Effect of ultrasound treatment on swelling behavior of cellulose in aqueous N-methyl-morpholine-N-oxide solution

Abstract

The present study deals with the effect of ultrasound on the swelling and dissolution behavior of the cellulose pulp. Hardwood, acid sulfite cellulose pulp sheets were sonicated at different temperatures, operated at a fixed frequency (37 kHz) and power (320 W) to break the intermolecular forces and hydrogen bonds of crystalline region. The obtained samples were evaluated for crystallinity, intrinsic viscosity, molecular weight (MW), molecular weight distribution (MWD) and surface morphology. It was observed that the crystallinity reduced from 61.9 to 18.9% after 20 min of ultrasound treatment at 30 °C, which was equivalent to the swelling at 75 °C for 20 min without the use of ultrasound frequency. It was also found that ultrasound pre-treatment significantly decreased the particle size of the slurry and shortened the dissolution time and temperature requirement without affecting the cellulose solution quality.

Strengthening Cellulose Nanopaper via Deep Eutectic Solvent and Ultrasound-Induced Surface Disordering of Nanofibers

“…The swelling of the BC-NFs under the application of ultrasound agrees with the decreasing DP and the increase in the nanofibers’ surface roughness that can relate to the destruction of the cellulose packaging on the fibril surfaces. The enhanced swelling of the cellulose fibers under the application of ultrasound is in agreement with previously reported data on the treatment of cellulose with an aqueous N-methyl-morpholine-N-oxide solution [ 80 ].…”

Sonication amplitude and processing time influence the cellulose nanocrystals morphology and dispersion

“…The reduction in the particle size of CNCs was mainly as a result of fiber breakage due to particle agitation [14] which happened at higher ultrasonication amplitude known as harsh condition. Time of sonication was another factor which governed the amount of acoustic energy delivered to the suspension and higher sonication times slightly degraded the structure of the CNCs and this in turn, reduced the length of the CNCs.…”

Ultrasound-Stimulated PVA Microbubbles for Adhesive Removal from Cellulose-Based Materials: A Groundbreaking Low-Impact Methodology

“…The frequency of the US used (1 MHz) is the best trade-off between high-penetrating low-frequency (tens of kilohertz) US treatments reported in the literature, , which warns about the mechanical damage they produced, and higher-frequency (∼tens of megahertz) US characterized by a very low penetration and potentially causing thermal damage onto cellulose fibers due to remarkable US absorption. Finally yet importantly, 1 MHz US is adequate to allow a nonresonant oscillation of the PVAMBs (i.e., small oscillations, preventing a violent and immediate breaking of the shell of the entire irradiated population), enabling the exploitation of the MB cavitation along the time of treatment.…”