food safe plastics are nylon and pet. the problem is that a 3d print is not waterproof for the most part so liquids work their way in and can grow bacteira. for food contact i would limit it to dry foods. like you said popcorn and things like that. as for acetone, that will flash off and nothing will be left behind. how long that takes varies with environmental conditions and application. usually 24 hrs is a safe bet. acetone isnt that crazy hazardous anyway. flammable yes but from a heath standpoint its about one of the safest solvents. hell your body actually produces acetone on its own.