The effect of gamma radiation on molecular stability and mechanical properties of biodegradable polyurethanes for medical applications

Abstract

Experimental biodegradable medical polyurethanes with varying hydrophilic-to-hydrophobic segment ratios based on hydrophilic poly(ethylene oxide) MW=600 (PEO) and hydrophobic poly(ε-caprolactone) diol MW=530 and 2000 (PCL), were exposed to gamma radiation at the standard dose of 25 kGy used for sterilization. Irradiated polymers degraded to a various extent, this being associated with a reduction of mechanical properties. For the more hydrophobic polyurethanes based exclusively on polycaprolactone diol the decrease of molecular weight was in the range of 12–30% and the decrease of tensile strength was 12%. For the more hydrophilic polyurethanes based on mixtures of polycaprolactone diol and polyethylene oxide the decrease of molecular weight was in the range of 30–50% and the decrease of tensile strength was 50%. Gamma radiation insignificantly affected surface roughness of hydrophobic polycaprolactone-based polyurethanes and caused a slight increase of contact angle. For the hydrophilic polymers based on polycaprolactone diol and polyethylene oxide, gamma radiation increased by 36–76% surface roughness and decreased by 20–45% contact angle. There was also an evident change in thermal properties of the irradiated materials.