Indentation force-deflection is a process used in the flexible foam manufacturing industry to assess the "softness" of a sample of foam such as
memory foam
Memory foam consists mainly of polyurethane with additional chemicals that increase its viscosity and density. It is often referred to as " viscoelastic" polyurethane foam, or low-resilience polyurethane foam ( LRPu). The foam bubbles or ‘cellsâ ...
. To conduct an IFD test, a circular flat indenter with a surface area of 323 square centimeters (50 sq. inches - 8" in diameter) is pressed against a foam sample usually 100 mm thick and with an area of 500 mm by 500 mm (
ASTM
ASTM International, formerly known as American Society for Testing and Materials, is an international standards organization that develops and publishes voluntary consensus technical standards for a wide range of materials, products, systems, an ...
standard D3574). The foam sample is first placed on a flat table perforated with holes to allow the passage of air. It is then "warmed up" by being compressed twice to 75% "strain", and then allowed to recover for six minutes. The force is measured 60 seconds after achieving 25% indentation with the indenter. Lower scores correspond with less firmness; higher scores with greater firmness.
US measurements are given in
pounds-force
The pound of force or pound-force (symbol: lbf, sometimes lbf,) is a unit of force used in some systems of measurement, including English Engineering units and the foot–pound–second system.
Pound-force should not be confused with pound-ma ...
, and European ones are given in
newtons.
References
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External links
* Joint Industry Foam Standards And Guidelines https://www.pfa.org/industry-standards/
ASTM standards