Cr Neoprene and Cr/SBR/EPDM Neoprene Blends
Commonly referred to as soft stretch neoprene
Most all neoprene sheets are imported from Asia. The sheets are made of 100% CR or a blend of approximately 30% to 40% Chloroprene Rubber and 60% to 70% materials such as SBR (styrene-butadiene rubber) or EPDM (ethylene-propylene-diene-monomer). SBR and EPDM are polymers more familiar to shoe soles, roofing materials and gaskets. The process to create neoprene sheets begins with cooking of the ingredients. Once the CR, SBR and EPDM are cook to a liquid state the CR or CR blend is poured into a mold to air cure. This process creates a very soft material with a great deal of stretch, but at the same time it also reduces the thickness of the cell wall. The thicker the cell wall the more pressure the cell can withstand without losing gas. Because the cell walls of CR neoprene and CR/SBR/EPDM neoprene blends are very thin, they compress more rapidly, reducing thermal insulation.
Some CR neoprene and CR/SBR/EPDM neoprene blends compress to as much as 1/2 their thickness in the first atmosphere of water. The deeper the dive the more compression and less recovery to the original thickness.
CR neoprene and CR/SBR/EPDM neoprene blends will also suffer thickness loss during recovery from very shallow dives of long duration. Thickness loss can be as high as 25% base on 30 dives to an equivalent of 40 feet, with a 24 hour recovery period. When thickness loss occurs, CR neoprene and CR/SBR/EPDM neoprene blends lose their soft, stretchy characteristics making a wetsuit more difficult to put on and take off, not to mention the loss of thermal properties. CR neoprene and CR/SBR/EPDM neoprene blends may completely collapse in as few as 8 to 10 dives in excess of 130 feet. Upon collapsing the neoprene takes on a washboard appearance, exhibiting ripples in the material, especially in the areas of the knees and elbows.
CR neoprene and CR/SBR/EPDM neoprene blends are easily identified by examining a cross section or raw edge of the material. The cross section will look like solid rubber, lacking the porous cell structure of a nitrogen composed or nitrogen blown neoprene. There is virtually no visible cell structure in CR neoprene and CR/SBR/EPDM neoprene blends. When examining a finished wetsuit, it is best to check zipper flaps as most raw edges have been finished with a binding material.