Effects of multilayered cellulose-based coatings on the barrier properties of paperboard

Coating a paperboard is the most important finishing process to achieve a good barrier against oxygen, water vapor and grease, which are typically obtained with fossil-based plastics. In this study, three different cellulose-based coating components—methyl nanocellulose (MeNC), microfibrillated cellulose (MFC) and hydrophobically modified ethyl(hydroxyethyl) cellulose (HM-EHEC)—were investigated. One to five coating layers were applied to the paperboard using spray and rod coating. Combinations of different coating components, coat weights, and barrier properties at different temperatures and relative humidities were studied. Scanning electron microscopy, air permeance and contact angle measurements using water and oil were used to characterize the uncoated and coated surfaces. It was shown that the MeNC and MFC layers increased the surface wettability. On contrary, HM-EHEC coating provided surface hydrophobicity, but reduced oil repellence. According to oxygen barrier measurements, HM-EHEC seemed to provide resistance at high humidities. In addition, a coating with a low weight could not close the surface completely and resulted in a poor grease barrier. However, high-weight coatings with MFC and HM-EHEC layers were greaseproof, even at elevated temperature and humidities.