Highly stable and dispersible nanocrystalline cellulose (NCC) was successfully isolated from oil palm empty fruit bunch microcrystalline cellulose (OPEFB-MCC), with yields of 93% via a sono-assisted TEMPO-oxidation and a subsequent sonication process. The sono-assisted treatment has a remarkable effect, resulting in an increase of more than 100% in the carboxylate content and a significant increase of approximately 39% in yield compared with the non-assisted process. TEM images reveal the OPEFB-NCC to have rod-like crystalline morphology with an average length and width of 122 and 6nm, respectively. FTIR and solid-state C-NMR analyses suggest that oxidation of cellulose chain hydroxyl groups occurs at C6. XRD analysis shows that OPEFB-NCC consists primarily of a crystalline cellulose I structure. Both XRD andC-NMR indicate that the OPEFB-NCC has a lower crystallinity than the OPEFB-MCC starting material. Thermogravimetric analysis illustrates that OPEFB-NCC is less thermally stable than OPEFB-MCC but has a char content of 46% compared with 7% for the latter, which signifies that the carboxylate functionality acts as a flame retardant.
TEMPO-oxidize nanocellulose (TONC) suspension has been obtained from total chlorine free (TCF) oil palm empty-fruit-bunches (OPEFB) pulp using 4-acetamido-TEMPO (2,2,6,6-tetramethyl piperidin-1-oxyl) mediated oxidation with sodium hypochlorite and sodium bromide in water at 25 °C and pH 10. TONC suspension with varied content from 0.5 to 6% (w/w) reinforced polyvinyl alcohol (PVA) polymer based nanocomposite films were prepared by the casting method. The structural interaction between the TONC and PVA was characterized by the Fourier transform infrared (FT-IR) spectroscopy, nuclear magnetic resonance (NMR) spectroscopy, X-ray diffraction (XRD) and scanning electron microscopy (SEM). It was found that the 4% (w/w) TONC content reinforced nanocomposite exhibited the highest tensile strength and modulus with an increase of 122% and 291% respectively, compared to PVA while the elongation at break decreased about 42.7%. Thermal stability of PVA based nanocomposite films was improved after incorporation of TONC. Incorporation of TONC in PVA film increases its crystallinity due to strongly linking between the hydroxyl groups of materials however considerable decreases beyond 2 wt% loading are observed. TONC incorporation beyond 2 wt% also reduces the melting temperature peaks and enthalpy of nanocomposite films. FT-IR spectra, NMR and SEM indicate that there is interaction between the TONC and PVA.
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