Visco Elastic Foam Matress

There is a large debate as to what viscoelastic foam is. In simple terms, the foam is viscoelastic since it manufactured using a viscoelastic polymer.

While messing with the cell structure to leave vestigial cell walls can create comparable initial behavior, they're not true viscoelastic products, which require a good open cell construction. While viscoelastic foams, have open cells, cellular structures are not necessarily wide open and this increases the viscoelastic effect a little. Pseudo-viscoelastic foam can be achieved with a closed cell structure, but this is unlikely to be viscoelastic over any useful period of time. A foam with plenty of closed cells can seem to be 'slow,' because when crushed it requires time to recover, but this is just slowness in taking up air again.

Some suppliers do a little bit of a cheat, by raising the number of closed cells, that may make a foam lazy. It is easy to pick these foams out, though, because it is difficult to draw air out of them. These feel like a lazy foam to the touch, however the temperature dependence is small.

The temperature dependence occurs for the reason that the glass transition temperature of the foam has been made to be inside the proper region--about body temperature. Normal foam has too low a transition temperature and is also generally highly resilient rather than highly damping.

Formulations are already made to raise the glass transition temperature to usually around 30 Celsius. For pressure-relieving mattresses the transition temperature needs to be between 15 degrees and 30 Celsius. Part of the engineering is to try to make the transition temperature close to room temperature, and therefore give slow recovery. Viscous damping is wanted, so you need glass relaxation over room temperature to achieve this. But, you don't want to leave an impression long-term, you want recovery.