No abstract

Polyisocyanate was used to chemically functionalize carboxylated cellulose nanofibers (CNF-C). Composites of CNF-C/ monomer casting nylon (MC nylon) and modified CNF-C/MC nylon were fabricated by anionic ring-opening polymerization. The mechanical characteristics of the MC nylon composites and the dispersion of the CNF-C in the MC nylon were studied. The tensile strength and impact strength of composites were first increased with CNF-C addition, but then decreased as further CNF-C was added. The composites had good mechanical properties when CNF-C was added to MC nylon at 1.0 wt%, and the tensile strength and impact strength were increased by 21.2% and 34.9%, respectively, compared to MC nylon. When modified CNF-C was added at 1.5 wt%, the tensile strength of composites was increased by 47.90%. The addition of CNF-C causes an increase in the melting point, crystallinity, and crystallization temperature, which was confirmed by differential scanning calorimetry (DSC). The modified CNF-C had better dispersibility in MC nylon which was confirmed by scanning electron microscopy (SEM).

Through analysis of the transformation of carbon sources including glucose, fructose, and 5-hydroxymethylfurfural in hydrothermal carbonization (HTC) and the adsorption of carbon tubes (CNTs) with them, the formation mechanism of a hydroxyl-rich carbon layer on the CNT surface is clearly revealed. During HTC, the adsorption of furan and aromatic clusters and even primary particles by CNTs by π–π interaction is noticed as the key condition to improve the utilization rate of carbon sources and the quality of the carbon layer. The coated CNTs own a hydroxyl-rich carbon layer with a thickness of several nanometers on its surface, which provides the ability for functional applications. With the use of the hydroxyl-rich carbon layer-coated CNTs, a low-acid aqueous system is established for the hydrolysis of cellulose to sugar. Accordingly, the cellulose conversion and glucose yield are obviously improved. The route of HTC for hydroxylation of CNTs not only fundamentally avoids the use of strong acid oxidation in traditional method but also provides the useful guidance to prepare functional carbon materials with application prospects.