펠렛형 MWCNT를 사용한 PP/MWCNT 나노복합체 물성 연구

남병욱(Byeong Uk Nam),정동석(Dong Seok Jeong) 한국고분자학회 2011 폴리머 Vol.35 No.1

본 연구에서는 폴리프로필렌(PP)/다중벽 탄소나노튜브(MWCNT)복합체를 이축압출기를 사용하여 펠렛형 MWCNT를 20 wt%까지 함량별로 제조하고, MWCNT가 20 wt% 첨가된 복합체를 마스터배치(M/B)로 사용하여 함량별로 다시 PP와 컴파운딩하여 희석하였다. PP/MWCNT 복합체는 함량 변화에 따라 전기전도도, 열전도도, 모폴로지, 열적, 고체 점탄성, 기계적 성질을 조사하였고, 또한 희석된 PP/MWCNT 복합체와 1단계 PP/MWCNT 복 합체간의 물성을 비교하였다. 전기전도도와 열전도도는 MWCNT의 함량이 3 wt% 일 때 percolation threshold 현상을 보였고, M/B로 제조된 복합체가 더 우수한 전도도를 보였다. 복합체의 MWCNT 함량이 증가하면 비등온 결정화 온도 및 열분해 온도가 증가하였다. 모폴로지를 통하여 M/B로 제조된 복합체의 MWCNT 길이가 짧아진 것을 확인하였고, 이는 기계적 물성의 향상에 도움을 준 것으로 나타났다. Polypropylene/multi-walled carbon nanotube(PP/MWCNT) composites along with various MWCNT contents up to 20 wt% were prepared by a twin screw extruder. Nanocomposites having 20 wt% MWCNT as a master batch(M/B) were diluted with PP by way of melt compounding. The electrical/ thermal conductivity, morphology, thermal/viscoelastic/mechanical properties were investigated with the variation of MWCNT contents. Also, we compared some properties between 1-step PP/MWCNT and the diluted PP/MWCNT composites. The percolation threshold of electrical and thermal conductivity was measured at about 3 wt% MWCNT. And conductivity of diluted PP/MWCNT composites were superior to those of PP/MWCNT composites. The non-isothermal crystallization temperature and thermal decomposition temperature appeared at higher temperatures with increasing MWCNT contents. Morphology showed that length of MWCNT in diluted PP/MWCNT composites was shortened by twice melt blending, which contributed to improve the tensile strength of PP/MWCNT composites.

Toughening of PLA stereocomplex by Impact modifiers

남병욱(Nam, Byeong-Uk),이범석(Lee, Bum-Suk) 한국산학기술학회 2012 한국산학기술학회논문지 Vol.13 No.2

광학 이성질체인 PLLA와 PDLA를 전 조성에서 블렌드하여 PLA stereocomplex(SC)를 제조하였고 DSC를 통 해 PLLA matrix안의 SC결정 형성 정도를 파악하였다. 결과적으로 PLA SC blend의 PDLA 함량이 SC 결정 생성 정 도에 영향을 주며 PLLA/PDLA=50/50의 조성일 때 가장 많은 SC 결정이 생성되었다. 더 나아가 고유의 낮은 충격강 도를 보강하기 위하여 PLLA/PDLA=92/8, 85/15 조성에서 충격보강제(Impact modifiers)를 도입하였다. 제조된 PLA SC/Impact modifiers의 열적기계적 성질은 DSC, HDT, Izod Impact tester, UTM을 통해 측정하였다. DSC 측정 결과 PLA SC 결정은 Strong120(Impact modifier)가 10-20wt% 도입되면 감소하는 경향을 보이나 반면에 Elvaloy가 도입될 때에는 아무런 영향을 주지 않는 것으로 관찰되었다. HDT의 값은 PDLA의 도입에 따라 급격하게 100℃이상으로 증 가하였다. 하지만 Strong120과 Elvaloy가 도입됨에 따라 감소하는 경향을 보였다. 결국 Toughening된 PLA SC에서 10wt%의 Impact modifier를 blend하여 가장 최적의 충격강도와 굴곡탄성율을 갖는 물성을 발견할 수 있었다. We tried to blend PLLA and PDLA at overall compositions to form PLA stereocomplexes (SC). The presence of the SC crystalline phase in the PLLA matrix was verified by differential scanning calorimetry (DSC). As a result, a various PDLA composition of the PLA SC blends can influence PLA SC formation. And the largest amount of PLA SC crystallites was formed when PLLA/PDLA ratio is 50/50. In addition, we have tried to do PLA SC toughening with two impact modifiers in 92/8, 85/15 ratio of PLLA/PDLA to enhance the mechanical properties such as impact strength. Thermal and mechanical properties of PLA SC were investigated by DSC, HDT, Izod impact tester and UTM. PLA SC formation decreased when 10-20 wt% of Strong120 (impact modifier) was added. On the other hand, there is no effect on PLA SC formation when 10-20% of Elvaloy (impact modifier) was added. HDT values dramatically increased over 100℃ with the addition of PDLA. However, HDT decreased as Strong120 and Elvaloy content increased. Finally, we could find well balanced composition of toughened PLA SC with 10wt% of impact modifier in flexural modulus and impact strength.

Comonomer 도입한 상용화제가 Polypropylene / clay 나노복합재료에 미치는 영향

남병욱(Nam, Byeong-Uk) 한국산학기술학회 2007 한국산학기술학회논문지 Vol.8 No.2

본 연구에서는 극성 monomer인 HEMA와 GMA 를 이용하여 PP를 개질한 상용화제를 제조하였고, 이를 이용하여 용융컴파운딩 방법에 의해 PP계 나노복합재료를 제조하였다. 제조한 나노복합재료는 comonomer 도입 유무에 따른 상용화제 효과를 관찰하고자 XRD를 이용하여 분산성을 확인하였고, UTM등을 통하여 기계적 성질을 측정하였다. XRD 분석 결과, comonomer가 도입된 상용화제를 이용하여 제조된 나노복합재료는 Clay의 층간삽입이 개선되어 분산성이 향상됨을 볼 수 있었다. 또한, 기계적 성질 평가 결과 GMA monomer로 개질된 상용화제를 사용하여 제조한 나노복합재료가 굴곡탄성률과 충격강도 측면에서 더 향상된 결과를 보여주었다. Comonomer를 도입하여 제조한 나노복합재료는 Comonomer를 도입하지 않은 나노복합재료에 비해서 그라프팅 수율이 향상되었고, 반면에 용융지수가 감소되는 경향을 보였다. 본 연구에서 제조한 comonomer가 도입된 나노복합재료는 monomer 와 comonomer의 비율이 1:1 인 경우에 가장 향상된 기계적 성질과 분산성을 보임을 확인 할 수 있었다. Nanocomposites prepared by PP(polypropylene) based compatibilizers modified with GMA(Glycidyl methacrylate) and HEMA(Hydroxyethyl methacrylate) were used to investigate the clay dispersion and mechanical properties of them. XRD patterns showed the improvement of dispersion through clay intercalation according to the compatibilizers and comonomer. GMA modified polypropylene gave the best mechanical properties of the nanocomposite with respect to the balance of Flexural modulus (FM) and Notched izod impact strength(IS). Compatibilizers with comonomer commonly have highei grafting yield and lower melt flow rate than those of comonomer free. And they enhanced the clay dispersion and mechanical properties of nano-composites. Optimum ratio of monomer to comonomer for nanocomposites having better mechanical properties is about 1 to 1 ratio.

고분자 나노복합재료의 가공조건 및 물성 최적화

남병욱(Byeong Uk Nam),홍채환(Chaehwan Hong),황태원(Taewon Hwang) 한국자동차공학회 2007 한국 자동차공학회논문집 Vol.15 No.6

PLA Stereocomplex의 제조 및 열적 특성

남병욱 ( Byeong Uk Nam ),정동석 ( Dong Seok Jeong ),장미옥 ( Mi Ok Jang ),홍채환 ( Chae Hwan Hong ) 한국공업화학회 2010 응용화학 Vol.14 No.1

Polylactide (PLA) is considered a good alternative to fossil fuel based plastics as it is biodegradable and nontoxic to human. However PLA crystallize at a very low rate and has a relatively low melting temperature (Tm) in comparison with other commercial polymers. PLLA/PDLA stereocomplex has been expected to be potential high-performance polymer, because it shows its Tm at 220℃ which is 50℃ higher than homo-PLA. In this work, Thermal properties and crystallization behaviors of stereocomplex were analyzed by using DSC (Differential Scanning Calorimetry), WAXD (Wide angle X-ray scattering) and Polarized microscope. We could find that stereocomplex crystallites exhibit much higher spherulite growth rate. Also, thermal stability is maximized when a 50/50 blend is used.

Tetramethyl Bisphenol - A Polyarylate 의 합성과 Poly ( styrene - co - acrylonitrile ) 과의 상용성에 관한 연구

남병욱(Byeong Uk Nam),엄달호(Dal Ho Um) 한국고분자학회 1992 폴리머 Vol.16 No.6

용융 블렌딩법에 의한 PPC/EVAc 블렌드의 모폴로지 및 열적 특성

남병욱 ( Byeong Uk Nam ),정동석 ( Dong Seok Jeong ),이범석 ( Bum Seok Lee ) 한국공업화학회 2010 응용화학 Vol.14 No.1

PPC (Polypropylene carbonate) has been an charming green material due to containing carbon dioxide. PPC is made from copolymerization of CO2 with propylene oxide (PO) using a catalyst. However this polymer has fool mechanical property and relatively low glass transition temperature (Tg) and thermal decomposition temperature. Therefore, we blended PPC and EVAc (ethylene vinyl acetate) with overall compositions to enhance mechanical property and thermal property. Mechanical property and thermal property of PPC/EVAc blends was investigated by DMA (Dynamic Mechanical Analyzer) and TGA (Thermogravimetric analysis) respectively. Compatibility of PPC/EVAc blends was proved by FESEM (Field Emission Scanning Electron Microscope). As a result, we could find all compositions of PPC/EVAc blends are immiscible. However we could see thermal stability is improved as EVAc content increased.

Butyllithium과 Hexyllithium을 이용한 다중벽 탄소나노튜브의 분산 특성 평가

남병욱 ( Byeong Uk Nam ),유정현 ( Jeong Hyun Ryu ) 한국공업화학회 2010 응용화학 Vol.14 No.1

Carbon nanotubes (CNTs) are difficult to disperse in solvents and polymer matrices. Therefore, CNTs have need to do modification from functional groups. In this study, to improve the CNT`s dispersion, we tried to modify the CNT`s surface by butyllithium and hexyllithium solution with multi-walled carbon nanotubes (MWNTs). To find the addition of small functional groups, we analyzed Raman spectrometer and thermogravimetric analysis (TGA) and used various solvents and investigated the dispersity. As a result, functional groups of attached the CNT`s surface are confirmed through Raman and TGA. A small amount of functionalized-MWNTs is dispersed only in chloroform and tetrahydrofuran.

PLLA/EGMA 블렌드의 모폴로지 및 기계적특성

남병욱 ( Byeong Uk Nam ),정동석 ( Dong Seok Jeong ),장미옥 ( Mi Ok Jang ),홍채환 ( Chae Hwan Hong ) 한국공업화학회 2010 응용화학 Vol.14 No.1

PLA is too brittle for room-temperature applications. Therefore, It can be toughened through blending with other polymers. In this study, PLLA/EGMA blends were prepared by melt blending with biodegradable poly-L-lactic acid (PLLA) and Poly(ethylene-co-glycidyl methacrylate) (EGMA). Blend compositions of PLLA/EGMA were 100/0, 25/75, 50/50, 75/25 and 0/100, respectively. The morphology and mechanical properties were characterized by FESEM, DMA, UTM and Izod impact tester. Throughout FESEM image, we observed that domain was well diffused into matrix. DMA and Izod impact test data show that storage modulus of room temperature with increasing EGMA content decreased, and impact strength increased. The tensile strength and flexural modulus were decreased with increasing the content of EGMA in them.

습식화학법을 이용한 고순도 석영유리 기판 제조 및 특성평가

박성은,남병욱,안정숙,신지식,오한석,Park, Sung-Eun,Nam, Byeong-Uk,An, Jung-Sook,Shin, Ji-Shik,Oh, Han-Seog 한국반도체디스플레이기술학회 2007 반도체디스플레이기술학회지 Vol.6 No.4

Quartz glass panel was prepared by a colloidal silica through the heat-treatment only without any additives in wet-chemical method. This colloidal silica used in slurry process has the uniform distribution of particle size and lower cost. The results show that 6N as a degree of purity and the 86 percentage of violet transmittance in 1mm thickness. AFM(Atomic Force Microscopy) pattern shows that the surface roughness are less than lnm. Also, we investigated the characteristic of quartz panel according to the concentration and distribution of hydroxyl group, viscosity and thermal expansion coefficient.