Styrofoam is a mass noun, it is already plural.
It is most often encountered as an adjective - i.e. a Styrofoam mug, a Styrofoam container ... and these do not have a plural just as there is no plural for "big" in 10 big mugs or 20 big containers, we just say 10 Styrofoam mugs, 20 Styrofoam containers.
The plural form of plastic is plastics.
The plural form of building is buildings.
The plural form is technologies.
The plural form for the noun 'material' is materials.
The plural form of system is systems.
The noun 'Styrofoam' is an uncountable noun as a word for a substance.Some uncountable nouns for substances use a plural form exclusively for 'types of' or 'kinds of''. However, I don't know if there is more than one kind of Styrofoam.
Styrofoam is a form of polystyrene - (C8H8)n.
There is no plural form. Do and Do not are verbs
The plural form of him, her, or it is them. (objective pronouns)
Bridges is the plural form of bridge.
The plural form of "is" is "are."
The plural form of "was" is "were."
The plural form of "I" is "we."
"Groceries" is the plural form of "grocery."
"Beliefs" does not have a plural form, as it is already plural. Beliefs is the plural form of belief.
The plural form of mouth is mouths. The plural form of month is months. The Mounth is a range of hills in Scotland and does not have a plural form.
The plural form of the demonstrative pronoun 'that' is those.