Characterization of Bamboo Nanocellulose Prepared by TEMPO-mediated Oxidation

Abstract

The synthesis of TEMPO-oxidized bamboo cellulose nanofibrils (TOBCNs) was attempted using two locally available species in Thailand (Dendrocalamus asper and D. membranaceus). Bamboo powder was first delignified with NaClO2. The obtained bamboo holocelluloses (BHs) were then oxidized via a TEMPO/NaBr/NaClO system in water at pH 10 for 2 h. The effects of NaClO addition level on the weight recovery ratio, carboxylate content, and nanofibrillation yield were studied. At a higher level of NaClO addition, the weight recovery ratio of TEMPO-oxidized bamboo holocelluloses (TOBHs) decreased from 90% to 70%, while the carboxylate content of TOBHs increased up to 0.8 mmol/g to 0.9 mmol/g for both species. Fourier transform infrared spectra indicated that C6-hydroxyl groups of cellulose were converted to negatively-charged carboxylate groups. After a gentle mechanical treatment with water, transparent liquid of TOBCNs were obtained after the removal of unwanted fraction, which gave a nanofibrillation yield of more than 90% at a NaClO addition level of 7.5 mmol/g to 15.0 mmol/g-BHs. Well individualized TOBCNs were successfully prepared and had a length of several microns and an average width of 5 nm to 7 nm under transmission electron microscopy. Thus, ultra-long TOBCNs are applicable for use as nano-reinforced polymer composites in non-food industries.

Effect of Length of Cellulose Nanofibers on Mechanical Reinforcement of Polyvinyl Alcohol

“…It indicates that the chemical structure of CNF largely remains the same. Specifically, a strong absorption peak around 3300 cm −1 is observed, corresponding to the stretching vibration of the hydroxyl group [ 50 ]. The intensity of the O–H stretching absorption peak was more pronounced for the CNF20 and CNF10 compared with CNF5, showing a higher proportion of cellulose within fibers [ 51 ].…”

“…The vibration peak at 2910 cm −1 is assigned to the C–H stretching vibration of the methylene group, whereas the C–H symmetric bending of CH 2 appears at 1410 cm −1 [ 52 , 53 ]. At the same time, CNF exhibit characteristic bonds at 1595, 1105 and 898 cm −1 , which are attributed to the stretching vibration of COONa derived by the TEMPO-mediated oxidization, C–O–C stretching of the ether bond and characteristic absorption of the cellulosic anomeric carbon C1, respectively [ 46 , 47 , 48 , 49 , 50 , 51 ]. Moreover, the intensity of the COO − peak exhibits the following order: CNF20 > CNF10 > CNF5, indicating the degree of carboxylation increased with increasing NaClO contents, which consists with conclusion of Puangsin et al [ 51 , 54 ].…”

Preparation of Silver Nanoparticles Deposited on TEMPO-Oxidized Cellulose Nanofibers

“…During the oxidation treatment, the hydroxyl groups in primary carbon at the C-6 position are changed to sodium carboxylate groups. This generates electrostatic forces, which facilitate the fibrillation of CNFs with lower energy consumption [4,5]. Additionally, the sodium counterions in TEMPO-oxidized cellulose can effectively exchange the silver ions in silver nitrate solution [6].…”

Surface Modification and Mechanical Properties Improvement of Bamboo Fibers Using Dielectric Barrier Discharge Plasma Treatment

“…The extractive-free bamboo can be converted to micro- or nanoscale cellulose materials by a chemical treatment process. The 2,2,6,6-tetrametylpiperidine-1-oxyl (TEMPO)-mediated oxidation system is one potential and efficient process to extract holocellulose from the original plant [ 20 ]. The BFs were oxidized using a TEMPO oxidation; when oxidation occurs, they mostly disintegrate into individual holocellulose after being removed from the undesired fraction [ 21 ].…”