에폭시 고분자복합체 상에서 그래핀 기반 네크워크 설계 및 다기능적 응용에 관한 연구

Abstract

In this dissertation, the contents were involved five chapters that discussed the design and analysis of graphene based network (HRGO, RGO, and RFG-AlNWs) nanofillers in epoxy polymer nanocomposites, as well as their multifunctional applications such as electrical conductivity, thermomechanical properties, and electromagnetic interference shielding application, etc. Firstly, epoxy resins owing to their high versatility from chemical and processing perspectives and hence their capability of being tailored for required properties that are used in a wide range of applications. However, the usage of electronic, electrical equipment and electronic packaging are still less. In this work, the structure of diglycidyl ether of bisphenol A (DGEBA) has a few drawbacks that lead to brittle failure, low impact resistance, and poor conductivity, which limit extensive application of DGEBA epoxy resin in various engineering applications. Modifier-polyetherimide (PEI) and graphene based nanofillers are incorporated to enhance the properties and energy dissipation mechanisms of the pristine DGEBA. These modifications result in appreciable improvement in the multifunctional DGEBA nanocomposites. Secondly, this work discussed the selective localization of nanofillers by different interfacial tension in polyblends, the effectiveness of curing reaction-induced phase separation (CRIPS) in the polyblend, and the interface and interphase in the polyblends. Meanwhile, the simple self-assembly processing technology to incorporate graphene based network nanofillers in DGEBA/PEI by controlling its localization, the synergistic effect between nanofillers and the DGEBA/PEI polyblend and the technique of characterization have also been discussed. Thirdly, this work focused on a feasible and effective approach to building an electrically conductive and double percolation network-like structure via incorporating highly reduced graphene oxide (HRGO) into DGEBA/PEI polyblend. The evolution of the phase structure of DGEBA/PEI/HRGO nanocomposites was investigated by varying content of PEI. The 0.5wt.% HRGO delivered a high electrical conductivity in DGEBA/PEI polyblends, wherein the value increased from 5.03 × 10−16 S/m (neat DGEBA) to 5.88 S/m (DP30H). Due to selective localization behavior, an interconnected network of HRGO is formed in the phase-separated structure of the DGEBA/PEI polyblend using the CRIPS technique. Then, the research focused on optimizing and analysis of DGEBA/PEI/RGO in various content of RGO. The selective interfacial localization of RGO was predicted numerically by the harmonic and geometric mean technique and further confirmed by field emission transmission electron microscopy (FETEM) analysis. Due to selective interfacial localization, the electrical conductivity was increased to 366 S/m with 3 wt.% RGO reinforcement (DP30R3). The thermomechanical properties of nanocomposites were determined by dynamic mechanical analysis (DMA). The storage modulus of 3 wt.% RGO-reinforced polyblend (DP30R3) exhibited an improvement of ~15%, and glass transition temperature (Tg) was 10.1 °C higher over neat DGEBA. Furthermore, the total shielding effectiveness (SET) was increased to 25.8 dB in the X-band region, with only 3 wt.% RGO, which represents ~99.9% shielding efficiency. Furthermore, the research concentrated on fabricating an efficiently reduced hexylamine functionalized graphene oxide/ Aluminium nanowires (RFG-AlNWs) conductive network nanofiller in the DGEBA/PEI polyblend system. The Al nanowires were synthesized on the hexylamine functionalized graphene oxide substrate by a simple high temperature treatment process without any catalyst. Meanwhile, the morphology, electrical, thermal, and EMI shielding properties of RFG-AlNWs and its nanocomposites, as well as the selective localization of hybrid RFG-AlNWs nanofiller in the DGEBA/PEI, were discussed. Finally, the above results showed the graphene based network nanofillers (HRGO, RGO, and RFG-AlNWs) in DGEBA/PEI nanocomposites might have great potential in various applications, such as electronic coatings, EMI shielding, aerospace structural materials, and microelectronics.