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Characterisation of Bionate polycarbonate polyurethanes for orthopaedic applications
C Geary1, C Birkinshaw, E Jones
1Department of Materials Science and Technology, University of Limerick, Limerick, Ireland.
Journal of Materials Science. Materials in Medicine
|June 13, 2008
Summary
Polycarbonate polyurethanes (Bionate 75D and 80A) were tested for joint replacements. Compounding and molding significantly reduced molecular weight, especially with hydroxyapatite filler, impacting mechanical properties.
Area of Science:
- Biomaterials Science
- Polymer Science
- Orthopedic Engineering
Background:
- Polycarbonate polyurethanes (PCUs) are candidates for biomimetic joint replacement systems.
- Understanding material degradation and property changes during processing and aging is crucial for implant longevity.
Purpose of the Study:
- To characterize Bionate 75D and Bionate 80A PCUs for joint replacement applications.
- To evaluate the effects of compounding, molding, and filler incorporation (hydroxyapatite, carbon fibers) on material properties.
- To assess the impact of aging on mechanical performance.
Main Methods:
- Molecular weight determination (Mw) via gel permeation chromatography.
- Melt rheometry to assess viscosity.
- Mechanical testing (tensile tests) on conditioned and aged specimens.
- Differential scanning calorimetry (DSC) for glass transition temperature (Tg).
Main Results:
- Molding Bionate 75D reduced molecular weight by 30%; twin-screw extrusion had similar effects.
- Carbon fiber inclusion caused further degradation (Mw halved), while hydroxyapatite drastically reduced Mw (to <25%) suggesting chemical interaction.
- Fillers reduced melt viscosity; Tg slightly increased.
- Carbon fibers showed reinforcing effects but suffered from poor wetting and pull-out.
- Water absorption stabilized after 2 weeks, but tensile properties degraded between 1-5 months of exposure, showing lower stress levels.
Conclusions:
- Processing significantly degrades PCUs, particularly with hydroxyapatite filler, necessitating careful control.
- While fillers offer some benefits, issues like poor fiber-matrix adhesion and long-term water-induced property changes must be addressed for joint replacement applications.
- Further research is needed to optimize PCU formulations and processing for enhanced durability in orthopedic implants.
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