Datasheet Self-Fusing Silicone Datasheet (Scotch)

Self-Fusing Silicone Rubber
Electrical Tape 70 HDT with
Tapered Edge

Data Sheet

1.0 Product Description

Scotch® Silicone Rubber Electrical Tape 70

HDT is a high-temperature arc-and track­resistant tape composed of self-fusing,
inorganic silicone rubber and easy-tear
and easy-strip liner. The 70 HDT product
also has a triangular (tapered edge) profile
and blue guidelines to make half-lapping
application easier.

Tape Features

• Excellent track resistance

• Excellent arc resistance

• Excellent ozone resistance

• High dielectric strength

• Class “H” material
(180°C continuous operation)

• Workable at extremely low temperatures

• Excellent conformability

• Excellent instantaneous fusion; does not
need to be held down

• Matches Sky Blue Gray Munsell
5BG7.0/0.4

• Excellent weathering characteristics

• AA-59163 Class-I Type-II

2.0 Applications

• As an overwrap for protection of
terminating high-voltage cables against
arcing and tracking. High-voltage
cables with these insulations should be
overwrapped:

- Butyl rubber

- Oil-base rubber

- Ethylene propylene rubber

- PVC

- Low and high-density polyethylene
cross-linked

• As primary insulation where Class

"H" (180˚C/356˚F) temperatures are
encountered i.e., silicone rubber cables.

• As splice overwrap on spacer cable

operating at 15 kV and above.

3.0 Data

Scotch 70 Tape has a peak thickness of 20

mils, an edge thickness of 8 mils, and a blue
center guideline. It is available in roll size 1
in. wide x 30 ft. long. The core is 1 in. I.D.

4.0 Specifications

Product

The insulating tape must be composed

of self-fusing, inorganic silicone rubber
with an easy-tearing and easy-stripping
polyester liner. The product must be Sky
Blue Gray and conform to Munsell Color
No.5BG7.0/0.4. The tape must be capable
of operating continuously at Class H
temperatures (180°C/356°F). The tape
must be compatible with all synthetic
cable insulations as well as cable splicing
compounds.

Engineering/Architectural Specifications

All tape or tape-like terminations which

will be operated either outdoors or in areas
subjected to contamination or moisture shall
be overwrapped with at least one layer of
Scotch Silicone Rubber Electrical Tape 70
HDT.

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The exposed cable insulation on the lug

side of assembled stress cone kits, which
will be operated either outdoors or in areas
subjected to contamination or moisture,
shall be overwrapped with at least one layer
of Scotch® Silicone Rubber Electrical Tape
70 HDT.

All splices on spacer cable operating at 15

kV and above shall be overwrapped with
Scotch 70 HDT Tape.

All splices on silicone rubber cables or

other cables which can operate at room
temperatures in excess of 130˚C/266˚F,
but not exceeding 180˚C/166˚F, shall
use Scotch 70 HDT Tape as the primary
insulating material.

Dielectric Constant

Table 2 shows the dielectric constant versus

temperature of 70 HDT Tape. This test was
run according to ASTM-D-150-8 at a stress
of 50 V/mil and a frequency of 60 cycles
per second.

Dielectric Constant vs. Temperature

Scotch 70 HDT Tape

Temperature

(˚C/˚F)

23/73

90/194
130/266
150/302

Table 2

Dielectric
Constant

3.0

2.9

2.6

2.5

6.0 Performance Tests

5.0 Characteristics and Test Data

Typical Electrical and Physical Properties

Physical Properties

Color Munsell 5BG7.0/0.4 Sky Blue Gray

Thickness - Peak
ASTM-D-2148

Thickness - Edge
ASTM-D-2148

Tensile Strength
ASTM-D-412

Elongation at Break
ASTM-D-412

Electrical Properties

Dielectrical Strength
ASTM-D-2148

Arc Resistance
ASTM-D-495

Fusion (Self Adhesion)
ASTM-D-2148

Volume Resistivity
ASTM-D-1458

Dissipation Factor

Table 1 shows the dissipation factor versus
temperature of 70 HDT Tape. This test was run
according to ASTM-D-150 at a stress of 50 V/mil
and a frequency of 60 cycles per second.

Dissipation Factor vs. Temperature

Temperature

(˚C/˚F)

23/73

90/194
130/266
150/302

.020 in.

.008 in.

1000 psi

300%

600 V/mil

1 min. (minimum)

0.125 in.

7 x 1014 ohm•cm

Scotch 70 Tape

Dissipation

Factor

1.3%

1.1%

0.5%

0.7%

Table 1

Termination Tracking Test

Reduced-dimension terminations are

prepared according to 3M print 2047-B-16
(Se Figure 1). Each specimen consists of 8
feet of 15 kV cable and two terminations.

The contaminant employed in this test is the

formula called out in ASTM Dust and Fog
Test D-2132, as shown below:

Flint (SiO

floated) 240 mesh 85 parts

2

Clay 325 mesh 19 parts
Salt (Na Cl) technical grade 3 parts
Paper, filter pulp 3 parts
all by weight

This mixture is then ball milled using 3/4

inch diameter ceramic cylinder. The milled
dust is then mixed with equal parts by
weight of water to make a slurry of paint
consistency.

Next, each termination is carefully coated in

such a manner as to deposit a uniform and
reproducible amount of contamination. The
following procedure is used:

1. Mix the slurry thoroughly.

2. Submerge the inverted termination into
the slurry.

3. Withdraw the termination from the
slurry, taking care not to throw off
too much excess slurry in rotating the
termination from the inverted to an
upright position. The majority of the
excess slurry should drain off when the
termination is upright.

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4. Allow the termination to air-dry in the
upright position before applying the
voltage.

samples are recontaminated every seven
days. The new contaminant is applied over
whatever contaminant remains.

This method, when tested on various

surfaces including silicone rubber and glazed
porcelain, has repeatedly produced a coating
thickness of from 0.12 to 01.15 grams per
square inch of surface.

The terminations are then tested in a

contamination building. All terminations are
mounted vertically. The uniform fog rate
called out in ASTM-D-2132 is obtained by
the use of special atomizing, wide-angle
nozzles.

An on/off cycle is controlled to give a fog

rate of 7 to 9 milligrams per square inch per
minute.

Each sample is energized at 8.7 kV. The

system is set up such that approximately
500 milliamps trip the circuit breaker. All

The sample is considered to have failed

when:

1. 500 milliamps over the surface
continuously cause the circuit break to
trip.

2. Cable failure occurs.

3. The surface of the termination is
severely burned.

The time in hours for each failure is

recorded the results are as follows:

Tape Termination

Protection

No protection

Scotch® Silicone Rubber

Electrical Tape 70 HDT

self-fusing

Time to

Failure

15 hrs.

100 hrs. MIN

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7.0 Installation Techniques

Scotch® Silicone Rubber Electrical Tape 70

HDT should be applied in half-lap layers
using moderate tension.

70 HDT Tape should be applied on all tape-

like terminations which will be operated
either outdoors or in areas subjected to
contamination or moisture. The following
procedure should be used:

If possible, connect the termination to its

final position. Otherwise, take care not to
damage the final overwrap of silicone tape
during installation. Overwrap the end seal
with several half-lapped layers. Overwrap
the entire termination with one additional
half-lapped layer. For upright termination,
begin from one inch on cable jacket and
end at the lug. For inverted termination,
end taping on the cable jacket. Wrap with

moderate tension (10 to 100% elongation).
Apply last lap with zero stretch. Press down
to avoid endlifting before fusion takes place.

NOTE REGARDING LINER REMOVAL:

To separate the liner from the tape when

starting a new roll, simply stretch the liner
and tape until the silicone tape breaks. The
liner will then separate at the point.

8.0 Shelf Life

Scotch 70 HDT Tape has a 5-year shelf

life (from the date of manufacture) when
stored under the following recommended
conditions. Store behind present stock in
a clean dry place at a temperature of 70°F
and 40 to 50% relative humidity. Prolonged
exposure to temperatures in excess of 49°C
(120°F) can cause a loss of fusion in the
tape. Proper stock rotation is recommended.

9.0 Availability

Scotch 70 HDT Tape is available from your

electrical distributor in 1-inch by 30-foot
rolls.

70 HDT Tape can also be applied over the

exposed cable insulation and/or end seal
used in conjunction with molded (slip-on)
stress cones.

Techniques for the proper use of 70 HDT

Tape are contained in standard and special
prints available through the 3M Systems
for Splicing and Terminating Program.
This material may be obtained through
your local 3M Electrical Markets Division
representative.

3M and Scotch is a trademark of 3M Company.
Other trademarks used herein are properties of their respective owners.

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accuracy or completeness is not guaranteed. Before using this product, you must evaluate it and determine if it is suitable for your intended
application. You assume all risks and liability associated with such use. Any statements related to the product which are not contained in
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upon, in writing, by an authorized ofcer of 3M.

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OTHER WARRANTIES INCLUDING, BUT NOT LIMITED TO, ANY IMPLIED WARRANTY OF MERCHANTABILITY OR FITNESS FOR
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theory asserted.

Electrical Markets Division

6801 River Place Blvd.
Austin, TX 78726-9000
800-626-8381
Fax [phone]
www.3M.com/electrical

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© 3M 2006 78-8131-7357-8-A

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