Thermal insulation is the Primary Defense against heat or cold. Heat transfer through solid materials and still fluids (and semisolid gas) occur by conduction. Heat flows from warmer to cooler areas until there is no longer a temperature difference. Most insulation material work by slowing conductive heat flow and convective heat flow. In the Cold Chain Packaging industry, conduction is the Primary mode of heat transfer considered. An insulation material’s resistance to conductive heat flow is measured or rated in terms of thermal resistance or R-Value. The higher the R value, the greater the insulating effectiveness. R value depends on the insulating products’ thickness and density. The most common insulating materials in the packaging industry include cellulose, polyurethane foam, EPS (Styrofoam) foam, PLA (polylactic acid) as well as recycled/modified products such as shredded cotton fibers or paper products. It is important to note semantics: Thermal ‘conductivity’ is independent of the thickness of a material. However, ‘conduction’ and the ‘R value’ do depend on the materials thickness. In addition, EPS foam has greater heat diffusion (Q, conduction) than PU, which is greater than VIP. Conversely, VIP has a greater insulatory capacity (R value) than PU, which is greater than EPS. (ISTA)
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