Hi Sonic,
This is an ongoing discussion all over the web which has been going on for many years … much of it based more on what people like rather than on fact. The actual durability of any latex will also depend a great deal more on how it is used and how it is protected as it will break down with exposure to ozone and ultraviolet and certain solvents and some of the other substances that are listed here.
IMO … neither can accurately be called better than another as it entirely depends on the use they are being put to. In certain applications … Dunlop is clearly superior when a higher compression modulus is desirable. In other applications … Talalay is superior when softer more consistent foam is desired. Some of the newer continuous pour Dunlop materials are somewhat in between the two in that they are available in softer ILD’s and can be more consistent in terms of ILD variances across the surface and from top to bottom than molded Dunlop (see post #6 here).
I realize though that you are asking strictly about durability so I will deal with that … starting with a comparison with NR vs SBR.
In general terms … denser natural latex is more durable in instances where stretching is required as it is more stretchy (elastic) while SBR is less elastic. NR has a higher tear strength. NR has slightly less abrasion resistance and weathering degradation or thermal oxidative degradation than SBR (according to most research) which is why SBR is often used in tire compounds. 100% NR Talalay is less dense than 100% NR Dunlop but has a more even internal cell structure which is considered by many to be less prone to internal breakdown (although there is little research here … it makes sense).
Overall (balancing all the competing factors that I’m aware of from a great deal of research and many conversations with manufacturers and producers) … I would rate 100% NR Talalay, blended Talalay, and 100% NR Dunlop about equal in the higher ILD’s with a slight edge to Dunlop and blended Talalay as the ILD goes down … but how long each lasts would depend more on the use it was put to than on which type of latex in most cases. The difference in real life is likely to be rather insignificant in the higher ILDs.
As ILD goes down … particularly into the low twenties and teens … 100% NR talalay is likely to be less durable than blended Talalay or NR Dunlop because internal shear forces in the 100% NR in the lower density Talalay may well cause its greater elasticity to work against it and “stretch” the less dense lower ILD NR talalay to the point of “breaking” the cell walls more often. So in terms of the lower ILD’s both Dunlop and blended talalay would likely be more durable than 100% NR talalay.
Latex International introduced 100% NR talalay not because it was a better material in terms of performance but because they wanted to have a product that was more desirable to those who wanted materials that were more natural regardless of durability. They know that it is likely to be less durable … especially in the lower ILD’s … than the blend (or Dunlop) which is why their guarantee is shorter on the NR than on the blend. They themselves will readily acknowledge this.
So to recap … blended Talalay, NR Talalay, and NR Dunlop are likely to be about equal in the higher ILDs. In practical terms this means that used in a mattress core they are likely to be close to equal.
As the densities go down … 100% NR talalay may start to fall behind the other two … assuming the materials being compared are of the same ILD. In practical terms this means that in a comfort layer the lower the ILD the durability advantage may go to the NR Dunlop and blended Talalay … even though Dunlop is not usually seen in ILD’s that are as soft as Talalay so an “apples to apples” comparison cannot really be made for the lowest ILD NR Talalay.
There are also some types of Dunlop being made now that use a continuous pour process from either Latexco or Mountaintop in various blends (including synthetic Dunlop from Mountaintop) that are comparable to Talalay in terms of ILD and consistency and are also proving to be very durable materials. Blended Talalay can be made in lower ILD’s than the NR Talalay and is generally considered to be more durable in the lower ILD’s than NR talalay. This would be particularly true with Latex International Talalay. Radium has told me they use a different “curing paste” in their lower ILD NR Talalay products which creates a smaller cell structure and which they claim and their testing indicates is just as durable as the blend in lower ILD’s.
While there is no way to “quantify” all this because there are so many variables involved and there is no specific comparative information that is publicly available and because the different strengths and weaknesses of each material will have as much to do with durability in a particular application as the material itself (given the exact same use and the exact same ILD) … based on the experiences of manufacturers that have been working with latex for decades and on the information that is available … this is likely to be as accurate as it’s possible to be.
Since all latex is more durable than most other materials and other types of foam … I would make choices based on which had the more desirable qualities in the application it was being used for, on budget considerations, or on individual criteria and preferences rather than a “better worse” comparison.
There is also more about the differences in how Dunlop and Talalay “feel” and respond in post #7 here.
Phoenix