광경화 아크릴레이트 단량체의 복합경화 특성

배진우(Jin Woo Bae),정재현(Jae Hyun Jung),왕혁식(Hyuck Sik Wang),김석현(Seok Hyeon Kim),김일중(Il Joong Kim),김익재(Ik Jyae Kim),송기국(Kigook Song) 한국고분자학회 2017 폴리머 Vol.41 No.2

광경화와 열경화능을 가진 아크릴레이트 단량체를 사용하여 광경화-열경화 또는 열경화-광경화의 순서에 따른 경화속도 변화를 고찰하였다. Isocyanatoethyl acrylate(ICEA)와 2-hydroxyethyl methacrylate(HEMA) 처럼 광경화와 열경화 메카니즘이 다른 단량체 혼합물에 먼저 UV에 의한 광반응을 진행한 후, 2차로 열경화를 하는 복합경화시스템을 조사하였다. 이 경우 1차 광경화에 의해 고분자 사슬이 형성되면, 2차로 열경화에 의해 우레탄 반응에 참여하는 관능기들이 고분자 사슬에 묶이게 되어 열경화에 의한 우레탄 반응을 더 높은 온도에서 진행하여야 하며, 전환율도 낮아지는 것을 확인하였다. 반면에, 같은 조성의 혼합물에 열경화를 먼저 진행하고 광경화를 하는 복합경화의 경우에는 열경화에 의해 우레탄 아크릴레이트 단량체가 먼저 생성된 후, 단량체 양 말단에서 반응이 진행되어 빠르게 광경화 반응이 진행되었다. Dual curing systems of acrylates with thermo- and photo-reactions were studied to understand the effect of curing sequence on the curing reaction kinetics. A combined curing system that photochemical reaction with UV light followed by thermal cure was applied to acrylate monomer mixtures such as isocyanatoethyl acrylate (ICEA) and 2-hydroxyethyl methacrylate (HEMA). In such case, the polymer chain was formed by the first photo-curing and, then the functional groups participating in the urethane reaction were bound to the polymer chain, so that the urethane reaction by the thermal curing should be carried out at a higher temperature and the conversion rate was low. On the other hand, in the case of a dual curing process in which the photo-curing proceeded after the thermal curing, the urethane acrylate monomer was first formed by the thermal reaction, and then the faster photo-reaction proceeded at both ends of the monomer.

FTIR을 이용한 아크릴레이트 단량체의 광-열 복합경화 거동 연구

김석현(Seok Hyeon Kim),왕혁식(Hyuck Sik Wang),이승혁(Seung Hyuk Lee),부석형(Seok Hyung Bu),송기국(Kigook Song) 한국고분자학회 2018 폴리머 Vol.42 No.4

우레탄 열반응이 가능한 아크릴레이트 단량체의 UV 광경화 거동을 in-situ로 시분해 푸리에 변환 적외선 분광법(FTIR) 실험과 광 DSC 실험을 수행하여 조사하였다. 아크릴레이트 단량체 사이의 우레탄 열반응을 먼저 진행한 후 UV를 쪼여 아크릴레이트 광반응을 유도한 열-광 복합경화 공정이 UV 광경화만 진행한 경우보다 아크릴레이트 반응은 더 빠르게 진행되었지만, 아크릴레이트의 최종 경화율은 약간 감소하였다. 이와 같은 아크릴레이트 단량체 시스템에 긴 사슬의 아크릴레이트 올리고머를 첨가한 시스템에서도 복합경화 공정이 UV 광경화만 진행한 경우 보다 반응은 더 빠르게 진행되었고, 아크릴레이트 경화 정도는 큰 차이 없이 끝까지 진행되었다. The photo-curing behaviors of acrylate monomers capable of urethane thermal reaction were investigated using time-resolved Fourier transform infrared spectroscopy and photo-differential scanning calorimetry. Faster photo-reaction and lower conversion of acrylate reactions were observed in the thermal-photo dual curing process compared to the photo-curing only process. In the case of the acrylate system with long chain oligomers, faster photo-reaction was also observed in the dual curing process although no difference was found in the degree of conversion for acrylates between two photo-curing processes.

The complete genome sequence of <i>Bacillus velezensis</i> strain GH1-13 reveals agriculturally beneficial properties and a unique plasmid

Kim, Sang Yoon,Song, Hajin,Sang, Mee Kyung,Weon, Hang-Yeon,Song, Jaekyeong Elsevier Science Publishers 2017 Journal of biotechnology Vol.259 No.-

<P>The bacterial strain Bacillus velezensis GH1-13, isolated from rice paddy soil in Korea, has been shown to promote plant growth and have strong antagonistic activities against pathogens. Here, we report the complete genome sequence of GH1-13, revealing that it possesses a single 4,071,980-bp circular chromosome with 46.2% GC content. The chromosome encodes 3,930 genes, and we have also identified a unique plasmid in the strain that encodes a further 104 genes (71,628 bp and 31.7% GC-content). The genome was found to contain various enzyme-encoding operons, including indole-3-acetic acid (IAA) biosynthesis proteins, 2,3-butanediol dehydrogenase, various non-ribosomal peptide synthetases, and several polyketide synthases. These properties are responsible for the promotion of plant, growth and the biosynthesis of secondary metabolites. They therefore have multiple beneficial effects that could be applied to agriculture. Through curing, we found that the unique plasmid of GH1-13 has important roles in the production of phytohormones, such as IAA, and in shaping phenotypic and physiological characteristics. The plasmid therefore likely influences the biological activities of GH1-13. The complete genome sequence of B. velezensis GH1-13 contributes to our understanding of this beneficial strain and will encourage research into its development for agricultural or biotechnological applications, enhancing productivity and crop quality.</P>

탄소섬유 에폭시 복합재료 연삭온도에 의한 연삭특성

한흥삼,이동주 韓國工作機械學會 2000 한국생산제조학회지 Vol.9 No.6

Although the net-shape molding of composites is generally recommended, molded composites frequently requires cut-ting or grinding due to the dimensional inaccuracy for precision machine elements. During the composite machining oper-ations such as cutting and grinding, the temperature at the grinding area may increase beyond the allowed limit due to the low thermal conductivity of composites, which might degrade the matrix of composite. Therefore, in this work, the tem-perature at the grinding point during surface grinding of carbon fiber epoxy composite was measured. The grinding tem-perature and surface roughness were also measured to investigate the surface grinding characteristics of the composites. The experiments were performed both under dry and wet grinding conditions with respect to cutting speed, feed speed, depth of cut and stacking angle. From the experimental investigation, the optimal conditions for the composite surface grinding were suggested.

피로하중이 가해지는 외면겹치기 동시경화조인트의 파괴에 미치는 부식의 영향

신금철(Kum Cheol Shin) 대한기계학회 2010 大韓機械學會論文集A Vol.34 No.3

반복 인장하중이 가해지는 외면겹치기 동시경화조인트는 피접합물의 경계면 가장자리에서 균열이 발생하여 전체 파손에 이르게 되는데, 그 과정 중 피접합물의 경계면에서 발생하는 부식 현상이 중요한 영향을 미치게 된다. 그러므로 본 논문에서는 외면겹치기 동시경화조인트의 피로 파괴에 미치는 부식 현상의 영향을 규명하기 위하여 접합부 계면의 표면조도와 피접합물의 하나인 복합재료의 적층 각도의 변화에 따른 피로실험을 수행하였으며 유한요소해석을 통하여 얻은 경계면 응력 분포와 비교, 분석하였다. Co-cured single lap joints under cyclic tensile loads fail initially at the tip of the interface corner between the two adherents. The failure mechanism is complex because it is related to corrosion fatigue. Corrosion behavior at the interface affects the failure of the joints because corrosion deteriorates fatigue resistance. In this study, we clarified the cause of interfacial corrosion in co-cured single lap joints under cyclic tensile loads. The failure mechanism was also analyzed by observing the failed surfaces of specimens and the stress distribution along the interface. The surface roughness at the interface and the stacking sequence of the composite adherent were examined to investigate their effects on failure of the joint.

GC 연삭숫돌을 이용한 탄소섬유 에폭시 복합재료의 평면 연삭특성에 관한 연구

한흥삼,윤혁중,이동주 韓國工作機械學會 2000 한국생산제조학회지 Vol.9 No.4

Since carbon fiber epoxy composite materials have excellent properties for structures due to their high specific strength, high specific modulus, high damping and low thermal expansion, the hollow shafts made of carbon fiber epoxy compos-ites have been widely used for power transmission shafts for motor vehicles, spindles of machine tools, motor base, bear-ing mount for tool up and manufacturing. The molded composite machine elements are not usually accurate enough for mechanical machine elements, which require turning, drilling, cutting and grinding. The experiment are surface grinding of the grinding wheel GC60 to the car-bon fiber epoxy composite specimen with respect to stacking angle [0]_nT, [45]_nT, [90]_nT on the CNC grinding machine. In this paper, the surface grinding characteristics of composite plate, which are surveyed experimentally and analytically with respect to the grinding force, surface roughness and wheel loading according to the variable depth of cut, wheel velocity and table feed rate are investigated.