Polyurethane Foam (also called polyfoam or even just poly) is commonly found in most sofas, car seats and mattresses. Polyfoam is very durable and available in different densities depending on the targeted use. High Density (HD) and is renown for providing good support and excellent pressure relief.
Generally a conventional polyfoam is used in the thinner comfort layers of a mattress as it is soft and pliable and well suited to quilting type uses like pillow and pillow-top functions. This lower density foam, which is less than 1.5 pounds per cubic foot, is not suited for the ‘core’ of a mattress, that is the role of the High Density and High Resiliency polyfoam.
These denser foams are often used in the deeper comfort layers of a mattress and as the base or core of the mattress. They offer densities at 1.5 to 1.8 pounds per cubic foot and upward of 2.5 pounds per cubic foot respectively. (HD and HR.)