Strength and Moisture-Related Properties of Filter Paper Coated with Nanocellulose
The aim of this study was to assess selected properties of coatings incorporating nanocellulose, with the potential of being applied as a surface modification for cellulosic and lignocellulosic materials, particularly for applications within biodegradable packaging. Cellulose nanocrystal (CNC) and cellulose nanofibril (CNF) coatings were produced and applied on both sides of pure cellulose samples in the form of filter paper with a Mayer bar. Selected organosilicon compounds, albumin, and the TEMPO reagent were used as additional modifying substances. Coating parameters were determined, such as water contact angle, water absorption, hygroscopicity, and tensile strength. The presence of the coatings resulted in a significant increase in water vapor absorption by the substrate. Nanocellulose coatings proved to be sensitive to the water vapor and showed no barrier properties against it. However, the samples coated with nanocellulose had a noticeably lower tendency to absorb liquid water. The samples coated with modifying substances had a contact angle of &ge;90&deg;, proving that such coatings were an additional barrier to the penetration of liquid water. In the case of cellulose material coated with nanocellulose (i.e., without the addition of silane), there was no barrier effect established, thereby allowing full wetting of the substrate. The nanocellulose coatings increased the tensile strength of the samples. This increase was observed for all tested coating variants. The results obtained offer several potential routes to the manufacture of more environmentally friendly coatings and packaging materials.