Visco-elastic Memory Foam
One of the most recent additions to the mattress industry is memory foam. It is a specially processed polyurethane foam. The response to pressure of this "space age" foam is slow and temperature activated. You will find this highly advertised product in most stores. Two benefits of memory foam are fairly good pressure point relief and very little motion transference; that is motion moving from one partner’s side to the other side.
There are varying qualities of memory foam, and if you do decide to pursue this as a potential sleep surface, here are some tips to help you find something a little more durable. The density of the foam will have an impact on both the conformity that you feel and the durability of the mattress. These densities (which are rate by their ILD or Indentation Load Deflection) can be a gauge of the potential quality of a mattress. Generally, the higher the number the longer it will continue returning to its original shape.
Mattresses normally use anywhere from a 10–20 ILD rated memory foam. However, the memory foam will not be the only foam in a memory foam mattress. What you are often not told is that an 8" memory foam mattress has only 1–3" of memory foam; the rest is 5–7" of polyurethane foam, or perhaps latex in a high end mattress. Be sure to clarify with the salesperson exactly how much of the mattress is standard polyurethane foam. Poly foam is a much less expensive material; and if you do choose this as your sleep surface, you will want to make sure you aren’t paying too much. Remember, buyer beware!
Tempurpedic, among others, has managed to create a market for specialty sleep products through their direct mail, and informercial campaigns. Memory foam mattresses have become a billion dollar industry all by themselves. However, across the mattress industry memory foam mattresses are the most returned mattresses today. It has become a highly controversial product , one of the reasons being the chemical odor that it emits; which is especially potent when they are first opened, but continues for the life of the mattress. Additionally, the press surrounding the 7 carcinogenic chemicals it off gasses has prompted some stores to pull it from their displays. It is unclear what the long term health impact will be. The chemical issue is not the only reason for controversy however.
Other reasons for its frequent return include the tendency it has to "sleep hot" and an inability to move freely on the mattress due to its delayed response. The slow response actually creates a rut that people cannot easily roll out of. Also, when trying to roll over to get comfortable, or cooler, people may have to wake up to reposition themselves.
When memory foam mattresses first came upon the market they appeared to be a unique and exciting sleep solution. It is unfortunate that it can not live up to the hype around this marketing driven product. At roughly the same cost, latex foam rubber can provide all of the benefits of memory foam without any of the drawbacks. Furthermore, unlike memory foam, latex is not a petroleum based foam, and it will biodegrade rather than fill up landfills.