Hi yabssor,
[quote]I’m curious about your repeated comments about lower-density foams being universally less desirable than higher. Referencing Sleep Like the Dead’s memory foam density data we can see that owner satisfaction is even between all densities. What is it about lower-density foam that makes you consider it a “weak link”?
I’m also confused by why you consider 1.5lb poly foam undesirable since you specifically list it as acceptable for a support core repeatedly on this forum.[/quote]
Foam density is the single most important factor in the durability of a foam material but any foam material can can be formulated to be either softer or firmer or to have a range of different properties that can affect how it feels and performs regardless of its density. In other words … both lower density and higher density foams can feel very similar of the same because you can’t really “feel” the quality and durability of a memory foam or polyfoam material.
I would be very cautious about using other people experiences or reviews on a mattress (which is SLTD’s source of statistics), either positive or negative, as a reliable source of information or guidance about how suitable a mattress may be for you or the durability of a mattress and in many cases they can be more misleading than helpful because a mattress that would be a perfect choice for one person may be completely unsuitable for someone else either in terms of “comfort”, firmness, or PPP (Posture and alignment, Pressure relief, and Personal preferences) or in terms of durability (see post #13 here).
All other things being equal … lower density polyfoam and memory foam will soften and break down more rapidly than higher density versions of the same material.
There is more about the many variables that can affect the durability of foam materials or a mattress as a whole relative to different people in post #4 here and the posts it links to.
A mattress will generally soften and break down from the top layers down because ongoing foam compression and deflection is the primary reason that foam materials break down and lose their integrity. The firmer deeper layers in a mattress will deflect and compress less than the upper layers so using lower density materials in the deeper layers of a lower budget mattress is a reasonable compromise or “tradeoff” that can reduce the cost of the mattress that will have much less effect than using lower density foams in the upper layers. I would still be cautious with 1.5 lb density polyfoam even in support layers in higher weight ranges though which is the reason for the caution in the guidelines I linked and for the frequent cautions I’ve posted on the forum for those that are in higher weight ranges if they are considering a mattress that uses a lower density support core. In other words … the risks of premature softening and breakdown for some people would be higher with 1.5 lb polyfoam.
“Comfort specs” are the specs of a mattress (such as ILD or IFD which is the firmness rating of a foam) which affect how a material “feels” but they don’t have a significant affect on the durability of the material (although firmness is a secondary factor in durability because firmer foams will compress and deflect less than softer foams). “Durability specs” are the specs that have a significant effect the durability and useful life of the material or how long it will maintain it’s original properties withing a reasonable percentage of height and firmness loss and for memory foam and polyfoam density is the most important of these.
Phoenix