Related Experiment Videos
In vivo testing of a biostable polyurethane
M Szycher1, A M Reed, A A Siciliano
1PolyMedica Industries, Inc., Woburn, MA 01801.
Journal of Biomaterials Applications
|October 1, 1991
Summary
Medical grade urethane elastomers suffer from environmental stress cracking (ESC) due to enzyme-induced ether linkage degradation. ChronoFlex urethane, engineered without ether linkages, is expected to resist this degradation.
Area of Science:
- Biomaterials Science
- Polymer Chemistry
- Medical Device Materials
Background:
- Commercially available medical grade urethane elastomers are susceptible to environmental stress cracking (ESC).
- ESC manifests as surface microcracking in elastomers under strain in vivo.
- Harder urethane compounds generally exhibit a higher strain threshold for ESC compared to softer ones.
Purpose of the Study:
- To investigate the mechanism of environmental stress cracking in urethane elastomers.
- To develop a urethane elastomer formulation resistant to in vivo degradation.
- To introduce ChronoFlex urethane as an ESC-immune alternative.
Main Methods:
- Analysis of urethane elastomer compositions and their susceptibility to ESC.
- Hypothesizing enzyme-mediated degradation of ether linkages as the cause of ESC.
- Molecular engineering of ChronoFlex urethane to eliminate ether linkages.
Main Results:
- Environmental stress cracking (ESC) in urethane elastomers is linked to the presence of ether linkages.
- Softer urethane compositions with more ether linkages show increased susceptibility to microcracking.
- Harder compositions demonstrate a higher strain threshold, but are not immune to ESC.
Conclusions:
- Enzymatic attack on ether linkages is the primary mechanism driving ESC in urethane elastomers.
- ChronoFlex urethane, lacking ether linkages, is theorized to be immune to environmental stress cracking.
- This novel composition offers a potential solution for long-term in vivo applications requiring material stability.