Rubber does not conduct electricity. It is a lengthy chain of polymers with strong covalent bonding that prevents electrons’ movement or vibration in the valence shell. When there is no movement, conduction will occur.
On the flip side, there are conductive rubbers. Examples include silicone elastomers, neoprene, and nitrile. This type of rubber is not pure. Instead, they feature supporting materials like carbon black or silica. The process must also occur under certain conditions.
Moving forward, this guide will explain the various types of rubbers and their properties, including why they are naturally poor conductors of electricity and how they can be made conductive.
You will also learn about electrical conductivity and the real-life applications of both conductive and nonconductive rubbers.
Types and Properties of Rubber
There are 2 major types of rubber:
1. Natural rubber or Indian rubber or latex
From the name, you can tell that this type of rubber is naturally occurring. They are a product of tapping (cutting a tree to extract latex). This latex has a milky white juice appearance in its raw form.
Natural rubber contains proteins, resins, fatty acids, and inorganic salts. It is a derivative of 2-methyl-1, 3-butadiene, or monomer isoprene. Since its structure is very similar to silicone, its double bonds are in a z configuration and contribute to elasticity.
2. Synthetic rubber or neoprene
Synthetic rubbers are artificial polymers made from crude oil and petrochemical substrates. Unlike natural rubber, which requires just one conjugated diene, synthetic rubber requires three:
- Isoprene (2-methyl-1,3-butadiene)
- Chloroprene (2-chloro-1,3-butadiene)
The properties of natural and synthetic rubber are mostly similar. They include:
- Strong covalent mixed with Van Der Waal bonding.
- High tensile strength and resistance to abrasion.
- They also have a very high electrical resistivity at 20°C.
Does Rubber Conduct Electricity?
Rubber does not conduct electricity because it is a non-metallic material. It is a hydrocarbon comprising hydrogen and double bonds of carbon in a ratio of 5:8.
Each monomer (a unit of the polymer) exhibits a covalent bond. This means its valence electrons are tightly connected and will not move freely in the presence of an electric potential. When no electron jumps from one atom to another, conduction will fail.
Alternatively, using band theory, you can understand the relationship between rubber and electricity. In other words, the energy gap between the sigma (strong covalent) and non-overlapping pi bond is very large.
This ensures that all valence electrons assume positions without high voltage or reinforcing materials.
When is Rubber Conductive?
Products primarily made of rubber sometimes feature foreign materials. While these materials are designed to support the product, conductivity can occur if it’s carbon-centric, as seen in products like shoes, gloves, and wetsuits.
This is because carbon or carbon fiber is naturally conductive. When they come in contact with rubber at a certain temperature and pressure, they displace the covalent bond, causing stability.
As a result, electrons will begin to move freely and help the rubber product conduct when a potential is introduced.
Electrical Resistivity of Rubber
Since rubber is all about little or no conductivity, it is important to know how much they resist current in the presence of additives or not.
Rubbers containing additives are conducting rubber, hence, they have lower electrical resistivity usually in the 10-1 to 10-3 ohm meter.
Pure rubber, on the other hand, is generally an insulator. Their electrical resistivity is very high–usually in the order of (1-100) x 1013 ohm meter.
Factors that Affect the Electrical Conductivity of Rubber
Now that you are aware of how rubber can be made conductive, let’s take a look at the several factors that can affect this conductivity:
Ideally, a rise in temperature increases the vibration of ions in conductors. However, an increase in temperature does not affect how rubber conducts electricity.
The only effect you may spot is a bit of deterioration and discoloration due to its polymer structure. It may also cause its long chain to shrink.
For any material to conduct electricity, its atoms or ions must be free. In the case of rubber, conductivity will only occur in molten form in the presence of additives like carbon.
When this occurs, its ions become free. The higher the number of free ions, the better the conductivity.
Rubber has a high density (69 to 74 lb/foot), hence, its electrical conductivity is low. However, in a molten state, their density reduces and allows better conduction of electricity.
Does Rubber Conduct Heat?
Thermal conductivity measures how much heat can pass through the material. Just like plastics, wood, and glass, rubber does not conduct heat or electricity.
As a result, it has a low thermal conductivity of 0.5 W/(m·K).
Uses of Rubber
Rubber is a major raw material in various industries. Let’s take a look at some of its real-life applications:
- Rubber is the chief component of surgical gloves used in medical facilities.
- They also play a crucial role in manufacturing car tires and conveyor belts.
- Rubber is a great adhesive. It can be used to join different materials.
- Balloons and rubber bands are also a product of rubber.
Can rubber be electrified?
Pure rubber is an insulator and will not let electric current flow through.
However, it may conduct current slightly when combined with additives or pass extremely high voltage.
Is rubber resistant to lightning?
Rubber cannot resist lighting because the voltage in it is very high.
Hence, it is not your car’s rubber tire that protects you from lightning; it is your car’s metal roof or metal components.
Is rubber a worse conductor than air?
No, rubber conducts better than air.
This is because air has an electrical resistivity that is a thousand times greater than that of rubber.
Rubber is naturally a poor conductor of electricity. When it conducts, it does it poorly too. This is why its major uses revolve around insulation as seen in window blinds, car tires, kitchenware, and balloons.
Conductive rubber, on the other hand, helps produce computer and smartphone accessories. They are also used to produce medical devices such as CT scanners.
I hope you found this article helpful. Like rubber, plastics are also poor conductors. Please see how plastic conducts electricity to learn how it can be made to do so effectively.
Thanks for reading.