Soft Natural Rubber Sheets

Experiments and results. From concepts and experimental data outlined above, we have studied the rebound of a polished rigid ball (steel ball) on the flat and glass-smooth surface of a soft natural rubber sample (22). The steel ball was kept in position under a glass sheet with the help of a magnet. The vertical distance between the bottom of this ball and the cleaned surface of a thick (16mm) and soft natural rubber block was measured accurately. Six steel balls (from ball bearings) of diameter 2, 3, 4, 6, 8 and 10 mm and four indenters made from steel balls in order to obtain, on the one hand, three masses (0.173, 0.262 and 0.327 g) with the same diameter (4 mm) and, on the other hand, three radii of curvature (3, 4 and 6 mm) with the same mass (0.262 g) were employed. They were dropped onto the horizontal, plane, smooth, cleaned (with pure ethanol) and dried surface of the thick natural rubber sample. 

PLY is a sheet lining consisting of a layer of hard natural rubber sandwiched between two layers of soft natural rubber,... 

The type of sheet most frequently used today is still natural rubber. It may be compounded with a number of different modifiers or fillers, depending on the service for which it is intended, varying from soft to hard, and from a uniformly calendered sheet to laminates of soft and hard or laminates including fabric-reinforcing. 

While sheeting in a calender, the stock must be soft so that they penetrate the interstices of the layers easily, and tacky so that ready adhesion between plies is ensured. Inevitably, such stocks can give rise to handling problems and call for compromise compounding . Natural rubber and Neoprene rubbers compounded with resins such as coumarone indene or petroleum resin produce good sheeting stocks. 

Ebonite bonding The adhesive layer in this case is unvulcanized ebonite (or hard rubber , USA) applied to the metal either as a solution or as a thin sheet" Ebonite contains 30-50 parts sulphur per hundred parts of rubber (phr), whereas soft rubber seldom has more than 3 parts phr of this vulcanizing agent. The method dates back to the mid-nineteenth century and is most closely identified with natural rubber, but can be applied to other diene-type elastomers, including nitrile rubber. 

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