by Diane Hansen
Contributing Editor

Testing… The TV Commercial Way

Toss it, try to crush it, drop it off a building if they must, ad agencies have shown us over and over again that tough products can be abused and come out in gleaming, perfect condition in spite of the most brutal conditions.  Although destructive testing does exist for medical devices, it’s doubtful the process will be appearing on the small screen anytime soon.

And Now… Our industries’ Way

So how are medical packages tested for strength?  One of the most common tests is the ASTM F-88 Peel Test, also called tensile seal strength testing.  This test measures the strength of seals by pulling apart the flexible films such as Mylar and Tyvek® using a pre-defined sample width of a sealed medical pouch.  A peeling mechanism, moving at a defined constant rate, pulls the seal apart.  While it is separating the seal, the force gage measures the force during the testing session for evaluation.

There are two key reasons for the F-88 Peel Test…

1. To ensure the integrity of the package and assure that it is sealed
2. To assure that no weaknesses in the sealed areas of the package exist that would cause leaks during sterilization, handling, transportation and storage

The F-88 Peel Test determines the force that is required to open a peelable package.  Force data is also provided, which can be used in developing a DOE (design of experiments) for the validation of the sealing process.  If the seal is too strong, the end user will either not be able to open it or become frustrated while trying to do so.  However, if the seal is too weak, the product is in risk of the loss of sterility during transportation and storage. Of course the stronger seal strength is not and issue if the seal that is created is a butt seal, which by design is not meant to be peeled open by the end user, however the seal cannot be over treated (heated), as that may constitute a burnt seal that may fail in long-term storage.

F-88 Peel Test Types and Techniques

According to ASTM, there are three techniques used in peel testing.  Full standards and techniques can be found at www.astm.org

Technique A: Unsupported – In this test, each tail of the sample is secured in opposing grips and the seal remains unsupported while the test is being conducted.

Technique B: Supported 90°– In this test, also known as the “free tail” method, each tail of the sample is secured in opposing grips and the seal is hand-supported at a 90° perpendicular angle to the tails while the test is being conducted.

Technique C: Supported 180°—In this test, also known as the “supported tail” method, the least flexible tail is supported flat against a rigid alignment plate held in one grip. The more flexible tail is folded 180° over the seal and is held in the opposing grip while the test is being conducted.

The results will vary depending on the condition of support.  The F-88 Peel Test calls for an “apples to apples” comparison of results.  If different support conditions exist, test results are not comparable. 

How strong should your seal be?

This has been under some debate, as the 1lbs requirement sometime cannot be met with some types of tricky films. Remember that the 1lbs requirement came out of the 1960’s when the bulk of flexible sterile pouches were surgical paper, and seal strength was a product of the internal bond strength of the paper. At present device makers should evaluate a pass-fail plan based on the highest peel values that they can obtain with their unique pouch. Also your converter should be able to supply you with good feedback in terms of seal strength values you should expect with their pouches. Appling a generic one size fits all 1lbs panacea may not be prudent, however be ready to sell your rationale for the peel strength you selected when audited.

Responsibility and Test Frequency

Package testing frequency should be based on a host of variables such as throughput, class of device, confidents index, etc. But no one disagrees that regular testing is the best way to assure that the original seal strengths do not creep out of your acceptance program. Some medical device companies only test annually and they me be a risk of months of possible failures that shipped into the hospital or point of care. It is therefore prudent to test on shorter cycles as this could prompt product recalls.

The F-88 is a fast way to evaluate your seal strength and the equipment is typically easy to use so production staff can be trained to test and report issues back to the quality team on a regular basis. Again, although peel testing may not be the final word in whole pouch seal integrity, its merits are irrefutable.

The ASTM F-88 Peel Test standard does not claim to answer all of the safety concerns that may be present when dealing with the sterile sealing of medical packaging.  ASTM advises the manufacturer and user of the standard to establish their own protocols and to research regulatory limitations prior to employing this standard.

Avoid Product Recall

Products can be recalled for a variety of reasons.  Packaging is the last thing manufacturers need to be worried about.  By choosing the right vendors and knowing what methods are available for ISO compliant testing, manufacturers can avoid a costly recall due to seal failure.  ASTM F-88 is one essential test that will help assure you that your medical device packaging is sterile and easy to open.   Product testing might be hilarious on TV.  But in the real world, testing can save a manufacturer millions, possibly billions of dollars.

The medical packaging Swiss army knife

When an industry has a problem there is sure to be an innovative company to provide the solution. Enter the MS-451PV medical device-packaging machine from Van der Stahl Scientific. This novel sealer integrates sealing, inspection and peel testing all in a single tabletop machine. Company spokesman Charlie A. Webb a certified packing engineers states “It is simply intuitive to our design group that these functions should be incorporated in a single unit as sealing and testing should be seen as a circle of operation.” This patented sealer is designed to stop the packaging operation and force line operators to inspect and peel a pouch at pre-determined intervals. Only after the seal strengths have met minimum seal strengths will the machine continue to package. Van der Stahl Scientific also reports that the sealer will hold test report on the machine’s on-board memory for up to a year and can be purged to the included software for archiving. According to Webb, “This technology will help medical device maker stay compliant, it almost like having a robot quality assurance member” The MS-451PV has been designed and built for the specific task of sealing flexible medical pouch films such as Tyvek®, foil, poly, Mylar.

So the future of medical packaging compliance may be though smart machines like the MS-451PV that schedule and integrate testing functions within the very machines that creates the seals. We all have the shared aim of compliance and we should therefore exploit the latest technologies that make our products more efficacious and assure that they arrive in the sterile field intact.

More information on these products can be found at http://www.vanderstahl.com/medical.html