Viscoelastic Foam Mattresses

During the last 10 years, a whole new kind of flexible foam--commonly called 'viscoelastic' or 'slow' foam--has reached a top profile within the mattress market. Its marketing and advertising might lead you to think that this is a wonder material with quite amazing properties However for once, the claims for the materials are not just marketing hype. What enthralled us most about viscoelastic foam was that it had benefits in addition to a story. Anybody can promote a product well but it is different when the product has key advantages over competing materials--as viscoelastic foams have in health attributes.

A key feature of 'visco' foam is that it is lazy or slow, with high damping. Certainly one of its principal characteristics is very low resilience; there is no spring in it. But undoubtedly the more important quality is the foam's heat sensitivity, the crucial active property of viscoelastic foam. Slow recovery is an evident feature, utilized in marketing the product. When you sink your hand into viscoelastic foam, it leaves an indentation which vanishes only gradually. Conventional high resilience foams are two-dimensional (density and hardness could be varied); viscoelastic foams are four dimensional, with hardness, density, temperature and time effects.

The majority of foam experts detailed similar important properties: The novelty is that it has very slow recovery characteristics and conforms to body shape. Most flexible foams are more lively, highly resilient and bouncy. Viscoelastic foams, become more lively when you heat them up--all of them have this to some degree or other. This is detailed as a slow recovery, rather soft, but supportive. The foam is also temperature sensitive in its indentation hardness. The reduced indentation hardness of these foams allows the body to sink rather far into the foam, while still maintaining the firm feel of a excellent resilient foam.

Viscoelastic foam is formulated to offer a specific low resilience and hardness at 20 Celsius. If the temperature falls, the foam gets very hard, like a bit of wood. If you need to determine if a piece of foam is genuinely viscoelastic, put it in the freezer, to find out if it hardens. Above about 30 Celsius, the foam gets softer and this temperature dependence is the reason the foam is used in applications like hospital beds.

With standard flexible furniture foam, a hardness of 20 at room temperature will be the same if the temperature is raised to 30 Celsius or if it is dropped to 0 Celsius. For normal flexible PU foam, throughout the ambient temperature range, hardness values aren't temperature-dependent.

Common furniture foam has normally 65 % resilience: you drop a steel ball bearing on it from a meter and it rebounds 65 cm. On a bit of slow foam it will only rebound 2 cm since, visco foam is incredibly low resilience, it's dead, with no bounce. A normal metal spring bed base can give perhaps 95 cm rebound.