PETpla.net Insider 03 / 2016

CAPPING / CLOSURES 39 PET planet insider Vol. 17 No. 03/16 www.petpla.net Figure 4.18 Sports drinks cap in cross- section In glass bottles, for example, prac- tically all the oxygen ingress into the package can be attributed to the clo- sure as glass does not allow oxygen inside the package. Oxygen may enter the package through the wall of PP or HDPE and the liner, the space between the bottle neck and the clo- sure wall, and the interface between the closure seal and the bottle. There are several factors that contribute to the performance of a closure with respect to barrier performance:  Headspace: This is the space between the top of the liquid and the bottom of the cap. The larger the headspace, the more oxygen is trapped, and it can interact with the product. Most juice bottles are now filled brimful to avoid any oxygen. Other products are topped off with a shot of nitrogen replac- ing headspace air.  Closure size:The larger the clo- sure, the more the oxygen trapped inside the headspace. Additionally, the larger surface area allows for more opportunities for oxygen to migrate into the bottle.  Type of seal: Whenever an end user is concerned about oxygen ingress, the best seal for the type of neck should be chosen regard- less of other considerations, e.g., price!  Type of liner: Besides the mechan- ical seal, liners have been devel- oped that incorporate several func- tions in a multilayer package. 4.3.5 Multilayer liners A lot of development work has been done to make multilayer liner materials that not only seal the bottle but also use passive and active components against oxygen ingress whether it resides in the headspace or migrates from the outside. Experiments have shown that around 80% of the oxygen ingress can be attributed to the bottle side- wall and 20% to the closure. Closure design plays, therefore, a crucial role in protecting the product. There are commercial closures with eight layers of various materi- als. Usually EVA is present for the mechanical seal. A passive barrier may be provided with EVOH or Nylon. This is necessary as the PP or HDPE wall is permeable to oxygen over time. For carbonated beverages such as beer, the passive layer increases carbona- tion retention up to five times. As an active component an oxygen scav- In cooperation with In cooperation with IMDvista CLDP Closure Digital Print Full flexibility in formats & design with integrated vision system. IMDvista / PackSys Global SDL Inspection, Slitting and Folding Complete downstream equipment for closure production. IMDvista PECO LUX Inline Preform Process Monitoring In perfect combination with IMDvista Offline Offline Preform Sorting. www.imdvista.ch CLOSURE, PREFORM, BOTTLE and BARRIER Testing New SMART Line | Swiss Made