• Proceedings of the Korean Fiber Society Conference
• /
• 2001.10a
• /
• pp.345-347
• /
• 2001

전기방사(Electro-spinning)는 기존의 방사방법과는 달리 전기장의 힘을 이용하여 방사하는 방법으로 고분자용액의 적용범위가 넓고, 저렴하고 간단한 공정을 통하여, 나노크기의 섬유를 제조할 수 있는 장점이 있다. 목재 펄프를 아민옥시드계 용제의 하나인 NMMO(N-methyl-morpholine-N-oxide)에 용해시켜 습식 방사를 통하여 섬유를 제조한다. (중략)

• Journal of the Korean Ceramic Society
• /
• v.55 no.2
• /
• pp.145-152
• /
• 2018

Although many bone graft materials have been developed, powder graft materials are somewhat difficult to use in surgery. To solve this problem, a bone graft material in the form of a viscous paste was prepared. Hydroxyapatite was used as a bone graft material, and methyl cellulose was used to impart viscosity. Three cases of samples were prepared, and freeze-dried block type and sintered specimens were made from the paste. The recrystallization of the graft material in a simulated body fluid and the degree of graft adhesion with a tooth were observed by scanning electron microscopy (SEM). The test for cytotoxicity was carried out and the sample was grafted into the back of a mouse to confirm the presence or absence of side effects in the animal's body. Based on these investigations, composites of this type are expected to be applicable for bone grafts.

• International Journal of Oral Biology
• /
• v.43 no.2
• /
• pp.83-91
• /
• 2018

Nonthermal atmospheric plasma has been studied for its many biomedical effects, such as tooth bleaching, wound healing, and coagulation. In this study, the effects of dentinal tubules occlusion were investigated using fluoride-carboxymethyl cellulose (F-CMC) gel, nano-sized hydroxyapatite (n-HA), and nonthermal atmospheric plasma. Human dentin specimens were divided to 5 groups (group C, HA, HAF, HAP, and HAFP). Group HA was treated with n-HA, group HAF was treated with n-HA after a F-CMC gel application, group HAP was treated with n-HA after a plasma treatment and group HAFP was treated with n-HA after a plasma and F-CMC gel treatment. The occlusion of dentinal tubules was investigated using scanning electron microscopy (SEM) and energy dispersive x-ray spectroscopy (EDS), which shows Ca/P ratio. In the EDS results, a higher Ca/P ratio was shown in the groups including n-HA than in the control group. The specimens of group HAP and HAFP had a higher Ca/P ratio in retentivity. In the SEM results, there was not a significant difference in the amount of times applied. Therefore, this study suggests F-CMC gel and n-HA treatment using nonthermal atmospheric plasma will be a new treatment method for decreasing hypersensitivity.

• Proceedings of the Korea Technical Association of the Pulp and Paper Industry Conference
• /
• 2008.04a
• /
• pp.178-182
• /
• 2008

The bleached red algae fiber(BRAF) showed very similar crystallinity to the cellulose, furthermore, it has higher thermal decomposition temperature than that of the microcrystalline cellulose(MCC). Polypropylene biocomposites reinforced with BRAF have been fabricated with various BRAF contents by compression molding method and their mechanical and thermomechanical properties have been studied. The mechanical strength as tensile, impact and flexural modulus of BRAF/PP biocomposites were gradually improved with increasing the BRAF content, and thermal property which against the thermal expansion was markdly improved, especially. These results are compared with chopped non-woody fibers as Henequen or Kenaf, BRAF was more effective for fabrication of biocomposites reinforced small-sized fibers. The red algae fiber reinforced biocomposites has the applicability such as electronics, biodegradable products and small-structure composites.

• The Journal of Advanced Prosthodontics
• /
• v.7 no.6
• /
• pp.484-495
• /
• 2015

PURPOSE. This study was to evaluate the effects of bacterial cellulose (BC) membranes as a barrier membrane on guided bone regeneration (GBR) in comparison with those of the resorbable collagen membranes. MATERIALS AND METHODS. BC membranes were fabricated using biomimetic technology. Surface properties were analyzed, Mechanical properties were measured, in vitro cell proliferation test were performed with NIH3T3 cells and in vivo study were performed with rat calvarial defect and histomorphometric analysis was done. The Mann-Whitney U test and the Wilcoxon signed rank test was used (${\alpha}<.05$). RESULTS. BC membrane showed significantly higher mechanical properties such as wet tensile strength than collagen membrane and represented a three-dimensional multilayered structure cross-linked by nano-fibers with 60 % porosity. In vitro study, cell adhesion and proliferation were observed on BC membrane. However, morphology of the cells was found to be less differentiated, and the cell proliferation rate was lower than those of the cells on collagen membrane. In vivo study, the grafted BC membrane did not induce inflammatory response, and maintained adequate space for bone regeneration. An amount of new bone formation in defect region loaded with BC membrane was significantly similar to that of collagen membrane application. CONCLUSION. BC membrane has potential to be used as a barrier membrane, and efficacy of the membrane on GBR is comparable to that of collagen membrane.

• Membrane Journal
• /
• v.21 no.1
• /
• pp.98-105
• /
• 2011

Cellulose triacetate (CTA) polymer among cellulose esters were used for preparing hollow fiber membranes by phase separation method to investigate the gas permeation properties. To endow gas separation properties, 1,4-dioxane and LiCl were used as additives in the polymer dope solution. The spinning conditions including spinning temperature were controlled to form an active skin layer on the hollow fiber surface. Scanning electron microscopy was used to examine morphology of surface and cross section of the prepared CTA hollow fibers. The gas permeation performance of CTA hollow fiber membranes showed $P_{CO2}$ = 17 GPU and ${\alpha}_{CO2/N2}$ = 48.

• Journal of the Korean Wood Science and Technology
• /
• v.41 no.4
• /
• pp.302-309
• /
• 2013

The highly porous cellulosic aerogels were prepared by freeze-drying method using sodium hydroxide-urea aqueous solution in the process of dissolution, gelation, regeneration and organic solvent substitution. The structural characteristics of porous aerogel were analyzed using scanning electron microscopy and nitrogen adsorption apparatus. As a result, the dissolving pulp was completely dissolved, but filter papers and holocellulose were divided into two layers (dissolved and undissolved parts) in the process of centrifugation. The structure of aerogel from dissolved pulp showed porous pores in the surface and net-shaped network in the inner part. Aerogels from filter paper and holocellulose had the condensed porous network surface and the open-pore nano-fibril network inner structure. Undissolved form of fibers was observed in the aqueous solution of aerogel from holocellulose. The BET value ($S_{BET}$) of aerogel from dissolved pulp was ranged in 260~326 $m^2/g$, and it was decreased with the increase of concentration. Whereas, the $S_{BET}$ value of aerogel from filter paper (198~418 $m^2/g$) was increased with the increase of concentration. The $S_{BET}$ value of aerogel from holocellulose were 137 $m^2/g$ at 2% (w/w) of cellulose, and it was increased to maximum 401 $m^2/g$ at 4% (w/w) of cellulose. Then, it was decreased at 5% (w/w) of cellulose.

• 한국생물공학회:학술대회논문집
• /
• 2003.10a
• /
• pp.468-472
• /
• 2003

Recently, genetic engineering techniques have been used to display various heterologous peptides and proteins (enzyme, antibody, antigen, receptor and fluorescence protein, etc.) on the yeast cell surface. Living cells displaying various enzymes on their surface could be used repeatedly as 'whole cell biocatalysts' like immobilized enzymes. We constructed a yeast based whole cell biocatalyst displaying T. reesei cellobiohydrolase I (CBH I ) on the cell surface and endowed the yeast-cells with the ability to degrade cellulose. By using a cell surface engineering system based on ${\alpha}-agglutinin,$ CBH I was displayed on the cell surface as a fusion protein containing the N-terminal leader peptide encoding a Gly-Ser linker and the $Xpress^{TM}$ epitope. Localization of the fusion protein on the cell surface was confirmed by confocal microscopy. In this study, we report on the genetic immobilization of T. reesei CBH I on the S. cerevisiae and hydrolytic activity of cell surface displayed CBH I.

• Journal of Korea Technical Association of The Pulp and Paper Industry
• /
• v.47 no.6
• /
• pp.154-163
• /
• 2015

Because of acute or chronic intoxication by carbon disulfide, viscose rayon industry is strictly subjected to environment regulatory approval. Recently, non-wood fibers are frequently considered as a raw materials for the manufacture of specialty paper for the higher physical strength and functionality. Among the non-wood fibers, hemp bast fiber is one of the most widely used materials in viscose rayon yarn industries. In this study, the handsheet for manufacturing the viscose rayon yarn was prepared with wood pulp fibers and hemp bast fibers. The proper mixing ratio of wood fibers and hemp bast fibers with dry-strength agent and nano-celluloses was analysed in terms of physical and mechanical strength of sheet for viscose rayon yarn. The papermaking conditions for high mechanical strength of sheet were obtained by mixing the SwBKP and HwBKP fibers with freeness level of 200 mL CSF. The dual polymer system by controlling the addition ratio of PVAm and anionic PAM was also important. The addition of nano-cellulose into wet-end furnishes increased the physical strength of sheet, and improved the paper structure for the production of viscose rayon yarn.

• Journal of the Korean Ceramic Society
• /
• v.55 no.1
• /
• pp.90-93
• /
• 2018

In this study, n-type $Bi_2Te_3$ in thermoelectric scrap is recovered through a wet reduction process. The recovered powder (tellurium) is grafted onto gas sensor in a new application that is not a thermoelectric device. Bismuth-rich powder is prepared by adding hydrazine when pH of the solution is brought to 13 using NaOH. The pH of the filtered solution was reduced using $HNO_3$, and then hydrazine was added to perform the re-reduction reaction. The tellurium-rich powder can be obtained through this reaction. The elemental analysis for these powders is confirmed by energy dispersive X-ray spectroscopy (EDS) analysis ; the successful separation of bismuth and tellurium is confirmed. Separated tellurium powder is mixed with DMF solvent and ethyl cellulose binder to confirm gas sensing properties. The tellurium paste was exposed in $NO_x$ atmosphere and exhibited a rapid reaction rate and recovery rate of less than 3 minutes for the gas.