PETpla.net Insider 01+02 / 2014

BOTTLE MAKING 22 PET planet insider Vol. 15 No. 01+02/14 www.petpla.net Looking into the crystal ball At PETnology 2013, Agr International Inc. unveiled its new approach to the management of crystallinity in the manufac- ture of PET containers. Mr. Georg Wolfe, Agr’s Chief Tech- nical Officer, discussed the topic of Total Process Control and the molecular orientation in the re-heat stretch and blow process. A key point of his presentation was crystallinity levels in PET bottles. Mr. Wolfe detailed the reheat stretch blow process and illustrated how certain factors affected crystal- linity levels of a finished bottle. He said that the management of preform energy distribution during the heat- ing process has a significant effect on both crystallinity levels and material distribution. Wolfe’s findings are the outcome of a series of experiments (DOE) that were structured to gain a statis- tical understanding of the relation- ships between preform and mould temperature (energy), the resulting container crystallinity and its effects on container performance. Data gen- erated by the experiments showed that, across a broad range of con- tainer mould processing tempera- tures, crystallinity is closely linked to preform energy levels and that it can be actively managed by adjusting the preform temperature set point. “It is extremely important for the preform to have the right amount of energy at the right location to blow a proper bottle . . . especially in very light weight bottles,” claims Wolfe. “The experimental findings showed that, if you get the correct level of energy in the right places of the pre- form, you can manage material distri- bution as well as optimising the level of crystallinity.” Real world applications Mr. Wolfe announced that Agr International is in the process of incorporating crystallinity manage- ment into its Process Pilot automated blowmoulder control system. This will effectively utilise the relationship between preform energy and crys- tallinity to manage not only material distribution, but also control the level of crystallinity of production bottles. This capability will make it possible to fine tune and control the process to maintain crystallinity and material distribution at optimal levels, consist- ently, for every bottle in a complete production run. Agr’s Process Pilot system works in conjunction with the reheat stretch blowmoulder to proactively manage and maintain container material distri- bution to within ~0.01mm of specified thickness. This is accomplished by continuously monitoring every bottle for material distribution, analysing minute changes and adjusting the blowmoulder controls to maintain pre- defined distribution levels. The addition of crystallinity man- agement takes this one step further. Mr. Wolfe explained that the theory behind the Process Pilot is based on the continual management of material distribution during bottle production.