Thermoplastic and Thermosetting Insulation 

By on

While there are a vast array of cable insulation materials, these are often divided into two general  types;  Thermoplastic or  Thermosetting.   For example the current capacity determination of a cable in accordance with  the UK Wiring Regulations is categorized into thermoplastic and thermosetting cables.

Thermoplastic materials are composed of chains of  molecules (polyethylene for example).  When heat is applied the energy will allow the bonds to separate and the material can flow (melt) and be reformed.

Thermosetting materials are formed when materials such as polyethylene undergo specific heating or chemical processes. During this process the individual chains become cross linked by smaller molecules making a rigid structure.    Thermosetting materials cannot reheated, melted and remolded.

While thermoplastic materials have the advantage of being able to be reformed, thermosetting materials are generally more heat resistance and have greater strength.

The operating temperature of any cable is an important parameter in determining the maximum allowable current.   While the actual temperature varies depending on the material used, the UK Wiring Regulations limits the choice in calculating the current rating to two temperatures only:

  • Thermplastic 70 0C
  • Thermosetting 90 oC

Note: more specific calculations based on actual material properties are allowed.  However, for ease of use most practical application will use 70 oC or 90 oC and the methods outlined in the regulations.

See Also



Steven McFadyen's avatar Steven McFadyen

Steven has over twenty five years experience working on some of the largest construction projects. He has a deep technical understanding of electrical engineering and is keen to share this knowledge. About the author

myElectrical Engineering

comments powered by Disqus



8 Steps to Low Voltage Power Cable Selection and Sizing

A recurring theme on our forums is cable sizing. Now many installations are unique and require special consideration. However, a lot of the time things...

Understanding electric motor insulation & temperature

Anyone specifying or using electric motors should have a basic understanding how the insulation is related to temperature. Three classes of insulation...

Cable Sheath and Armour Loss

When sizing cables, the heat generated  by losses within any sheath or armour need to be evaluated. When significant, it becomes a factor to be considered...

Capacitor Theory

Capacitors are widely used in electrical engineering for functions such as energy storage, power factor correction, voltage compensation and many others...

How to Check a Circuit is Dead

If you want to check a circuit is dead (not live), you should always use the three point method. First check a known live circuit, then check the dead...

Capacitors - Energy Storage Application

Capacitors have numerous applications in electrical and electronic applications.  This note examines the use of capacitors to store electrical energy....

Voltage Levels to IEC 60038

The standard aims to consolidate AC and traction voltages within the industry and defines the following bands: band 1 - A.C. systems 100 V to 1...

Inductance

When current flows within a wire, a magnetic field is created. The potion of this magnetic field perpendicular to the wire is called the magnetic flux...

Understanding Motor Duty Rating

One of the comments on my Motor Starting Series was asking for something on duty cycles. Here it is. As a purchaser of a motor, you have responsibility...

Wiki Depreciation

We have had the Wiki with us for a long time now, but at last I have decided to say bye bye – more details on why below.

Have some knowledge to share

If you have some expert knowledge or experience, why not consider sharing this with our community.  

By writing an electrical note, you will be educating our users and at the same time promoting your expertise within the engineering community.

To get started and understand our policy, you can read our How to Write an Electrical Note