Gas Barrier, Hot Fill Bottles, Carbonated Beverages

What is the benefit of using an oxygen barrier material?

What is the process for adding a barrier material?

Using barriers with Polyolefins  (HDPE, LDPE, PP, PE)

What is a polyolefin?

What is the difference between a CSD (carbonated soft drink) bottle and still beverage bottle?

What is the benefit of using a CO2 barrier material?

How do you create a heat resistant bottle used for hot fill applications?

Vegetable and fruit juices which are rich in color are usually more sensitive to oxygen and spoilage which turns the product brown.  Using a PET bottles with an oxygen barrier over a standard PET bottle will significantly extend the life of the product.  For example; a standard PET bottle containing orange juice will turn brown in a matter of days.  Using an oxygen barrier bottle will prevent oxygen ingress of <1 ppm ingress per month.  For products which have no tolerance for oxygen or which require a 90 to 120 day shelf life will require the use of an oxygen barrier.

Oxygen can also enter in through the closure; to prevent oxygen ingress through the closure an EVOH or induction liner is used in the closure. 

The product within a bottle could also spoil from the oxygen left in the head space of the bottle. To solve this problem there are a number of solutions which can be utilized; nitrogen drip, filling the product higher to reduce the amount of oxygen left in the bottle or implementing other solutions.

It really depends on the reason why you are putting in the barrier.  Primarily, barriers are used to protect the product from oxygen; the goal is to place the barrier material as close to the outside of the package (closer to the oxygen) as possible. 

A PET barrier property can be achieved by one of three ways, through homogenization of a barrier material (same as would be done with a colorant additive), by running a multi-layer preform that puts the barrier material between two layers of PET (this would be a three layer structure), or by using a monolayer bottle with either an exterior or interior barrier coating.

Generally speaking the multilayer approach is more expensive but does provide a better barrier protection.  There are a number of different materials used as oxygen barriers; for PET, nylon is typically the barrier material used. 

Bottles which use an oxygen barrier will continue to use the “#1” SPI resin code on the bottom of the bottle.  Such a small amount of barrier material is typically used that it does not impact the PET bottle recyclability.  Most of the time oxygen barriers are loaded at less than 2% but some applications might go as high as 3% for beverages such as wine.

Generally the oxygen barrier used in a multilayer preform would be nylon.  The FDA requires that nylon is not in direct food contact.  MXD6 Nylon is ok to use with direct food contact.  Nylon is also homogenous with PET and requires no tie layer and will also form a bond layer with PET.

When working with HDPE or PP type resins a barrier of either EVOH or nylon is used as a middle layer because it cannot be homogenized into the HDPE or PP resin material.  It also requires a tie layer that ties the barrier layer together with the inner and outer layers (five layer structure).  The trade name for a polyolefin multilayer package is called a “Lamicom” package. 

When using oxygen barriers with polyolefin resins due to the high levels of oxygen bearer material required to minimize oxygen permeation the bottle must use a “#7” SPI resin code.

A polyolefin is a polymer produced from a simple olefin (also called an alkene) as a monomer. For example, polyethylene is the polyolefin produced by polymerizing the olefin ethylene. An equivalent term is polyalkene; this is a more modern term, although polyolefin is still used in the petrochemical industry. Polypropylene is another common polyolefin which is made from the olefin propylene.  These polymers typically float in water whereas polymers like PET which are much denser will sink in water.  Polyolefins include Polyethylene, High Density Polyethylene, Low Density Polyethylene, and Polypropylene.

Because of the high pressure and concern for CO2 loss with carbonation there are several characteristics of CSD bottles.

1. The bottle is created with a petaloid base (the base with “feet”) this helps prevent bottle deformation and make sure the bottle continues to stand upright.
2. The bottle is typically a heavier gram weight to increase the bottle strength and reduce CO2 out gassing and creep (the expansion of the bottle under pressure to create additional headspace and CO2 loss.)
3. The neck of the bottle is created with gas vents to allow pressure to escape without projecting the cap toward the user upon opening.
4. The thread on the neck has an additional twist.

These design features are not found with still beverage bottles which can lead to cost savings in the manufacturing of the bottle.

When PET was first introduced CO2 retention was a huge issue with maintaining a 16 week shelf life.  With the introduction of NutraSweet which has a 12 week shelf life it caused the companies to learn to manage their inventory on a 12 week timeline verse 16 weeks, once they did this the issue went away.  One key factor to maintaining CO2 is temperature, if the bottle gets up to 100F the timeline drops dramatically. 

There are three main reasons a bottle will lose CO2;

• Because of the internal pressure from the CO2 PET bottles will begin to creep or get a little larger which results in more head space thus filling with the CO2 gas out of the product.
• Absorption results in the CO2 being absorbed into the PET bottles sidewall, this and creep both happen within the first 24 hours of the bottle being filled.
• Migration is the third issue, which is the passing of the CO2 through the sidewall of the bottle and this takes longer, approximately 16 weeks.

In creating hot fill bottles, there are specific resins and process required.  A heat set resin is used and is then blown into a hot mold on a heat set machine, this provides the heat resistance required so that the bottle will not deform when subjected to the heat from hot fill liquids.  For the hot fill bottles to work properly it must be initially designed to be heat resistant, must use a heat set resin and be blown in a hot mold on a heat set machine to thermally set the PET, otherwise when the bottle is filled with the hot fill product at 190F the bottle will either as a result of the heat or as a result of the vacuum naturally formed in the cooling process distort.

ENSO Bottles, LLC

Phone: 1 (866)-936-3676 or 602-639-4228

Company Brochure