Medical Polyoxymethylene: A Versatile Thermoplastic Polymer for Medical Devices
Medical Polyoxymethylene |
Polyoxymethylene (POM), also known as acetal, is a thermoplastic polymer derived from formaldehyde. It is known for its self-lubricating properties, dimensional stability, transparency, and wear and chemical resistance. Due to its biocompatibility and mechanical properties, POM is increasingly being used in medical devices.
Properties That Make it Suitable for
Medical Applications
POM exhibits good biocompatibility, making it suitable for internal medical
uses. In cytotoxicity tests as per ISO 10993-5, POM extracts show no toxic,
irritant, or sensitization effects. It is non-pyrogenic and has a long history
of safe clinical use. Medical
Polyoxymethylene self-lubricating properties reduce friction and wear
on moving parts. This results in lower particulate generation, which is
important for implants and devices in direct contact with body tissues or
fluids. It is also very abrasion resistant.
POM has high impact strength across a wide temperature range from -40°C to
+95°C. This allows devices to withstand drops or impacts without damage. Its
dimensional stability means devices maintain tight tolerances through
autoclaving or repeated uses. POM is also transparent, which is beneficial for
devices where visualization is important. It is impermeable to water, steam,
and most chemicals, protecting devices from degradation. POM's
radio-transparency enables use in CT and MRI guided procedures without image artifacts.
Uses in Medical Devices
Due to the above properties, Medical Polyoxymethylene is increasingly used in
medical devices like:
Surgical and Dental Instruments: POM replaces metal in devices like bone mills,
surgical blades, and dental probes for its self-lubricity, transparency, and
chemical resistance. This reduces hand fatigue and improves visualization.
Orthopedic Implants: POM bushings and bearings in orthopedic implants offer
low-wear performance. Its strength and resilience withstand impacts from
activities of daily living.
Endoscopy Tools: POM components in gastrointestinal, urological, and
arthroscopic endoscopes offer chemical resistance and transparency for clear
visualization. Its strength and flexibility withstand repeated bending, twisting,
and cleaning cycles.
Dialysis Components: POM pumps, valves, and connectors in dialysis machines
provide leak-proof performance over many blood-contact cycles due to its
impermeability.
Diagnostic Devices: Touch probing tips and inserts in 3D surface scanning
devices use POM for its smooth, low-friction surface to scan without damaging
tissues.
Advantages Over Competing Materials
Compared to other thermoplastics like PVC, polycarbonate and polyamide, POM
provides better strength, chemical resistance and impact resistance. Though
more expensive than these, its mechanical properties enable thinner wall
sections for lighter devices.
Metals are stronger but increase device costs and weight. POM matches many
strength requirements of aluminium and stainless steel at lower densities. It
eliminates issues of corrosion, delamination or galvanic interactions seen with
some metal combinations.
POM outperforms thermosets like acrylic and epoxies through its Ability to
undergo gamma, EB, and EtO sterilization without degradation. Its melt
processability allows integration of complex parts and close tolerances
compared to machined thermosets.
Emerging Areas of Use
3D printing of Medical Polyoxymethylene is gaining ground for prototyping and
low-volume production of complex, personalized medical components. POM
multi-material prints combine materials like nylons for structural parts and
POM for bearings in one print.
Nanocomposite POM incorporating carbon nanotubes or hydroxyapatite shows
potential to deliver properties like conductivity, osteointegration and
antimicrobial effects for next-gen implants. Surface modification by plasma
etching or coating can further enhance POM's hemocompatibility or antibacterial
efficacy.
Thanks to a unique blend of mechanical, chemical and processing advantages,
polyoxymethylene continues expanding its role in medical devices. Ongoing
material and process developments aim to sustainably deliver next-gen
capabilities like multi-functional performances and personalized manufacturing.
Its versatility and track record establish POM as a polymer well-suited for
medtech innovations.
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