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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>
도공원지의 원료 조성 및 구조에 따른 고평량 도공지의 접힘 터짐
심규정(Kyujeong Sim),윤혜정(Hye Jung Youn),오규덕(Kyudeok Oh),이학래(Hak Lae Lee),여승욱(Seung Uk Yeu),이용민(Yong Min Lee) 한국펄프·종이공학회 2015 펄프.종이기술 Vol.47 No.4
Fold cracking is one of quality troubles of coated papers. In this study, the fold cracking of high grammage (250 g/㎡) coated paper made with the different pulp composition and layer structure of base paper was investigated. The single layered, high grammage base paper was prepared by mixing of hardwood and softwood bleached kraft pulp fibers with the different ratios. The high grammage coated paper showed the higher fold cracking than low grammage coated paper because of the increase in thickness. The increase in the content of softwood pulp fibers reduced the fold cracking in the case of high grammage coated paper. When the creasing process was conducted before folding process, the fold cracking of coated paper decreased. By manufacturing the base paper with multiply structure, the fold cracking of coated paper could be reduced significantly, especially when the BCTMP and OCC were used as a middle layer and the creasing process was carried out. The delamination of layers in base paper affected the fold cracking positively.