Choices in Package Strength Testing

Apr 25, 2014
By M.Turner

There are a number of choices when it comes to package strength testing for medical devices. It is a design validation requirement that packages must protect devices up to their point of use, at the end of their shelf life, and there are a number of ways this can be tested.

The first big choice is whether to carry out package strength testing using a peel test or burst test. Peel testing is effectively a ‘peel open’ tensile strength measurement of all or part of the seal area. This test is described in two standards; EN868-5*, and the FDA recognised ASTM F88 ASTM F88 / F88M Standard Test Method for Seal Strength of Flexible Barrier Materials.

These methods essentially involve the cutting of a section of the seal area and peeling in a tensile machine at a variety of angles (normally perpendicular) to the weld). These analyses have the advantage of an acceptance criterion appearing in the standards. They have the disadvantage, though, of only examining a section of the seal, and should be accompanied by a complete pack peel or other more comprehensive test.

Burst (strength) testing is a type of package strength testing with the advantage of stressing the entire seal and packaging material. Burst testers identify the weakest point in the package (blister or pouch).

There are two key standards, presenting a choice between a restrained burst and an unrestrained burst. At MET we generally use the restrained burst (ASTM F2054 / F2054M Standard Test Method for Burst Testing of Flexible Package Seals Using Internal Air Pressurization Within Restraining Plates) for packages with a surface area over 100cm2. This allows more even expansion of the pack and the avoidance of peel.

For larger products, we deploy the unrestrained burst test (ASTM F1140 / F1140M Standard Test Methods for Internal Pressurization Failure Resistance of Unrestrained Packages).This is due to the forces generated and the impracticality of the tooling.

This standard gives a choice of test methods (A, B and C). The first choice (method A) is inflation to burst, recording the maximum pressure attained. This method of package strength testing works well with porous packs up to about 3-400cm2 in surface area.

The second (method B) describes a creep test, where the pack is inflated to a predetermined pressure and held there for a period of time. This method is useful for large non porous packs which can generate a very loud bang on bursting.

The final method, ‘creep to burst’ (method C), involves inflating to a predetermined pressure, holding that pressure and then carrying on to a burst. This method is useful to obtain some measure of the ‘ease of peeling’ prior to gauging the ultimate strength of the seal.

All tests are applicable to both pouch and blister packages and permeable and impermeable materials. You can find out more about this kind of testing on our seal strength testing page.

Please contact MET to find out more, or for verification of your medical device packaging performance against any of these strength testing standards.

*Packaging for terminally sterilized medical devices. Sealable pouches and reels of porous and plastic film construction. Requirements and test methods.

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