2.2.3. Thermal Post-Treatment

PET/PLA films and PET/PLA/SiO2 films were annealed by placing the PET coated films between Teflon sheets in a hydraulic hot-press model-4122 from Carver, Inc. (Wabash, IN, USA) without applying pressure. Firstly, different temperatures (90 ◦C, 120 ◦C, 140 ◦C, 160 ◦C, and 170 ◦C) were applied to the PET/PLA samples in order to find a balance between hydrophobicity, layer adhesion, and film transparency. An annealing time of 15 s was applied to obtain homogenous sample morphology where the structure of the mat was no longer seen. Similarly, for the PET/PLA/SiO2 samples, different temperatures (150–170 ◦C) were applied to optimize interlayer adhesion.
