The bags normally used for potato chips are laminated from typically about four layers, one of which is a vacuum coating of aluminum and another of which is polyethylene terephthalate which has been strained to work-harden it, and hermetically sealed with industrial machinery that heats the bag to the melting point of its innnermost layer, typically with an inert atmosphere inside. Potato-chip bags are probably the most sophisticated packaging used for any food you see routinely.