• Journal of the Korean Applied Science and Technology
• /
• v.25 no.3
• /
• pp.341-346
• /
• 2008

Cellulose nanofibers from microfibril cellulose (MFC) was prepared by hydrobromic acid (HBr) treatment at different concentrations. Polyvinyl alcohol (PVA) composite films at various loading level of nanofibers were manufactured by a film casting method. The analysis of degree of polymerization (DP), crystallinity ($X_c$) and molecular weight ($M_w$) of cellulose after acid treatment was conducted. The mechanical and thermal properties of the cellulose nanofibers reinforced PVA films were characterized using tensile tests and thermogravimetric analysis (TGA). The DP and $M_w$ of MFC by HBr hydrolysis considerably decreased, but $X_c$ showed no significant change. After acid hydrolysis, the diameter of cellulose nanofibers was in the range of 100 to 200 nm. The thermal stability of the films was steadily improved with the increase of nanofiber loading. There was a significant increase in the tensile strength of PVA composite films with the increase in MFC loading. Finally, 5 wt.% nanofiber loading exhibited the highest tensile strength and thermal stability of PVA composite films.

• Textile Coloration and Finishing
• /
• v.7 no.2
• /
• pp.32-39
• /
• 1995

Various grades of hydroxyethyl cellulose (HEC, MS 0.65-3.20) were prepared throngh reaction of the knit-cotton-waste with ethylene oxide(EO). The knit-cotton-waste was composed of 98% of $\alpha$-cellulose and 2% of other components, and the cellulose was highly pure. The molar ratio of EO to knit-cotton-waste and that of NaOH to knit-cotton-waste, and the agitation speed were the important factors determining the molar substitution(MS) during the preparation of HEC. The MS of HEC was remarkably increased with increasing molar ratio of EO' to knit-cotton-waste. When the molar ratio of EO to knit-cotton-waste was 3.5, that of NaOH to knit-cotton-waste was 1.25, and agitation speed was 450rpm, it was possible to prepare HEC of MS 2.5. The structure and crystallinity of HECs prepared were determined by FT-IR and X-ray diffraction.

• Journal of the Korean Wood Science and Technology
• /
• v.21 no.4
• /
• pp.73-78
• /
• 1993

Crystal structure of tension, opposite and lateral wood of Platanus orientalis L. were analysed in some aspects of crystallinity index, crystallite size, d-spacing of (200) and (004), and integrated intensity ratios with X-ray diffraction method. Crystallinity index and crystallite width in tension wood appeared somewhat larger than opposite or lateral wood. However, d-spacing and integrated intensity ratios were nearly identical irrespective of tension, opposite, and lateral wood.

• Journal of the Korean Wood Science and Technology
• /
• v.25 no.3
• /
• pp.83-95
• /
• 1997

The degradation mode of lignocellulose by anaerobic ruminal cellulolytic bacterium Ruminococcus albus F-40 was investigated. Birchwood holocellulose and filter paper were incubated as the sole carbohydrate sources with using the Hungate techniques. After 2 or 4 days of incubation, samples were employed for chemical and electron microscopic evaluations. The degradation rate of cellulosic substrates and the adhesion rate of bacteria to the substrates increased proportionally with the decrease of relative crystallinity of cellulose, indicating the preferential breakdown of amorphous cellulose, by this bacterium. X-ray diffraction analyses and polarized light microscopy showed, however, that crystalline cellulose was also degraded by R. albus. FT-IR spectra indicated that not only cellulose but hemicellulose was also degraded by this bacterium. Electron microscopic investigations showed the protuberant structures on the surface of R. albus. These structures were much more significant when bacterial cells were grown in the media containing insoluble substrates, such as cellulose, indicating clearly that bacterial protuberant structures were induced by the substrates. Protuberant structures extended from the bacterial cells adhered tightly to the substrates and numerous vesicles covered the surface of cellulosic substrates affected. Cellulosome-like structures were distributed on the cellulose matrix. Electron microscopic works showed that diverse surface organells of R. albus were involved in the degradation of cellulosic materials. SEM examinations showed the breakdown of cellulose by R. albus was proceeded by severeal routes : short fiber formation, defibrillation and destrafication of cellulose microfibril.

• Journal of Korea Technical Association of The Pulp and Paper Industry
• /
• v.36 no.1
• /
• pp.24-29
• /
• 2004

Alkaline cellulolytic enzymes from cultured medium of Coprinus cinereus 2249 were purified with gel and ion-exchange chromatography and characteristics of those enzyme proteins were investigated. A fiber length distribution and a crystallinity of cellulose and sugar composition of enzyme treated Mixed Office Wastepaper(MOW) and Unbleached Kraft Pulp(UKP) were analysed. The conclusion could summarized as follows; \circled1 Alkaline and acidic, endo- and exo-glucanases were purified from cultured medium of Coprinus cinereus 2249. \circled2 The approximate molecular weight of alkaline endo-glucanase was 42 kDa, and also that of alkaline exo-glucanase was 50 kDa. A fiber length distribution and a crystallization of cellulose and sugar composition of enzyme treated MOW and UKP were not so much changed with original paper and pulp.

• Journal of the Korean Wood Science and Technology
• /
• v.29 no.1
• /
• pp.60-67
• /
• 2001

The microscopic characteristics and cellulose structures of primary and secondary tissues in Pinus densiflora S. et Z. were examined. Cells of primary tissue in cross section showed an irregular arrangement and round shape. Fiber lengths were 200 to $250{\mu}m$ in primary tissue, and 1,500 to $1,600{\mu}m$ in secondary tissue. Cell diameters in primary tissue were larger than those in secondary tissue; 40 to $50{\mu}m$ in former and 10 to $20{\mu}m$ in latter. Crystallite width and d-spacing of (200) in both tissues did not show any significant differences. However, crystallinity indices by Segal's method showed significant differences as 23% in primary tissue and 35% in secondary tissue. In the orientation of cellulose microfibril, primary tissues had a random pattern, whereas, secondary tissues presented an oriented pattern with 20 to 30 degree. The cellulose crystalline of primary tissue was easily transformed into cellulose II by mercerization, but that of secondary tissue hardly transformed. It is considered that the difference of crystal transformation in both tissues could be caused by the difference of lignification.

• Journal of Korea Technical Association of The Pulp and Paper Industry
• /
• v.48 no.1
• /
• pp.53-60
• /
• 2016

Abiotic-stressed tobacco stems as a non-wooden biomass were analyzed for their chemical characteristics. Light-stressed tobacco stems (LST) have a relatively high nitrogen concentration, much more extractive content, and a similar amount of lignin and higher contents of acid sugars than those of Non stressed tobacco (NST). It also has low cellulose crystallinity and a high degree of condensation. Guaiacyl units having a lower molecular weight distribution consist of rich lignin. Tension stressed tobacco (TST) growth differentiation under tensile stress was significantly different between normal tissue and cell walls, with the exception of the slightly higher cellulose crystallinity observed for.

• Journal of Korea Technical Association of The Pulp and Paper Industry
• /
• v.47 no.5
• /
• pp.23-32
• /
• 2015

In this study, chemical and physical changes of dissolving pulps which have similar viscosity by dry milling and fractionation were investigated. We used two types of dissolving pulp made from wood and cotton linter fiber, respectively. Dry milling was executed by knife cutter and pulp powders were fractionated by sieve shaker into 4 grades. We analyzed fiber properties, crystallinity index, viscosity, molecular weight of pulp sheet and powders. It was found that poly-dispersity index of cotton linter pulp was smaller than that of wood pulp, meaning that cotton pulp has more narrow molecular weight distribution. It was assumed that these were related to exposure times to chemical treatment which cut cellulose chains not evenly. At least 4 times of chemical treatments for wood pulp were executed and only two times of chemical treatments for cotton linter pulp were done. After dry milling average molecular weight and crystallinity index of cotton linter pulp powders were reduced and these were related to fines content and shape of pulp powders.

• KOREAN JOURNAL OF PACKAGING SCIENCE & TECHNOLOGY
• /
• v.29 no.1
• /
• pp.51-57
• /
• 2023

Because of the global pollution caused by plastic disposal, demand for eco-friendly transformation in the packaging industry is increased. As part of that, the utilization of polylactic acid (PLA) as a food packaging material is increased. However, it is necessary to improve the crystallinity of PLA by adding nucleating agents or to improve the modulus by adding fillers because of the excessive brittleness of the PLA matrix. Thus, the cellulose nanofiber (CNF) was fabricated and dried to obtain a powder form and applied to the CNF/PLA nanocomposite. The effect of CNF on the morphological, thermal, rheological, and dynamic mechanical properties of the composite was analyzed. We can confirm the impregnated CNF particle in the PLA matrix through the field emission scanning electron microscope (FE-SEM). Differential scanning calorimetry (DSC) analysis showed that the crystallinity of not annealed CNF/PLA nanocomposite was increased approximately 2 and 4 times in the 1st and 2nd cycle, respectively, with the shift to lower temperature of cold crystallization temperature (T_cc) in the 2nd cycle. Moreover, the crystallinity of annealed CNF/PLA nanocomposite increased by 13.4%, and shifted T_cc was confirmed.

• Journal of the Korean Wood Science and Technology
• /
• v.47 no.3
• /
• pp.299-310
• /
• 2019

This study was carried out to investigate the effect of heat-treatment and particle size on the crystalline properties of the wood cellulose. The color of wood flours was changed from light yellow in control sample to dark yellow or deep brown by heat treatment at $100^{\circ}C$ to $200^{\circ}C$. Relative crystallinity of the heat treated wood cellulose decreased with decreasing particle size from wood chips to 200 mesh, and there was little change in the crystal width. As the temperature was increased, relative crystallinity of the wood increased and crystal width was not changed. As a result of the FT-IR analysis, it was confirmed that the peaks were gradually decreased at -OH elongation as the heat-treated temperature was increased. The lignin C-H bending of $1425cm^{-1}$ and the hemicellulose C-H bending of $1370cm^{-1}$ did not change with the increase of the heat treatment temperature. In addition, it was revealed that C-C stretching of carbohydrate near $1031cm^{-1}$ decreased with increasing heat treatment temperature. Consequently, it is suggested that particle size and heat treatment affected the crystalline properties of wood cellulose.