We are performing OQ and PQ for sterile packaging. This is a new process for our company. We are using PETG thermoformed trays and Tyvek 1073B coated lids. We are seeing a thin line of no seal in a number of sealed trays. On a very obvious one, we peeled the lid off and there was no adhesive on the tray in that thin line. It is very hard to tell which ones are OK and which ones are not. When looked at through light, the lined area appears darker. The lid material also feels raised in that area and the line of raised material extends across several inches. Is this a defect in either the lid or adhesive application or is this common? @ Ask The Experts

Jason Crosby
Plastic Ingenuity, Inc.
Medical Business Manager
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Jason Crosby is the Medical Business Manager for Plastic Ingenuity, Inc., located in Cross Plains, Wisconsin. Plastic Ingenuity, a custom thermoforming manufacturer, has formed its reputation in the industry by providing innovative packaging solutions, being customer focused and flexible. Jason is responsible for all facets of Plastic Ingenuity’s medical packaging business; dealing daily with operations, business development, product development, package engineering and validation. Jason has been instrumental in the growth of Plastic Ingenuity’s medical packaging business by focusing on unmet market needs, such as the development of the SafeEdge platform launched in 2008. Jason has a bachelor’s degree from the University of Wisconsin-Whitewater and an MBA from the University of Wisconsin. He has 13 years of thermoforming industry experience with Plastic Ingenuity. He is a member of the Society of Plastic Engineers and Institute of Packaging Professionals. Jason has presented nationally on various topics related to medical packaging and thermoforming.

Thermoforming Q&A

We are performing OQ and PQ for sterile packaging. This is a new process for our company. We are using PETG thermoformed trays and Tyvek 1073B coated lids. We are seeing a thin line of no seal in a number of sealed trays. On a very obvious one, we peeled the lid off and there was no adhesive on the tray in that thin line. It is very hard to tell which ones are OK and which ones are not. When looked at through light, the lined area appears darker. The lid material also feels raised in that area and the line of raised material extends across several inches. Is this a defect in either the lid or adhesive application or is this common?

Asked November 9th, 2009

It sounds like what you are describing are the veins that can be found in the Tyvek. Tyvek is produced by DuPont in its flash-spinning and bonding process, in which HDPE fibers are flashspun and laid onto a web. These fibers are layered and create the Tyvek structure. It is this “crossing” of the fibers that create the “tortuous path” (per DuPont) and prevents the microorganisms from getting through the Tyvek, helping create the sterile barrier.

If you hold the Tyvek up to the light you can see these fibers within the lid. In most cases, they are small in diameter, and on occasion there are larger fibers. The process of flash-spinning does create a thickness range within the Tyvek structure; the range for Tyvek 1073B is from 3.5 mils to 11.1 mils (per DuPont). To compensate for such variation, converters typically utilize an air knife coating of up to 7 mils thick.

It is possible that this large vein impacted how the adhesive was applied to the Tyvek. However, I would advise you to contact your lid supplier to get some feedback from them regarding this issue. They should be able to advise you on what rejection rate you should expect to see and help you develop inspection protocols.

Jason Crosby Tyvek

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