The influence of UV irradiation on the mechanical properties of chitosan/poly(vinyl pyrrolidone) blends

The mechanical and surface properties of chitosan, poly(vinyl pyrrolidone) (PVP) and chitosan/PVP blends before and after UV irradiation have been investigated by mechanical testing (Instron) and by contact angle measurements. Air-dried specimens were submitted to treatment with UV irradiation (wavelength 254 nm) for different time intervals. The changes in mechanical properties, such as breaking strength, percentage elongation and Young's modulus have been investigated. The results have shown that the mechanical properties of the blends were greatly affected by UV irradiation, but the level of the changes of these properties were smaller in the blend than in pure chitosan and strongly dependent on the time of irradiation and the composition of the samples. The contact angle and the surface free energy were altered by UV irradiation, which indicates photooxidation and an increase of polarity. The range of these changes points to greater sensitivity of chitosan to photooxidation in comparison with PVP and chitosan/PVP blends. (c) 2004 Elsevier Ltd. All rights reserved.