Insulating materials are considered to be those materials that offer resistance to the conduction of energy ( thermal or electrical ), in contrast to conductive materials , which are those that easily conduct energy.
Insulating materials are usually classified into two large groups:
- Electrical insulators. They are materials that have a very low capacity to conduct electrical charges. This occurs because in these materials a potential barrier is generated between the valence band and the conduction band, which makes it difficult for free electrons capable of conducting electrical currents to exist. The valence band is the highest electronic energy level that is occupied by electrons, above this band there is a forbidden band and then the conduction band appears, which is an even higher electronic energy level where electrons can be accelerate by an electric field and generate an electric current. Electrical insulators are widely used when you want to avoid discharges in an electrical system, when you want to prevent people using electrical appliances from coming into contact with electrical current and to avoid short circuits. For example:plastic, glass, rubber.
- Thermal insulators . They are materials that, if subjected to a heat source , offer significant resistance before an increase in temperature occurs. This does not mean that thermal insulators do not conduct heat energy (since all substances conduct heat at least in small proportions), but that they do so in a small enough measure to make them useful in case of wanting to isolate a certain source of heat. caloric energy. Thermal insulators are widely used in the metallurgical industry, in the aeronautical industry, in the energy industry and in construction. For example: cotton, cellulose, airgel.
Examples of electrical insulators
Examples of thermal insulators
- Expanded cork
- Expanded polystyrene
- Glass foam
- Glass wool
- Wood chips
- Wood fiber
- Mineral wool or rock wool
- Phenolic resin foam
- Expanded perlite plates
- Elastomeric foam
- Extruded polystyrene
- Polyethylene foam film
- Polyurethane foam
- Cellulosic foam
- Wood wool slabs
- Cereal pellets
- Polyethylene foam
What makes an insulating or conductive material ?
The high or low electrical conductivity of a material is determined by how tightly electrons (which are subatomic particles with a negative electrical charge) are attached to its structure. This means that electrons in conductive materials require low amounts of energy to move through the material, while in insulators these amounts of energy must be much higher.
- Insulating materials . There are certain materials that are good insulators in general, such as glass and plastic, while others are only so under certain specific conditions of temperature, pressure, or under a certain state of aggregation. For example: pure water, air, quartz.
- Semiconductor materials . There are even certain materials that have the property of being good insulators when they are in a pure crystalline state, as well as good conductors when the crystal atoms are combined with other materials, which is why they are called semiconductors. Semiconductors are sometimes conductive and sometimes insulating as well depending on the temperature and pressure conditions to which the material is subjected. For example: silicon, germanium.
- Conductive materials . They are those materials that offer little resistance to the passage of electric current. For example: copper, brass, steel.
- Superconducting materials . Superconductors are those materials that when cooled stop exerting resistance to the transmission of electric current, which implies that they have the ability to conduct electric current without any resistance. For example: tin, aluminum.