It is extremely imperative to choose the right pressure sensitive adhesive (PSA) for electrical insulation applications since several factors such as adhesion, strength and so on need to be considered.

To understand how to choose the right PSA, we should first understand the following aspects:

  • Structure and components of PSA tapes
  • The basic properties that control the performance
  • Electrically Insulating PSA tapes
  • Applications required

What does the structure of the PSA look like?

As you can see in this image, this is what the structure of the PSA tape looks like:

You have the release coat on top, followed by the carrier, then the primer and then the adhesive at the bottom.

Structure of PSA Tapes

One of the main components of PSA Tapes is the carrier. The carrier is the support that we use for the tape. In Electrical Insulation Tapes, we use a filmic, like a PET Film, Polyimide Film as shown in photo.

PET Film

 A fabric backing such as cotton cloth, rayon cloth, glass cloth, acetate cloth tape and foil-based carrier.

The carrier can be reinforced to enhance performance, examples are PET film reinforced with fiberglass yarn.

Pressure Sensitive Adhesive

Pressure Sensitive Adhesive forms a bond with light application of pressure.

It is a Polymeric material which is a large molecule, or macromolecule, composed of millions of repeated linked units, each a relatively light and simple molecule.  So, in simple words, it is a molecular structure of many similar units bounded together in a chain.

Examples are PSA rubber, silicone, acrylic, hotmelt.

So the performance of the tape can be described based by the carrier alone, the adhesive alone and the combination of two together.

The performance of the tape can be described based by the carrier, the adhesive, and the combination of two together.

What are the basic properties that control the performance of PSA Tapes?

There are many factors or specifications which are particular for electrical tapes.

The properties of a carrier and adhesive controls the performance of an electrical tape.

Carrier Properties  Adhesive Proprieties
Thermal Class
Dielectric Strength
Tear Resistance

Dielectric Strength

The Dielectric Strength of the electrical tape is extremely important.

The dielectric strength of a material is a measure of the electrical strength of an insulator. It is defined as the maximum voltage required to produce a dielectric breakdown through the material and is expressed in terms of Volts per unit thickness.

In electrical tapes the Dielectric strength indicates the tape’s ability to insulate and can also help compare different tapes, tapes with a higher Dielectric Strength value show a better quality of insulating material.

The industry standard for electrical tapes is ASTM D-1000.

Comparison of Dielectric Strength values in Sunbrand Products

 CarrierDielectric Srenght Value
PET film4500V-7000V
Polymide film7000V-7500V
PTFE coated Fiberglass9500V-15000V
Cross Filament5000V-6000V
Glass Cloth2500V-3500V
Acetate Cloth2000V
Rayon Cloth2000V

Tensile strength

The Tensile strength or breaking strength, the force required to break a tape while pulling in opposite directions, of the tape is another important property.  A tape with a high tensile strength can withstand tight winding which helps to eliminate wrinkles and more importantly air gaps. Air is a poor insulator and if the gaps are not eliminated, the equipment the tape is used for will degrade extremely fast. Also, a thicker and reinforced carrier will always perform best.

The Industry Standard is ASTM D-1000. 

Here we can see the tensile strength of different carriers:

CarrierTensile Strength
PET film45N/cm -70N/cm
Polymide film53N/cm-115N/cm
PTFE coated Fiberglass141N/cm-250N/cm
Cross Filament516N/cm-657N/cm
Glass Cloth300N/cm-350N/cm
Acetate Cloth>55N/cm
Rayon Cloth>65N/cm

Peel Adhesion

Peel Adhesion is the strength of the bond between the tape and the surface it is applied to. The industry standard is ASTM D -1000 (adhesion to steel). Poor adhesion can result in a failure in electrical insulation therefore it is imperative that the right adhesive is used.

 Acrylics provide the best adhesion after which would come the rubber and silicone adhesives.

Thermal Class

The Thermal class is a standard industry classification, it indicates the maximum temperature for a specified amount of life or performance level through thermal aging.

 So why is that important? Thermal aging is the most common cause for material degradation which can reduce design performance and compromise safety. Thus, depending on the usage, it is particularly important to know the thermal class of the carrier.

Here you can see the thermal class by substrate of material

Carrier Type ProductThermal Class
Polyester FilmAS-074, AS-075, AS-023-DFor use at temperatures not to exceed 130ºC (Class B)
Polymide filmAS-079, AS-77, AS-78For use at temperatures not to exceed 180ºC (Class H)
PTFE coated FiberglassAS-084, AS-087For use at temperatures not to exceed 250ºC (Class H)
Cross FilamentAS-023-DFor use at temperatures not to exceed 130ºC (Class B)
Monofilament For use at temperatures not to exceed 130ºC (Class B)
Glass Cloth Glass ClothAS-043, AS-044For use at temperatures not to exceed 155ºC (Class F) For use at temperatures not to exceed 180ºC (Class H)
MicaAS-062H class
Acetate ClothAS-146For use at temperatures not to exceed 130ºC (Class E)
Rayon ClothAS-070For use at temperatures not to exceed 130ºC (Class B)

To summarise the properties, the main and important key properties of a reliable and trustworthy electrical insulating tape are that it must:

  • Act as an effective insulator against electricity, protecting circuitry and users by not conducting current easily
  • Compatibility with varnish and other chemicals
  • Heat-resistant and fireproof to a reasonable degree for the application it is being used in
  • Flexible, user-friendly, and easy to apply to a range of wires, circuits, and connections (often in relatively tight spaces)
  • Safeguard the life of the electrical equipment
  • Operational stress: good dielectric strength and mechanical strength
  • The properties for electrical insulation tapes are depends on the backing and PSA

The Common Applications Examples

For Holding and banding of a layer during coil winding, you require a tape that has a high tensile strength. Thus, we would suggest the following tapes:

Class F,155 C or below  AS-023-D

Class H,180 C                AS-044    

For end winding wrap in motors and generators, wrapping the phase insulation, and for the outer wrap for toroidal cores, tapes with good conformability and those with low tensile strength are required. Here we suggest the following tapes depending on temperature of the application:

Insulation Class B,130 C Polyester film thermosetting rubber adhesives AS-075 ,

Class H, 180 C Polyimide Tape with silicone adhesive AS-079

For oil transformers we need to use tapes which are the oil compatible, have high tensile strength tapes.  and absorption and have a class B.

The applications such as              

  • Core, Layer and final insulation of coils and transformers.
  • Sealing connection leads for final insulation.
  • Phase and coil end insulation
  • Strengthening of edges in slot insulation and for slot insulation in general.
  • General electrical insulation requiring high impact and tensile strength.

The tapes required for insulation in oil transformers

Class B, 130 C Polyester film tape with acrylic solvent adhesive AS-074 , AS-023, AS-064

Class E , Acetate Cloth tape AS-146,

Class H, 180 C, AS-079

Class F, 155 C, AS-043

Dry transformers require tough, strong high tensile insulation tapes that produce a tight coil construction. Resin compatibility and absorption is important too.

Thermal class B or class H is suitable for same applications

We suggest the Polyester film tape AS-074, AS-075,  PET tape with various adhesives, AS-79 Polyimide tapes, AS-127 Aramid paper tape, and AS-044, AS-043 Glass Cloth tapes, AS-070, AS-146 fabric tapes

Toroidal transformers require a product that is thin and conformable, and encapsulate compatible.

 In such cases where the equipment exposes out, we suggest the black colour tape, and typically Class B or class H.

We suggest AS-074, AS-075, PET tape with various adhesives, AS-79 Polyimide tapes, AS-127 Aramid paper tape, AS-044, AS-043 Glass Cloth tapes, AS-146, Fabric tapes

Motors and generators require tapes with resin compatible, class B – class H

For the motors and generators, we suggest the following tapes: AS-074, AS-075,  PET tape with various adhesives, AS-079 Polyimide tapes, AS-127 Aramid paper tape, AS-044, AS-043 Glass Cloth tapes, AS-146, AS-070,  Fabric tapes and AS-084 PTFE tapes

For battery insulation we need a conformable, high temperature resistant tape, typically class F or class H is used.

We suggest AS-074, AS-079 Polyimide tapes, AS-127 Aramid paper tape, AS-044, AS-043 Glass Cloth tapes, AS-146, AS-070, Fabric tapes, AS-084, AS-085 PTFE tapes, AS-062 Mica, AS-122 PVC Wire harness

If you would like more information with regard to the right tapes for your applications, feel free to visit our website or email us on

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