There are a range of methods our experts use to assess pack closure integrity, the selection of which is dependent on several factors; whether the material is porous or non-porous, the intended purpose of the packaging and the contained product. These methods are:
The dye penetration test involves injecting a dye solution, including a surfactant, into the package and allowing it to contact each seal for a specific time. The package is examined for evidence of seal failure evidence by dye penetrating through the seal.
Smithers Pira usually tests medical device packages for dye penetration in accordance with either ASTM F1929, ASTM F3039 or EN 868-1. ASTM F1929 is more applicable to porous material packaging such as Tyvek® pouches; whereas ASTM F3039 and EN 868-1 are more suitable for non-porous materials including foils.
The integrity of non-porous packages can be tested using a pressure decay method. In this method, the pack is pressurised to a small overpressure - typically 50 mbar - and the rate of pressure decay is monitored using a pressure transducer.
Smithers Pira uses a Lippke 4500 Package Testing System to determine the pressure loss over time in accordance with ASTM F2095 Method A and Method B (with or without restraining plates).
The method is capable of detecting microleaks, but is less sensitive when testing packages containing wet products as the leakage route can become 'plugged'.
Tracer Gas Detection
Gas leak detection systems are used to 'sniff' for a test gas which has been earlier introduced into the package.
Smithers Pira uses a Qualitek 200 electron capture detector. The Qualitek 200 responds to SF6 and other electron capturing compounds and can detect leak rates as low as 1x10-8 ml/sec SF6.
The gas is injected into the test package and the injection point sealed with tape. The leakmeter fitted with a miniature "sniffer" probe is used to locate any leakage routes.
The technique is easily capable of detecting microleaks in non-porous medical device packaging and modified atmosphere (MAP) food packaging. In the latter application it is often used to identify leakage routes after a high oxygen content has been determined.
The technique is similar to helium leak detection which uses a mass spectrometer detector. One advantage of sulphur hexafluoride as a test gas is that it has a higher molecular weight that helium and less likely to give a false "leak" result from gas permeation through the packaging material.
The vacuum method is suitable for packages having a well-defined headspace. It relies on gas or liquid flow because the pressure inside the package is higher than the pressure in the vacuum chamber. It is suitable for detecting gross leaks (≥ 100µm) and for testing the seal strength of packages under differential pressure conditions such as those which can occur during air transportation.
Smithers Pira employs a Vacuubrand MZ 2C NT diaphragm pump with CVC 3000 controller to test smaller packages using vacuum methods including ASTM D3078 "Standard Test Method for Determination of Leaks in Flexible Packaging by Bubble Emission".
Vacuum methods are not suitable for detecting smaller leaks, especially when the package contains a wet product which may "plug" the leakage route.
Smithers Pira also tests packages in accordance with ASTM D4991.This test method covers the testing of empty containers for resistance to leakage under differential pressure conditions such as those which can occur during air transport. A larger bespoke made vacuum chamber is used for this purpose.
In the external pressure method, the external pressure causes the test gas or liquid to flow from the outside to the inside of the package. A greater differential pressure can be used compared to the vacuum method and the method does not require a headspace in the package.
We also offer testing to assess the leak resistance of closures.