Superhydrophobic Bio-Coating Made by Co-Continuous Electrospinning and Electrospraying on Polyethylene Terephthalate Films Proposed as Easy Emptying Transparent Food Packaging

Interest in coated films with micro/nanofeatures has grown rapidly in recent years due to their enhanced functional performance and better durability under demanding contact conditions or aggressive environments. In the current work, it is reported a one-step co-continuous bilayer coating process to generate a multilayer film that rendered superhydrophobicity to a polyethylene terephthalate (PET) substrate. A continuous coating based on ultrathin polylactide (PLA) fibers was deposited onto PET films by means of electrospinning, which increased the water contact angle of the substrate. Sequentially, nanostructured silica (SiO2) microparticles were electrosprayed onto the coated PET/PLA films to achieve superhydrophobic behavior. This multilayer was then treated at different annealing temperatures, that is, 150 °C, 160 °C, and 170 °C, in order to create interlayers’ adhesion to each other and to the substrate. It was found that co-continuous deposition of PLA fibers and nanostructured SiO2 microparticles onto PET films constituted a useful strategy to increase the surface hydrophobicity of the PET substrate, achieving an optimal apparent water contact angle of 170° and a sliding angle of 6°. Unfortunately, a reduction in background transparency was observed compared to the uncoated PET film, especially after electrospraying of the SiO2 microparticles but the films were seen to have a good contact transparency. The materials developed show significant potential in easy emptying transparent food packaging applications.