Silane modification of nanofibrillated cellulose and its effect on the properties of waterborne acrylic resin

Nanofibrillated celluloses (NFC) have attracted tremendous attention as nanofillers to improve the mechanical properties of waterborne resin. In this study, NFC was prepared by mechanical fibrillation, and then modified respectively with three different types of silane coupling agents:.-aminopropyltriethoxysilane (KH550),gamma-(2, 3-epoxypropoxy) propyl trimethoxysilane (KH560), and gamma-(methacryloyloxy) propyl trimethoxysilane (KH570). The obtained NFC and modified NFCs were physically mixed with water-based acrylic resin (WAR) to prepare films by casting method. The NFC, silanized NFC, and films were analyzed by Malvern laser particle sizer, scanning electron microscopy (SEM), Fourier transform infrared (FTIR), thermogravimetric analyzer (TGA), water contact angle (WCA), rotational rheometer, and power stretchers, respectively. Results showed that NFCs were successfully prepared and modified. The KH570 modified NFC had a slightly smaller particle size, higher absolute Zeta potential and yield stress values, good thermal stability, and exhibited better dispersion and suspension stability in solution. However, the NFC modified by KH560 had the best improvement effect on the mechanical properties and hydrophobicity of WAR membranes. Adding only 0.3 wt% KH560 modified NFC could increase the tensile strength of WAR film by 131.9%, and the WCA of the film could be increased from 85.2 degrees to 101.6 degrees, which makes this study beneficial for promoting the application of nanofibrillated cellulose in WAR.