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Mattress support cores - Polyurethane


Polyurethane (also called polyfoam or just poly) is the most common type of foam you will see in mattress and in its medium or higher grades can be successfully used as a support layer. Unlike its memory foam cousin, it is made to compress under pressure rather than soften or (melt) under pressure and heat. This gives it a higher resilience and progressive resistance than memory foam and it can hold up the heavier parts of the body much more effectively. This is the reason it can be used as a support layer while memory foam can not. It comes in 3 basic grades and the lower grades have less resilience and less progressive resistance than the higher grades. All its grades can be made in softer or firmer ILD's although the middle HD grade tends to be more commonly available in firmer ILD's. Softness or firmness is not in any way an indicator of its quality and the best indicator of quality and durability in polyfoam is density or weight per cubic foot (in both polyfoam and memory foam). In this article we will deal mainly with polyurethane used as a support core of a mattress however I would also encourage you to read about its use in the comfort layers section as polyfoam in general used in comfort layers is the source of many of the biggest issues in mattress manufacturing and the body impressions and material breakdown that are so common today.

Regular conventional polyfoam: This is the lowest grade of polyfoam and weighs less than 1.5 lbs per cubic foot. It is the least expensive and is not really suitable for use in a mattress at all ... either as a soft comfort layer (unless it is in the range of around an inch or so or less in a quilting layer) or as a support material ... unless the mattress is for occasional use or is meant to last a very short time. Mattresses with regular polyfoam in a support layer should be completely avoided for regular use as they will break down quickly and do not have the desireable qualities that are needed in a support layer.

High Density conventional polyfoam (HD): This is polyfoam that typically weighs 1.5 lbs per cubic foot or more (although I would use 1.8 as a better standard for HD unless you are in lower budget ranges) and can go as high as the mid 2 lb range.  It is sometimes difficult to find this in a softer version but the firmer versions are quite suitable for a support layer under memory foam or under a softer top layer of good quality polyfoam or latex. It lasts longer and will keep its firmness longer than lower density conventional polyfoam (depending on the density) but typically not as long as a high quality innerspring or higher grades of polyfoam, or latex foam. It is less resilient and has less progressive resistance (doesn't hold you up as well) as the highest grade of polyfoam, innersprings, or latex. Although it is inexpensive to manufacture, you will often see this grade of foam in the support layers of mid range and even rather expensive mattresses under higher quality materials such as latex or high quality memory foam. The lower end of this range would be a suitable material for a lower or mid range mattress and the higher end of this range would be more appropriate for mattresses that were in a higher budget range. Since the support layers of a mattress are not usually its "weak link" ... I would consider this grade of polyfoam ... especially in the higher densities ... to be perfectly acceptable and a durable choice in a mattress with good quality comfort layers and of course higher density would indicate greater durability and quality. There are some good quality mattresses use this grade of polyfoam (usually in the 2.0 lb range and higher) in their mattresses.

High Resiliency polyfoam (HR): This is the highest grade of polyfoam and weighs 2.5 lbs per cubic foot or more and uses a different formulation than conventional polyfoam. It also must have a support factor (progressive resistance) of 2.4 or higher and resilience of 60% to qualify for this grade.  Because it is made with a different combination of chemicals than the other two grades, it is more durable and has better properties than the lower grades and since it can be made from very soft to very firm, it can be used successfully anywhere in a mattress. Because it is also more expensive to manufacture than the lower grades though, and is not as profitable to use, you will rarely see it in mattresses outside of local or regional manufacturers who use higher quality materials in their mattresses. As a support material it would be suitable for use anywhere that latex foam or an innerspring would be used. It is more expensive than many innersprings and less expensive than latex so the price of your mattress should reflect this.

One caution worth knowing about is that HR polyfoam is among the most commonly mislabeled foams and it often seems that any polyfoam that has a density of more that 2.5 lbs/cu. ft. or even lower is called HR yet you will not be told that it does not have the required support factor of 2.4 or higher to be HR. The internet is filled with false claims of HR polyfoam. If you even ask some of these merchants or even many retail outlets about "support factor" or use another term for the same thing (comfort factor, sag factor, or compression modulus) the sales person will often look at you as if you were from another planet and make up an answer that is vaguely connected to how comfortable the mattress is rather than admit that they know very little if anything about one of the most important properties of a mattress core material. These higher density foams that are actually HD grade will not have the same desirable qualities or durability of true HR polyfoam even though the price of the mattress may be as high. The best true HR polyfoams come close to latex and are very good quality, have good resilience, and other qualities and will last for many years.

Unless you specifically know the quality of polyfoam in a mattress core, it is usually wise to assume that it is HD and it should be priced accordingly.

In a lower cost "throwaway" or lower budget mattress, or in a slightly higher priced mattress with high quality materials above it in the comfort layers, HD polyfoam used as a support layer may be part of a good value mattress. Higher densities of HD polyfoam or HR polyfoam can be a good, slightly less expensive alternative to latex in a core layer for those who are on a more restricted budget and are looking for a good quality foam mattress core.


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St3v3k4hn replied the topic: #2 06 Jun 2018 12:32
Hi Phoenix
I read thru this post and also saw you describing (in other posts) high density and high performance polyfoam similar to what is used in the top layer of a Tuft and Needle mattress. You said there are several types of improved poly foams that have more point elasticity, and that are more pressure relieving and softer than standard poly foams. You even mentioned some names - Energex, Activus, Spring-tex, Avena and Futuratex.

I need to replace a 4” foam layer (some type of soft memory foam) in an air bed and would very much like to get one of the improved poly foams you mentioned above. Are there any in particular you recommend? Preferably available from a site member?

For reference, I own a Tuft and Needle bed (its in a guest room) and I really like the feel of it. I seem to prefer poly foam to memory, latex, or springs.

Thanks for your help!

Phoenix's Avatar
Phoenix replied the topic: #3 07 Jun 2018 13:38
Hi Steve/St3v3k4hn.

If you like the feel of polyfoam, then you are correct that high-performance polyfoam (HPP) could be a good comfort layer choice to replace the worn-out memory foam in your current air bed. HPPs , depending on the formulation, offer the conformation and point elasticity found in memory foam but can be made to be more open-cell and breathable, faster in recovery, and not so temperature dependent (You probably came across this post here about the high performance” polyfoams ). If you are trying to replicate the feel of Tuft & Needle they use a top layer of higher density (about 3 lbs ) and higher performance polyfoam. The foam itself is being formulated in consultation with their foam pourer/manufacturer to meet their specific criteria and you’d need to find someone who is familiar with this particular foam to guide you. The Activus is an HR polyfoam which was specifically developed by FXI/Foamex but it's rarely seen in mattresses because it is much more expensive than other polyfoams.

As far as recommending one type of HPP over the other… they are not all equal.... some are formulated to replicate many of the viscous characteristics of memory foam, others are designed to be closer to latex in their characteristics, and then some are simply designed to be more durable versions of low-density polyfoam. You’d have to contact each manufacturer/supplier as only you can decide what you like best based on your personal testing and the balance between comfort/pressure relief and support/alignment that may be suitable for you ..... you are the only person who can feel what you feel on a mattress. More detailed discussions with the more knowledgeable people at the retailers or manufacturers that sell the HPPs that you are considering would probably be your fastest way to asses if these are what you are looking for.

You may wish to comb through and contact some of the trusted members listed here that offer custom to order mattresses and have a more detailed discussion explaining the feel you are trying to accomplish as they would be the best source of knowledge regarding the HPPs that you are considering (provided that they have that particular type)
Christeli has Energex and could send you a layer, but they recommend it only for the transition layer rather than for thicker or softer comfort layers.
You may also wish to place a phone call to Magic Sleeper as not only that they have many products and components for Mattress Repairs &componentry but they also do Sleep Number repairs and even if you do not end up purchasing from them they’d be happy to give you some tips.
SleepEZ has the float foam which is a high-performance polyfoam that is formulated to have some of the feel and contouring properties of memory foam without the low resilience, slow recovery, and temperature sensitivity of memory foam.

Hope this helps

St3v3k4hn replied the topic: #4 07 Jun 2018 17:21
Thanks Phoenix, you rock!
St3v3k4hn replied the topic: #5 12 Jun 2018 00:50
After looking around I am leaning towards using HR foam to replace the 4” memory foam in my Sleep Number M7 bed. The existing memory foam worked ok, I set the bed number around 50, which seems pretty ideal. The foam is over the air chamber but under the tufted cover; its also wrapped in an allergy encasement which makes everything feel a bit firmer than it would otherwise.
I found HR foam (maybe?) at the following sites:
- FoamOnline looks like it has real HR foam, in a variety of firmnesses.
- The foam factory has HD36 High Quality foam, which doesnt quite seem like HR foam.
- FoamOrder sells everflex 3.2 lbs/ft3, ILD: 24.
- I tried the A1 Foam site but they dont seem to sell mattress foam anymore. (There was a link to another url that didn't work for me.)
Assuming I want real HR foam, would you recommend any of these? And if so, what firmness do you think would work best?
Thanks again...
Phoenix's Avatar
Phoenix replied the topic: #6 13 Jun 2018 00:40
Hi St3v3k4hn.

Assuming I want real HR foam, would you recommend any of these? And if so, what firmness do you think would work best?

Rebuilding your own mattress involves a lot more knowledge of how different materials, layers, and components interact than many people suspect. Unfortunately it's not possible to make specific suggestions or recommendations for either a mattress, manufacturers/retailers, or combinations of materials or components that might be suitable for you because the first "rule" of mattress shopping is to always remember that you are the only one that can feel what you feel on a mattress and there are too many unknowns, variables, and personal preferences involved that are unique to each person to use a formula or for anyone to be able to predict or make a specific suggestion or recommendation about which mattress or combination of materials and components or which type of mattress would be the best "match" for you in terms of "comfort" or PPP (Posture and alignment, Pressure relief, and Personal preferences) or how a mattress will "feel" to you or compare to another mattress based on specs (either yours or a mattress), sleeping positions, health conditions, or "theory at a distance" that can possibly be more reliable than your own careful testing (hopefully using the testing guidelines in step 4 of the tutorial) or your own personal sleeping experience (see  mattress firmness/comfort levels in post #2 here  ). Posts 15 - 17 here may be worth reading and I would normally recommend working closely with a manufacturer who will be able to give good advice about all the different components.

As far as the foam suppliers you are considering... based on my conversations with Foamonline a while ago, I have no reason to doubt their polyfoam specs and assuming that the specs are correct then their HR polyfoam would be a good quality product yes.
The Foam Order foam descriptions are here and you can see that the Everflex V 24 is 2.6 lb (HR range) and has an ILD of 24. and V34 an ILD of 34. They consider this to be a very high-quality foam that can last 15 years.
Foam Factory (AKA FBM or any of their other URL's such as Foambymail, mattressbymail, usafoam, foamdistributing etc) is not a business I would personally recommend or support. They are "cheap" ... and for some people, this may be more important than knowing what they are actually buying ... and reason enough to buy from them. Post #2 here talks about some of the reasons why and a f orum search on FBM (you can just click this) will bring up more comments about them.


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