Closed cell sponge rubber

Processes and ingredients used in the manufacture of rubber latex foams and open- and closed-cell sponge rubber are described. 11 refs. 

Cellular rubber may be described as an assembly of a multitude of cells distributed in a rubber matrix more or less uniformly. The cells may be interconnected (open cells) as in a sponge or separate (closed cells). Foam rubber made from a Uquid starting material such as latex, described earKer, is of open-cell type. Cellular products made from solid rubber are commonly called sponge (open cell structure) and expanded rubber (closed cell structure). 

Until 1920, the only flexible foam available was the natural sponge, but chemically foamed rubber and mechanically foamed rubber latex were introduced before World War II. These foams may consist of discrete unit cells (unicellular, closed cell), or they may be composed of interconnecting cells (multicellular, open cells) depending on the viscosity of the system at the time the blowing agent is introduced. Over 1.5 million tons of foamed plastic is produced annually in the United States. 

In the case of cellular rubber, the ASTM uses several classifications based on the method of manufacture [11,12]. Cellular rubber is a general term covering all cellular materials that have an elastomer as the polymer phase. Sponge rubber and expanded rubber are cellular rubbers produced by expanding bulk rubber stocks, and are open-cell and closed- cell, respectively. Latex foam rubber, which is also a cellular rubber, is produced by frothing a rubber latex or liquid rubber, gelling the frothed latex, and then vulcanizing it in the expanded state. 

AMS 3193-B-85 Silicone Rubber Sponge, Closed Cell, Medium, Extreme Low Temperature, 6 pp (DOD Adopted) (FSC 9320) (AS)... 

MIL-R-46089B(MR) Rubber Sponge, Silicone Closed Cell, 12 February 1981, 7 pp (FSC 9320) (MR)... 

Covers only sponge rubber items, including chemically blown or expanded-rubber items having either open or closed cells. Also includes cellular products made from chemically or mechanically foamed latices or liquid elastomers. Provides word descriptions and photographs of defects. 

Cellular forms of neoprene are used primarily for gasketing, insulation, cushioning, and soimd and vibration damping. This material provides compressibility not foimd in solid rubber but still retains the advantageous properties of neoprene. It is available as an open-cell sponge, a closed-cell neoprene, and a foam neoprene. 

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