Expanded rubber

A form of cellular rubber in which the cells are non-intercommunicating, self-contained units. It has low thermal conductivity. Expanded rubber is buoyant and does not absorb water and was therefore initially used in both the soft rubber and ebonite forms in the construction of lifebuoys and other marine buoyancy equipment. The most commonly used polymer is now polyurethane for both flexible and rigid systems. 

There are four basic types of expanded rubber ... 

Expanded Rubber This class of product has an essentially closed cell structure. These products are most usually formed by moulding or extrusion processes and have a solid outer skin around the cell structure. Organic blowing agents are used for this type of process. 

Unlike ADCA, which is affected by moisture, OBSH can be used in alkaline latex conditions. In these conditions it generates nitrogen and forms acidic decomposition products which coagulate or gel the latex compound thus producing an expanded rubber product. 

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. 

ASTM D 1056-78, Specification for Cellular Materials - Sponge or Expanded Rubber, American Society for Testing and Materials Philadelphia, PA, 1982. 

ASTM D 1056-85, "Standard Specification for Flexible Cellular Materials—Sponge or Expanded Rubber," in Vol. 09. 02, Annual Book of ASTM Standards. 

ASTM D 1056-85 Standard Specification for Flexible Cellular Materials Sponge or Expanded Rubber, 14 pp (DOD Adopted) (FSC 9320) (MR) (Comm-11)... 

These pads are for cushioning interior surfaces of mUitary vehicles to protect personnel from injury. There are two types. Type I -Facial Contact, and Type II - Head and Body Contact, with five classes, including closed-cell expanded rubber and cellular vinyl elastomer. 

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 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). 

The curing is carried out either freely using hot or steam or in a mold that is only partially filled with the molding compound. Synthetic rubbers, particularly SBR, are preferred as they allow precise control over level of viscosity required for obtaining consistent product quality. The sponge and expanded rubber products include carpet backing, sheets, profiles, and molding. 

Coupled Changes The bathtub can help us once again to understand another aspect that we will need to deal with later on. In the above, we discussed the special features resulting when the same entity (measured by the same quantity water volume) of a system can be exchanged with its surroundings simultaneously via various paths. Let us now replace the person in the tub with an expandable rubber... 

Rubazote Natural rubber Expanded Rubber, Great Britain... 

Fig. 8. Hypopigmentation of the dorsal hand believed to be due to an allergic reaction to hydroquinone. Note the patchy involvement which, in some areas, is almost confetti like. The patient was found to be allergic to the offending glove and to only hydroquinone on an expanded rubber tray. The manufacturer would not verify the glove s components. Reproduced with the permission of Donald V. Belsito, M.D., Division of Dermatology, University of Kansas Medical Center, Kansas City, KS...

A unique process for chemical stabilization of a cellular elastomer upon extrusion has been shown for ethylene-propylene rubber the expanded rubber obtained by extrusion is exposed to high energy radiation to cross-fink or vulcanize the rubber and give dimensional stability (113). EPDM is also made continuously through extrusion and a combination of hot air and microwaves or radio frequency waves, which both activate the blow and accelerate the cure. 

The technology to manufacture sponge or expanded rubber is not so critical, but long retention of product quality is very difficult, unless a strict process control system is adopted. This paper highlights a process control system to be followed at all stages in production of expanded rubbers. 

D1056 Flexible Cellular Materials—Sponge or Expanded Rubber 6916-1... 

Expanded Rubber 8 Plastics Ltd (BXL) 675 Mitcham Road Croydon CR9 3AC Surrey 01 -684 3622... 

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