The effect of strain state on the biostability of a poly(etherurethane urea) elastomer

Abstract

The effect of deformation state on degradation of a PEUU without added stabilizers was examined in an oxidative environment that simulates the in vivo biodegradation of the polymer. Polymer tubes were stressed uniaxially and biaxially over glass mandrels and treated in 20% hydrogen peroxide/0.1 M cobalt chloride solution for 12 days at 37 degrees C. The amount of degradation was determined from the ATR-FTIR peak height of the amorphous aliphatic ether absorbance at 1110 cm-1. If a uniaxial stress was applied, degradation was inhibited and the amount of surface ether remaining after treatment increased linearly with strain. If the stress was biaxial, the amount of degradation was not reduced unless the strain was greater than 200%. Decreased degradation correlated with the amount of soft-segment orientation. The decreased degradation rate was attributed to compaction of the polyether phase by orientation, which resulted in lower permeability to oxidative agents, particularly oxygen. Macroscopic damage was confined to a thin peeling surface layer if the stress was uniaxial. In comparison, biaxially stressed PEUU ruptured.

Relationship between nanoscale deformation processes and elastic behavior of polyurethane elastomers

“…Although the melting point was sub-ambient, the possibility existed that stretching induced some amount of soft segment crystallization at ambient temperature. The most distinctive indication of crystallization was a band at 996 cm K1 in the infrared spectrum [22]. The effect of strain on this region of the infrared spectrum of PEU and PEUU is shown in Fig.…”

Environmental stress cracking performance of polyether and PDMS‐based polyurethanes in an in vitro oxidation model

“…Control and test specimens were held in a clinically relevant strain state by inserting them into glass vials (15 × 45 mm) to hold them in a U‐shape (Figure ). This is a novel strain state compared to those used in other published studies on the oxidative degradation of medical polyurethanes; other studies have used unstrained specimens or constant or dynamic uniaxial or biaxial tensile loading . This strain state was chosen to most accurately represent strain states that are possible for cardiac leads in vivo .…”

Biodegradation mechanisms of polyurethane elastomers

“…1 Several in vitro and in vivo experiments have provided strong evidence to support this synergistic effect of oxidation and residual stress. 7,17,18 For example, the elimination of residual stress through annealing has been shown to prevent ESC but not surface oxidation. Whereas, a thin film coating that served as a barrier to reactive oxygen species and protein interactions protected the polyurethane from both surface oxidation and ESC.…”