Natural rubber, a vital natural resource for modern economies, is completely dependent upon tropical cultivation of the Para rubber tree (Hevea brasiliensis). Guayule (parthenium argentatum) is currently being promoted as a domestic al- ternative to imported Hevea NR.
Guayule rubber (GNR) particle cores retain flexibility below the material's ap- parent glass transition temperature, whereas Hevea rubber particles do not. This property, so far unique to guayule, could prove to be a valuable attribute for cold temperature, high performance natural rubber products.