Morphological and property characteristics of surface-quaternized nanofibrillated cellulose derived from bamboo pulp

In this work, quaternized nanofibrillated cellulose (Q-NFC) was isolated from bamboo bleached kraft pulp through the pre-treatment using 2, 3-epoxy-propyltrimethylammonium chloride (EPTAC) in an aqueous alkaline media and subsequent high-pressure homogenization. A series of aqueous Q-NFC dispersions with different contents of positively charged trimethylammonium groups on the surfaces of fibrils were obtained. With the amount of added EPTAC increased, the solid recovery ratio, surface charge contents, zeta potential values, and extent of nanofibrillation gradually increased for the as-obtained Q-NFCs. TEM images of Q-NFCs revealed that the incorporation of quaternary ammonium groups contributed to the defibrillation into finer nanofibrils with more uniform width distribution. With an increase in the positive charge contents, both degree of polymerization and decomposition temperature of the Q-NFC films decreased slowly. Steady-state rheological result demonstrated that the maximum shear viscosity was achieved for the Q-NFC0.6 dispersion with the medium charge content. The Q-NFC films with higher charge content displayed superior transparency and tensile strength. Furthermore, the oxygen transmission rate of PLA films was remarkably decreased dramatically from 216.0 to 10.3 mL m −2 day −1 after laminating a thin layer of Q-NFC0.6 on the one side. As compared to TEMPO-oxidized NFC from the same pulp, the surface-charged Q-NFC exhibited higher optical transmittance, shear viscosity, and thermal stability as well as comparable oxygen-barrier properties. Graphical abstract