PETpla.net Insider 06 / 2017

PREFORM PRODUCTION PET planet Insider Vol. 18 No. 06/17 www.petpla.net 8 PREFORM special The challenge of providing ade- quate product protection increases as package sizes decrease. The rate of gas ingress (or loss) is proportional to the surface area of a package, while the total amount of gas that can be allowed to enter or leave a package is dictated by the product volume. Surface to volume ratio increases as package volumes decrease. This requires packages to have improved barrier properties to support the necessary product shelf life. Market trends, driven by a consumer pref- erence for smaller packages and the ever-increasing need for brand owners to differentiate their prod- ucts on store shelves, suggest that smaller volume packages will become increasingly more common. There are multiple approaches to extending the barrier properties of a PET package and the choice of technology will be dictated by multi- ple factors. Among those factors are the level of required barrier improve- ment, the need to maintain production flexibility, constraints placed by the logistics chain and of course, the total cost to produce. The easiest solution to improving the barrier properties of a traditional PET package is to blend PET at the injection system extruder with one of the many barrier materials available on the market. The resulting blend will have improved resistance to gas permeation (passive barrier) or may even actively trap oxygen molecules (active oxygen scavenger) in the polymer matrix. Not requiring any equipment changes other than the polymer dosing and mixing auxiliaries, this may be an appropriate solution in some situations. At the same time, the simplest solution, as often happens, has serious limitations or even penal- ties. The barrier improvement factor is directly proportional to the amount of barrier material added to the blend. As the additive level is increased, the clarity and transparency of a PET bottle typically suffers, placing a limit on how much improvement can be reached while maintaining the desired package appearance. Even more significant is the barrier material cost penalty of a blend solution and its potential impact on recyclability when compared to a multi-layer package. Bottle coating is another avail- able option to improve the resistance of a monolayer PET package to gas permeation. A thin glass-like coat- ing on the internal surface of a bottle can constitute an effective passive barrier to gas permeation. The coat- ing is applied in a plasma treatment following the blow moulding process. Silicon oxide coating is clear and transparent, while amorphous carbon coating imparts a light yellow tint to a clear package. The effectiveness of such coatings may be limited by the bottle creep, which may disrupt its integrity and lower the net improve- ment of the barrier properties. In Unlocking PET packaging potential with Multi-Layer Technology Multiple layers extend barrier properties by Peter Yankov, Team Leader, Advanced Solutioning Process & Technology, Husky Injection Molding Systems In addition to the functions of containing and dispensing a product, as well as delivering a marketing message to the consumer, a package must provide necessary protection for its content, at least for the duration of the planned shelf life. Some simple examples include the need to keep the carbon dioxide content of a carbonated beverage from escaping, preventing oxygen from reaching sensitive juice and sauce products and limiting exposure to light for dairy applications, including visible, ultra-violet or infra-red. While PET provides a better gas barrier than many other packaging polymers, it is still permeable and some gas exchange takes place between the content of a package and the environment, often becoming the factor that limits product shelf life. Barrier requirements become more challenging as package volumes decrease. Husky’s Multi-Layer Technology positions the barrier exactly where it is needed. Pictured left is a biased black layer positioned away from the surface towards the core. Pictured right is a fully encapsulated dome.