Layer-by-layer filtration of cellulose nanofibrils and poly(vinyl alcohol) for grease and oxygen barriers on paper
摘要
The production of biodegradable coatings using aqueous suspensions of cellulose nanofibrils (CNFs) and solutions of poly(vinyl alcohol) (PVOH) is costly due to the energy expenses associated with evaporating water. To address this issue, CNF-PVOH composite coatings were prepared through a two-step filtration process, where a low basis weight CNF coating was formed during the first filtration, acting as a matrix that absorbed PVOH in the second filtration. The CNFs used in this study were fibrillated by refining, maintaining some fiber presence, which made the material more economical while creating pores for PVOH to fill. By adjusting the dewatering methods and the target basis weight of the initial CNF layer, we controlled the solids content of the CNF coatings prior to PVOH filtering. When filtering PVOH through CNF coatings prepared by various methods, PVOH accumulated on the surface more readily in CNF samples that underwent heated compression prior to filtration due to densification of the CNF layer, achieving PVOH weight percentages near 100% on the surface. The grease resistance of the CNF-PVOH coatings improved with the addition of PVOH. Creating the CNF-PVOH composite yielded an oxygen transmission rate of 0.054 cm3 m−2 day−1 atm−1 was achieved with a 35.5 g basis weight of 24% CNF and 76% PVOH.