Thermal Resistance
Thermal conductivity is the measurement of how capable a material is to conduct heat. Insulated materials contain properties that can withstand thermal conductivity to prevent the transfer of heat from seeping into the container. This phenomenon is known as thermal resistance. Insulated boxes must have a high level of thermal resistance in order to shield the inside of the box from any thermal changes, such as heat, that occur on the outside. In scientific terms, the thermal resistance is called R-value.
Moisture Absorption
Moisture absorption is a significant property when it comes to insulated boxes. A box's ability to absorb moisture is necessary for maintaining a constant temperature inside the container. The reason for this is due to the way that thermal insulators work. A thermal insulator traps the pockets or bubbles of gas, which is how it is able to reduce the transmission of heat. Dry gas is one of the most effective types of insulating materials, according to the Food and Agriculture Organization of the United Nations. However, without moisture absorption properties, such as a moisture-proof layer on the outside of the box, the gas bubbles fill up with moisture and become less effective for protecting the insulated environment.
Box Density
The density of the box's walls impact the transfer of heat. Simply put, the thicker the walls of the box, the better the insulation will be able to keep the heat out. The thermal resistance property is directly related to the proportion of the density. So, a box with a higher density insulation material will provide a more effective barrier to heat transfer due to the higher amount of thermal resistance.
Cell Count
The cells within an insulation material refer to the bubbles or pockets that are able to trap the gas necessary for maintaining a constant temperature. Boxes that have more, and smaller, cells will have a more effective insulation system. However, it's important that these cells are not connected or else they lose their effectiveness. Polyurethane foam is known as an effective insulation material because of its high count of cells that are filled with gas.