Ever wonder why the sides of plastic container suck in after a long stay on the shelf? All extreme temperature and pressure changes excluded, the answer is called paneling. A perfect example of paneling is shown above. Contents in the untreated bottle on the left have compromised the plastic walls, causing the container to resemble a water bottle at 35,000 feet. The Fluorinated bottle, which looks perfectly normal, has been treated to prevent paneling. The secret behind its strength is fluorination.

The Fluorination Fix

Plastic bottle paneling is prevented by a process called fluorination, in which the surface of container is treated by fluorine gas. Fluorine atoms bond to the plastic, creating a permanent protective barrier. After treatment, the plastic container is less receptive to permeation, discoloration, weight loss, odor emission and (most of all) panelling.

There are two types of surface fluorination. Post-mold fluorination occurs when containers are exposed to fluorine gas in a sealed reactor. Don’t have one of those lying around? The second approach, in-mold fluorination, takes place during the blowing process by mixing fluorine and nitrogen into the air supply. The prior is approved by the FDA for food and pharmaceutical containers. The latter creates a higher level of fluorination, but it is still awaiting clearance.

Five levels of fluorination are available. The appropriate level depends on the type of plastic and product being packaged. Fluorinators must work closely with customers to determine the proper treatment.

Compatible Chemicals

There are a variety of chemicals that prefer to be packaged in fluorinated containers. The following table outlines some of them.

Acetone	Kerosene
Auto Additives	Lubricants
Charcoal Lighter	Plant growth products
Cleaners	Surfactants
Degreasers	Solvents
d-Limonene	Terpenes
Electronics Chemicals	Trichloroethylene
Essential Oils	Toluene
Flavors	Wax or polish
Fragrances	Wood Preservatives
Gasoline	Herbicides
Insecticides	Paint Thinners

It is not an exhaustive list, but it is a good place to start, or at least start considering strengthened plastics. All of the products above are prone to hydrocarbon transmission through their plastic packaging.

Why Fluorinated Plastic?

Panelling and concerns regarding container integrity might cause some to consider packaging alternatives. Why not go with metal cans? What about brown bottles? Plastic containers, even fluorinated plastics, are still more cost effective than metal or glass in many circumstances. Like glass, plastic can be clear or opaque depending on the demand. It also maintains its integrity like metal, making it ideal for transportation or handling. Another advantage is weight. Plastics are considerably lighter than both metal and glass packaging.

View our video on paneling and fluorination:

Video Transcript:

Hello and welcome to the Qorpak packaging laboratory.Today, we are discussing plastic paneling and the benefits of fluorination. You might be wondering why you would want to fluorinate a bottle. Certain products react with the plastics in a bottle, which causes paneling, such as a sucking in that you might see on your store shelves.

Products that can cause paneling include:

• cleaners and solvents, especially those that have a citrus smell to them
• any product with a strong flavor or odor
• shampoos and bodies washes that are organic or contain enzymes, such as this enzymatic shampoo right here
• waxes and polishes
• automotive fluids, especially those containing oil, such as this crack filler here
• paint thinners
• tanning products
• weed killers

The paneling on the bottles tends to indicate that there is an incompatibility between the product and the resin that the bottle is made out of.

Fortunately, there are solutions to these products so that we can continue to handle them in plastic. You can make the bottle structurally stronger by adding ribs or changing the shape of the bottle, like oil bottles that are square. But, maybe, making a mold is not an option for you. That’s where fluorination comes into play.

The process of fluorination bombards the plastic with fluorine ions. When they do that, they replace the hydrogen atoms on the outside of the surface with fluorine atoms, which are larger. It essentially plugs the holes so the product does not escape and air does not get in.

This can be done during the forming process or after forming the bottle. If you are thinking about small quantities, it is cheaper and easier to do it after the bottle has been formed.

Fluorination is FDA safe because it causes a permanent modification to the plastic. It does not wear off or seep into food. Fluorinated bottles are also just as recyclable as any other bottle of the same material.

Now, what materials can be fluorinated? Common packaging materials include polypropylene, polyethylene and PVC. Examples of polypropylene are closures, high-density bottles, such as a typical shampoo bottles, and LDPE squeeze bottles.

It is important to note that PET, which is the material that water bottles are made out of, is not able to be fluorinated.

Thanks for joining us in Qorpak’s packaging laboratory. If you have any questions about today’s topic or suggestions for future topics, please reach out to us on Twitter.