The stretching behavior of PET Preforms is well recognized at converters and brand-owners, leading to stable blowing procedures, even for complicated bottle designs. The addition of a buffer layer can have a significant influence on the overall preform stretching behavior and as a result on the processability into the bottle shape.
The processing window will likely be affected by the quantity and location in the buffer coating, but notably also from the barrier materials which is used. In this post the stretching out behavior of the significant incumbent barrier material is going to be compared with a new buffer material which will go into the market in 2024: Polyethylene furanoate or PEF. Produced by Avantium Green Polymers, PEF is a polyester made from green sources and contains exceptional gas buffer properties. It really is therefore really suitable as a barrier layer in PET-based multilayer bottles. Making use of the Suggest machine from Blow Moulding Systems this short article investigates the stretching out behavior of buffer preforms during the blowing procedure. It concludes that the impact of a PEF barrier layer on the blowing behavior of the preform into a bottle is even lower compared to an incumbent buffer solution. This confirms findings from coming trials with PEF-that contains PET multilayer preforms on pilot outlines and gives confidence around the processability and application of PEF as being a buffer coating in commercial bottle blowing equipment.
Barrier requirements in firm packaging
PET is definitely the material preferred by drink packaging because of its perfect combination of overall performance, design freedom, simplicity of handling and ideal recyclability. However, in terms of the gas buffer, limitations of PET are rapidly reached with regards to sensitive drink and food items or products which face long logistic timeframes. In these instances PET alone is not really enough to ensure sufficient shelf life as well as an additional buffer is introduced in the form of an inorganic plasma coating; a dynamic o2 scavenger; or even a passive barrier coating. Plasma coatings are effective but provide limited versatility in bottle style and need high preliminary purchase expenses, while energetic scavengers are really easy to incorporate into PET but effect recyclability. Active scavengers can also only be used as a buffer for o2, necessitating an (additional) passive layer whenever a barrier for CO2 is required. Therefore, in the following paragraphs we focus on a passive buffer layer as the middle coating of any PET dependent multilayer (MLY) bottle. Within the current marketplace the main materials for this kind of layer are (semiaromatic) polyamides, which offer an outstanding buffer against O2 and especially CO2. Polyamide (PA) has poor compatibility using the polyester PET, leading to easy delamination in the buffer layer and haze development when blended. Recycling of such multilayer bottles therefore relies on thorough separation of the polyamide layer after shredding and cleaning.
The impact of the PEF buffer coating around the coming actions of the preform into a bottle is lower compared to an incumbent buffer solution.
PEF as a barrier layer in PET bottles
Avantium recently released a post in Closure Aluminium Seal Liners the possibilities of using PEF as a replacement gas barrier coating in PET bottles and also the possible advantages it has over incumbent technologies /1/. In this article the technological feasibility of producing PET/PEF/PET multilayer preforms was demonstrated, as well as the potential of coming these preforms into bottles with the exact same dimensions and weight distribution as bottles made from mono-material PET preforms. All this could be carried out in conventional multilayer preform coinjection molding machinery and bottle blowing gear using configurations comparable to these employed for PET without a buffer coating.
What is not noted but is definitely the impact the buffer coating has in the coming actions from the bottle throughout the stretch out blow molding procedure. The current article aims to provide information into and quantify the influence of the PEF barrier coating around the stretching out behavior of a preform in to a bottle. An assessment will likely be made out of a simple monolayer PET preform along with a multilayer PET preform containing a polyamide coating.
The INDICATE totally free stretch blow molding gadget of Blow Moulding Technologies /2/ was used to research the consequences of a barrier coating on process is recorded with two high-velocity digital cameras. This way picture correlation can be employed to discover the away from plane corrected stress in the preform/balloon as being a function of time. Using the mixture of all sensor data the (local) stressstrain actions can calculated for your material in practical bottle (pre-)coming conditions.
3 preform kinds were looked into, all created by Husky on their own HPP5 Multiple-Layer System:
Monolayer PET preform without a buffer coating
Multilayer PET preform containing a PA barrier layer
Multilayer PET preform containing a PEF buffer layer
For preform 2 a barrier coating of 6 wtPercent polyamide was applied, which is a common quantity in commercial products to accomplish containers with sufficient buffer properties. The bottle coming procedure for such preforms is proven to be achievable from numerous use cases and therefor gives an outstanding benchmark.
For preform 3 a core-biased buffer layer of 10 wtPercent PEF will give buffer qualities comparable to PA layer in preform 2, as well as the main outcomes are demonstrated applying this preform. Preforms using a either a 10 wtPercent PEF center-biased buffer coating or a 5 wtPercent PEF core-biased buffer layer were also investigated and will be briefly discussed to show the influence of barrier materials quantity and coating positioning.
The preforms had been all heated up to 115 °C in the oil bath and had an external temperature of 105 °C at the beginning of the stretch blow molding. The configurations utilized for the stretch out PET Preform were the following: 6 club line stress; 150 ms blow period; 1. m/s stretch rod speed.
As mentioned previously, the entire coming procedure was documented utilizing a high-speed camera, and Shape 1 demonstrates what the balloons caused by three of the preforms look like during the blowing process, from left to djtmcs 45 ms, 55 ms, 75 ms, 90 ms and 150 ms right after procedure initiation. The color indicates the regional strain in the hoop path.