Polyethylene Coating: A thin layer of polyethylene on either side offers toughness. The outer layer guards the look and printing, though the internal layer acts being a sealant, earning the carton totally leakproof. The initial patents for food paperboard containers day back again to the beginning of the final century. https://www.diigo.com/item/note/b5sxz/pq9y?k=67d2da1967c1a3387dbfae19f2467b09