Ultrasonication-assisted manufacture of cellulose nanocrystals esterified with acetic acid

Distinct Chiral Nematic Self-Assembling Behavior Caused by Different Size-Unified Cellulose Nanocrystals via a Multistage Separation

Cellulose nanocrystals (CNCs) are perfect rodlike nanofibers that can self-assemble and form a chiral nematic phase. We found that different self-assembling morphologies could be formed by different size-unified CNCs. This study reported a facile and new approach of fractionating raw (unseparated) CNCs in a wide particle size distribution (9-1700 nm) into a series of narrower size ranges to obtain size-unified CNCs via a well-designed multistage separation process composed of layered filter membranes with different pore size cutoffs followed by a fast pressurized filtration. The smaller size-unified CNCs readily self-assembled into polish chiral nematic phases with larger pitch value as compared to larger size-unified CNCs. Such a distinction among different chiral nematic phases and pitch values as functions of size was addressed by a mathematical evaluation, which suggested that the reduced volume fraction of the anisotropic phase as a function of both increased ionic strength and reduced crystallinity of rigid-rod-like CNCs is a critical factor. In addition, Fourier-transform infrared spectroscopy, thermogravimetric analysis, and X-ray diffraction results revealed that different size-unified CNCs exhibited particular thermal stabilities and crystallinities even though their chemical and crystalline structures remained unchanged. The discrepancies in physicochemical characteristics and self-assembling chiral nematic behavior among different size-unified CNCs may benefit the specific functionalization of cellulose materials using size-unified fibers instead of raw CNCs containing mixed small and large fibers.

Hybrid composites of polyvinyl alcohol (PVA)/Si–Al for improving the properties of ultra-low density fiberboard (ULDF)

The hybrid composites of polyvinyl alcohol (PVA)/Si–Al were synthesized to improve the thermostability and mechanical properties of ultra-low density fiberboard (ULDF).

One-pot tandem reactions for the preparation of esterified cellulose nanocrystals with 4-dimethylaminopyridine as a catalyst

Esterified cellulose nanocrystals were manufactured via one-pot tandem reactions with DMAP as a catalyst. During the process cellulose nanocrystallization and acetylation occurred simultaneously.

Preparation, characterization and optimization of nanocellulose whiskers by simultaneously ultrasonic wave and microwave assisted

Simultaneously ultrasonic wave and microwave assisted technique (SUMAT), as a method of process intensification, was first applied to the preparation of nanocellulose whiskers (NCWs) from filter paper by sulfuric acid hydrolysis. The effects of temperature, sulfuric acid concentration, and mass of raw material and time on the yield of NCWs were investigated by single-factor experiments, and the preparation conditions were optimized with response surface methodology. The obtained NCWs were characterized by transmission electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction and thermal gravimetry. The results showed NCWs were facilely prepared by using SUMAT. However, some harsh reaction conditions such as high temperature, strong acidity and long time treatment easily induced the reduction of the yield of NCWs. Under the optimal conditions, the yield and the crystallinity of NCWs with the crystal form of cellulose Iα is 85.75% and 80%, respectively.