In flexible packaging, aluminum foil (hereafter foil) is the benchmark for barrier substrates when the requirements are protection against gases, moisture, and light. Throw in protection against grease, oil, and (many) chemicals and foil's preeminence is further established. No wonder foil has been a component in the packaging of foods, beverages, medicines, pharmaceuticals, cosmetics, and luxury items, among other categories.
As formidable as foil is, the competition is not deterred (to the good fortune of end-users). For the most part, a particular competing material might not replicate all of foil's properties but instead compete against one or more of those properties that are deemed most important to a targeted industry or application.