THE EFFECT OF STRAIN STATE ON THE BIOSTABILITY OF A POLY(ETHERURETHANE UREA) ELASTOMER

The effect of deformation state on degradation of a PEUU without added stabilizers was examined in an oxidative environment that simulates t he in vivo biodegradation of the polymer. Polymer tubes were stressed uniaxially and biaxially over glass mandrels and treated in 20% hydrog en peroxide/0.1M cobalt chloride solution for 12 days at 37 degrees C. The amount of degradation was determined from the ATR-FTIR peak heigh t of the amorphous aliphatic ether absorbance at 1110 cm(-1). If a uni axial 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 correl ated with the amount of soft-segment orientation The decreased degrada tion rate was attributed to compaction of the polyether phase by orien tation, which resulted in lower permeability to oxidative agents, part icularly oxygen. Macroscopic damage was confined to a thin peeling sur face layer if the stress was uniaxial. in comparison, biaxially stress ed PEUU ruptured. (C) 1997 John Wiley & Sons, Inc.