PETpla.net Insider 07+08 / 2015

Please order your copy at the PETplanet insider book shop: https://www.petpla.net/books Bottles, Preforms and Closures A Design Guide for PET Packaging Second Edition by Ottmar Brandau € 115,00 180 pages © Copyright Elsevier 2012 CAPPING CLOSURES 33 CAPPING CLOSURES 33 PET planet insider Vol. 16 No. 07+08 * This article was published in Bottles, Preforms and Closures, Ottmar Brandau, Chapter 4.2 Copyright Elsevier 2012 ing conditions, and most importantly filling temperatures how strong a neck the bottle must have to withstand all requirements. Fig. 4.5 Necks for hot-fill bottles feature thicker walls and are therefore heavier than necks for other bottles. An interesting solution to some of the problems men- tioned above is to thermally crystallise the neck. This is done by heating the neck in a specialised machine to a temperaturerange where PETcrystallises rapidly and then letting it to cool down slowly. Thermally induced crystals,the so-called spherulites, are large enough to refract light and the refore appearwhite to our eyes.These crystals are stronger and especially more heat resistant than amorphous PET, and crystallised necks can be designed thinner and at a lower weight (Fig. 4.6). Fig. 4.6 Crystallization of the neck can save weight. Crystallised necks are far more popular in Asia than they are, for example, in North America. There are sev- eral reasons for this, most notably that the initial patent owner Yoshino Kogyosho granted licenses to only a small number of US companies. There are also a number of products that always need the crystallised neck, such as carbonated juice without preservatives, but these are not popular in North America. Companies here have worked around the problem by lowering filling temperatures with increased hygiene to the point where a crystallised neck is of less importance. SDWHQWV UHVHDUFKHUV DQG WHFKQLFLDQV LQVWDOOHG SODQWV EUDQFKHV ZRUOGZLGH ,I ZH KDGQêW JRQH VR IDU ZH ZRXOGQêW EH VR QHDU <RXU IXWXUH VHHQ IURP QHDU