Webcast Wrap Up: Package Integrity: A Look at False Alarms

The Sterilization Packaging Manufacturers Council discusses integrity test sensitivity.

In November, PMP News hosted the Webcast, “Package Integrity: A Look at False Alarms.” Moderated by Marie Tkacik, director of product development and optimization for Beacon Converters, the event featured the following speakers from the Technical Group of the Flexible Packaging Association’s (FPA) Sterilization Packaging Manufacturers Council (sterilization packaging.org): Ferdos Siadat, Quality Director, Amcor Flexibles; Geoff Pavey, Senior Principal Engineer, Oliver-Tolas Healthcare Packaging; Dhuanne Dodrill, President, Rollprint Packaging Products Inc., as well as Tkacik.

The event was sponsored by SPMC member companies Oliver-Tolas Healthcare Packaging, Rollprint Packaging Products Inc., and Technipaq Inc.

Here the team addresses industry questions. If you have some, please e-mail PMP News editor Daphne Allen at daphne.allen@ubm.com. To view the archived Webcast, please visit www.pmpnews.com/webinars.

Please also visit www.sterilizationpackaging.org for more on the SPMC.

Q: Why can’t dye penetration tests be used for nonporous materials?

SPMC: A method to detect channels in seals of nonporous packages as well as holes in nonporous materials is currently under development by ASTM. This method has some important differences from ASTM F1929, Standard Test Method for Detecting Seal Leaks in Porous Medical Packaging by Dye Penetration, with one of the key differences being the dye penetrant solution formulation.

The dye penetrant solution in F1929 is specifically designed to test porous materials. The dye penetrant solution will wick through the porous material. To slow this process, the surface tension of the solution is kept relatively close to the surface energy of the materials it is testing.

If this same solution is used on a nonporous package, it performs very slowly and can result in the user failing to detect holes. To address this, the surfactant level of solution used in the proposed method for nonporous materials has been increased by a factor of six. This yields a dye penetrant solution with a surface tension well below the surface energy of commonly used packaging materials.

Q: How do you determine the minimum burst value of a pouch? Example would be a pouch measuring 5 x 5 in. ID with a seal strength of 1 lb/in.

SPMC: It is important to understand that the burst value of a pouch of a given seal strength (e.g., 1 lb/in.) is dependent upon a number of factors including:

•    The dimensions of the pouch—  the size of the pouch as well as the width-to-length ratio directly impact the burst value. In general, the larger the pouch, the lower the value.
•    The configuration of the pouch—e.g., the same size chevron, three-side seal, and header bag will yield different burst values.
•    The materials of construction— nonporous pouches will yield significantly different results than pouches that include a porous material. In addition, the extensibility of the materials used to construct the pouch can affect the results.
•    Test equipment.
•    Rate of air flow into the package.
•    Sensitivity of burst test equipment (machine response to pressure drop). 
•    Whether or not restraining plates are used, and if so, their gap separation.

Because of the complexity of the stresses that the seal experiences, theoretical models for predicting the correlation between seal strength values as tested via a tensile test (i.e., ASTM F88) and burst value historically have had very poor results. Therefore, empirical studies are the preferred method of determining the relationship between tensile seal strength and burst test values. This can be accomplished through a ladder study where packages with differing tensile seal strength values are created and the corresponding burst strengths value determine. Regression analysis can then be employed to characterize the relationship between the values.

Q: Is there a published case study for barrier integrity of gels and contaminants?

Most film producers have conducted barrier integrity tests on film possessing high gel count, however, there is a limited amount of published data available. In terms of bacterial barrier, the presence of a gel will not impact the barrier of a film so long as the gel’s size is not so large as to have caused a hole in material adjacent to the gel. 

Gels in multilayer high-barrier films (oxygen, moisture, CO₂) will have minimal impact on total package barrier.  

Q: Gels were said to not be a critical defect. Is this also true for film used in a FFS application?

SPMC: As in all applications, the size of the gel will determine if it poses a potential problem in its respective application. In form-fill-seal applications, large gels have the potential to cause the pocket to blow out in the forming process. Determining what gel size and in what package location is acceptable is done through testing and discussion with the film supplier. 

Q: Do the gels pose any risk to sterile barrier, or are they considered simply a visual defect?

SPMC: In most cases, gels do not pose a risk to package sterility. There are a number of factors that should be considered when determining if a gel poses a risk to sterility: gel size, proximity to other gels, film type, final film structure, and application. If the gels are smaller pinpoint type gels, then they are typically an aesthetic defect.  

What is the maximum gel size I should consider acceptable?

SPMC: Occurrence of gels is inherent in resin and extrusion processes. Condition of equipment, maintenance, raw material, and other manufacturing practices affect the occurrences. Acceptable level of occurrence and size of gels are determined based on material, application, and use by both manufacturers and customers during specification agreement.

Q: Are there any technologies or systems that will allow for non-contact and non-destructive detection of packaging integrity issues in sealed foiled

There are a number of nondestructive test methods that can be utilized for evaluating package integrity. However, most require some contact with the package during testing. Trace gas and vacuum decay methods can be used with minimal contact to the package, and typically the packaged product is usable post-testing.

There are emerging technologies that are noncontact and nondestructive. One of the technologies utilizes airborne ultrasound. This technology transmits ultrasonic waves through a seal and is picked up by a receiver. As the ultrasonic waves pass through the material, dissimilar densities are identified. Because air in the channel has a different density than the surrounding solid areas of the seal, channels can be discovered. The equipment incorporating this technology may be limited to detecting only “gross” channels.

Can dye penetration testing (F1929) be used for the entire package and not just seals?

SPMC: The ASTM F1929 Dye Penetrant Test Method is intended for packages with at least one porous material. Conducting integrity testing is not recommended for the evaluation of an entire package. This is due to severe wicking in the porous material, making it difficult to detect pinholes. A test method for nonporous materials is presently under development by ASTM, in which a dye solution with a greater surface tension than F1929 is required to detect channels and/or pinholes. Of the current methods, bubble leak and emission are examples of simple test methods, which may be a better choice for whole package integrity testing. These methods are commonly used in medical device package testing and evaluation.

Q: How do you recommend performing dye penetration on a double package (i.e., inner and outer pouch)?

Dye penetrant testing techniques for testing double barrier packages, like a pouch within a pouch, often require removal of the inner package. In some cases, it is possible to cut the center of the outer package and remove the inner pouch. This must be done in a way which will not affect the ability of the outer to be tested. By leaving enough uncut material surrounding all seals, this can be accomplished. The feasibility of this method is dependent on the packaging configuration.

Another way is to incorporate one of the newly proposed ASTM F1929 techniques, which expose the package to the dye solution from the outside of the package. Both the new edge-dip and eye dropper application techniques allow for external exposure of the seal to the dye solution. In this manner, the outer pouch can be tested with minimal dye exposure to the inner package. Once testing has been completed, then the outer package can be removed and the inner can be tested. 0

Q: What is the minimal size of pinholes that can be detected with Vacuum Decay and Pressure Decay testing? Currently, I see methods detecting as small as 35 to 10 microns. Are there more-sensitive methods? I am a microbiologist and my experience with sterility is that 0.2 microns is required as barrier to keep microorganisms from penetrating past the barrier. How can 10 microns and 35 microns be acceptable for a sterile barrier? 

During the development of the SPMC Webinar, a number of ASTM Integrity tests were reviewed for sensitivity of detection level. A number of these standards ran interlab studies using a specifically sized orifice or specifically sized implements for creating defects such as channels in seals. The reported sensitivity of these methods is based on the hole or channel size evaluated and reliably detected; in some cases, the actual sensitivity may be greater. The pressure decay, vacuum decay, and trace gas tests define sensitivity levels based on flow rates. In order to translate these units of measure (standard cubic centimeters/second) into an effective hole size, we contacted members of the subcommittee task groups involved in the development of the standards and the interlab studies. They were able to give us the additional details needed to work through an on-line orifice calculator. The ASTM F2391 Standard Test Method for Measuring Package and Seal Integrity Using Helium as the Tracer Gas indicates the ability to test down to 0.1 micron.

The FDA Web site lists many of these methods as Recognized Consensus Standards, which may be acceptable for use to test packaging for medical device products in 510K applications. Package testing levels for integrity are continuing to be developed in ASTM to improve the sensitivity of detection. The choices span methods with very high detection sensitivities using highly precise equipment and those less sensitive that can be used quickly, inexpensively, and at a large scale. Whatever limits are to be set for a package, the criteria and method for detection should be agreed upon and appropriate for the packaged product use.

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