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This paper is presented courtesy of TM Electronics,
Inc.
Flexible Package Seal Strength Testing
Stephen Franks
T.M. Electronics, Inc.
Presented November 18, 1996
at the IoPP Medical Device Task Force
Introductory
Remarks:
Thank
you for the opportunity to speak to you today
in an open, non-competitive, and problem solving
format that is a growing benefit for the medical
packaging industry.
I
want to discuss one of the test techniques used
in package seal strength testing. As you know,
there are two types of testing, the tensile pull/peel
tests and the burst and creep tests. The burst
and creep tests are inflation tests of the package
and the tensile pull/peel is a mechanical peel
test.
We
had an excellent discussion of the tensile test
at our last meeting and I am delighted to be able
to present information on the burst and creep
tests as well as an enhanced creep test called
the "Creep to Failure" test.
I
am one of the principals in T.M. Electronics,
a manufacturer of instrumentation for seal strength
testing and leak testing of medical devices. I
have been involved in the design and manufacturing
of medical devices, IVD’s and medical instrumentation
since 1972. The growth of innovation and sophistication
of the devices and their packaging has been tremendous
in those years, which is a real tribute to this
industry. I want to share some of the history
of the seal strength tester to show its evolution
and how it parallels the growth of the industry.
First
let me define seal strength as the mechanical
strength of the seal. Seal strength testing is
then a measure of the sealed article’s ability
to resist the forces applied. This force may arise
from processes such as sterilization or air transport
which cause differential pressures in the package
or from forces applied by the device contained
in the package, or other external means.
These
instruments are used to measure some analog of
the package resisting forces while being subjected
to a repeatable testing process.
Introduction:
History and Background of the Burst and Creep
Test
About
1979, Earl Clifford, and engineer for ARO Corporation
was asked to develop a new heat sealer for flexible
medical packaging . As he worked diligently at
his project he soon saw the need to quantify his
progress.
Earl
was aware of the usual tensile peel test used
in the adhesive industry, but as he describes
it ( I quote) "it took a lazy engineer to
find a way to do all those evaluations without
cutting up thousands of samples."
It
seemed to Earl that testing the entire seal at
once was a more effective procedure than, perhaps,
missing the weak spot in the seal by sampling
the perimeter of the seal. Thus was born the idea
of the "burst" test, a test that inflates
the pouch until one of the seals fails and then
capturing that peak pressure value.
Earl,
tells the story of his first showing of his new
heat sealer to the Association of OR Nurses. When
he returned from a demonstration, his boss asked
how the sealer was received. Earl said "they
liked it, but they really went nuts over the tester".
From there both the burst and creep test were
empirically derived for flexible pouches. The
"creep" test was developed to test peel
strength pre and post sterilization by holding
a fixed pressure on the pouch for a fixed time.
This paper is presented courtesy
of TM Electronics, Inc.
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