In vitro stability of polyether and polycarbonate urethanes

Area of Science:

• Materials Science
• Polymer Chemistry
• Biomaterials Engineering

Background:

• Polyurethanes (PUs) are widely used in medical devices.
• Understanding their degradation under physiological conditions is crucial for device longevity.
• Poly-ether-urethanes (PEUs) and poly-carbonate-urethanes (PCUs) differ in their backbone structure, potentially affecting stability.

Purpose of the Study:

• To evaluate the in vitro structural stability of PEUs and PCUs.
• To compare their degradation resistance under acidic and alkaline oxidative conditions.
• To assess the influence of applied strain on PU stability.

Main Methods:

• Samples of PEUs and PCUs (sheets and catheter tubes) were subjected to 100% uniaxial elongation.
• Specimens were immersed in acidic (HNO3) or alkaline (NaClO) solutions at 50°C for 7-14 days.
• Degradation was assessed via molecular weight analysis, tensile testing, and scanning electron microscopy.

Main Results:

• PEU Pellethane showed more degradation in alkaline conditions, particularly without applied strain.
• PCUs were more susceptible to acidic oxidative conditions.
• Overall, PCUs demonstrated superior stability compared to PEUs across tested conditions.
• Material processing (shape, organization) influenced oxidation susceptibility.

Conclusions:

• Poly-carbonate-urethanes (PCUs) offer enhanced in vitro oxidative stability over poly-ether-urethanes (PEUs).
• The chemical environment (acidic vs. alkaline) differentially affects PEU and PCU degradation.
• Applied strain may influence degradation, with PEUs showing sensitivity in its absence under alkaline conditions.