Papers by Keyword: Cellulose Microfibril

Abstract: Cellulose microfibrils were extracted from kenaf fiber by alkali treatments under various conditions to further characterize their properties and verify the factors which induce fiber degradation. Before treatment, the surface morphologies of the base, middle and tip of the raw fiber were observed. The tensile strength of untreated and treated fibers was measured with a universal tensile machine (UTM). Changes in surface morphologies of cellulose microfibrils were characterized by scanning electron microscopy (SEM). Fourier transform infrared (FTIR) spectroscopy was used to characterize the functional group related to cellulosic and non-cellulosic phases. Surface morphology of the middle of the fiber was denser and stronger than that of the periphery and therefore used to define an initial condition of fiber specimen. Alkali treatment in 6% NaOH at room temperature for 1 h increased the tensile strength of the microfibril; 9% NaOH at 100°C for 2 h results in a marked decrease. Damage to the fiber surface and loss of crystallinity were associated with decreased tensile strength.

Abstract: Cellulose microfibril from banana pseudo-stem fiber waste has been isolated and characterised. Isolation of microfibril cellulose from raw fibers was achieved using alkaline treatment and bleaching. The treated and untreated samples were characterized using x-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM). Characterizations of treated and untreated samples were compared. XRD studies shows that the treated cellulose prepared by alkaline and bleaching treatment was more crystalline than the untreated banana fiber. Surface morphological studies using FESEM shows there was a reduction in fiber diameter during the chemical treatment.

Abstract: The property of cellulose microfibril reinforced natural rubber film was studied. Cellulose microfibril was prepared from banana powder (300 µm). The interconnected structure of cellulose microfibril having a diameter of 27 nm was observed by TEM. The effect of cellulose microfibril content (0.8-3.2 % wt) in the property of NR nanocomposite film was studied. Tear strength and thermal properties of the NR nanocomposite film is improved by increasing the cellulose microfibril content. Moreover, water absorption of the nanocomposite film is increased by increasing cellulose microfibril content. Increasing of cellulose microfibril content also enhances water permeation of nanocomposite films.

Abstract: X-ray scattering techniques have been a very useful tool for the non-destructive analysis of the wood structure. X-rays are sensitive to structural parameters such as the composite structure of wood cell walls, the crystal structure of cellulose microfibrils and their helical arrangement in the cell wall, which is usually described by the microfibril angle (MFA). With the availability of synchrotron radiation sources novel experiments on wood have become possible. The increased flux of X-rays makes the in situ and time-resolved investigation of structural changes upon mechanical stress possible. The low-divergence synchrotron radiation X-rays can be focused down to sub-micrometer size, enabling scanning studies of the wood nanostructure with (sub-)microscopic position resolution. This chapter highlights very recent advances in the understanding of wood micro- and nanostructure, which were only possible using synchrotron radiation. Examples include the MFA determination in the individual layers of the secondary cell wall, the imaging of the helical structure of the cellulose microfibrils in the cell wall, lattice strain as induced by applied mechanical stress and the structural changes of different wood types under external tensile stress.

Abstract: Illuminating fundamental aspects of plant cell wall mechanics will lead to novel biological and engineering inspired strategies for application in the cotton and wood fiber industries and in developing novel plant-derived materials that are increasingly seen as environmentally friendly alternatives. The stiffness properties of cell wall polymers such as cellulose microfibrils and xyloglucans are known but the relationship between the composite structure of the wall and its effective stiffness remains poorly understood. Understanding this relationship is important to engineers using and designing plant-derived materials and to biologists studying plant growth. We have developed a software system to generate microfibril-xyloglucan networks resembling those found in cell walls. Finite element analysis was implemented to predict the effective Young’s modulus of varying sizes of the microfibril-xyloglucan network. Results from the finite element models show that the network’s effective moduli of the cell walls having microfibrils parallel to applied loadings are relatively high (~90-215MPa) compared with those of the walls having randomly oriented microfibrils (~20-47MPa). The walls having microfibrils parallel to each other but perpendicular to applied loadings have lowest stiffness (~17-118kPa). The Young’s moduli are significantly lower than those of its constituent polymers and generally in agreement with experimentally measured values.

Abstract: Environment-friendly “green” composites were fabricated from a starch-based, dispersion-type biodegradable resin and cellulose nanofibers. The mixture of the dispersion-type biodegradable resin and cellulose nanofibers were blended well by using a home-use mixer and a stirrer, and then dried in air or in a vacuum. Composites were prepared by conventional hot pressing at a constant temperature of 140°C and at pressures from 10 to 50 MPa. Their flexural strength as well as flexural modulus increased with increasing the molding pressure, and were also affected by preparation methods and conditions. Their mechanical properties such as strength and modulus had a good correlation with their density. Especially it can be seen that there is significant effectiveness in a stirrer mixing process, which results in the improved uniform dispersion of nanofibers.