Xiaoyi Wei

Homogeneous isolation of nanocellulose from sugarcane bagasse by high pressure homogenization

Nanocellulose from sugarcane bagasse was isolated by high pressure homogenization in a homogeneous media. Pretreatment with an ionic liquid (1-butyl-3-methylimidazolium chloride ([Bmim]Cl)) was initially involved to dissolve the bagasse cellulose. Subsequently, the homogeneous solution was passed through a high pressure homogenizer without any clogging. The nanocellulose was obtained at 80 MPa for 30 cycles with recovery of 90% under the optimum refining condition. Nanocellulose had been characterized by Fourier transformed infrared spectra, X-ray diffraction, thermogravimetric analysis, rheological measurements and transmission electron microscopy. The results showed that nanocellulose was 10-20 nm in diameter, and presented lower thermal stability and crystallinity than the original cellulose. The developed nanocellulose would be a very versatile renewable material.

Study on nanocellulose by high pressure homogenization in homogeneous isolation

Nanocellulose from cotton cellulose was prepared by high pressure homogenization (HPH) in ionic liquids (1-butyl-3-methylimidazolium chloride ([Bmim]Cl). The nanocellulose possessed narrow particle size distribution, with diameter range of 10–20 nm. Weight average molecular weight (Mw) of nanocellulose treated by HPH was lower (173.8 kDa) than the one ILs treated cellulose (344.6 kDa). X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FT-IR), and Solid-state CP/MAS 13C NMR measurements were employed to study the mechanism of structural changes, which suggested that network structure between cellulose chains were destructed by the shearing forces of HPH in combination with ionic liquids. The intermolecular and intra-molecular hydrogen bonds of cellulose were further destroyed, leading to the long cellulose molecular chains being collapsed into short chains. Therefore, the nanocellulose could provide desired properties, such as lower thermal stability and strong water holding capacity. Results indicated that it had great potential in the applications for packaging, medicines, cosmetics and tissue engineering.

Homogeneous isolation of nanocelluloses by controlling the shearing force and pressure in microenvironment

Nanocelluloses were prepared from sugarcane bagasse celluloses by dynamic high pressure microfluidization (DHPM), aiming at achieving a homogeneous isolation through the controlling of shearing force and pressure within a microenvironment. In the DHPM process, the homogeneous cellulose solution passed through chambers at a higher pressure in fewer cycles, compared with the high pressure homogenization (HPH) process. X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) demonstrated that entangled network structures of celluloses were well dispersed in the microenvironment, which provided proper shearing forces and pressure to fracture the hydrogen bonds. Gel permeation chromatography (GPC), CP/MAS (13)C NMR and Fourier transform infrared spectroscopy (FT-IR) measurements suggested that intra-molecular hydrogen bonds were maintained. These nanocelluloses of smaller particle size, good dispersion and lower thermal stability will have great potential to be applied in electronics devices, electrochemistry, medicine, and package and printing industry.

Synthesis and Characterization of Superparamagnetic Fe3O4 Nanoparticles Modified with Oleic Acid

The effect of oleic acid on the superparamagnetic Fe3O4 nanoparticles has been investigated in this study. The addition of oleic acid could improve the particle size distribution by the formed protective layer on the surface of Fe3O4 nanoparticles. All of Fe3O4 coated with oleic acid displayed superparamagnetic characterizations, and the interaction between two competing mechanisms, agglomeration and chelation, was discussed to explain the function of oleic acid. The optimal addition of oleic acid was fixed to be 4 wt%, which obtained the highest magnetization saturation value (Ms) of 82.066 emu/g.

Preparation of pH- and salinity-responsive cellulose copolymer in ionic liquid

A novel biodegradable pH- and salinity-responsive cellulose copolymer was prepared by grafting 2-(Dimethylamino) ethylmethacrylate (DMAEMA) onto bagasse cellulose in ionic liquid. The grafting polymerization was achieved in 1-butyl-3-methylimidazolium chloride ([Bmim]Cl) under microwave irradiation. Copolymers were then characterized by Fourier transform infrared spectroscopy, scanning electron microscopy, X-ray diffraction and thermo gravimetric analysis measurements. The results revealed that polymer chains had been successfully bonded to the cellulose backbone. Furthermore, the self-assembly of cellulose-g-DMAEMA copolymers at various salt concentrations and pH solution were investigated by means of swelling behavior measurement. It indicated that the copolymers presented dual pH and salinity-responsive properties. The synthetic strategy showed great potential in the modification of other cellulosic biomass to afford new biomaterials with desired properties.

Study on Electromagnetic Properties of Fe3O4 Nanoparticles Dispersed in Cellulose Matrix with Core-Shell Structure

Fe3O4/cellulose composite, a novel microwave absorption material, was successfully synthesized by the surface-initiated free-radical polymerization. The broad absorption peak at ∼3000 cm−1 indicated that the Fe3O4 polymerized with nanoscale cellulose through hydrogen bonding and electrostatic interactions. Synthesized composite consists of two phases, matrix (cellulose) and substrate (Fe3O4) with a uniform distribution of Fe3O4 nanoparticles in the matrix from SEM micrographs. Compared to other inorganic–organic composites, the composite showed a lowest density of 1.48 g/cm3, fulfilling the requirements of an excellent electromagnetic (EM)-wave absorbing material. The permeability and permittivity of the composite using 5 wt% initiator varied remarkably at ∼17 GHz, and the reflection loss value reached –13 dB at 17 GHz. The partial demagnetization caused by the uniform dispersion of Fe3O4 nanoparticles enhanced the magnetic anisotropy of the composite, thus increasing the EM-wave absorption characteristics. The excellent physiochemical and microwave absorption properties could promote the development of EM-wave absorbing material consisting of inorganic–organic composites.

Advanced technology for nanostarches preparation by high speed jet and its mechanism analysis

Nanostarches were successfully prepared by high speed jet (HSJ) after pretreatment of micronization. The nanostarches were obtained at the conditions of micronization treatment for 60min, and then one cycle at 240MPa of HSJ (188.1nm). Moreover, after HSJ treated for three cycles, the particle size could reach the level of nanometer materials (66.94nm). The physicochemical properties of nanostarches had been characterized. Rapid Visco-Analysis (RVA) showed that the viscosity of nanostarches significantly decreased compared with native tapioca starch and slightly decreased with increasing processing cycles of HSJ. Steady shear analysis indicated that all samples displayed pseudoplastic, shear-thinning behavior, while the flow curves of nanostarches were little impact by the processing cycles of HSJ. X-ray diffraction analysis showed that the complete destruction of tapioca starch crystalline structure was obtained after HSJ treatment. Molecular characteristics determination suggested that the degradation of amylopectin chains occurred after the treatment of micronization and HSJ, which was proved by the decrease of weight-average molar mass. The results demonstrated that nanostarches were obtained due to the breakdown of starch molecules. This study will provide useful information of the nanostarches for its potential industrial application.

Effects of temperature on cellulose hydrogen bonds during dissolution in ionic liquid

Ionic liquids have been powerful solvents for cellulose. Mechanistic investigations of the dissolution processes have been extensively studied. In this paper, an experimental study has revealed that temperature also comes into play in cellulose dissolution. The supramolecular stuctrure of cellulose has been measured by X-ray diffraction, Fourier transform infrared spectroscopy, Solid-state CP/MAS 13C NMR, X-ray photoelectron spectroscopy and Gel permeation chromatography analysis, and the effects of temperature on hydrogen bonds of cellulose in ILs were investigated. These results indicated that hydrogen bonds of cellulose might be cracked by different ways at different temperature: The disruption of intramolecular hydrogen bonds (O(3) H-O (5)) could promote the dissolution process at lower temperature. And the disruption of intramolecular hydrogen bonds (O(2) H-O (6)) might be responsible for cellulose dissolution at higher temperature. It was suggested that higher dissolving temperature might be a way to avoid cellulose degradation with a high cellulose yield.

Preparation and physicochemical properties of nanostarches produced by high speed jet

After pretreatment of micronization for 60 mins, the nanostarches were obtained by high speed jet (HSJ) of one cycle at 240 Mpa. The nanostarches were also observed by morphological analysis. Moreover, the zeta potential of nanostarches (-17 mv) dramatically decreased compared with native (-4.90 mv), and the pasting properties of nanostarches significantly changed, indicating the disruption of the crystalline structures. The obtained nanostarches were related to the breakdown of starch molecules. This study will provide useful information of the nanostarches for its potential industrial application.

Study of bagasse/tapioca starch film preparation and characterization

Bagasse/tapioca starch films (BT) were prepared with various contents of bagasse (10, 20, 30, 40 and 50 wt% based on tapioca starch), and the effect of bagasse concentration was studied by the performance of the BT films. Then, the BT films characteristics were analyzed using the instruments about ultraviolet spectrophotometer (US), SEM, TGA and XRD. The dispersion of the bagasse became better with bagasse concentration increasing, the intermolecular hydrogen bonding became stronger while the transparency values of the films decreased.