Performance of Advanced\nWaterborne Wood Coatings Reinforced\nwith Cellulose Nanocrystals

Abstract

The main objective of this study was to examine the impact\nof cellulose\nnanocrystals (CNCs) in advanced waterborne wood coatings such as polycarbonate\nurethane (PCU) and hybrid alkyd varnish (HAV) in terms of coating\nperformance, mechanical properties, optical properties, and water\npermeation and uptake properties. The influence of CNCs on the overall\nquality of the various waterborne wood coatings was investigated by\nincorporating different percentages of CNCs. Varying CNC content in\ncoating formulations showed that CNCs are effective for waterborne\nwood coatings; CNCs offer both higher scratch and impact resistance\nas compared to neat coatings and have a significant reduction in water\nvapor permeation through a film with little increase in water vapor\nuptake at high concentrations. It was observed that the CNC darkened\nand reduced gloss in the coatings and viscosified the dispersion.\nThese research findings suggest that CNCs are well-dispersed at lower\nconcentrations, but at high concentrations, agglomeration occurred.\nThus, while CNCs can give better mechanical and permeation performances\nat contents of up to 5 wt %, at 1 wt % CNCs can still provide modest\nscratch and chip resistance improvement without loss of optical properties\n(gloss and color) while retaining a similar water uptake. Overall,\nit can be concluded that CNCs have the potential to be used as a reinforcement\nfiller in high-performance waterborne wood coatings.