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



Cost Performance and Time

Often us engineers get so bogged down in equations, using software, producing drawings and writing specifications that this becomes the sole focus.   ...

Railway Electrification Voltages

This post is quick introduction and overview to different railway electrification voltages used in answer to a question sent in via email. While there...

Alternating Current Circuits

Alternating current (a.c.) is the backbone of modern electrical power distribution. In this article I’ll be pulling some of the more important concepts...

How to Size Current Transformers

The correct sizing of current transformers is required to ensure satisfactory operation of measuring instruments and protection relays. Several methods...

Variable Frequency Drive

Variable frequency drives are widely used to control the speed of ac motors.  This note looks at the mechanisms which enable drive units to control the...

Write your best report

Years ago I was told that you should always try to write the best report you can.  Many years later I still think on this as one of the better pieces of...

Electromechanical Relays

Electromechanical relays have been the traditional backbone of electrical protection systems.  While over recent years these have been replaced by microprocessor...

E-Ink

Before the technical, some general information. E-ink display are found in a lot of e-readers, some mobile phones and similar devices and the intent is...

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...

How to Write an Electrical Note

Electrical notes are a collaborative collection of electrical engineering information and educational material. Any registered user can add content. ...

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