Sustainable micro/nano-fibrillated cellulose containing linerboard packaging with enhanced ply-bond strength by controlled fibrillation, addition rate, and retention

Abstract

Ply-bond or interply bond strength, is critical for linerboard packaging, which is typically manufactured using a multi-ply structure. In this study, lignin-containing micro- and nanofibrillated cellulose (LMNFC) from unbleached softwood kraft pulp was prepared at low and high fibrillation levels. Ply-bond performance was evaluated by incorporating LMNFC at varying concentrations and fibrillation levels into the top ply of two-ply sheets. The incorporation of LMNFCs at 10.5 % and 20.9 % reduced air permeability and improved sheet density, tensile strength, and tensile energy absorption. High-fibrillated LMNFC at 20.9 % increased ply-bond strength by 75.6 %. However, functionalizing low-fibrillated LMNFC with 0.8 wt% cationic starch produced a synergistic effect, increasing the ply-bond strength by 146 %, tensile strength by 14 %, and short-span compression by 10 %. These findings suggest that the ply-bonding is strongly influenced by LMNFC concentration and fibrillation level. The synergistic effect of starch and LMNFC supports the hypothesis that starch enhances LMNFC, resulting in exceptionally high bonding. This research provides an eco-friendly process to significantly enhance linerboard properties for packaging applications.