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최은엽,김무현,이승연,김창근,신정채 한국공업화학회 2019 한국공업화학회 연구논문 초록집 Vol.2019 No.1
Life of thermoplastic polyurethane (TPU) hose used in underwater acoustic sensor was predicted by using accelerated life test (ALT). The ALT was conducted by aging the TPU hose in four different heating conditions at 40, 70, 85, 100, 110 and 125 °C. After aging, the mechanical properties of TPU hose measured for given periods. Changes in the mechanical properties were expressed as master curves by regression method and then the failure times of TPU hose was obtained from the master curves. To interpret the ALT data of TPU hose, mathematical relations including life distribution and acceleration models were used and their parameters were estimated by using the maximum likelihood estimation (MLE) method. The MLE result indicated that Arrhenius model and Weibull distribution provides the best fit for the ALT data. From the Arrhenius-Weibull model, the failure time of half of TPU hose for tensile strength and tear resistance were estimated to be 90.0 and 16.4 years, respectively.
최은엽,이승연,김창근 한국공업화학회 2021 Journal of Industrial and Engineering Chemistry Vol.100 No.-
To produce nylon 6,6 (N66)-based composites with carbonfiber (CF) having extremely high mechanicalstrength, CF covalently bonded with carbon nanotube (CNT), CF–c–CNT, wasfirst produced by reactingfunctionalized CF and CNT and then a composite of N66 and CF–c–CNT was produced by melt extrusion. Two types of CF–c–CNT were prepared: CF and CNT functionalized with acyl chloride (COCl) and aminegroup (NH2), respectively (COCl–CF–c–CNT–NH2), and CF and CNT functionalized with NH2 and COCl,respectively (NH2–CF–c–CNT–COCl). N66 bonding to CF–c–CNT occurred during extrusion by thereaction of COCl with amine groups in N66. Thus, N66 bonded to CF (N66–CF–c–CNT) and N66 bonded toCNT (CF–c–CNT–N66) were formed. The N66/CF–c–CNT–N66 composite exhibited the highest interfacialadhesion, the bestfiller dispersion, and the greatest amount of N66 bonding tofiller among thecomposites tested. As a result, the N66/CF–c–CNT–N66 composite had the highest tensile strength andfatigue life among the composites. The tensile strength and fatigue life of the N66/CF–c–CNT–N66composite were 20% higher andfive times longer than those of the N66/CF composite, respectively.
최은엽,신정채,이재영,김무현,김창근 한국고분자학회 2020 Macromolecular Research Vol.28 No.5
The lifetime of thermoplastic polyurethane (TPU) encapsulants used in underwater acoustic sensor (UAS) was predicted using accelerated life testing (ALT). The TPU specimens for tensile and tear strength tests were aged at six different temperatures, and the strengths of the aged specimens were then measured. The measured tensile and tear strengths as a function of aging temperature were used as ALT data for the analysis of the TPU encapsulant lifetime using ReliaSoft’s ALTA software. For the analysis of ALT data, the acceleration models and the life distribution models in the ALTA software were combined. The maximum likelihood estimation (MLE) method was used to find the most reliable acceleration-life distribution model when interpreting ALT data for tensile and tear strengths. It reveals that the Arrhenius-Weibull distribution model best fits the ALT data of the TPU encapsulant. The lifetime of the TPU encapsulant for tensile and tear strength was estimated using the Arrhenius-Weibull distribution model. The estimated results exhibited that the lifetime for tear stress was much shorter than that for tensile stress at 25 °C. Tensile and tear stresses are applied simultaneously to the TPU encapsulant during UAS operation. Thus, its replacement time should be determined by its tear strength lifetime.
최은엽,김성원,김창근 한국공업화학회 2015 한국공업화학회 연구논문 초록집 Vol.2015 No.1
Multi-walled carbon nanotubes (MWCNTs), expected as effective fillers of polymer composites, were chemically treated with hydrogen peroxide (H<sub>2</sub>O<sub>2</sub>) to improve their morphological disabilities. Morphology of MWCNTs were changed by reacting with H<sub>2</sub>O<sub>2</sub>, and waviness of MWCNTs were also decreased with time and temperature dependently. It has been shown that H<sub>2</sub>O<sub>2</sub> is used for introducing hydroxyl groups on the surface of MWCNTs, and it mainly attacks defect sites of MWCNTs such as non-aromatic structures. As a result, waviness of MWCNTs were changed because defect sites affects curliness of MWCNTs. Polymer composites such as PC, PA66, PBT and PE were fabricated with chemically treated MWCNTs and tensile test were conducted to confirm the improvement of morphological properties affected on the mechanical properties of CNT-filled composites.
폴리우레탄이 그래프트된 다중벽 탄소나노튜브가 포함된 폴리우레탄 복합소재의 특성
최은엽(Eun Yeb Choi),김성원(Sung Won Kim),이재영(Jae Young Lee),하지훈(Ji Hoon Ha),김창근(Chang Keun Kim) 한국고분자학회 2017 폴리머 Vol.41 No.3
열가소성 폴리우레탄 탄성체(TPU)와 TPU가 그래프트된 다중벽 탄소나노튜브(MWCNT)의 (TPU-g-MWCNT) 복합체를 제조하기 위해 TPU와 이소시아네이트기로 기능화된 MWCNT를 이축 압출기를 사용하여 용융 압출하였다. MWCNT에 형성된 이소시아네이트기와 TPU에 존재하는 수산화기가 용융 압출 동안 반응하여 TPU-g-MWCNT가 형성됨을 계면 접착 에너지 변화, 복합체의 기계적 물성 변화 등으로 확인하였다. TPU와 TPU-g-MWCNT 간의 계면 접착 에너지 값이 TPU와 화학 처리 전 MWCNT간의 값에 비해 높았다. 이 결과로 TPU/TPU-g-MWCNT 복합체가 TPU/화학처리 전 MWCNT 복합체보다 향상된 MWCNT 분산과 계면 접착을 나타내었다. 일정한 MWCNT 함량에서 TPU/TPU-g-MWCNT 복합체가 TPU/화학처리 전 MWCNT 복합체보다 높은 기계적 강도를 나타내었다. Thermoplastic polyurethane elastomer (TPU) and multi-walled carbon nanotubes (MWCNTs) functionalized with isocyanate groups were melt mixed in a twin extruder to produce TPU composites containing TPU grafted MWCNTs (TPU-g-MWCNT) by reacting isocyanate groups on MWCNTs with the hydroxyl groups in TPU. Formation of TPU-g-MWCNTs by reactive extrusion was explored as were their resulting properties including interfacial adhesion energies between TPU and MWCNT and mechanical properties of TPU/MWCNT composites. The interfacial adhesion energy of the TPU/TPU-g-MWCNT composite was higher than that of the TPU/pristine MWCNT composite; a result, the TPU/TPU-g-MWCNT composite exhibited a higher level of dispersion of MWCNTs in the TPU matrix and better adhesion at the interface between TPU and MWCNTs than the TPU/pristine MWCNT composite. For a fixed MWCNT content in the composite, the mechanical strength of the TPU/TPU-g-MWCNT composite was higher than those of the corresponding TPU/pristine MWCNT composite.