Estimation of Surface Free Energy of Poly(lactic acid) During UV-Grafting with N-Vinylpyrrolidone.

The surface free energy (SFE) of polylactic acid (PLA) during grafting with N-vinylpyrrolidone (NVP) was determined from contact angle measurements using the vOCG, Fowkes', and Owens-Wendt methods (Harmonic and Geometric mean approximation equations). A good correlation between the results of the three methods was found. Polymer film was obtained by melt extrusion and grafted with NVP using UV light and benzophenone (BP) as photoinitiator. Comparison of SFE results with those from the literature for pristine PLA showed that the correlation depends on the method used for contact angle determination and the properties of the liquids used for this measurement. This finding might promote the rational design of surface modification of biocompatible films. [ABSTRACT FROM AUTHOR]