Characterization of microwave liquefied bamboo residue and its potential use in the generation of nanofibrillated cellulosic fiber
Bamboo raw feedstocks with large particle size (20-80 mesh) were subjected to a microwave liquefaction system, and the liquefied products were separated into biopolyols and liquefied residues. Biopolyols were first analyzed by gas chromatography mass spectrometry (GC-MS), and the main components were sugar derivatives with 2-4 hydroxyl groups and phenolic compounds derived from lignin. The residues were collected and evaluatedfor potential use in the production of nanofibrillated cellulosic fibers. Results show that liquefied residue content as well as its physicochemical properties varied with respect to particle size, liquefaction temperature, and reaction time. It was also found that residues from liquefaction reaction with the minimum residue content in this study still exhibited traced fiber structure with remaining cellulose attached with recondensed lignin. Pure white cellulose fibers were extracted from the residues with yield of 65.61% using a combination of bleaching and acid hydrolysis treatment. Nanofibrillated cellulosic fibers were generated by given the purified cellulose fibers to high-intensity ultrasonic treatment. The resulted nanofibrillated cellulosic fibers had a range of 4-2018 nm in diameter and length of 550 nm or longer, indicating the nanofibers obtained from liquefied bamboo residues hold great potential in reinforcing polymeric matrix materials. The successful isolation of nanofibrillated cellulosic fibers from liquefied residues offers a novel approach to make full use of the liquefied bamboo for value-added green products.