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Understanding The
Complexities Of Medical Grade Polymers
A list of common considerations in polymer
selection are shown below:
• Biological Performance
- Biocompatibility
- Biostability
- Hemocompatibility
- Infection risk
• Application Performance
- Strength
- Flexibility
- Fatigue resistance
- Heat and/or electrical resistance
• Chemical Resistance
- Cleaning product resistance
- Drug resistance
- Sterilization stability
• Processability
- Thermal methods (extrusion, molding, forming)
- Solvent (casting, dipping, spinning)
- Secondary assembly (reflow, bonding)
- Compatibility with other materials within the device
• Regulatory and Compliance Requirements
- Does the material contain REACH, RoHS or other substances of
concern?
- Has the material been used in devices cleared by regulatory
agencies?
• Cost:
- Volume specific pricing
- Annual access, licensing and/or royalty fees
In addition to balancing the complex set of
material related requirements above, a device designer may
also consider whether to evaluate only materials designated by
a supplier as “medical grade.” This consideration can quickly
become challenging, as although regulatory scrutiny of devices
and demands for polymer performance has increased, there is no
universally accepted or regulated definition of a “medical
polymer.”
Beyond Biocompatibility: Why A Robust
Medical Polymer Goes Further
While formulation, manufacturing and
testing of materials for biocompatibility is a distinct and
important characteristic of a medical grade polymer, other
services such as regulatory support, change management and
security of supply are of utmost importance, and may sometimes
be overlooked during initial material selection activities.
The Association of German Engineers, VDI,
recently published a voluntary guidance document for defining
“Medical Grade Plastics.” The document attempts to provide
both polymer suppliers and medical device manufacturers and
designers clarity on best practices relating to polymer use.
Within the document, the following are
described as essential for a medical grade plastic:
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Intended to be used in a medical device,
in-vitro diagnostic or pharmaceutical packaging application
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Maintained under a change management system
for the polymer’s specification, composition, regulatory
status and manufacturing technology and site
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Quality management system for a polymer’s
development, production and handling
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Provided by the supplier with support to
the end device owner to fulfill required regulatory
requirements
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Security of supply, availability and
logistics considerations
While a globally accepted definition for a medical grade
polymer is not yet established, the above attributes speak to
LLS Health’s core definition of a medical grade thermoplastic
polyurethane (TPU). As a leader in TPU materials for medical
devices, we are encouraged and supportive of efforts to
clarify and explain essential requirements for medical grade
polymers.
Is a Non-Medical Grade Polymer “Good Enough”?
In some cases, a non-medical grade polymer may seem attractive
from a perceived efficiency perspective, especially when OEMs
plan to conduct their own biocompatibility
evaluation(s). In such cases, it can be easy to
overlook the value of change control and notification for
materials specifically designed for medical applications.
In other cases, a non-medical grade polymer
may have been used in a device for decades, as it was
evaluated prior to the availability of medical grade materials
and the validation cost to the OEM to change materials is
significant. Often, however, any efficiencies accrued by
selecting a non-medical grade polymer are more than negated
when changes or discontinuations are made to non-medical grade
polymers. Non-medical grade polymers are designed for
applications that do not require evaluation of impact on
biocompatibility and medical device regulatory and compliance
status. These situations can leave OEMs in danger of getting
stuck in a constant and costly revalidation loop for their
important product lines without the benefit of supporting
material biological and medical regulatory information.
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