what chemical is use to make floral foam?

what are the chemicals use to make floral foam or packaging foam
also need some detail of the mixture and process
and where to acquire them if ever
what are the chemicals use to make floral foam or packaging foam
also need some detail of the mixture and process
and where to acquire them if ever

and if theres Parts A and B
some detail composition of A chemical
some detail composition of B chemical

i know petroleum is one of the main ingredients