\Polyurethane Foam Specifications:
Foam mattresses are made mainly of materials such as latex foam, viscoelastic (memory) foam and polyurethane
foams. The primary properties, that affect design considerations, and with which distributers should be familiar are:
Modulus (Support Factor)
is a measure of weight (pounds per cubic foot) and it is unrelated to firmness. Generally, as foam density increases, comfort and durability also increases.
is the measure of foam firmness, and is independent of density.
IFD is measured by indenting a foam sample 25% of it's height. The amount of force (in Lbs) required to compress the foam is it's 25% IFD.
Even high density foams can be soft. For upholstery, 25 percent IFD can range from five pounds (super soft) to 80 pounds (super firm). Softer foams may be laminated to firmer foams to provide surface softness.
is the resistance to compression near the surface of a mattress. It is measured by the surface Indentation Force Deflection (IFD) measurement.
is the IFD under severe compression.
is another IFD measure, taken by indenting the foam 65% of it's height. Typically, the greater the difference between a product's 25% and 65% IFD (the Support Factor is the ratio of the two), the greater ability to support weight. Support Factors range between 1.5 to 2.6
is primarily a function of the type of foam. Conventional foams have compression modulus in the range of 1.9 to 2.1; filled foams 2.1 to 2.4; and high resilience grades 2.2 to 3.0. Within a foam grade, the modulus is typically a function of the foam density. In most cases, the higher the density the greater the compression modulus.
Laminating hard and soft foams together can also increase compression modulus for the composite cushion structure. However the firmness of the laminated foams cannot be too far apart or the cushion may seem to "bottom out" on the firmer portion.
is an important measurement of durability, and an indicator of a cushion's long term ability to provide the proper cradling and TVM (Total Vertical Motion). Foams that have good flex fatigue values will tend to retain their original firmness and support levels, which means that the cushion can retain more of its original characteristics.
also affects comfort an design. Foams with high resilience feel springy and provide a good "hand" for cushioning.