Routine quality control (QC) testing of polymer and packaging barrier properties, throughout the film-to-package production process, is important to ensure final package quality.
Recent advancements in permeation measurement technology have resulted in new instruments which can test the Oxygen Transmission Rate (OTR) and Water Vapor Transmission Rate (WVTR) more efficiently and with reduced labor. This is due to automated test parameter setup, improved sensor, and decreased background leaks and electronic noise. The increase in sample throughput can help new material developers, resin suppliers, converters, and brand name product manufacturers assess their barrier materials more efficiently and improve QC testing.
Ongoing permeation testing for quality control purposes helps to ensure product consistency over time and contribute to business success. Various tests, including barrier permeation tests, should be carried out along each step of the manufacturing process, from film production to converting, to packaging, to shipping. Here are a few scenarios to consider.
1. Brand Owners
As brand owners, you rely on your suppliers to provide films and formed packages. If your product is sensitive to moisture and oxygen, it’s important to test WVTR and OTR of these materials from your suppliers. You want to ensure these incoming materials meet stated specifications.
During the packaging process, you want to make sure your machinery is set to the correct parameters and that the packaging material survives all the phases of packaging while providing the desired protection. Many packers focus only on flat film testing but neglect to test the finished package. How do you know if the barrier quality of the final formed package offers the same barrier protection as the original flat material? Test a formed empty package and you may see barrier properties (such as OTR and WVTR) have changed. For more information we recommend you read the article titled "The Importance of Testing the Whole Package".
Barrier property testing independent of the product and under ideal conditions is one thing. Testing barrier properties after exposure to “real world” conditions is another thing. For instance, did you know that, some packages can be damaged by the products they are designed to protect? Think about potato chips, or computer chips, which need to be isolated from ambient moisture and oxygen. There are a variety of very good barrier materials such as a metalized pouch, or multi-layer barrier with foil, that can be sourced through various suppliers that can protect the product. However, with enough vibration during shipping, the sharp edges of the chips can compromise the package rendering damaged product at the destination. In this case, additional tests such as the Gelbo-Flex test should be conducted before the permeation test so that the material is examined after exposure to harsher conditions. As a rule of thumb, QC tests are most diagnostic when they are set up under the conditions experienced by the package.
2. Film Manufacturers and Converters
Well, if you thought the above situations wouldn’t apply to you because you merely manufacture films and don’t deal with product packaging, think again. For best practices, film manufacturers should test their manufactured films weekly if not daily. This is because resin suppliers do not always provide the correct material or the same grade of material. Also, variations in the resin and the manufacturing process, and deficiencies in extrusion equipment mechanisms, could all affect your polymer film’s quality. Due to the many variables that can change in film production and source materials, it is imperative that film testing is an integral part of any quality control program.
For example, consider a manufacturer making AlOx coated PET film, where a section of the coating machine stopped applying AlOx coating. Because it was hard to detect, no one noticed there was coating missing when the film came off the machine. Fortunately, the company had a very good QC procedure in place where the film was sampled daily for OTR testing. The operator noticed samples from one location on the web always had higher OTR values than in other areas. Further investigation traced the malfunction to the coating machine. The problem was solved and situation corrected. What if you hadn’t performed testing and the defective film reached your customers? This could cause a whole list of issues, affecting your brands reputation, the relationship with your customers, recalls and ultimately your bottom line.
In another example, several companies’ products failed to reach their expected shelf life. After OTR testing the packaging material, they realized that the Metalized Polypropylene lamination from the same manufacture didn't meet the barrier level that was promised in the specifications. Later, the film manufacturer found that the metal layer created cracks during the lamination process, causing them to recall the film. The film manufacturer could have discovered the problem sooner if they had the right QC process in place that included OTR testing of their films. Instead, there was significant financial loss to remedy the situation. In this case, both the film maker and the companies that used the films incurred loss, in not only money and time, but also losing the trust of their customers. This situation would have been easily avoided if the packers tested the incoming films’ specification, and the film maker had checked their film prior to shipping it.
Other reasons that you should test OTR and WVTR of your materials or packages routinely is because changes to the raw material suppliers, and the environmental conditions under which the films are made, commonly occur, and can often affect barrier properties negatively. QC testing of barriers may need to be increased when changing resin suppliers, when adding new ingredients to your products, or when extending your distribution to regions with different climates.
Whether you are a packer who uses polymer films or a film manufacturer, it is important to continuously monitor the barrier properties of polymer films and finished packages. This is the key to ensure top quality control and continuous business success!
To learn more about barrier film testing and WVTR visit www.mocon.com