The Origin of Memory Foam
In the early 1970’s NASA’s Ames Research Centre funded a development project designed to create a substance that could help protect Astronauts from the incredible g-forces experienced during space mission take offs and re-entry. They believed that one of the key secrets to reducing g-forces on the body was to use a foam material that could conform to the shape of each astronaut and, more importantly, hold this conformity. While a foam mould of the Astronaut’s body shape could accomplish this, any movement would take the Astronaut out of this position and create incorrect pressure points against the body. Instead, they created a new foam material that was visco-elastic and therefore able to conform to the shape of the Astronaut, but return to its normal shape once pressure was removed from the foam. This could allow an even distribution of pressure or body weight over the entire surface of the memory foam, but, at the same time, quickly adapt to any movements of the body.
With this amazing discovery, Fagerdala World Foams of Sweden, Europe’s leading foam producing company, began experiments in the 1980’s to perfect this substance for consumer use. They trade marked the word Tempur to note the fact that this material was sensitive to temperature.
In 1991, the Tempur-Pedic, a Swedish mattress company introduced this material in a mattress form to the Swedish market place and received excellent results. In 1992 the same products were launched in North America and similarly, received excellent results.
With the success of Tempur-Pedic, other foam manufacturers in Canada and the United States began to develop their own visco elastic memory foam material to offer Mattress, Upholstering and specialty product companies the ability to allow consumers a wide variety of products and prices to choose from.
How does Foam Get a memory?
To give a piece of foam memory, you start with a synthetic polyurethane foam material and add certain types of chemicals, which increase the weight or density of the foam. With the addition of these chemicals, a non toxic, visco-elastic foam material is created. However, there are many features along the way that determine what type of memory foam you end up with. To understand exactly what differences are found I each final product, first you have to understand how foam is graded.
How is Foam Graded?
For a material to be Visco-elastic, it will have to be temperature sensitive, having the ability to rebound fairly quickly, returning to its original shape. Memory foam is graded by its visco-elastic nature and durability by breaking down the grading system as follows: -
Weight (Density in pounds per square foot)
The weight of the foam is determined by the amount of chemicals used in the composition of the polyurethane foam. The more chemicals, the higher the density and the more visco-elastic it will become. This density will not determine the hardness of the material, this is done through utilizing the ILD rating structure. Most memory foam mattresses use a 5lb density, but some use as low as 2 or 3lb densities.
ILD Rating (Indentation Load Deflection)
The ILD rating is going to tell you how hard or soft a material is. The 25% ILD rating is the number of pounds required to achieve a 25% compression of a 4” thick foam using a 50 square inch indentation. An example of this would be: - 20lb ILD foam indicates that this foam took 20 lbs of pressure to indent it 25%.
Resilience
This measures the foam’s springiness by determining the percent rebound of a steel ball dropped from a height of 36 inches. The term HR foam refers to a highly resilient foam that will give a very high ‘ball rebound’ reading.
Tensile
This indicates the extent to which foam can be stretched, measured in pounds per square inch and how much elongation in terms of percent of stretch before rupture. This value has very little relevance to memory foam mattresses because they are not usually stretched and will become compressed only when slept on.
NOTE: It is important to remember that these rating can vary from each foam batch that is poured and that no mattress company can predict an exact rating on their mattress each time they produce the final product. As an example, a 10 ILD rated foam could vary from 8 - 12 ILD each time the foam is poured.
