In 1966, aeronautical engineer Charles Yost created an open-cell, polymeric memory foam material with unusual viscoelastic properties, which possessed both high-energy absorption and soft characteristics, according to NASA's 2005 "Spinoff" article Forty-Year-Old Foam Springs Back With New Benefits.
The foam's properties are the result of its ability to match exerted pressure and regain its shape once the pressure is removed. Marketed as Tempur Foam, Yost's Dynamic Systems company sold the rights to the technology in the mid-1970s but later developed a more eco-friendly and less temperature-sensitive formula.
Materials and Process
Though the exact formulas are highly guarded secrets, memory foam is made from polyurethane, the product of a complex chemical reaction between water and two materials: a polyol---an alcohol containing multiple hydrogen-oxygen, or hydroxyl, groups--- and a diisocyanate---a chemical compound comprised of carbon, hydrogen, nitrogen and oxygen. When the materials are combined, the reaction forms cells similar to bubbles and the mixture expands to form flexible foam.
The liquid mixture forms into a shape when it is poured into a mold (or onto a raised-sides conveyor belt) and allowed to set. It takes only minutes to dry, at which point it can be cut or trimmed to size and used in any number of applications.
Memory foam is a popular choice for bedding in home applications. The pressure-relieving properties of the foam allow the spine to align even while lying on your side, a distinct advantage over traditional box spring mattresses. Memory foam mattresses are comprised of multiple layers---usually a thick, firm base layer that supports a more viscous top layer---for comfort and air flow. Whole mattresses are, however, very expensive. Many consumers on a budget choose memory foam mattress toppers, which can be placed on top of a less expensive mattress and can vary in thickness from 1 to 4 inches.
In addition to home applications, memory foam is used commercially. Football helmet padding, airline seat cushions, hospital beds, prosthetics and shoe inserts are just a few of the foam's uses. The way the material is made for these applications varies, but the primary differences lie in the memory foam's density.
Memory foam is made by a number of manufacturers, each of which have different chemical compounds for unique properties as well as product applications. Popular manufacturers include Tempur-Pedic, ECO-CELL, Dynamic Systems, SunMate and Pudgee. Other brands purchase the foam from suppliers and market it for specific applications, such as Serta and Dr. Scholl's.
Memory foam, if properly manufactured, is inert, has been approved by the EPA and other agencies for home use and is designated safe for consumer markets. However, polyurethane is a chemical compound made from known toxic substances. If possible, look for soy-based or environmentally friendly alternatives, especially for children's bedding, and always replace foam that has been damaged due to heat, chemical spills or fire.