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Degradation of a Biomedical Polyurethane: Surface Integrity and Fatigue Effects

  • M. M. Sinnott
  • D. W. Hoeppner

Abstract

Polyurethanes degrade under a variety of conditions. In cardiovascular applications of polymeric materials emphasis is placed on elastomers that have extended fatigue lives. The effect of surface integrity on the performance properties of Biomer®, a segmented poly(etherurethaneurea) used on many blood contacting surfaces, has been investigated using tensile tests at room temperature, and biaxial fatigue tests at body temperature. No significant differences other than ultimate tensile strength (UTS) were noted in the stress-strain curves of the specimens with varying surfaces, however preliminary results from fatigue tests indicate a decreasing fatigue life with increasing surface roughness.

This study reports on specimen analysis prior to and following fatigue testing in an attempt to describe mechanisms for mechanical degradation related to differences in surface integrity and fatigue loading. Analysis methods used include Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM). FTIR indicated degradation of the polymer occurred related to cyclic stresses applied to the material. All fatigued specimens showed signs of degradation regardless of their surface roughness. Surface evaluation using SEM indicated the presence of micropores prior to and following cyclic loading of the specimens. Micropores seen following cyclic loading were larger and in some instances more numerous. Microcracks were observed propagating between micropores in a typical fatigue failure mechanism.

Keywords

Fatigue Life Cyclic Loading Ultimate Tensile Strength Fatigue Test Surface Finish 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

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Copyright information

© Springer Science+Business Media Dordrecht 1990

Authors and Affiliations

  • M. M. Sinnott
    • 1
  • D. W. Hoeppner
    • 1
  1. 1.University of UtahSalt Lake CityUSA

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