Introduction and Objectives
Tension free polypropylene multifilament meshes are widely used for the treatment of female stress urinary incontinence. The aim of the study was to evaluate the long-term viscoelastic properties of the meshes manufactured from woven polymer filaments before and after storage in simulated body fluids. Different levels of strain were used in stress relaxation experiments in order to study the viscoelastic response of the material against in-vitro ageing conditions.
Material and Methods
Stress relaxation testing experiments were performed in specimens cut from polypropylene meshes on a TMA Q800 Dynamic Mechanical Analyzer (DMA). Constant strain levels were set at ɛ0 = 1 and 5% for both aged and non-aged specimens, respectively. The stress relaxation experiments were conducted at isothermal body temperature conditions (37°C). Dynamic Thermal response of these materials was also studied by DMA thermal scanning.
Relaxing stress levels increased with increasing ɛ0 level at t = 0, but relaxation speed remained almost constant. DMA thermal scans showed a reduction in the mesh stiffness above 40°C. Long-term viscoelastic relaxation behavior was successfully modeled by using Zener's viscoelastic solid. By applying this model on the experimentally obtained stress relaxation curves, the viscoelastic properties of the meshes were determined with satisfactory accuracy.
Results from stress relaxation testing showed that polypropylene meshes appear to be a very suitable material with respect to their viscoelastic response for the treatment of urinary incontinence.
© 2009 European Association of Urology. Published by Elsevier Inc. All rights reserved.