Managing Crystallinity to improve quality and performance of PET bottles

Agr International, Inc., a leader in the field of PET bottle material distribution management, has recently announced that it is in the process of commercializing the technology for PET bottle crystallinity management, and will market it under the trade name “CrystalView™”.    According to Mr. Georg Wolfe, Agr’s Chief Technical Officer, CrystalView™ will be incorporated into Agr’s Process Pilot® automated blowmolder management system and when released, will provide the means to produce PET bottles with consistent crystalline structure while maintaining desired thickness distribution.

At a recent industry conference, Mr. Wolfe provided an update on the progress his team has made over the several months. In his presentation, he detailed the results from extensive studies that his team has done on the relationships that affect the crystalline structure of PET bottles as they are produced, using both hot and chilled mold production process.

Asked about the value of managing crystallinity, Mr. Wolfe commented that for CSD bottles manufactured using the cold-mold process, “our experiments showed that improved time to stress cracking is a function of the temperature achieved in the stretching process as shown in Figure 1. Time to stress crack improved significantly by maximizing orientation in the cold process.” Additionally, he stated, “By optimizing crystallinity/orientation there was no down side.  Our findings showed that bottle performance factors either improved or stayed well within the required performance specifications.  The CrystalView™ process provides stronger, better performing containers and enables the bottle producers to further light-weight with minimal risk. “The CrystalView™ product will take advantage of the extensive knowledge base created over the last two years of our research and development effort,” stated Wolfe.  Data from the experiments (DOE) are the foundation for the sophisticated blowmolder control algorithms incorporated into the CrystalView™ product to actively manage crystallinity within the reheat/stretch-blow process.

Mr. Wolfe pointed out that adjusting crystallinity is only part of the equation. The process objective to adjust crystallinity while maintaining proper material distribution is almost impossible without the assistance of technology.  “Agr’s Process Pilot® blowmolder management system precisely controls and maintains material distribution at a specified thickness to within ~0.0025mm. When coupled with CrystalView™, we will have the capability to fine tune and control the process to optimize crystallinity and maintain material distribution at optimal levels consistently for every bottle in a complete production run.”  This is significant, especially with the push to take light weighting to the limits.  The benefits are considerable.  “If you can actively manage crystallinity and at the same time control thickness, you have much greater control over the bottle attributes that affect performance, especially with very light bottles,” concluded Mr. Wolfe.

Agr’s Process Pilot automated blowmolder control system has been on the market for several years and has amassed a significant global install base of major bottle converters and self-manufacturing brand owners. The Process Pilot product has proven to be a vital tool in the production of light weight bottles, while improving overall bottle performance and quality.  Agr’s Process Pilot automated blowmolder control system is unique in that it manages the blowmolder based on direct bottle measurements, on every bottle produced.  By controlling the blowmolder based on direct feedback from bottle measurements rather than just blowmolder performance indicators, the Agr system can ensure that the final product has the desired quality and performance attributes in spite of environmental, blowmolder or material variations that occur during the production process.