​​Flexible polyurethane foam has many different uses.
• For cars or under carpet,
• For packaging materials to protect delicate instruments.
• And it’s the cushioning material of choice in almost all furniture and bedding.

Support: The foam has to be able to support the proper amount of weight to properly cushion an object or person.

Comfort: Foam cushioning has to feel good for the user and provide not just cushioning but also comfortable use.

Durability: The foam has to hold up through use without losing its original properties.

These are the basic benefits that foam cushioning provides, and if the needs in each of these three areas are evaluated first, selecting the proper foam for a given purpose becomes fairly simple. A sofa seat cushion has to have good support, comfort, and durability, while the arm and back cushions for the same sofa need to last and be comfortable, but won’t necessarily be required to support much weight. The foam used to line the case for a video camera needs to support the weight of the camera and hold up through use, but the camera cares nothing about comfort.

Density: Density is a measurement of the mass per unit volume. Measured and expressed in pounds per cubic foot (pcf) or kilograms per cubic meter (kg/m3), density is one of the most important of all properties. Density is a function of the chemistry used to produce the foam and additives included with the foam chemistry. For specification purposes, it is advisable to use the polymer density of foam, or the density of the material made up strictly by the foam chemistry without fillers or reinforcements included.

Density affects foam durability and support. Typically, the higher the polymer density, the better the foam will retain its original properties and provide the support and comfort it was originally designed to produce.

IFD: Indentation Force Deflection (IFD) is a measurement of foam firmness. Firmness is independent of foam density, although it is often thought that higher density foams are firmer. It is possible to have high density foams that are soft – or low density foams that are firm, depending on the IFD specification. IFD specification relates to comfort. It is a measurement of the surface feel of the foam.

IFD is measured by indenting (compressing) a foam sample 25 percent of its original height. The amount of force (in pounds) required to indent the foam is its 25 percent IFD measurement. The more force required, the firmer the foam. Flexible foam IFD measurements range from 10 pounds (super soft) to about 80 pounds (very firm).

Example: The foam type is 18/35 The 18 means a cubic foot of this foam weighs 1.8 pounds. The heavier a piece of foam, the longer it will maintain its shape. The 35 means it takes 35 pounds of pressure to compress a piece of this foam to 25% of its original height. The higher this number means the firmer the piece of foam