Standard Test Method for Detecting Seal Leaks in Porous Medical Packaging by Dye Penetration
ASTM F1929 testing defines materials and a procedure that will detect and locate a leak equal or greater than a channel formed by a 50 μm (0.002 in.) wire in package edge seals formed between a transparent film and a porous sheet material. A dye penetrant solution is applied locally to the seal edge to be tested for leaks. The package will be visually inspected for dye penetration after contact with the dye penetrant for a specified time.
Harmful biological or particulate contaminants may enter the device through leaks. These leaks are frequently discovered at seals between package components of the same or dissimilar materials. Leaks may also result from a microscopic pinhole in the packaging material that is invisible to the human eye.
The dye solution used in penetration testing will wick through any porous material over time, but normally not within the suggested maximum time. If wicking does transpire, it may be verified by observing the porous side of the subject seal area. The dye will have discolored the surface of the material.
There is no general consensus regarding the level of leakage that is likely to be detrimental to a particular package. However, since ASTM F1929 testing is designed solely to detect leakage, components that illustrate any indication of leakage are usually rejected.
- ASTM F1929 testing is limited to porous materials which can retain the dye penetrant solution and prevent it from discoloring the entire seal for a minimum of 20 seconds.
- Prior to ASTM F1929 testing, all test specimens must be conditioned.
- If ASTM F1929 testing is used as the quality control method, the test specimen must consist of a complete packaged device.
- Packaging must be free of condensation or any other source of liquid water. Water already in the seal defects may render them undetectable with a dye penetrant.
- ASTM F1929 procedure requires that the dye penetrant have good contrast to the opaque packaging material.
In the Burst Test, air is introduced into the package at a predetermined pressure and flow rate. The porosity (or lack thereof) of the package material determines the inflation rate for the burst test. Because air escapes through the walls of a porous package during inflation, the flow rate must be increased to compensate for the lost air through the walls and create the back pressure in the porous package. This pressure creates the force needed to rupture the seal.
In the Creep Test, a whole package is inflated to a constant pressure, which is then held for a specified time, resulting in a pass / fail result. The Creep Test provides a test for slow shear of the adhesive bond similar to a dead weight hanging on the seal.