Hi Bstar,
This is an ongoing debate in the “latex community” about blended vs 100% natural Talalay and much of the information that is out there is based on promoting one over the other based on somewhat inaccurate information rather than recognizing the small differences between the two. these comments apply to Talalay and there are other factors involved in Dunlop.
SBR latex (synthetic) is a less dense material with a slightly different chemical structure than natural rubber. It is made from two chemicals which are Styrene and Butadiene while natural rubber is primarily Isoprene.
These two polymers (SBR and Isoprene) are similar but not the same. In addition to being primarily Isoprene … natural rubber also contains other compounds in varying amounts including proteins, resins, fatty acids, and sterols. These additional ingredients are missing from synthetic rubber (including synthetic Isoprene).
Natural rubber is more elastic, denser, and less consistent in its structure and particle size. It also softens as it ages (the crosslinks in its chemical structure break over time)
SBR rubber is less elastic, less dense, and more consistent in it’s particle size and structure. If becomes stiffer as it ages (the crosslinks in its chemical structure increase over time).
Natural rubber has particles of different sizes which tend to “agglomerate” (stick together) so it is thicker and more sticky than SBR which is thinner and has a more consistent particle size. This means that natural rubber is more difficult to work with and “gums up” the machinery more. NR is also more expensive than SBR. This means that natural rubber products including Talalay latex tend to be more expensive than synthetic or blended rubber products including Talalay.
Because natural rubber is a more dense material … it weighs more than SBR and would have a higher compression modulus (gets firmer faster) but because of it’s elasticity would also be a little more conforming.
NR resists impressions better than SBR but NR will tend to soften more than SBR (although there are other variables here which may affect this)
There are other differences between the two materials as well … some of which which come from the different types of rubber itself and some which come from the additional ingredients that are mixed in with the natural rubber which alter how it acts … but these are the primary “practical” differences.
In practical terms all of these differences are relatively small in the cured foam and many people would not feel significant differences between the two in side by side testing. Natural would be slightly more “springy or buoyant” and more “supportive” while synthetic would generally feel a little softer and be slightly more pressure relieving (would allow for slightly more sinking in and cradling). The thicker the layers that are being compared the more it may be possible to feel a difference (for example someone may not feel the difference between two 3" layers of each material but they may feel a difference between 9" of each material).
In the higher ILD’s which use more rubber and less air … any differences in durability between them would be negligible. In the lower ILD’s which use less rubber … these differences may be more noticeable. Latex International acknowledges the differences between their natural and blended Talalay here while Radium has told me that they use a special curing past for their 100% natural in the lower ILD’s which should negate any differences in durability.
So the bottom line is Talalay made from natural rubber is more expensive, comes in a less specific range of ILD’s, is heavier, slightly more elastic and springy, has a higher compression modulus and more supportive, may get softer and develop impressions slightly faster in lower ILD’s, and is more natural. The primary reason that it was introduced (in 2005) is to cater to the “natural” market who are willing to pay more for a product which has has a more natural source even though it may not be as durable.
Both are Oeko-Tex standard 100 certified in terms of harmful substances or VOC’s and offgassing.
Those who value a more natural product for personal reasons and are willing to pay for it (in price and possibly lower durability), or who can feel a difference and prefer the feel that comes from the greater elasticity and compression modulus of the natural would likely choose the 100% natural Talalay.
Those who value the increased consistency, greater choice of softness/firmness levels, or lower cost of the blend or who can feel a difference in pressure relief, would likely choose the blend.
Both are great choices and in the end the choice between them is part of each person’s individual “value equation”
Phoenix
PS: I wanted to make sure that people who read this discussion are clear that it is about Talalay and not Dunlop which is denser and generally has a higher rubber content than Talalay and where higher amounts of natural rubber would tend to outperform and be more supportive and durable than blended Dunlop. Post #2 here has more information about the differences between SBR and NR rubber and post #6 here has more about all the different types and blends of latex.