Dependance of the shelf-life of carbonated soft drinks from PET performances as required by "the Coca Cola Company"

PET (Polyethyleneterephthalate) is one of the most important resins used for the package of carbonated water and soft drinks. Preforms are intermediate products which are manufactured in a wide range of designs and colours by injection moulding of PET. The cost of the resin covers a high percentage in the overall cost of the produce, especially due to the recent increments on the price of petroleum, from which PET is derived. As a consequence, according to the numerous standards fixed by " The Coca-Cola Company (R)", Sibeg S.r.l. decided to test a new cheaper PET preform which was suggested by a possible new supplier. The experiment consisted in the comparison of the main performance characteristics of the old PET bottles in comparison with the ones obtained from the new preforms. " The Coca-Cola Company (R)" requires specific test procedures to authorize a new package. Among the methods used to test new materials, the gas-barrier properties have a main importance as they are directly linked with the shelf-life of the bottled produces. Shelf-life of carbonated soft drinks is determined by the internal CO2 level, and limits for this parameter are different for different the types of beverages. Therefore a material with higher CO2-barrier property would be effective in extending the shelf-life of carbonated drinks. Results evidenced a similar behaviour of the two materials tested for what concerns the characteristics of the bottles (dimensions, appearance, distribution of the material, stress cracking test), showing, in particular, comparable CO2 internal pressure after 12 weeks of storage.