outer insu-
lating layer.
Example 3
125 um of a blend of polytetramethylene tere-
phthalate and a poly(ether-ester) block copolymer
r a a~ r.k
:
-
:
~' ~ '~ . ' , :
~3~73~
~ 24 - RK339
comprising approximately 57% by weight polybutylene
terephthalate hard blocks and approximately 43% by
weight poly(butylene glycol polyether terephthalate)
soft blocks in the ratio of 70:30 as the inner insu-
lating layer with 125 ~um of polyaryletheretherketone as
the other insulating layer.
Example 4
As Example 3 with the exception that the inner
insulating layer also contains 20% by weight hydrated
zinc borate.
Example 5 (Control)
250 pm polyaryletheretherketone as a single insu-
lating layer.
Example 6
100 ~m of a polyether block amide as the inner
layer, and 100 lum of a polyetherimide as the outer
layer.
Example 7
100 lum of polyethylene terephthalate as the inner
layer and 100 lum of a polyetherimide as the outer
layer.
Example 8 (Control)
100 ~m of polyaryletheretherketone as the sole
layer.
', .
- : .
'
~L3~ ~7~
- 25 - RK339
Example 9 ~Control)
100 pm of polyetherimide as the sole layer.
Example 10
100 ~m of an amorphous polyamide based on
laurinlactam, isophthalic acid bis~(4-amino-3-methyl-
cyclohexyl) methane, as the inner layer and 100 ,um of
polyaryletheretherketone as the outer layer.
ExamPle 11
100 ~m of polytetramethylene terephthalate as the
inner layer and 100 ~m of polyaryletheretherketone as
the outer layer.
Example 12
100 ~m of the same polyamide as in Example 1 for
the inner layer, and 100 ~m of polyaryletheretherketone
as the outer layer.
"' ` ' ' ~ ' : '
:, :
.
'
,
-
~3~73~
26 - RK339
1~13[E I
..~
q~ P~ts
5 V, 50 ~lz
1~ Q~r Initi~l ~;b. aE
L~ Ia~er (J) _ a~ ~_
1 ~tic-ali~ic pt~Lyard~b ~EK 2~8 0
2 ~/Surlyn E~K 200 0
3 E~/EWy(e~r~ster)~ilDdc E~K 180 0
C~yr~r
4 ~/E~y(et~rff~r)~lDcl~ EEX 105 0
~yr~r/z~r~ }~
5 (~.) EEK EEK 1030 4
;` ' .
7 ~ ~
-- Z7 --~339
D~ ~
1~5 V, 400 E~, 3 ~:h39e
E~,e ~ O~r Ck~it2~. d ~res ~it~*i~
~ 1~ k~ o/c s~ r~
,. ~
6 ~ ULt9n 0 1 ~,/A
7 E:r~lLt~m O 1 2~A
8 E~K - 5 7 ~;
9 UL~%~ - 6 7 ~3
(~il~ E~K O 1 ~A
11 ~ K O 1 ~A
~2 ~dd ~ O ` 1 ~
