Incorporation of ligno-cellulose nanofibrils and bark extractives in water-based coatings for improved wood protection

CNFs (cellulose nanofibrils) and BEs (bark extractives) are low-cost, sustainable, and biodegradable materials, which had potential to be used in numerous applications, including biomass composites, food packaging, and polymer materials. In this study, CNFs with high lignin content (LCNFs) and BEs were prepared from western red cedar and lodgepole pine bark, respectively. These were then homogeneously dispersed in water-based acrylic coatings to paint on the surfaces of spruce and sugar maple wood samples. The results showed that the distribution of LCNFs and BEs in the coatings was homogeneous and uniform. The LCNFs had a significant effect on improving the hardness (2-3 levels higher than neat coating) and abrasive resistance (40% higher wear-out rotations), and a content of 2% was sufficient to realize these optimum coating properties. Moreover, the incorporation of LCNFs and BEs increased the aging resistance of the water-based acrylic paints due to an effective inhibitory effect on crack formation and extension conferred by the LCNFs and the free radical scavenger activity provided by the BEs during the aging process. The optimum content of 2% for LCNFs (2% in primer and 2% in top coating) and BEs (in top coating) substantially increased the effectiveness of water-based acrylic coatings in regard to wood protection.