The Pressure That Soda Exerts on a Bottle
If you leave a glass of soda out, it will quickly lose its carbonation and go flat. The carbon dioxide gas must be forced into the soda at pressures up to 8,300 kilopascals, or 1,200 pounds per square inch. The finished soda doesn’t exert that much pressure on the bottle, though. At room temperature, the pressure in a bottle of soda is somewhere between 276 and 379 kilopascals, or 40 to 55 pounds per square inch. Heat makes gasses expand, increasing the pressure, so a bottle of pop in a hot car can get as high as 689 kilopascals, or 100 pounds per square inch.
Plastic Bottle Design
Most two liter bottles are made of polyethylene terephthalate plastic, or PET, and designed to hold carbonated beverages. The thickness of the plastic and the shape of the bottle both contribute to its resistance to bursting. Quality control measures include pressure testing, as well as checking for leaks and cosmetic flaws. Most two liter bottles begin to fail at pressures around 1,034 kilopascals, or 150 pounds per square inch. The pressure at which the bottle will burst is more than it would normally encounter during packaging or normal use.