Green fabrication of thermally-stable oxidized cellulose nanocrystals by evolved Fenton reaction and in-situ nanoreinforced thermoplastic starch

High performance fibers and improved interfacial interaction can enhance the properties of polymer composites. Herein, microcrystalline cellulose (MCC) was oxidized by H2O2/CuSO4, a new Fenton process, to achieve oxidized MCC (OCNCs) with 16 +/- 1% carboxyl content. Noteworthy, the thermal stability of OCNCs was superior to CNCs prepared by acid hydrolysis. Interestingly, the primary alcohol groups of MCC were selectively oxidized and OCNCs achieved 11.0 nm, 231.6 nm and 72% of average diameter, length and degree of crystallinity, respectively. Then glycerol, starch and OCNCs were reactive extruded to fabricate TPS/OCNC bionanocomposites and their structure and performance were evaluated systematically. Strikingly, significant improvement in glass transition temperature (from 63.1 to 94.5 degrees C) and notch impact strength (from 1.3 to 3.9 kJ/m(2)) were noted for the amorphous TPS/OCNCs with 1 wt % OCNCs, and its tensile strength achieved 20.5 MPa, simultaneously. The improved performance was ascribed to in situ formation of "carboxyl-hydroxyl" hydrogen bonds that acted as cross-links and improved the interfacial compatibility. We showcase the Fenton reaction and reactive extrusion as a facile strategy to prepare sustainable and biodegradable TPS/OCNC bionanocomposites with properties more suitable for everyday applications to replace petroleum-based plastic and eliminate the pollution by "microplastics".