por The Insulating materials They are those that reduce, resist or completely prevent the passage of some kind of energy such as heat or electricity. They serve to protect living beings, food and other objects from the elements and their conditions; such as the plastic covering of cables and the walls or roofs of houses.
In order to fulfill their function well, these materials mainly need to have a low thermal conductivity that allows them to reduce heat transmission. They must also have a high resistance to very high temperatures that prevents them from melting.
Air permeability is also a very important property of thermal insulators. They must be materials where air can flow through their pores. Good thermal insulators have a high permeability towards air, since this is an insulating substance itself.
This permeability must not allow the passage of steam or humidity, so as to avoid or minimize the condensation of liquids or corrosion of the materials. The best thermal insulators have very low permeability for vapor and moisture.
The insulating material must be resistant to water, solvents and chemicals; it must be durable and not lose its efficiency in a short time. It must be easy to install, non-flammable, not absorb odors and not attract fungus or vermin.
[toc]
Examples of thermal insulators
1- Fiberglass
It is one of the most used due to its low thermal transmission coefficient and high resistance. It also works to isolate electrical currents and sound. It is made by weaving fine filaments of glass polymers to form rods, sheets, or panels.
2- Mineral wool
It can be made from basalt rocks or from the surface residue of molten metal. It is used for its high resistance to fire, but it is advisable to combine it with other materials to obtain more efficient heat protection.
3- Cellulose
It is one of the most ecological insulating materials on the market. It is made from the recycling of various paper products.
It is a material that can be compacted quite a bit, which reduces the presence of oxygen between its particles. This property makes it excellent for minimizing fire damage.
4- Polystyrene
It is a very light and waterproof thermoplastic material that is very good as a temperature and sound insulator.
It is used to make blocks or tables of polyethylene foam molded to need. It is flammable, so it is advisable to cover it with other fireproof materials.
5- Polyurethane
It is an insulating foam that contains a gas in its cells, which is of very low conductivity and high thermal resistance. It can be used as a foaming liquid spray, in rigid foam blocks, or molded into sheets or panels.
6- Perlite
It is a type of inert volcanic rock composed mainly of silica and aluminum but with some impurities that make it absorb moisture.
It is used in small granules to fill small spaces and holes. It is a good thermal insulator but it only works if it is dry. Its use has been increasingly reduced due to its poisonous quality.
7- Cork
It is probably the oldest insulating material on the market and the most widely used insulator in the refrigeration industry. It is very resistant to compression and difficult to burn. It can only be used below 65°C and tends to absorb moisture.
8- Plastic fiber
It is mainly made from recycled polyethylene plastic bottles. The fibers are woven into a baton shape similar to fiberglass.
This insulation is worked with a retardant so that it does not burn as quickly, but it can melt when exposed to flames.
9- Airgel
Initially it was a material used by space projects to make pottery resistant to approximately 2000 °F with very little heat transfer.
It is currently available on the market in flexible sheets called Pyrogel XT. It is one of the most efficient industrial insulators in the world.
10- Vermiculite
Like perlite, it is dangerous to health. It is used in small pellets that are thrown between other materials or to fill holes. It was also used to mix with cement to create a concrete that is lighter and less heat conductive.
11- Polyisocyanurate
It is a thermosetting foamed plastic that contains in its cells a gas of low conductivity and high resistance, free of hydrochlorofluorocarbons. Liquid foam can be adapted to the required surfaces.
12- Cotton
As an insulator, it is combined with plastic fibers and borate to make it resistant to animals and retard their inflammation.
13- Animal wool
It is also borate treated to resist vermin, fire and mold. It can hold large amounts of water, but prolonged and intermittent exposure to the liquid can dissolve the borate.
14- Straw
Used for more than 150 years in the form of bales to insulate barns and houses from heat. They also serve to absorb sound.
15- Hemp
Material commonly used to make ropes, it is currently used as insulation like other similar vegetable fibers such as straw or wool.
Examples of electrical insulators
1- Wood
Wood is an electrical insulator, and it is still common to see light poles made of wood. However, it should be noted that it is not insulating as long as the wood is dry, since water (and therefore humidity) are conductors of electricity.
2- Rubber
This material, in addition to being very mouldable, flexible and resistant, is perfect for preventing the conduction of electricity. For example, professionals who work directly with electricity use boots made of rubber to preserve their safety.
3- Ceramic
Ceramic restricts ionic and electronic mobility, therefore it is a non-conductive material for electricity. This makes it ideal for the manufacture of high tension discs.
4- Silicone
This widely used material has, among other capabilities, that of insulating electricity. This makes it ideal for sealing electronic components and fixing components.
5- Aluminum oxide
Because it is a non-conductive material, aluminum oxide is perfect for making electrical or temperature insulators, laser tubes, or sealing rings.
Examples of acoustic insulators
1- Lead
It is the most used material for acoustic insulation due to its value for money. Its density, rigidity or porosity are some of its main strengths.
2- Steel
Steel causes sound to bounce back when it hits it, making it a very powerful sound insulator. Doors of buildings or panels in bars and leisure centers are usually made of steel to maintain insulation from internal or external sound.
3- Rock wool
It really is an acoustic absorber, but it also works effectively for sound insulation. It is a robust material and widely used in certain structures because it is aesthetically attractive.
4- Elastomers
Material used for the construction of houses for its ability to insulate sound, maintain heat and prevent cracks or fissures from being generated. It has a high life cycle.
How does the heat flow?
Heat will always move from hot areas to cold areas seeking to balance. If the inside of a tank protected by thermal insulation is colder than the air outside, the tank will attract heat from the outside. The more temperature difference there is, the faster the heat will flow to the cold area.
Driving
It is the way energy moves through materials from molecule to molecule. For this, physical contact between the particles and a certain temperature difference are necessary; When you place a spoon in a cup of hot coffee, heat is conducted from the liquid to the metal and through the handle to your hand.
Convection
It is the way liquids and gases carry heat when they move from one place to another. This is why lighter, warmer air seeks to rise, and cold, dense air tends to seek ground level.
Radiation
It is the transmission of energy directly through a completely transparent medium, heating all solid material in its path. This occurs, for example, with light as infrared radiation (a magnifying glass) or with some kind of electromagnetic waves.
References
Jessica Ring. What Are Insulators? Retrieved from science.com.
FAO Corporate Document Repository. Thermal insulation materials, technical characteristics and selection criteria. Fisheries and Aquaculture Department. Retrieved from fao.org.
ThermaXX Jackets (2011). 5 Most Common Thermal Insulation Materials. Recovered from thermaxxjackets.com.
gov. Insulation Materials. Us department of energy – Office of energy efficiency & renewable energy. Retrieved from energy.gov.
Loise Kinyanjui. The Properties of Insulators. Science. Retrieved from science.com.
Insulation materials and their thermal properties. Retrieved from greenspec.co.uk.
Thermal insulation materials. Connection Magazines. Retrieved from build.com.au.