Crushed Vs Compressed Foam
The success of Diving Unlimited International’s (DUI’s) Crushed Foam CF200 suits has spawned a number of imitations. With the advent of these imitations and their confusing marketing claims, the confusion has grown to the point that it is self perpetuating. Poorly researched articles have just added more spin to the confusion. The objective of this paper is to provide an overview of what DUI’s patented crushed foam is, and how its development came about. It is not that these imitations do not work to some degree. It is that these suits attempt to ride on the success of DUI’s CF200 series suits. In many cases, the purchaser of one of these imitations expects more from the suit than it is capable of providing. The poor performance of these suits not only blemishes the imitation’s reputation but the reputation of DUI’s CF200 series suits because the customer is not aware of the real differences. HISTORIC PERSPECTIVE The development of Compressed Foam (CF) suits
stemmed from DUI’s effort to develop a material that
would overcome the shortcomings of the available
drysuits at the time. The most common material in
use for making drysuit, then and now, is closed-cell
neoprene foam a.k.a. wetsuit material. The second
and less common materials used then were rubber-
coated fabrics or sheet rubber. At the time, durability
was a common problem in all these materials.
Drysuits made from rubber-coated textiles, or sheet
The down side of these rubber shell suits was that the
materials commonly used did not have any real
stretch. The lack of stretch requires that the suits
need to fit very loosely to allow for a full range of
motion. The rubber-coated fabrics that did stretch
developed pinhole leaks with repeated stretching. An
additional disadvantage of these suits was that the
outer rubber surface, which is the part of the suit that
maintains the diver dry, was subject to cuts and DEVELOPMENT OF THE CF PROCESS DUI undertook the development of a new drysuit
material, in part to respond to the U.S. Navy’s Diver
Thermal Protection System Program. The Navy’s
program required a shell drysuit that was both
durable and swimmable. One of the lines of the
investigation that DUI undertook was to look at the
advantage of permanently compressed foam. Why
permanently compressed foam? DUI’s experiences,
with the impact of saturation diving on closed-cell
foams provide the lead need. The challenge was to
find a method that would permanently compress the These insights lead to a series of experiments. The
experiments involved four major factors:
compression rate, decompression rate, gas mix and
exposure, and temperature profiles. The key to the The Navy Clothing and Textile Research Facility’s analysis of this material concluded that it was a new class of material. (Audet) Based on this analysis the US Patent Office issued two US Patents: 4,882,785 Underwater Diver’s Dry Suit Having A Permanently Compressed Cellular Layer 4,778,643 Method of Treating An Underwater Diver’s Suit These patented processes culminated in the development the CF200 material and the CF200 series suit. The success of the CF200 series suits has resulted in a series of imitations. The imitations utilize thin neoprene foam and plays on words, to imply that compression or crushing is used in their manufacture. This has even spread to the foam manufacturers. The Yamamota Corporation produces Type 88 Hyper-Compressed foam, which in reality has a density of 13.4 lb/ft3 and a very small cell structure. (Yamamoto) The foam rubber used in wet suits typically range in densities from 10-15 lb/ ft3. The reality is that the diver is purchasing closed-cell foam suits, where the thickness of the foam has been reduced. For example the foam thickness has been reduce from 6-mm to 3-mm. Though these thin foam suits do have some advantage in that they function more like shell drysuits with less intrinsic insulation and less buoyancy changes with depth. However, the cell structure of these suits will breakdown with repeated use. WHAT THE IMITATORS FORGOT The imitators have forgotten that if you compress a
sheet of 6-mm foam to a thickness of 3-mm or
smaller, the weight of the sheet of rubber would not
change. The density of the foam would change, for
example, from 10 to 20 lb/ft3 or greater. The weight
of this compressed 3-mm suit would be equal to that
of a 6-mm suit. For comparative purposes neoprene
rubber compounds, that are not foams, have specific
gravities in the range of 1.45, which relates to a CONCLUSION DUI and Abyss are the only manufacturers of suits made with foam in which the cell structure has been permanently removed via compressed or crushed. The CF200 or crushed foam material developed and patented by DUI in 1985 is sill a unique and durable suit material used as a benchmark by many. One can always measure one’s success by the number of imitators. The diver with the imitation 2, 3 or 4 mm suit gains
some incremental advantage in the form of reduced
buoyancy changes with changes in depth. However
these imitations are still subject to pinholing and
other durability issue present in all foam suits. One
cannot simply expect a suit perform at a high level by
attaching comparable name. BIBLIOGRAPY
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The result of this effort was a process by which foam
laminated with nylon on two sides (Fig-4) could be