Medical Design Briefs - October 2022 - 13

Resistance of Notched Specimens of Plastics, were sufficient
in yielding comparable results from one experimenter to the
next. However, ASTM D 543 left too much room for variation
from experimenter to experimenter. Strain levels, exposure periods,
and acceptance criteria were at the discretion of the experimenter
and, as mentioned previously, produced a breadth
of results, making data comparisons difficult.
The HSI Plastic Testing Standard Subcommittee proposed
strains as a function of the material's modulus. The new process
grouped materials into strain brackets based on their moduli,
mitigating the problem created when comparing material
with significantly different moduli conditioned at the same
strain levels. The minimum specimen amount was also set at
five specimens per sample set within a " modulus bracket. " In
addition to establishing strain brackets, two exposure periods
were proposed: a short exposure period (24 hrs) and prolonged
exposure period (7 days). By establishing exposure periods, like
defining strain brackets, OEMs should experience reduced burden
in data comparison when selecting materials for enclosures.
In addition to strain brackets and exposure periods, the
HSI Plastic Testing Standard Subcommittee refined the
test specimen exposure methodology. How chemical disinfectants
are applied to test specimens varies from experimenter
to experimenter. The HSI Plastic Testing Standard
Subcommittee outlined guidance within the boundaries of
ASTM D 543 for standard practices for applying chemical
disinfectants to test specimens, removing another source of
variance when testing thermoplastics of medical device enclosures.
This bodywork was followed with proof-of-concept
testing. The collaborative effort yielded a new integrated
standard for conditioning, exposing, and testing thermoplastics.
This integrated standard will hopefully provide harmony
across the medical device design and manufacturing industry
and guide plastic and chemical disinfectant manufacturers
in their respective product development. As of March 2022,
HSI filed a provisional patent for this test method as part of
the HSI Surface Material and Product Certification program.
Future Objectives
The next immediate objectives are to open this subcommittee
to include more participants. At this juncture, it is
hoped that a professional body of scientists and engineers
in the medical device space will champion this initiative and
help drive it forward. Greater participation from the medical
device design and manufacturing community would help this
integrated standard move forward and evolve. An increase
in participation and agreement will hopefully generate the
necessary momentum for widespread adoption across the
medical device industry, ultimately benefiting patient care
through extended medical device enclosure design life.
This article was written by Michael F. Zettel, Senior Materials
Scientist - Compatibility, PDI R&D, Woodcliff Lake, NJ; Yubiao
Liu, Global Technical Lead in Medical Applications, Development
Associate, Eastman Chemical Company, Kingsport, TN; Mark
Lamont, Director, Mechanical Engineering, Zebra Technologies,
Lincolnshire, IL; Kay Bernhard, Director of New Business Development
- Medical, Roehm GmbH, Darmstadt, Germany; and
James Hicks, Technical Development Engineer, Solvay Specialty
Polymers, Alpharetta, GA. For more information on the subcommittee,
contact Michael Zettel at michael.zettel@pdipdi.com.
Medical Design Briefs, October 2022
www.medicaldesignbriefs.com
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Medical Design Briefs - October 2022

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