polyfoam vs PU

polyfoam and PU both are nouns.

Word	Noun	Adjective	Verb	Adverb
polyfoam	Yes	No	No	No
PU	Yes	No	No	No

As nouns, PU is a hypernym of polyfoam; that is, PU is a word with a broader meaning than polyfoam:

polyfoam: a foam made by adding water to polyurethane plastics
PU: any of various polymers containing the urethane radical; a wide variety of synthetic forms are made and used as adhesives or plastics or paints or rubber

Other hypernyms of polyfoam include polyurethan, polyurethane, PUR.

polyfoam (noun)	PU (noun)
a foam made by adding water to polyurethane plastics	any of various polymers containing the urethane radical; a wide variety of synthetic forms are made and used as adhesives or plastics or paints or rubber