Electrical Applications

Construction of Tapes

Core	Spool in the center.
Base material (carrier)	Tape material providing insulation, mechanical strength, environment and temperature resistance and identification.
Primer	A thin layer between the adhesive and the carrier enabling a good hold by the adhesive to the carrier.
LAL (Low Adhesion Layer) or RC (Release Coating)	A very thin layer of material with low adhesion, where the adhesive holds less, applied on th glossy (upper) side of the tape without adhesive. Provides easier unwinding.
Liner	Glossy paper (silicone) or a film used for tapes which have adhesive from one or both sides to substitute the function of LAL and for adhesive-free tapes, e.g., for rubber self-fusing tapes.
PSA (Pressure Sensitive Adhesive)	Tapes with adhesive, where the degree of bond is a function of the pressure with which it is applied.
Adhesion	Well measurable power with which the tape bonds to a surface. Usually measured on a polished steel board.

Features of Tapes

 

Dielectric Strength

The tape's ability to insulate to prevent electric breakdown. As the tape thickness changes when stretched, it is stated how many kV a milimeter can withstand. One layer of a common PVC tape features a dielectric strength of  5 – 10 kV. However, PVC tapes are usually designed for insulation up to 1 kV only. It is necessary to use self-fusing rubber tapes for higher voltage.

 

Measurable Insulation Resistance

The negligible conductivity of a tape can be assessed by measurable insulation resistance. This usually ranges in the hundreds or thousands of megaohms. It can drop considerably  after getting damp in cheaper types. The values of insulation resistance demanded for telecommunication and data networks are higher than those for electrical power engineering.

 

Temperature Classes

These denote the resistance to temperature which the tape can stand for 20 thousand operational hours while certain features are maintained. Short-term temperature resistance is much higher. The tape life halves when the maximum operational temperature is exceeded by 10° C. The application temperature is the temperature in which the tape can be manipulated while certain features are maintained. The temperature range is  from 0°C to 40° or up to 60°C. In top quality tapes it may be as low as to -18°C.

Class	Maximum operational temperature
Y	90oC
A	105oC
B	130oC
F	155oC
H	180oC

 

Metal Corrosiveness

In humid environment a tape adhesive can start working as an electrolyte and can cause electrochemical corrosion of metal. This can be highly critical when used for small section wires which can then become completely disconnected.

 

Leakage Current Resistance

This feature is especially needed for applications involving higher voltage. It denotes the ability of the tape to resist creating conductive paths on the surface under voltage or dampness. Some materials are so little resistant that after some time in a damp environment, they become relatively good conductors for voltage of 230 V, e.g., bakelite and some laminated insulators across layers.

 

Puncture Resistance

Puncturing a tape completely degrades its ability to insulate. The most resistant tapes are needed when soldered joints are to be insulated as a solder creates sharp edges.

 

Self-Extinguishing Feature

Also incorrectly called non-flammability. This means the tape will burn in flame but when the flame is put away, the tape will go out, i.e., it does not support burning.
In special applications when non-flammable cables are demanded, we also explore the amount of halogens, corrosiveness, toxicity and the density of smoke produced by burning.

 

Tape Standards

The features and properties of tapes and their testing methods are defined in standards (norms). A Czech translation of European norm EN 60 454 is currently valid in the Czech Republic. Some features are tested using other norms, or company testing methods. For example, a widely used testing method is the method for testing self-extinguishing in compliance with UL510.

If the tape bears the mark of a well-known laboratory, e.g. VDE, ESČ and others, it means the material meets the regulations and is a guarantee of certain properties. However, it is not a mark of top quality. If the device is to be exported outside Europe,  American ASTM standards may be encountered, as well as Canadian CSA, etc. If the material is to be supplied for military purposes, American MIL standards are frequently used. In markets controlled by American regulations, there may be a requirement for the Yellow Card. This is a mark for materials which have been Classified or Listed by Underwriter Laboratories, in this case testing the safety of persons and property, i.e., materials which have been recognized as safe.