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.
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.
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.
The carrier can be reinforced to enhance performance, examples are PET film reinforced with fiberglass yarn.
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.
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 |
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
|Carrier||Dielectric Srenght Value|
|PTFE coated Fiberglass||9500V-15000V|
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:
|PET film||45N/cm -70N/cm|
|PTFE coated Fiberglass||141N/cm-250N/cm|
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.
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||Product||Thermal Class|
|Polyester Film||AS-074, AS-075, AS-023-D||For use at temperatures not to exceed 130ºC (Class B)|
|Polymide film||AS-079, AS-77, AS-78||For use at temperatures not to exceed 180ºC (Class H)|
|PTFE coated Fiberglass||AS-084, AS-087||For use at temperatures not to exceed 250ºC (Class H)|
|Cross Filament||AS-023-D||For use at temperatures not to exceed 130ºC (Class B)|
|Monofilament||For use at temperatures not to exceed 130ºC (Class B)|
|Glass Cloth Glass Cloth||AS-043, AS-044||For use at temperatures not to exceed 155ºC (Class F) For use at temperatures not to exceed 180ºC (Class H)|
|Acetate Cloth||AS-146||For use at temperatures not to exceed 130ºC (Class E)|
|Rayon Cloth||AS-070||For 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:
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
The tapes required for insulation in oil transformers
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
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.
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.
If you would like more information with regard to the right tapes for your applications, feel free to visit our website https://www.adhesivespecialities.co.in/ or email us on email@example.com.