there are many kinds of “rubber”
they have different melting points
gives the melting point of “natural rubber” as 350 deg F
melting point of elastomers is sometimes difficult to define as elastomers often get softer (or less viscous) with temperature rise and the change from “solid” to “liquid” is gradual
sometimes the term “pour point” is used to refer to the temperature where the viscocity of the material becomes low enough (liquid enough) to “pour”.
some elastomers, in air, will decompose/burn before they melt
Melting Point Of Rubber