Category: Plant / Production

Profiling PET

By John Peter Koss

For more than 25 years, observations, collaborations and manufacturing projects have witnessed the development, production and use of the PET container.  Returnable glass was phasing out, one-way glass was replacing the “long neck” and the plastic container for beverages was introduced as a viable replacement for both. The introduction required integrated compatibility of resin processes, mold designs and container specifications from economical, practical and mass production viewpoints. Container nomenclature (base, body, finish), container size (64 oz., 32 oz., 20 oz.) and quality control attributes and variables became the bases for specification development.  A brief chronology from resin to finished container will profile PET containers as it happened.

Food products in plastic, a long time issue, surfaced again as resin producers became the source/producer for the new PET bottle. Suffice to say, resin “food grade” purity was developed and provided the injection molding manufacturers with critical raw material. This first step also required mold makers to produce molds that would result in a quality parasson or “test tube” bottle form.  Step two required blow molding the “test tube” bottle form into a finished container. The finished container, in a 64 oz. size, was originally a body/base cup configuration involving different plastics. Base cups, glue and other quality attributes were problems and prompted creation of the current PETaloid container. The one piece container was a major step forward and provided incentive for manufacturers to combine the injection and blowing into an onsite operation with exporting capabilities.

Stabilizing PET bottle configuration was real progress! However, actual quality attributes such as pin holes, pearlescence, haze and finish, all transitioned through major specification development.  This was a major task and brought PET manufacturers and beverage producers together to establish industry wide standards.  Once these attributes were reconciled, a major issue of resin content focused on quality and cost. To what level could resin content be lowered? Would it enhance or hurt container handling?  What were economies of scale in minimizing resin content? These issues continue in the PET container arena today and will for some time.  

Two factors are important to the profile of the PET container. One is size, which started with 64 oz. and now includes a range from 8 oz. to 2 liter.  At one time 3 liter was considered, but the market did not accept this “huge” bottle.  Another factor is container finish which vacillated amongst 28mm, 38mm and other closures. In most cases, aluminum closures were originally used and have given way to plastics to provide a total plastic package. Size and finish will always impact container handling, filling and packaging throughout the production process.  Nevertheless, the PET container is an excellent example of continuous improvement.  

John Peter Koss, a beverage operations advisor, is a licensed registered professional engineer and has 50-plus years of beverage business experience. He can be reached at oleboss@aol.com.

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