To be a good thermal insulator, a material must be resistant to the conduction, convection and radiation of heat. A good insulator is made from an opaque, nonmetallic material without a crystalline structure, and its insulating properties may be enhanced by creating small air pockets inside its structure.Know More
The reason metals conduct heat so well is that metallic atoms have a poor hold on their outermost electrons. This allows the electrons to flow from one atom to another easily, and they carry energy as they move. When one end of a metallic object is heated, this increase in temperature excites the electrons and causes them to flow, carrying the heat along the object and heating it evenly. Insulating materials such as plastics resist the flow of electrons, reducing heat flow through the material.
Air pockets are another way to increase insulation. Under normal circumstances, air can transmit heat through convection, flows of air created by differences in temperature and pressure. If the air pockets inside a material are separated from one another, however, these flows cannot happen. The heat also cannot conduct through the trapped air, reducing its ability to flow through the material. Winter coats and other insulated clothing often utilize this technique, as do the insulating materials inside the walls and attics of residential homes.Learn more about Thermodynamics
According to HowStuffWorks, aluminum foil is a good insulator because it prevents the radiation of heat by reflecting it back at the source. Since aluminum foil reflects the emission of heat, it tends to be a better insulator than other materials that just slow down the flow of heat from one area to another.Full Answer >
Styrofoam works well as an insulator because it mostly consists of air confined to small pockets. These pockets hinder the convection process from carrying heat energy away from (or to) the substance inside the container.Full Answer >
Cloth can be a great choice for green and chemical-free insulation in the home. Using cloth as an insulator keeps fabric scraps out of the landfill and minimizes exposure to harmful chemicals common in modern insulation.Full Answer >
A poor conductor of heat is any material that can not transfer heat. Poor conductors have a low density thus the particles in a given volume of the material are not enough to collide and transfer heat. Examples of poor heat conductors include air, wood, paper, cloth and water.Full Answer >