PETpla.net Insider 03 / 2016

CAPPING / CLOSURES 38 PET planet insider Vol. 17 No. 03/16 www.petpla.net Different applications, neck finishes for various, part 6 Closure for PET bottles PETplanet insider is publishing extracts from successive chapters of Ottmar Brandau’s “Bottles, Preforms and Clo- sures”, which was published by hbmedia. A newly revised version is reissued under the Elsevier imprint. The flow through the open closure must be large enough to accommo- date the drinking behavior of users. Obviously, it can never match a fully open 28- or 30mm neck with the clo- sure unthreaded. However, today’s sports closures go through flow meas- urements, and a flow of around 2l/ min with a 20kg load seems to be a standard. For flip-tops, the distance between the opened hinged-top and the user’s lips is also important. If the hinge is too close to the cap it gets in the way. Around 30mm centre-to-centre cap and open top seem to be a minimum, with higher values of course being even better. Fillers and brand owners are also looking for caps that can be sterilised with a liquid agent to avoid costly irradiation sterilisation, and push–pull designs typically do not lend them- selves easily to this because rinsing liquid gets trapped in the crevices of the cap. 4.3.4 Closures and shelf life There are many products now filled in plastic bottles that are sensi- tive to oxygen ingress. The effects are different depending on the product. Juices may oxidise, lose vitamin C, and change colour. Horseradish may turn brown and become unsightly. Beer is also a very sensitive product that loses organoleptic properties when exposed to very small quantities (>5ppm) of oxygen. Although most of the work to improve the barrier properties of PET packaging is done on the bottles with multilayer and coating systems as well as improved materials, the closure plays an important role in the overall barrier performance of the package. Figure 4.17 This innovative flip-top design combines ease of opening and reclosure with child safety. The relatively long distance of 37.5mm between the center of the cap body and the center of the opened hinged- top together with a 180° opening angle contributes to a comfortable drinking experience for the consumer. (Pictures courtesy of Bericap). Another popular sports closure is a flip-top cap. Here the spout is moulded into the base and a hinged- top covers it. The top can then be flipped open with a thumb, thus allow- ing the one-hand operation. Over the years, several design criteria, many of them not obvious at first, have been developed. The dust cover has several dis- advantages. For once, it has to be thrown away and so leads to a pol- lution issue similar to the rip-loop on metal cans. The cover may also pose a choking hazard for young children and therefore has to be large and long enough so that it does not block a child’s throat. The opening torque for both the dust cover and the push or flip fea- ture must be small enough to allow weaker hands easy access but strong enough to hold the pieces in place during transport and use or when very small children try to pry them off. Easy reclosing of dust cover and spout or flip-top is of course also important for the overall functionality. Opening and closing forces between 20 and 30N allow children to handle the closure on their own and are target values.