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초고속 원심방사에 의한 아세트산프로피온산 셀룰로오스/폴리부틸렌 숙시네이트 다공성 마이크론 섬유 제조
김태영(Tae Young Kim),김미경(Mi Kyung Kim),김진수(Jinsoo Kim),이정언(Jungeon Lee),정재훈(Jae Hoon Jung),김영권(Youngkwon Kim),김태현(Tae Hyeon Kim),김기영(Ki Young Kim),염정현(Jeong Hyun Yeum) 한국염색가공학회 2023 韓國染色加工學會誌 Vol.35 No.4
Cellulose is an abundant biodegradable material in nature with excellent properties, but due to its poor processability, it has been widely studied for processing through modification. Cellulose acetate propionate (CAP) is a cellulose derivative in which the hydroxyl group of cellulose is replaced by acetyl and propionyl groups. CAP has several advantages, such as excellent solubility, structural stability, light and weather resistance, and good transparency. Porous nanofibers with excellent specific surface area, which can be applied in various fields, can be easily formed by the phase separation method using highly volatile solvents. High speed centrifugal spinning is a nano/micro fiber preparation method with advantages such as fast spinning and easy alignment control. In this study, a CAP/polybutylene succinate (PBS) spinning solution with chloroform as solvent was prepared to prepare porous microfibers and the fiber morphology was examined as a function of the disk rotation speed in an high speed centrifugal spinning device.
불균일계 비누화를 통한 폴리비닐알코올/셀룰로오스 필름 제조
김태영(Tae Young Kim),김미경(Mi Kyung Kim),김진수(Jinsoo Kim),이정언(Jungeon Lee),정재훈(Jae Hoon Jung),김영권(Youngkwon Kim),김태현(Tae Hyeon Kim),염정현(Jeong Hyun Yeum) 한국염색가공학회 2023 韓國染色加工學會誌 Vol.35 No.4
Poly(vinyl alcohol) (PVA) is a common hydrophilic polymer that is synthesized through the saponification reaction of poly(vinyl ester)-based polymers, mostly using poly(vinyl acetate) (PVAc) as a precursor. The heterogeneous saponification reaction of poly(vinyl ester)-based films leads to PVA films with new surface properties. Cellulose acetate (CA), in which the hydroxyl group of cellulose is replaced by an acetyl group, is a typical cellulose derivative capable of overcoming the low processability of cellulose due to strong hydrogen bonding. In this study, P(VAc/VPi)/CA blended films were prepared by the solvent casting, and then PVA/Cellulose blended films with improved surface properties were prepared by heterogeneous saponification. The structural changes caused by heterogeneous saponification were confirmed by FT-IR analysis, where both saponification and deacetylation reactions occurred in the saponification solution. In addition, the surface property changes were analyzed by FE-SEM and contact angle analyses, and the transmittance changes of the modified films were also assessed.
Kim, Yonggyun,Kim, Dongki,Lee, Jungeon Korean Society of Applied Entomology 2000 Journal of Asia-Pacific Entomology Vol.3 No.2
Effect of exogeneus juvenile hormones (JHs) on pupal development was assayed in the beet armyworm, Spodoptera exigua. Fenoxycarb, a potent JH mimic, was applied topically to different ages of the pupae, and showed significant inhibition of normal adult eclosion even at 0.1$\mu\textrm{g}$ dose when it was applied at the early pupal stage (day 0). As the pupal development underwent, the susceptibility of the pupae fenoxycarb decreased. RH5992, a potent ecdysteroid mimic, did not, however, any similar inhibiotry effect on the pupae. Natural JH types (JH I, JH II, and JH III) were applied on day 0 pupae to compare their inhibitory effects en adult eclosion. Both JH I and JH III significantly inhibited adult eclosion at 1.0$\mu\textrm{g}$ dose, but JH III did not even at 10.0$\mu\textrm{g}$ dose. It was meted that fenoxycarb-treated pupae showed little rectum development. Fenoxycarb did not, however, show any negative effect on the development of compound eye and wing imaginal discs, and on the pupal hemolymph protein pattern. These results suggest that there should be a commitment period requiring an absence of JH fur a normal adult metamorphosis during early pupal development and that the endogenous type of JH in S. exigua is JH I or JH II or both JHs like other lepidopteran species.
Jungeon Lee,Adrian M. Chung Baek,Namhun Kim,Daeil Kwon 국제구조공학회 2022 Smart Structures and Systems, An International Jou Vol.29 No.6
Metal additive manufacturing (AM), also known as metal three-dimensional (3D) printing, produces 3D metal products by repeatedly adding and solidifying metal materials layer by layer. During the metal AM process, products experience repeated local melting and cooling using a laser or electron beam, resulting in product defects, such as warpage, cracks, and internal pores. Such defects adversely affect the final product. This paper proposes the in situ monitoring-based warpage prediction of metal AM products with experimental feature extraction. The temperature profile of the metal AM substrate during the process was experimentally collected. Time-domain features were extracted from the temperature profile, and their relationships to the warpage mechanism were investigated. The standard deviation showed a significant linear correlation with warpage. The findings from this study are expected to contribute to optimizing process parameters for metal AM warpage reduction.