The stretching behavior of PET Preforms is well known at converters and brand-owners, leading to stable blowing procedures, even for complex bottle designs. The addition of a barrier coating can have a significant influence on the overall preform stretching behavior and as a result on the processability into the bottle shape.
The handling windowpane will likely be affected by the amount and site of the buffer layer, but notably also through the buffer material that is used. In the following paragraphs the stretching actions of a major incumbent buffer material will be in comparison with a new barrier materials that will enter in the market in 2024: Polyethylene furanoate or PEF. Created by Avantium Renewable Polymers, PEF is a polyester made from renewable resources and it has exceptional gas buffer qualities. It really is consequently very suitable as being a buffer layer in PET-dependent multilayer bottles. Utilizing the Suggest machine from Blow Moulding Technologies this post investigates the stretching actions of buffer preforms throughout the coming procedure. It wraps up that this impact of any PEF barrier coating on the coming actions from the preform right into a bottle is even lower than that of an incumbent barrier solution. This confirms findings from blowing trials with PEF-containing PET multilayer preforms on pilot lines and offers self-confidence in the processability and application of PEF as being a barrier layer in commercial bottle coming gear.
Barrier specifications in rigid packaging
PET is the material of choice for beverage packaging due to its ideal blend of overall performance, style freedom, ease of handling and ideal recyclability. However, in terms of the gasoline barrier, limitations of PET are rapidly reached in terms of delicate drink and food products or products which face long logistic timelines. In these cases PET on your own is not really sufficient to make sure adequate shelf-life plus an additional buffer is introduced as an inorganic plasma coating; an active oxygen scavenger; or perhaps a unaggressive buffer coating. Plasma films are effective but offer limited flexibility in bottle design and need high initial purchase expenses, whilst active scavengers are easy to incorporate into PET but effect recyclability. Energetic scavengers can also only be utilized as a barrier for o2, necessitating an (additional) unaggressive coating whenever a barrier for CO2 is necessary. Consequently, in the following paragraphs we focus on a unaggressive buffer coating since the center coating of a PET dependent multilayer (MLY) bottle. Within the current market the main components for such a coating are (semiaromatic) polyamides, which provide a great buffer towards O2 especially CO2. Polyamide (PA) has bad compatibility with the polyester PET, causing simple delamination in the barrier coating and haze formation when blended. Trying to recycle of these multilayer containers therefore relies on comprehensive separation in the polyamide coating after shredding and washing.
The influence of the PEF barrier layer around the blowing actions of the preform into a bottle is lower than that of an incumbent barrier solution.
PEF as being a buffer coating in PET bottles
Avantium recently published an article in Bottle Seal Liners the number of choices of utilizing PEF as a substitute gas barrier layer in PET bottles and also the potential advantages it offers over incumbent systems /1/. In this post the technical feasibility of producing PET/PEF/PET multilayer preforms was demonstrated, as well as the potential of blowing these preforms into bottles with similar measurements and weight syndication as bottles produced from mono-materials PET preforms. All this could be accomplished in conventional multilayer preform coinjection molding machines and bottle coming gear using configurations similar to those utilized for PET without having a barrier layer.
What is not noted yet is definitely the impact the buffer layer has in the blowing actions of the bottle through the stretch blow molding procedure. The present article seeks to provide insights into and quantify the impact of the PEF barrier coating on the stretching behavior of the preform in to a bottle. An evaluation is going to be made out of a plain monolayer PET preform and a multilayer PET preform containing a polyamide coating.
The INDICATE totally free stretch blow molding device of Blow Moulding Technologies /2/ was applied to investigate the consequences of a buffer layer on process is documented with two higher-velocity cameras. In this way picture correlation can be employed to discover the out of plane fixed stress in the preform/balloon being a function of time. With the mixture of all indicator information the (nearby) stressstrain behavior can determined for the material in practical bottle (pre-)blowing conditions.
3 preform types had been investigated, all made by Husky on their own HPP5 Multiple-Layer System:
Monolayer PET preform without having a barrier layer
Multilayer PET preform that contains a PA barrier layer
Multilayer PET preform that contains a PEF buffer layer
For preform 2 a barrier layer of 6 wt% polyamide was utilized, which is a typical amount in industrial products to attain containers with sufficient buffer qualities. The bottle coming process of this kind of preforms is proven to be achievable from numerous use instances and therefor gives an outstanding benchmark.
For preform 3 a core-biased barrier layer of 10 wt% PEF can give buffer qualities much like PA coating in preform 2, and also the primary outcomes are demonstrated applying this preform. Preforms with a either a 10 wtPercent PEF middle-biased buffer layer or perhaps a 5 wt% PEF primary-biased buffer layer were also looked into and are briefly talked about to show the impact of buffer materials quantity and coating placement.
The preforms were all heated up to 115 °C inside the oil bathtub along with an external heat of 105 °C at the start of the stretch blow molding. The configurations used for the stretch out PET Preform were the following: 6 bar line stress; 150 ms blow duration; 1. m/s stretch out rod velocity.
As mentioned earlier, the entire blowing process was recorded employing a higher-speed camera, and Figure 1 demonstrates exactly what the balloons originating from three of the preforms look like throughout the blowing procedure, from left to djtmcs 45 ms, 55 ms, 75 ms, 90 ms and 150 ms right after procedure initiation. The colour suggests the neighborhood strain inside the hoop path.