The fundamental science behind stretch blow molded polyethylene terephthalate (PET) has advanced considerably in its quarter-century history. Throughout California and the surrounding areas, the use of clear PET water bottles has grown significantly. We now have a far better understanding of the particulars involved in the successful production of PET containers, which display excellent performance at commercially feasible costs.
More than two decades have passed since the first stretch blow molded polyethylene terephthalate (PET) container was made. In filling the demand for inexpensive, high-performance, resealable containers to package food, personal care, and other products, biaxially oriented PET, in particular, has won great acceptance from consumers.
Bottle Grade PET
When all other considerations are equal, a container with a unique proprietary shape offers more in the way of shelf appeal than one with a plain appearance. However, uniquely shaped containers, as attractive as they may be and as popular as they are in California, can sometimes compromise other interests of the consumer or manufacturer. Such shapes often have variable contours that may evoke geometric yielding under lower carbonation levels and lower external forces, or cross sections that deviate from a circular geometry and create additional surface area. For instance, a bottle with a square cross section has 1.128 times the surface area of a bottle with a circular cross section, assuming equal volume and height.
The introduction of additional surface area, without an increase in bottle mass, results in lower wall thickness per unit volume, ultimately inducing carbonation loss. It is important to learn about plastic and materials used in our everyday products. Moreover, undesirable material distribution and nonuniform orientation are a consequence of complicating the stretch blow process. This only magnifies the detrimental effects on the container’s physical properties.