Originally, there was only natural rubber – until the large-scale technical production of synthetic rubber succeeded at the beginning of the twentieth century. However, natural rubber still has unrivalled mechanical and dynamic properties, which is why most natural rubber is still used in the tyre industry today.
Natural rubber, formerly simply called caoutchouc, also known as gum elasticum or resina elastica, is a rubbery substance found in the latex of many different rubber plants. The rubber-bearing latex is usually present as a milky liquid, but it can also be present in semi-solid form in the plants.
Washing and coagulation with acetic or formic acid yields the solid rubber, which is pressed into skins or dried. For preservation, the rubber is either smoked (smoked sheets) or chemically treated, resulting in pale-coloured skins (pale crepes).
Due to increased quality requirements, technically specified natural rubber grades (TSR) are used, which must meet certain purity requirements, e.g. SMR Standard Malaysian Rubber.
To produce TSR, the coagulated and washed latex is processed into crumbs (granules?), dried and compressed into bales. The rubber obtained in this way is therefore still plastic, because it is uncrosslinked and also contains no crosslinking chemicals.