Dispersing and stabilizing cellulose nanoparticles in acrylic resin dispersions with unreduced transparency and changed rheological property

This paper evaluates the potential of using 2,2,6,6-tetramethylpiperidin-1-yl)oxyl (TEMPO)-oxidized cellulose nanoparticles (T-CNPs) as additives to tune the rheology of water-based acrylic resin (AR) coatings for flexible packaging applications. Three T-CNPs of T-CNF, T-MCC, and T-CNC were prepared from three starting cellulosic materials: cellulose nanofibers (CNF), microcrystalline cellulose (MCC), and cellulose nanocrystals (CNC), respectively. Their sizes ranged from 20 nm to 20 mu m in diameter, and 234 nm to over 500 nm in length. The oxidation imparted carboxyl groups on the surfaces of nanoparticles ranging from 1.99 to 2.79 mmol/g and increased the zeta-potentials of the nanoparticles, clearly improving the dispersibility and stability of the CNPs in AR. The AR/T-CNP dispersion showed unreduced transparency. The morphologies of the T-CNPs affected the rheological properties of the AR/T-CNP dispersions. The larger aspect ratio of T-CNF and T-MCC resulted in the high viscosity and solid-like viscoelastic behavior of the AR/nanoparticle dispersions at a concentration of 0.78 wt%. The CNC and T-CNC with a smaller particle size and aspect ratio had less effect on the viscosity and rheological behavior of the resulting dispersions compared with the others-even at a high content of 1.30 wt%. Due to a lower aspect ratio but a relatively large particle size, the AR/T-MCC dispersions exhibited elastic gel-like rheological properties at a low content.