Dye Penetration Testing Methods For Nonporous Packaging Materials
*Note that the methods described in this article are for nonporous materials. ASTM has a separate dye penetration guidance for porous packaging materials.
What is dye penetration testing useful for, and how does it work?
Packaging leaks can inadvertently contaminate medical devices and products. These leaks are often found at small pinholes in the packaging or breaks in the seals between packaging components. Seal channel defects can be detected via the dye penetration procedures described. Dye penetration testing is a qualitative pass/fail test. Packaging with any indication of a leak will be rejected. Note that these testing methods can qualitatively verify and locate leakage sites. However, these methods are not quantitative, and the test results can’t infer leak size.
Dye penetration detection of pinhole and channel leaks relies on capillary action. Capillary action is the tendency for liquids to rise against the force of gravity when in small tubes. Capillary action occurs when the adhesive forces between the liquid and the surface of the tube walls are greater than the cohesive forces between the liquid molecules. An example of capillary action in everyday life is a paper towel’s ability to absorb liquids. Capillary action is also how water is transported through plants. Since a pinhole or channel leak is essentially a tube and the dye penetrant solution has a surface tension less than the surface energy of flexible packaging materials, the dye penetrant will readily wet the surface of the pinhole or channel. The dye penetrant solution does not need to be “pushed” into the channel or hole for leak detection due to capillary action.
What types of packages can be tested?
The dye penetration testing methods described herein are limited to nonporous packaging materials. All types of packages can be tested for seal leaks through dye penetration testing. For example, you can test fully packaged medical devices, empty packages, or seal edge samples. Commercial fully packaged and terminally sterilized medical devices are evaluated using dye penetration testing to ensure packaging systems meet FDA package integrity requirements.
What are the dye penetration testing conditions?
For a package to be tested, it must be free of any condensation or liquid water. Water on the packaging surface can obstruct a channel, hole, or potential leak and make these leaks undetectable with a dye penetrant. If any condensation or liquid water is found, the package must be thoroughly dried at its typical storage temperature before testing.
For this method, dye solutions must have good contrast to the opaque packaging material. Most commonly, a blue dye such as toluidine blue or Triton X is used. Make sure that your packaging material has good contrast with the dye penetrant used before testing.
How is dye penetration testing for nonporous packaging materials performed?
There are two types of dye application methods for nonporous materials, Method A and Method B. Toluidine blue is the most common dye indicator used for the dye penetrant solution for both methods.
Dye Penetration Test Method A
Method A detects seal channel leaks. Method A can detect and locate leaks equal to or greater than a channel formed by a 50-micrometer wire in the edge seals of a nonporous package. Channel leaks are detected by applying a dye penetrant solution to the seal edge. Allow the dye penetrant solution to contact the seal edge for approximately 5 seconds. Channels can be visually identified within this time. If the package has a transparent side, the seal is examined visually through this side. If the package is opaque, the outside seal edge is placed against an absorbent surface for approximately 5 seconds. Then the absorbent surface is examined for the presence of stains indicating a seal channel leak. During testing, the package is rotated, and each seal edge is tested with the dye penetrant solution.
Dye Penetration Test Method B
Method B detects holes or leaks on package surfaces. Method B can see and locate a leak equal to or greater than 10-micrometers in a nonporous flat sheet. Holes are detected by placing a flat sheet of packaging material onto an absorbent surface. If testing a package, the surface of the package inspected is cut so that the packaging material can lay flat upon the absorbent surface. Common absorbent surfaces used are white chromatography paper, white filter paper, or white paper towels. An uneven spot on the absorbent surface can inhibit consistent contact between the sample and the absorbent surface and interfere with leak detection. Thus, absorbent surfaces and package surfaces must be flat to ensure Method B testing accuracy. After the package and absorbent surface are in contact, a dye penetrant solution is spread across the surface of the package sample. The dye penetrant solution should contact all areas of the package material’s surface. Next, a small roller is used to apply pressure to the sample to ensure adequate contact between the absorbent surface and the bottom surface of the sample being tested. Finally, the flat packaging sheet is carefully removed, and the absorbent surface is inspected for staining from the dye. The presence of a stain indicates a hole or leak.
Summary
A dye penetration test is a pass or a fail method of detecting defects in packaging seals. There are two methods of dye penetration testing for nonporous material, Method A and Method B. Method A is used to detect channel leaks in seal edges. In contrast, Method B is used to detect holes in the packaging surface. Overall, dye penetration testing is an important testing parameter to prove the integrity of your medical device packaging. Ensure you choose a contract manufacturing and testing organization capable of providing appropriate package integrity tests, like dye penetration testing, for your unique medical device or medical product.
MycoScience is a contract manufacturing organization specializing in sterile syringe and vial filling. MycoScience also offers Preservative Efficacy Testing, Sterilization Validations, Bioburden Testing, Cleaning Validations, Microbial Aerosol Challenge Testing, Accelerated Aging, Microbiology Testing, Cytotoxicity Testing, Bacterial Endotoxin Testing, EO Residual Testing, Package Integrity Testing & Environmental Monitoring services medical devices and allied industries. MycoScience is an ISO 13485 certified facility.
References
American Society for Testing and Materials. Standard Test Method for Detecting Leaks in Nonporous Packaging or Flexible Barrier Materials by Dye Penetration. West Conshohocken, PA, United States. (ASTM F3039-15).
