7 Facts On Cotton As An Insulator(Why And Uses)

Cotton is a pure cellulose, waxes, fats, pectins and water-made staple fiber that are used to grow in tropical and subtropical regions. Let us focus on the facts related to cotton as an insulator.

Cotton can act as an insulator. This is because there are so many air molecules that are trapped in between the loose intertwined fibers of cotton. Air itself is a poor conductor of both heat and electricity and these trapped air molecules within cotton fiber also make it unable to act as a conductor.

Heat conduction needs medium molecules to be closely packed to transfer heat energy from one molecule to another. Let us focus on why cotton is a good electric insulator,whether cotton is a good heat insulator or not,uses of cotton as an insulator,whether cotton is a better insulator or not.

Why is cotton a good electric insulator?

Good electrical insulators are those materials which are used to have very low values of electrical conductivity. Let us know why cotton is considered a good electric insulator.

Cotton is a good electric insulator because it does not have free electrons which can carry electricity through the cotton. Absence of free electrons in a material makes it unable to conduct electricity as this movement of free electrons is the reason behind passing electricity through a material.

Besides, cotton has a very low value of electrical conductivity with a resistivity of 107 – 1016 ohm/m² which makes it behave like a perfect insulator.

Is cotton a good heat insulator?

Good heat insulators are those substances which do not pass heat energy through them easily or resist the flow of heat. Let us focus on whether cotton is a good heat insulator or not.

Yes, cotton is a good heat insulator. The reason is the very low values of thermal conductivity of both cotton fibers and the air trapped between them. The values of thermal conductivity of cotton and air are 0.026 – 0.065 W/m.K and 0.024 W/m.K respectively and these make cotton unable to pass heat.

Image Credits : Cotton by Bubba73 Jud Mc Cranie (CC BY-SA 4.0)

Uses of cotton as an insulator

There are several uses of cotton due to its insulating properties, availability and low cost. Let us see some of the major uses of cotton.

  • Structural integrity of houses
  • Cotton clothes in summer
  • Quilts
  • Strip conductors of DC machines
  • Thermo Flasks

1. Structural integrity of houses

The high density of cotton fibers helps in improving the structural integrity of houses by keeping out oxygen from the wall cavity which in turn reduces the possibility of spreading fire.

2. Cotton clothes in summer

Cotton clothes are used in summer to keep the human body cool. As cotton is an insulator it does not allow the external heat energy to enter into the body and keep the temperature of the body low.

3. Quilts

Quilts are usually filled with fluffy cotton. This is because pores of the cotton fibers are filled with air which is an insulator and this makes cotton able to resist heat energy from escaping out from the human body. This in turn keeps the body warm in the winter.

4. Strip conductors of DC machines

Cotton is also used in strip conductors of DC machines due to its insulating properties.

5. Thermo Flasks

Cotton is also used in thermos flasks to keep the liquid warm which is kept in the flask for a long time by resisting heat to escape out.

Is cotton a better insulator than wood?

Insulators are used to have tightly bound electrons in their atomic structures which resist them from conducting electricity. Let us know if cotton is a better insulator than wood or not.

Cotton is not a better insulator than wood. This is because dry cotton has a dielectric constant value in the range of 1 to 2.1 whereas dry wood has a dielectric constant value of 1.22 which is nearly the same as cotton. Besides, both cotton and wood can act as insulators only when they are dry.

In case of wet cotton the empty pockets are filled by water molecules which do not allow air molecules to be trapped there.

When does cotton conduct electricity?

Conductors pass electricity being equipped with free electrons in their atomic structure. Let us have a look at when cotton conducts electricity.

Cotton acts as an insulator when it is dry and conducts electricity when it gets wet. Water is a good conductor of electricity and air is an insulator. When the pockets of cotton become filled with water molecules replacing air molecules, the insulating properties of cotton reduce and it passes electricity.


In this article facts related to cotton as an insulator have been discussed with the reason why cotton is an insulator and what are its uses.

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