When you buy a new mattress for memory foam, the bottom line is how the bed creates a feeling. If you lie down on a bed and it looks like heaven, then you do not need any expert to tell you about the excellent technical characteristics of the foam or the exquisite detail that makes this bed the highest quality on the market. When the bed feels good, you are comfortable, and when you are comfortable, you sleep; period.
But for some reason people are just interested in the mattress. Perhaps this makes us feel obedient and responsible to do a little research before we lay out a piece of cash for important purchases on health or at home. Or maybe it is because we will never know what is inside the mattress, and we are curious. Whatever your reason, the following will tell you all the important technical properties of the foam so that you can compare different foam beds and make an informed purchase decision. These properties are the same for latex and memory foam (including Tempur-Pedic / Tempurpedic, which is also a memory foam, although they have branded it a “Tempur”).
Technical properties of latex mattresses and memory foam
A foam mattress is made of at least several different types of foam, and sometimes more. In their literature, sellers sometimes give the properties of the upper layers of a latex or memory foam mattress. The following foam properties refer to: polyurethane foam, latex foam or memory foam.
Density - Measurement of mass per unit volume, measured and expressed in pounds per cubic foot (units) Or kilograms per cubic meter (kg / m3). For example, a 1-foot square block of foam 5 pounds thick (pound) will weigh 5 pounds.
Indent Deviation (IFD) - also known as “Initial Load Deviation” (ILD). Measurement of the carrying capacity of flexible polyurethane foam. IFD is most often measured as the force (in pounds) required to compress a circular foot with an internal diameter of 50 square inches into a four-inch-thick specimen, usually 15 inches square or more, up to a specified percentage of the initial height of the specimen. The most common ILD values are generated at 25 and 65 percent of the initial height. The top layer of memory foam is typically between 12 and 15 ILD. Polyurethane foam with high elasticity, used in bedding, is usually 20-40 IFD.
Support Factor - Support factor = 65% IFD or 25% IFD is determined after one minute of rest or recovery. The support ratio can be used in conjunction with a known 25% IFD value to determine the 65% IFD value. Low-support foams are likely to bottom (fully compressed) under load.
Fatigue Flex (Dynamic Fatigue) - Normal softening or loss of durability over time and with use. Fatigue can be measured in the laboratory by repeatedly compressing the foam sample and measuring the change in IFD.
Tensile strength - The measure of force required to continue breaking in the foam after splitting or breaking was started and expressed in pounds per inch (psi). An important property in determining the suitability of a foam is when the material is crosslinked, crosslinked or otherwise attached to a solid.
Resilience - Indicator of surface elasticity or "elasticity" of flexible foam; measured by dropping a steel ball on a cushion of foam and measuring how tall the ball fits. Memory foam has almost no stability. High elasticity foams are used in the base layer of mattresses.
Hysteresis - Measurement of the ability to maintain the original support characteristics after bending. As a rule, hardness (IFD) is tested at 25% of indents, 65% of indents and again by 25% on the way up. Hysteresis is the percentage of 25% IFD loss measured when the compression tester returns to its normal position (25% IFD) after measuring 65% compression. Lower hysteresis values are desirable (less IFD loss). A low hysteresis in conventional foam is equal to less IFD loss in durability and fatigue tests.
Air flow - The amount of air, expressed in cubic feet per minute, that can be passed through a 2 "x 2" x 1 "foam sample with a 0.5" water pressure drop. A higher air flow indicates a more open foam cell structure.
