Ultrasonic spray deposition of PEGDE-crosslinked chitosan/graphene oxide coatings for enhancing gas barrier properties of polybutylene succinate films

Biobased and biodegradable polymers represent a valid and sustainable alternative to oil-based plastics, as they are renewable and address the issue related to the end-of-life of non-compostable materials. However, the poor gas barrier of biopolymers limits their use in several applications, including food packaging. In this work, chitosan/graphene oxide (CS/GO) nanocomposite coatings were successfully deposited by ultrasonic spray on a compostable polybutylene succinate (PBS) film. The moisture resistance of the chitosan coatings was improved by crosslinking with polyethyleneglycol diglycidyl ether (PEGDE). The resulting coatings were transparent, with thickness in the 1–2.5 μm range, and exhibited good adhesion to the PBS film and mechanical and scratch resistance due to the presence of GO nanofiller. In detail, the PEGDE-crosslinked CS/GO (CS/PEGDE/GO) nanocomposite coating containing 1 wt% GO allowed to reduce O2 and CO2 transmission rates by 85 % and 93 %, respectively, compared to uncoated PBS film. The permeability reduction is ascribed to the formation of compact coatings with GO nanoplates oriented parallel to the PBS substrate. Furthermore, the improvement in CO2 barrier properties was up two-time more than that related to oxygen, suggesting the use of CS/PEGDE/GO coatings in applications where gas permselectivity is required. This research demonstrates the potential of the ultrasonic spray technique for producing bionanocomposite barrier coatings with improved gas barrier performance.