*3.6. Wettability Performance of Films*

Another important issue in films for food packaging is their protection against humidity. Thus, the water contact angle was measured to get information regarding the surface hydrophilicity/hydrophobicity of the materials. Table 5 shows the water contact angle measurements. PLA presented a WCA value of 67.2◦ , similar to that obtained by Carbonell-Verdú et al. [22], while PBAT showed a significantly higher WCA value of 74.1◦ , being more hydrophobic. The PLA/PBAT blend showed even significantly higher values than those of PBAT, probably due to the high roughness of this formulation since the wettability is strongly dependent not only on the surface chemical properties but also on the surface topography [55]. The incorporation of GR into the PLA/PBAT blend produced a significant decrease (*p* < 0.05) of the WCA, particularly evident in those formulations with a high amount of GR (15 and 20 phr), increasing the hydrophilicity of the surface. Meanwhile, the incorporation of 5 and 10 phr led to a reduction of 3◦ of the WCA of PLA/PBAT matrix. An excess of GR, such as in the case of PLA/PBAT\_15GR and PLA/PBAT\_20GR, produced an increase in the size of PBAT domains. However, the WCA of these formulations were significantly lower than that of PBAT. These behaviors could be ascribed to the lower dispersion of PBAT domains into the polymeric matrix as well as the loss of the interfacial tension between PLA and PBAT [56].
