PETpla.net Insider 10 / 2020

BOTTLE MAKING 36 PETplanet Insider Vol. 21 No. 10/20 www.petpla.net Fig. 6.1: Standard preform for carbon- ated beverages. The ring underneath the thread, called neck support ring (NSR) or transition ring, is used throughout the blow moulding machine to hold the pre- form in place. 6.1 Process overview While individual features differ between different types and brands of machines, they all load cooled, injec- tion-moulded preforms, reheat them in an oven section, transfer them in a blow mould clamp, and stretch and blow them (for differences to the single-stage process see Chapter 8) (Fig. 6.1). Several questions arise that will be answered in this section of the book:  What is the optimal blowing tempera- ture?  What is the optimal heat profile in the preform wall?  How does polyethylene terephthalate (PET) absorb infrared energy and how can this knowledge be used to improve bottle properties?  How do material properties and stretch ratios affect blowing behav- iour?  How can optimal wall thickness distri- bution be achieved?  What amount of oven cooling should be used?  How does blow air timing affect bottle properties? These are questions that machine operators are faced with daily and often a compromise between machine capabilities, output requirements, and bottle properties has to be found. It is therefore paramount that processors understand all relevant process char- Stretch Blow Molding, part 13 Fundamentals of the Blow Process by Ottmar Brandau Ottmar Brandau has newly revised his book “Stretch Blow Molding”, first published by hbmedia / PETplanet Publisher, and now re-issued in a third edition under the Elsevier Imprint. PETplanet Insider is publishing extracts from successive chapters in a serie of articles.