The stretching behavior of PP Peel is well known at converters and brand-owners, leading to stable blowing operations, even for complex bottle styles. Incorporating a buffer coating can have a significant effect on the overall preform stretching actions and consequently on the processability into the bottle shape.

The processing windowpane will be relying on the amount and location of the buffer coating, but notably also from the buffer materials that is used. In the following paragraphs the stretching behavior of the major incumbent barrier materials is going to be compared with an all new buffer materials which will enter the market in 2024: Polyethylene furanoate or PEF. Made by Avantium Renewable Polymers, PEF is a polyester made from green resources and has outstanding gas barrier qualities. It is therefore very suitable as being a barrier coating in PET-based multilayer containers. Utilizing the INDICATE machine from Blow Moulding Systems this article investigates the stretching out behavior of buffer preforms during the blowing process. It concludes the influence of the PEF buffer coating around the coming actions of the preform right into a bottle is even lower than that of an incumbent barrier solution. This verifies observations from blowing trials with PEF-that contains PET multilayer preforms on pilot lines and provides self-confidence around the processability and application of PEF as a buffer coating in industrial bottle coming equipment.

Barrier specifications in rigid packaging

PET will be the materials preferred by drink packaging because of its ideal mixture of overall performance, design independence, ease of processing and ideal recyclability. However, in terms of the gasoline barrier, restrictions of PET are quickly reached with regards to delicate drink and food products or products which face long logistic timeframes. In these instances PET on your own is not sufficient to guarantee sufficient life expectancy plus an extra barrier is launched in the form of an inorganic plasma coating; an active oxygen scavenger; or a passive buffer coating. Plasma coatings work well but provide limited versatility in bottle design and need extremely high preliminary purchase costs, whilst energetic scavengers are easy to include into PET but effect recyclability. Active scavengers can also only be utilized for a barrier for o2, necessitating an (additional) unaggressive coating whenever a buffer for Carbon dioxide is needed. Consequently, in this post we concentrate on a unaggressive buffer layer because the center coating of any PET based multilayer (MLY) bottle. Within the current marketplace the primary components for this type of coating are (semiaromatic) polyamides, which offer an excellent barrier against O2 and especially Carbon dioxide. Polyamide (PA) has bad compatibility using the polyester PET, resulting in simple delamination of the buffer coating and haze development when mixed. Recycling of these multilayer containers consequently depends on thorough separation from the polyamide layer after shredding and cleaning.

The impact of the PEF buffer layer on the blowing actions from the preform right into a bottle is lower compared to an incumbent barrier solution.

PEF being a barrier coating in PET bottles

Avantium recently released a write-up in Closure Aluminium Seal Liners the options of employing PEF as an alternative gasoline barrier coating in PET bottles as well as the possible benefits it provides over incumbent technologies /1/. In the following paragraphs the technological feasibility of producing PET/PEF/PET multilayer preforms was shown, as well as the chance of blowing these preforms into containers with similar measurements and weight distribution as containers made from mono-materials PET preforms. This all could be carried out in traditional multilayer preform coinjection molding machinery and bottle coming equipment using configurations similar to these used for PET without having a barrier layer.

What has not been reported yet will be the impact that this buffer coating has in the blowing behavior of the bottle through the stretch out blow molding process. The present article seeks to offer insights into and quantify the influence of the PEF buffer coating in the stretching out behavior of a preform into a bottle. A comparison will be made out of a plain monolayer PET preform along with a multilayer PET preform containing a polyamide layer.


The INDICATE free stretch out blow molding device of Blow Moulding Technologies /2/ was utilized to research the effects of a buffer layer on process is recorded with two high-velocity digital cameras. In this manner image correlation can be employed to discover the from plane fixed strain in the preform/balloon as being a purpose of time. With the mixture of all sensor data the (nearby) stressstrain behavior can calculated for the material in practical bottle (pre-)blowing conditions.

3 preform types had been investigated, all created by Husky on the HPP5 Multiple-Layer System:

Monolayer PET preform without a buffer coating

Multilayer PET preform that contains a PA buffer layer

Multilayer PET preform containing a PEF buffer coating

For preform 2 a barrier coating of 6 wt% polyamide was utilized, which is a typical amount in commercial items to accomplish bottles with sufficient buffer qualities. The bottle blowing procedure for this kind of preforms is known as attainable from numerous use instances and therefor provides an outstanding standard.

For preform 3 a primary-biased buffer coating of 10 wtPercent PEF will provide buffer properties much like PA coating in preform 2, and the primary outcomes are demonstrated using this preform. Preforms using a either a 10 wtPercent PEF middle-biased barrier coating or perhaps a 5 wtPercent PEF primary-biased barrier coating had been also looked into and will be briefly discussed to show the influence of barrier material quantity and coating placement.

The preforms had been all heated up to 115 °C in the oil bathtub along with an outer heat of 105 °C at the start of the stretch out blow molding. The configurations used for the stretch Bottle Preform were as follows: 6 bar line stress; 150 ms blow period; 1. m/s stretch out rod velocity.


As said before, the complete coming process was documented using a high-velocity camera, and Figure 1 shows just what the balloons originating from the 3 preforms look like during the coming process, from left to djtmcs 45 ms, 55 ms, 75 ms, 90 ms and 150 ms after process initiation. Colour indicates the neighborhood stress within the hoop path.

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