buna vs synthetic rubber

buna and synthetic rubber both are nouns.

Word	Noun	Adjective	Verb	Adverb
buna	Yes	No	No	No
synthetic rubber	Yes	No	No	No

As nouns, synthetic rubber is a hypernym of buna; that is, synthetic rubber is a word with a broader meaning than buna:

buna: made by polymerizing butadiene
synthetic rubber: any of various synthetic elastic materials whose properties resemble natural rubber

Other hypernyms of buna include rubber.

buna (noun)	synthetic rubber (noun)
made by polymerizing butadiene	any of various synthetic elastic materials whose properties resemble natural rubber