코어쉘 구조를 가지는 고 열전도성 및 전기 절연성의 PPS 복합재료 : High thermally conductive and electrically insulating PPS composites having core-shell structure

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서울대학교 대학원
폴리페닐렌설파이드카본나노튜브질화알루미늄코어쉘 구조열전도성전기 절연성Polyphenylene sulfideMulti-walled carbon nanotubesAluminum nitrideCore-shell structureThermal conductivityElectrical insulation
학위논문 (석사) -- 서울대학교 대학원 : 농업생명과학대학 바이오시스템.소재학부(바이오소재공학전공), 2021. 2. 박종신.
Polyphenylene sulfide (PPS) is an outstanding material as an engineering thermoplastic polymer for diverse industrial applications. We investigated a highly thermally conductive PPS composite containing muti-walled carbon nanotubes (MWCNTs) and aluminum nitride (AlN) as a thermally conductive filler. For a stable formation of heat flow channel, the PPS composite was prepared by core-shell fabrication method in order to obtain high thermal conductivity with low filler contents, and thus overcome the demerits of melt mixing fabrication method. A comparison between conventionally melt mixed composite and the proposed core-shell composite showed that the consecutive chain of filler at the surface of each polymer pellet could enhance the thermal conductivity very much.
Moreover, the thickness of the AlN coating layer could be controlled by diluting the concentration of the adhesive epoxy resin using acetone as the solvent.
AlN/PPS core-shell pellets with various thicknesses were fabricated in order to analyze the effect of the coating layers thickness on thermal conductive properties.
A 1:0.2 weight ratio of epoxy and acetone has the highest thermal conductivity enhancement ratio compared to the melt mixed composite, and the optimum AlN contents of c-AlN(0.2) was 19 wt% from TGA analysis.
Hereafter, we fabricated PPS/MWCNTs/AlN composites via melt mixing and core-shell fabrication. The characteristics of composite materials according to fabrication method were compared and analyzed by FE-SEM, EDS, thermal conductivity analysis, TGA, void fraction analysis and tensile strength measurement. Compared to the composite materials fabricated by melting mixing method, it was confirmed that the thermal conductivity values were improved by more than 2.5 times in the core-shell composite materials containing the same amount of thermal conductive fillers. The composite material with the highest thermal conductivity improvement rate was found to be a core-shell composite material containing 2 wt% MWCNTs.
The electrically insulating AlN layer efficiently hindered a conduction of electron, which is the main problem with utilizing MWCNTs as a thermally conductive filler in polymer composites, in spite of their remarkable thermal conductivity. As a result, all core-shell composite materials showed electrical conductivity values of 10-8 S/cm or less, and all of the composite materials fabricated by melt mixing method showed electrical conductivity values of 10-8 S/cm or higher, indicating that core-shell composite materials had electrical insulating properties. Therefore, core-shell fabrication method may be used as a promising composite fabrication method for engineering plastic based thermally conductive materials, forming a 3D heat flow channels with electrically insulating effect.
본 연구에서는 폴리페닐렌설파이드에 뛰어난 열전도 특성을 가지는 카본나노튜브와 질화알루미늄을 보강재로 도입하고, 안정적인 열 흐름 통로의 형성을 위해 코어쉘 구조를 가지는 방열 고분자 복합재료를 제조하고 제조 방법에 따른 특성을 분석하였다. 먼저, 질화알루미늄 파우더 코팅 층의 두께에 따른 복합재료의 열전도도 특성 변화를 분석하기 위해 아세톤을 사용하여 에폭시 레진의 농도를 조절하며 코어쉘 복합재료를 제조하였다. 그 결과, 에폭시 레진과 아세톤의 중량 비율이 1:0.2인 조건에서 가장 높은 열전도도 향상률을 확인하였으며, 약19 wt%의 질화알루미늄 함량을 확인하였다. 폴리페닐렌설파이드/ 카본나노튜브/질화알루미늄 복합재료를 용융 블렌드 방식과 코어쉘 제조 방식으로 각각 제조하였다. FE-SEM, EDS, 열전도성 분석, 열 중량 분석, 공극률 분석, 기계적 특성 분석을 통해 제조 방식에 따른 복합재료의 특성을 비교 분석하였다. 용융 혼합법으로 제조한 복합재료에 비해, 동량의 열전도성 보강재가 함유된 코어쉘 복합재료에서 열전도도 값이 2.5배 이상 향상됨을 확인하였다. 가장 열전도도 향상률이 높은 복합재료는 카본나노튜브를 2 wt% 함유한 코어쉘 복합재료로 나타났다. 카본나노튜브가 유발할 수 있는 전자의 전도를 전기 절연성의 질화알루미늄 코팅 층이 효과적으로 차단하는지 확인하기 위하여, 고 저항 미터기를 사용하여 복합재료의 전기 전도도를 측정하였다. 코어쉘 복합재료는 모두 10-8 S/cm 이하의 전기 전도도 값을 나타냈고, 용융 블렌드 방식으로 제조한 복합재료는 모두 10-8 S/cm 이상의 전기 전도도 값을 나타내어 코어쉘 복합재료가 전기 절연 특성을 가짐을 확인하였다.
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College of Agriculture and Life Sciences (농업생명과학대학)Dept. of Biosystems and Biomaterials Science and Engineering (바이오시스템·소재학부)Theses (Master's Degree_바이오시스템·소재학부)
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