Why are beverages in aluminum and glass containers retain their carbonization for longer time, whereas those in two-liter plastic bottles “go flat” within a few months?

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One common item that presents some interesting material property requirements is the container for carbonated beverages.

The material used for this application must satisfy the following constraints:

(1) Should act a barrier to the passage of carbon dioxide, which is under pressure in

the container;

(2) Should be nontoxic, unreactive with the beverage, and, preferably be recyclable;

(3) Should be relatively strong, and capable of surviving a drop from a height of several feet when containing the beverage;

 (4)Should be inexpensive

 (5) if optically transparent, retain its optical clarity.

(6) capable of being produced having different colors and/or able to be adorned with

 decorative labels.

All three of the basic material types—metal (aluminum), ceramic (glass), and polymer (polyester

plastic)—are used for carbonated beverage containers .

Material	Point 1	Point 2	Point 3	Point 4	Point 5	Point 6
Metal (aluminum)	very good barrier to the diffusion of carbon dioxide	Nontoxic Unreactive Recyclable	relatively strong (but easily dented)	expensive to produce	cans are optically opaque	labels may  be painted  onto its surface
ceramic (glass)	impervious  to the passage of carbon dioxide w.r.t Aluminum	Nontoxic Unreactive Recyclable	allow cracks and factures easily, Heavy	Inexpensive in comparison to Aluminum	optically transparent	labels may  be painted  onto its surface
polymer (polyester plastic	more  impervious to the passage of carbon dioxide w.r.t  the aluminum and glass	Nontoxic Unreactive Recyclable	relatively strong than glass, light	Cheapest	optically transparent and optically opaque	labels may  be painted  onto its surface

Red: -ve point
Green: +ve point

All three of the basic material types—metal (aluminum), ceramic (glass), and polymer (polyester plastic)—are used for carbonated beverage containers .All of these materials are nontoxic and unreactive with beverages. In addition, each material has its pros and cons. For example, the aluminum  alloy is relatively strong (but easily dented), is a very good barrier to the diffusion of

carbon dioxide, is easily recycled, beverages arecooled rapidly, and labels may be painted onto itssurface. On the other hand, the cans are opticallyopaque, and relatively expensive to produce. Glassis impervious to the passage of carbon dioxide, isa relatively inexpensive material, may be recycled,but it cracks and fractures easily, and glass bottlesare relatively heavy. Whereas the plastic is relativelystrong, may be made optically transparent,is inexpensive and lightweight, and is recyclable, it is not as impervious to the passage of carbon dioxide as the aluminum and glass. For example, you may have noticed that beverages in aluminum and glass containers retain their carbonization (i.e., “fizz”) for several years, whereas those in two-liter plastic bottles “go flat” within a few months.