Optimizing lignocellulosic nanofibril dimensions and morphology by mechanical refining for enhanced adhesion

Characterization of CNC Nanoparticles Prepared via Ultrasonic-Assisted Spray Drying and Their Application in Composite Films

The ultrasonic-assisted spray dryer, also known as a nano spray dryer and predominantly used on a lab scale in the pharmaceutical and food industries, enables the production of nanometer-sized particles. In this study, the nano spray dryer was applied to cellulosic materials, such as cellulose nanofibrils (CNFs) and cellulose nanocrystals (CNCs). CNC suspensions were successfully dried, while the CNF suspensions could not be dried, attributable to their longer fibril lengths. The nano spray drying process was performed under different drying conditions, including nebulizer hole sizes, solid concentrations, and gas flow rates. It was confirmed that the individual particle size of nano spray-dried CNCs (nano SDCNCs) decreased as the nebulizer hole sizes and solid contents of the suspensions decreased. The production rate of the nano spray dryer increased with higher solid contents and lower gas flow rates. The resulting nano SDCNCs were added to a polyvinyl alcohol (PVA) matrix as a reinforcing material to evaluate their reinforcement behavior in a plastic matrix using solvent casting. After incorporating the 20 wt.% nano SDCNCs into the PVA matrix, the tensile strength and tensile modulus elasticity of the neat PVA nanocomposite film increased by 22% and 32%, respectively, while preserving the transparency of the films.

Tunable, thiol-ene, interpenetrating network hydrogels of norbornene-modified carboxymethyl cellulose and cellulose nanofibrils

Carboxymethyl cellulose modified with norbornene groups (NorCMC) and cellulose nanofibrils (CNFs) produced through mechanical refining without chemical pretreatment formed interpenetrating network hydrogels through a UV-light initiated thiol-ene reaction. The molar ratio of thiols in crosslinkers to norbornene groups off the NorCMC (T:N), total polymer weight percent in the hydrogel, and weight percent of CNFs of the total polymer content of the hydrogels were varied to control hydrogel properties. This method enabled orders of magnitude changes to behavior. Swelling in aqueous environments could be significant (>150 %) without CNFs to minimal (<15 %) with the use of 50 % CNFs. NorCMC and CNF networks interacted synergistically to create hydrogels with compression modulus values spanning 1 to 150 kPa - the values of most biological tissues. T:N and total polymer weight percent could be varied to create hydrogels with different CNF content, but the same compression modulus, targeting 10 and 100 kPa hydrogels and providing a system that can independently vary fibrillar content and bulk modulus. Analysis of the effective crosslinks, thiol-ene network mesh size, and burst release of the polymer indicated synergistic interactions of the NorCMC thiol-ene and CNFs networks. These interactions enhanced modulus and degradation control of the network under physiological conditions.

Advantages of treating sponge-gourd waste by mechanical refining on the properties of fiber-based poly(butylene adipate-co-terephthalate)/polylactide biocomposites

This study compares the morphology, thermal, and dynamic-mechanical properties of composites based on polybutylene adipate terephthalate/polylactide biocomposites with sponge gourd waste treated code as R, and non-treated sponge gourd, coded as NR, by mechanical disc refining after milled process. Extrusion followed by compression molding was used to produce biocomposites with fiber contents of 0, 2.5, 5, 10, and 15% wt/wt for R and NR sponge gourd fibers. Scanning electron microscopy analysis reveals that NR has the morphology of a rigid tubular shape, whereas R is a thinner, twisted, and fibrillated fiber. Regardless of the type of sponge gourd fiber used, the thermal stability of the composite decreases as the sponge gourd content increases. At 25°C, the biocomposite with 10%wt/wt R fiber has the highest storage modulus value. The comparison of Tangent  peak values reveals that the presence of sponge gourd fibers reduces the energy dissipation of the biocomposites. The analysis of the loss modulus at 25°C reveals that R fiber contributes more to the reduction of energy dissipation of the biocomposites than NR. Furthermore, the Cole-Cole plot shows that R and NR fibers are dispersed and do not significantly change the homogeneity of the biopolymer systems.

Recent Advances in Electron Microscopy of Carbohydrate Nanoparticles

Carbohydrate nanoparticles, both naturally derived and synthetic ones, have attracted scientific and industrial attention as high-performance renewable building blocks of functional materials. Electron microscopy (EM) has played a central role in investigations of their morphology and molecular structure, although the intrinsic radiation sensitivity of carbohydrate crystals has often hindered the in-depth characterization with EM techniques. This contribution reviews the recent advances in the electron microscopy of the carbohydrate nanoparticles. In particular, we highlight the recent efforts made to understand the three-dimensional shape and structural heterogeneity of nanoparticles using low-dose electron tomography and electron diffraction techniques coupled with cryogenic transmission electron microscopy.