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Isolation of oxidized nanocellulose from rice straw using the ammonium persulfate method
Oun, Ahmed A.,Rhim, Jong-Whan Blackie Academic Professional 2018 Cellulose Vol.25 No.4
<P>Oxidized nanocellulose was isolated from rice straw using the ammonium persulfate method. The effect of cellulose isolation methods such as a multistep process, pretreatments using NaOH and H2O2 on the properties of the nanocellulose were studied. Oxidized cellulose nanofibrils showed long fibrils of the web-like structure with the diameter of 14 nm, while oxidized-cellulose nanocrystals displayed a needle shape with the length of 118-212 nm and the width of 12-19 nm depending on the isolation method of cellulose. Properties of the oxidized-nanocellulose such as shape, size, crystallinity, and thermal stability were influenced significantly by the cellulose isolation method.</P>
Kim, K. J.,Lee, J. M.,Ahn, E. B.,Eom, T. J. BLACKIE ACADEMIC & PROFESSIONAL 2017 CELLULOSE Vol. No.
<P>Hardwood bleached Kraft pulp was treated with an endoglucanase prior to Valley beating. The Valley-beaten pulp slurry was further ground with a particle grinder in order to evaluate the effect of enzyme beating on preparation of microfibrillated cellulose (MFC). The time required to make 100 mL Canadian Standard Freeness pulp slurry was greatly reduced by enzyme pre-treatment. The viscosity of the enzyme-beaten MFC slightly increased with grinder pass number; however, the rate of change in viscosity was much lower than that of non-enzyme-beaten MFC. The crystallinity of MFC decreased with grinder pass number for both cases. The drainage of the pulp slurry containing enzyme-beaten MFC was higher than that of the pulp slurry containing non-enzyme-beaten MFC. Further, the enzyme-beaten MFC subjected to the 10 passes grinding had the same tensile index as the MFC subjected to the 15 passes grinding. Thus, the mechanical energy for MFC manufacturing can be greatly reduced with enzyme beating.</P>
Moisture transport in paper passing through the fuser nip of a laser printer
Lee, S.,Yoon, G. H. BLACKIE ACADEMIC & PROFESSIONAL 2017 CELLULOSE Vol. No.
<P>Paper curls in printers should be prevented since they cause paper jams and degradation of printing quality. Moisture transport due to high temperature in the fuser nip of a printer is one of main reasons for paper curls. In order to predict and control the paper curls, it is therefore essential to understand the mechanisms of heat and moisture transport in paper. In this paper, we derived a coupled heat and moisture transport model and applied it to the situation where a paper sheet moves between two rollers having different temperatures in a fuser nip. A series of simulations were carried out with varying parameters related to the characteristics of printer paper, the environment, and paper/environment interfaces. The simulation results provided a deep understanding of the moisture transport mechanisms and identified several key variables affecting changes of moisture profiles as a function of time. The time-dependent moisture contents data will be fed into a mechanical model to obtain the quantitative amount of the nip curl.</P>
Preparation of porous sheets with high mechanical strength by the addition of cellulose nanofibrils
Sim, Kyujeong,Youn, Hye Jung BLACKIE ACADEMIC & PROFESSIONAL 2016 CELLULOSE Vol. No.
<P>Porous sheets with high mechanical strength were prepared with natural pulp fibers (hardwood and softwood bleached kraft pulp) and polyethylene terephthalate (PET) by adding cellulose nanofibrils (CNF) through a wet-laid forming method. The structure and mechanical properties of the porous sheets were investigated in this study depending on the type of mixed fibers, the CNF ratio, and drying methods (cylinder-drying and freeze-drying). The apparent density and porosity of porous sheets changed according to the morphology of the mixed fibers. PET fibers resulted in a sheet with a bulkier structure, whereas natural pulp fibers produced relatively dense sheets. Sheets with high porosity could be prepared by freeze-drying due to the inhibition of hydrogen bonds and low shrinkage during drying. Pore characteristics were evaluated in terms of air permeability and average pore diameter. The air permeability of porous sheets decreased as the amount of CNF increased. Mercury porosimetry showed that the average pore diameter in sheets ranged from 0.6 to 36.7 A mu m depending on the type and mixing ratio of fibers and drying conditions. Sheet tensile properties were improved by the addition of CNF and changed depending on mixing combinations and drying methods. The applicability of freeze-dried porous sheets as filter media was examined by evaluating the filtration efficiency and pressure drop. Porous sheets with a HwBKP/CNF combination showed a filtration efficiency of 99.944 %, which approached the efficiency of a high efficiency particulate air filter. However, further study is required to reduce the pressure drop during filtration for better use as an air filter.</P>
Sim, Bomi,Bae, Dong Hun,Choi, Hyoung Jin,Choi, Kisuk,Islam, Md. Sakinul,Kao, Nhol BLACKIE ACADEMIC & PROFESSIONAL 2016 CELLULOSE Vol. No.
<P>We report on the electro-responsive electrorheological (ER) properties of microcrystalline cellulose (MCC) particles. It was synthesized from raw rice husk (Downes Rice) through the 3-step preparation of alkali treatment, bleaching, and hydrolysis. The MCC particles with mean particle size about 26 mu m were characterized by scanning electron microscopy, Fourier transform infrared spectroscopy and thermal gravimetric analysis. The MCC particles were then dispersed in silicone oil to create an ER fluid; its dramatic electro-responsive phase changes under an applied electric field were observed by an optical microscopy. The effect of electric field strengths on ER performances of the ER fluid were determined using a rotational rheometer equipped with a high-voltage generator from the controlled shear rate mode and dynamic oscillation measurements. The fluid showed typical ER effects of Bingham fluid behavior with yield stress and viscoelastic properties under an applied electric field.</P>