To Burst Test Or To Peel Test?
When testing the strength of your sterile package is it better to use a peel test or a burst test? The answer is not straightforward.
This article first appeared in Medical Packaging Innovation.
There are standards for both options: ASTM F 2054 and F 1140 for burst testing and for peel testing EN 868 or ASTM F88. All these standard test methods are referenced (and given equal weight) in ISO 11607.
The peel test has two huge advantages: it is comparable between laboratories and the standards give an acceptance criterion. The test method is to cut 15mm (or 1”) wide strips from the centre of each side of the pack. These strips are loaded into a tensile machine and the two layers of material separated in a 180° peel test. The pass mark is related to the peak separation force and the sample width.
The burst test has two massive advantages: it tests the entire seal length of the seal and a large number of samples can be processed quickly. If your pack seal has weak corners you would never know it with a peel test! It is of course possible to peel the entire length of the pack, but this is not the test in the standards and is not always easy to set up. The burst test involves inflating the pack (using air injection usually from a needle) whilst measuring the internal pressure. It is very difficult to produce a repeatable test between laboratories: the air injection rates and pressures vary; the A to D on the pressure sensors will vary (is the peak pressure actually recorded?); packs flex and move during testing; the overall set up (including taping of porous packs) can vary significantly. The lack of an acceptance criterion in the standards can be overcome using transit simulation. If the packs are still intact after transit then the seal strength found, at this stage, is sufficient to protect the contents.
So which is best? I recommend burst testing in production and validation. It is quick and can be applied to a large number of samples, but crucially it tests the entire seal. The place for peel testing is good inwards testing of 3 sided pouches, it produces results which can be compared to those of your pouch supplier.