NATURAL RUBBER

Natural rubber is an elastomer (an elastic hydrocarbon polymer) that was originally derived from a milky colloidal suspension, or latex, found in the sap of some plants. The purified form of natural rubber is the chemical polyisoprene which can also be produced synthetically. Natural rubber is used extensively in many applications and products as is synthetic rubber. The entropy model of rubber was developed in 1934.
The major commercial source of natural rubber latex is the Para rubber tree (Hevea brasiliensis), a member of the spurge family, Euphorbiaceae. This is largely because it responds to wounding by producing more latex.
Other plants containing latex include Gutta-Percha (Palaquium gutta), rubber fig (Ficus elastica), Panama rubber tree (Castilla elastica), spurges (Euphorbia spp.), lettuce, common dandelion (Taraxacum officinale), Russian dandelion (Taraxacum kok-saghyz), Scorzonera tau-saghyz, and Guayule (Parthenium argentatum). Although these have not been major sources of rubber, Germany attempted to use some of these during World War II when it was cut off from rubber supplies. These attempts were later supplanted by the development of synthetic rubbers. To distinguish the tree-obtained version of natural rubber from the synthetic version, the term gum rubber is sometimes used