Jinqiu Qi

Isolation and characterization of cellulose nanofibers from bamboo using microwave liquefaction combined with chemical treatment and ultrasonication

Cellulose nanofibers were successfully isolated from bamboo using microwave liquefaction combined with chemical treatment and ultrasonic nanofibrillation processes. The microwave liquefaction could eliminate almost all the lignin in bamboo, resulting in high cellulose content residues within 7min, and the cellulose enriched residues could be readily purified by subsequent chemical treatments with lower chemical charging and quickly. The results of wet chemistry analyses, SEM images, and FTIR and X-ray spectra indicated the combination of microwave liquefaction and chemical treatment was significantly efficient in removing non-cellulosic compounds. Ultrasonication was used to separate the nanofibrils from the purified residues to extract nanofibers. The TEM images confirmed the presence of elementary fibrils, nano-sized fibril bundles, and aggregated fibril bundles. As evidenced by the TGA analysis, cellulose nanofibers isolated by this novel technique had high thermal stability indicating that the isolated nanofibers could possibly be applied as reinforcing elements in biomaterials.

Dilute Alkali and Hydrogen Peroxide Treatment of Microwave Liquefied Rape Straw Residue for the Extraction of Cellulose Nanocrystals

Microwave-assisted liquefaction of rape straw in methanol was conducted to collect the liquefied residues for the extraction of cellulose nanocrystals (CNCs). The liquefied residue with content of 23.44% from 180°C/7.5źmin was used to fibrillate CNCs with dilute alkali (2% NaOH) and hydrogen peroxide (5% H2O2) treatments, followed by ultrasonication for 15źmin. The FT-IR spectra and SEM images revealed that the liquefied residue from 180°C/7.5źmin exhibited a relatively homogeneous texture and a huge surface with cellulose as core structure. The retained hemicelluloses and other impurities in the liquefied residue were eliminated by 2% NaOH treatment, and the surface and accessibility of the alkali treated sample were significantly increased by 5% H2O2 treatment. The TEM images confirmed the CNCs had an average diameter of 12.59źnm. The CNCs had good thermal stability with a maximum weight loss temperature of 376.5°C.

Characterization of Biobased Polyurethane Foams Employing Lignin Fractionated from Microwave Liquefied Switchgrass

Lignin samples fractionated from microwave liquefied switchgrass were applied in the preparation of semirigid polyurethane (PU) foams without purification. The objective of this study was to elucidate the influence of lignin in the PU matrix on the morphological, chemical, mechanical, and thermal properties of the PU foams. The scanning electron microscopy (SEM) images revealed that lignin with 5 and 10% content in the PU foams did not influence the cell shape and size. The foam cell size became larger by increasing the lignin content to 15%. Fourier transform infrared spectroscopy (FTIR) indicated that chemical interactions occurred between the lignin hydroxyl and isocyanate revealing that lignin was well dispersed in the matrix materials. The apparent density of the foam with 10% lignin increased by 14.2% compared to the control, while the foam with 15% lignin had a decreased apparent density. The effect of lignin content on the mechanical properties was similar to that on apparent density. The lignin containing foams were much more thermally stable than the control foam as evidenced by having higher initial decomposition temperature and maximum decomposition rate temperature from the thermogravimetric analysis (TGA) profiles.

Bio-based UV protective films prepared with polylactic acid (PLA) and Phoebe zhennan extractives

In this study, diethyl ether extractives were isolated from Phoebe zhennan wood and then added into PLA matrix for the preparation of UV protective films (UV-PF). The results revealed that the diethyl ether extractives had good compatibility with PLA. The prepared UV-PF with the addition of 24 wt% extractives showed complete absorption of UV-C (200-280 nm) and UV-B (280-315 nm) and more than 90% absorption of UV-A (315-400 nm), indicating the addition of extractives into PLA contributed to the super UV resistant ability of the PLA based films. The UV-PF still exhibited excellent UV absorbability after strong UV light irradiation. The differential Scanning Calorimetry (DSC) analysis of the films showed that the UV-PF had relatively low thermal degradation temperature compared to the neat PLA films (PF), while the UV-PF showed stronger tensile strength with comparison to that of the PF. The results on the chemical composition analysis of the diethyl ether extractives revealed that the UV absorbability of the UV-PF may own to the benzene structure, CO bonds, CC bonds in the constituents of the extractives, which all have strong absorption in the near UV-region (200-400 nm).

Anatomical characteristics and physical–mechanical properties of Neosinocalamus affinis from Southwest China

The anatomical characteristics and physical–mechanical properties of Neosinocalamus affinis culms from three locations in China were investigated. The fiber percentage, length, wall thickness, basic density, and mechanical properties all increased with culm height, while the fiber lumen diameter and volume shrinkage showed an inverse trend. The site had significant influence on the fiber percentage and physical–mechanical properties, while the influence on vascular bundle density and fiber morphology was not significant. Therefore, the influences of site on bamboo properties may be taken into consideration for constructional utilization, and those for pulping may be ignored.