Amcor PET Packaging finds success with 2.5oz hot-fill bottle

Amcor ingenuity and engineering was required to create this one-of-a-kind mini bottle. Steaz Energy Shot is a convenient and healthy way to build stamina and sustained energy, with 150mg of plant-based caffeine. The all-natural ingredients include organic, Fairtrade-certified green tea, Sambazon’s acai juice, Guayaki’s yerba mate, organic berry flavour and organic guarana from the rainforest. The bottle is produced at Amcor’s state-of-the-art facility in Nicholasville, Kentucky.

Amcor has long been the leader in hot-fill engineering, and the foundation for development of this project was based on proprietary technology that Amcor has developed over the years. The entire package is 100% recyclable, and although the 2.5oz bottle is a relatively simple cylindrical shape, adapting technology used in larger containers wasn’t a straightforward reduction process. Every size container and each design nuance impacts PET performance and presents new challenges.

“As far as we know, there was no heat set container this small on the market before,” said Amcor principal engineer, innovation, Kirk Maki. “Perhaps the most difficult part was getting heat set properties into a bottle this size. Vacuum control in hot-filling and cooling is the other critical issue, which also required considerable manipulation.”

Controlling the process in process control

“We had to take a step back and determine how to get the process control we needed on a much smaller container,” said Maki. “In theory, 2 over 1 equates to 10 over 5, but in practice it’s very different. First, we had to modify our equipment and add specialty machine controls. We had to downsize and modify the tooling to create a scaled-down version of how we would normally process the container in order to drive heat set properties to a level high enough to prevent deformation under the heat. We accomplished what we set out to do. The heat set testing has come back at levels equal to or better than some of our other larger heat set containers.”

Maki acknowledged there were challenges with the overall bottle design relating to vacuum control. Testing and calculations based on container diameter were run upfront to ensure that specialty panelling wouldn’t be needed. The panelling was fine when initial hot-filling and cooling trials were run, but “the panel rib design had issues. Nothing critical, but we felt it just wasn’t quite right,” Maki said.

So the team continued the quest for perfection by modifying the rib portion of the design. In the process, they developed a superbly smooth area of labelling. “If you make a container that looks good with a wrap label, it will look great in a shrink label,” Maki said.

The mini bottle’s finish area added to the complexity. Whereas the standard finish recalls an earlier PET era, it’s not the kind of heat set finish one typically finds on a store shelf. A wide mouth, 28mm finish is considered a natural-size opening to drink from, compared to the 20mm finish on energy drink bottles that have drawn criticism.

“When you have a relatively large 28mm opening on a 2.5oz container, compared to a 43mm opening on top of 500ml bottle, you can’t simply transfer technology,” revealed Maki. “Although not as light in weight as some newer designs, it has a versatile finish. What allowed us to use it here is the fact that the bottle is small, so there is relatively little heat capacity.”

The closure itself is a standard design, borrowed from pharmaceutical packaging for this beverage application. It also takes custom equipment to fill these small bottles. Not many fillers are currently set up to do it because there hasn’t been a demand for hot fill in bottles this size until now.

Source: Amcor