What Is Thermal Conductivity Insulators

Many systems on our planet would not function without insulator materials. They are the barriers that keep heat from escaping equipment, such as ovens, or from entering an occupant's living space.

These barriers use insulators of low tThermal Conductivity insulators. Insulation materials that are commonly used include rockwool, which is a synthetic textile made of a variety minerals.

Solids

Solid particles are more tightly packed and move slower than those in liquids and gases. The thermal conductivity (or temperature) of a material varies depending on its temperature.

Solids that conduct heat well at low temperatures, become insulators when they reach melting or boiling point. This occurs because molecules in liquids or gases move more quickly when they reach higher temperatures.

Many insulating materials work by trapping large pockets of gas, which block the flow of thermal energies. Fur and other biological insulators, such as feathers and fur, work in this way. This principle is also used in mineral wool and Styrofoam.

The thermal conductivity of a solid is given by the thermal resistivity (denoted by the greek letter lambda) divided by its Kelvin temperature. This is a complex number which can be fitted to data using various fitting methods.

Liquids

Liquids, in physics terms, are one of three principal states. They are a state in between the gaseous and solid crystalline states. Liquids have a definite volume but no fixed shape. They take the shape of their container just like gases, but they do not expand nearly as much. They are also generally incompressible.

Thermal conductivity of liquids varies greatly depending on their viscosity, a measure of the friction between molecules. Liquids with high viscosities move slowly and therefore have low thermal conductivity, while liquids with low viscosity move quickly and have high thermal conductivity.

Important everyday liquids include aqueous solutions (watery mixtures of different substances), mineral oils and gasoline, emulsions such as mayonnaise, suspensions like blood, and colloids like paint and milk. Foams with many gas-filled pocket, such as polyurethane foam, act as effective insulators because gasses have a relatively low thermal conductivity. The insulating properties of foam depend on both the thickness and thermal conductivity of the material.

Gases

The particles that make up gases are far apart from each other, and so do not conduct heat as well as those in liquids and solids. This makes gases excellent thermal isolators. Bubble wrap makes a great example. Even motor oil, used as a lubricant to reduce friction between moving parts in contact, can act as an insulation when not under pressure.

Scientists such as Boyle, Jacques Charles, and Joseph Louis Gaylussac conducted experiments in the laboratory with various gases at low pressures where they behaved perfectly (see image). These results led them to create laws that describe pressure and volume. They also described the number of atoms or particles (chemists categorize them by moles). These four macroscopic properties have a profound impact on the physics behind many physical properties including thermal conductivity. The advanced mathematical techniques required to analyze this effect are applied to safety calculations, including those for spacecraft reentry in extreme conditions.

Polymers

A polymer is formed by a series of molecules that form a continuous and long chain. When these chains are arranged a certain way they can act an insulator. This is because the bonds between molecules are stronger than the ones which hold the atoms of metals in place.

The length of a molecule's chain can affect thermal conductivity. Polymers with long molecules are more dense and rigid, while those that have shorter chains tend to be less stiff and lighter. The crystalline nature of a plastic can also affect the thermal properties. More crystallinity results in greater conductivity.

The large number gas-filled pockets within the foams' structures is responsible for their insulating properties. These pockets obstruct the pathways for heat conduction. In terms of the physics behind these phenomena, the key is that gaseous materials are poor conductors when compared to solids and liquids.