The stretching behavior of Bottle Seal Liners is well recognized at converters and brand-owners, leading to stable blowing procedures, even for complex bottle designs. The addition of a barrier layer can have a significant impact on the general preform stretching behavior and consequently on the processability into the bottle shape.
The handling windowpane will be influenced by the quantity and site of the buffer coating, but importantly also through the buffer material which is used. In the following paragraphs the stretching out behavior of a significant incumbent barrier material is going to be in comparison with a new barrier materials which will enter the marketplace in 2024: Polyethylene furanoate or PEF. Created by Avantium Renewable Polymers, PEF is a polyester produced from renewable resources and contains outstanding gas buffer properties. It is actually therefore really appropriate as a buffer coating in PET-dependent multilayer containers. Using the Suggest machine from Blow Moulding Technologies this short article investigates the stretching behavior of barrier preforms during the coming procedure. It concludes the influence of any PEF barrier layer on the blowing actions of the preform into a bottle is even lower compared to an incumbent barrier solution. This confirms findings from coming trials with PEF-that contains PET multilayer preforms on aviator lines and provides self-confidence on the processability and application of PEF being a barrier layer in commercial bottle coming equipment.
Buffer requirements in firm packaging
PET is the material preferred by beverage packaging due to the perfect mixture of overall performance, style freedom, simplicity of handling and ideal recyclability. Nevertheless, in terms of the gas barrier, limitations of PET are rapidly achieved when it comes to delicate food and drink products or products which face long logistic timeframes. In these instances PET alone will not be enough to make sure adequate shelf-life as well as an additional barrier is introduced as an inorganic plasma coating; an energetic oxygen scavenger; or even a unaggressive buffer layer. Plasma coatings work well but provide restricted flexibility in bottle design and need very high initial investment expenses, while energetic scavengers are really easy to include into PET but effect recyclability. Energetic scavengers can also only be utilized for a barrier for oxygen, necessitating an (additional) unaggressive coating each time a buffer for CO2 is needed. Consequently, in this article we concentrate on a passive buffer coating since the middle layer of any PET based multilayer (MLY) bottle. In the current market the primary components for this type of layer are (semiaromatic) polyamides, which offer a great buffer towards O2 and particularly CO2. Polyamide (PA) has poor compatibility using the polyester PET, resulting in simple delamination of the barrier layer and haze development when mixed. Recycling of these multilayer bottles consequently relies on comprehensive separation of the polyamide coating after shredding and washing.
The influence of the PEF barrier coating around the blowing behavior of the preform in to a bottle is lower compared to an incumbent buffer solution.
PEF as a barrier coating in PET containers
Avantium recently released a write-up in PE Foil Sealing Liner the possibilities of employing PEF as an alternative gasoline buffer layer in PET containers and also the potential advantages it offers over incumbent technologies /1/. In the following paragraphs the technological feasibility of producing PET/PEF/PET multilayer preforms was demonstrated, as well as the possibility of coming these preforms into containers with similar dimensions and weight syndication as bottles produced from mono-materials PET preforms. All of this could be done in conventional multilayer preform coinjection molding machines and bottle blowing equipment utilizing settings similar to these used for PET without a buffer layer.
What has not been reported but is definitely the impact the buffer layer has in the blowing behavior from the bottle through the stretch out blow molding procedure. The present post seeks to provide insights into and quantify the impact of the PEF buffer layer in the stretching out behavior of any preform in to a bottle. An evaluation will be made with a simple monolayer PET preform and a multilayer PET preform containing a polyamide coating.
The Suggest free stretch out blow molding device of Blow Moulding Systems /2/ was used to analyze the consequences of a barrier layer on procedure is documented with two higher-speed cameras. In this way picture connection can be utilized to ascertain the away from plane fixed strain from the preform/balloon as a function of time. With the combination of all indicator information the (nearby) stressstrain behavior can determined for the material in practical bottle (pre-)coming problems.
Three preform types were looked into, all produced by Husky on the HPP5 Multi-Coating System:
Monolayer PET preform without a buffer layer
Multilayer PET preform containing a PA buffer layer
Multilayer PET preform that contains a PEF barrier coating
For preform 2 a barrier coating of 6 wt% polyamide was used, which is a common quantity in industrial items to accomplish bottles with adequate barrier qualities. The bottle coming procedure for such preforms is known as achievable from countless use instances and therefor offers an outstanding standard.
For preform 3 a core-biased barrier coating of 10 wt% PEF can give buffer properties similar to PA coating in preform 2, and also the main results are shown using this preform. Preforms with a either a 10 wtPercent PEF middle-biased barrier coating or a 5 wt% PEF core-biased buffer layer were also investigated and will be briefly talked about to show the influence of buffer materials amount and coating placement.
The preforms had been all heated up to 115 °C in the oil bath along with an external heat of 105 °C at the outset of the stretch blow molding. The configurations used for the stretch PET Preform had been as follows: 6 club line pressure; 150 ms blow duration; 1. m/s stretch rod velocity.
As mentioned previously, the complete coming procedure was recorded employing a high-speed camera, and Figure 1 demonstrates just what the balloons caused by three of the preforms look like through the coming procedure, from left to djtmcs 45 ms, 55 ms, 75 ms, 90 ms and 150 ms right after procedure initiation. Colour suggests the local strain in the hoop path.