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Edge-functionalized graphene-like platelets as cocuring agents and nanoscale additives to epoxy resin

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Title
Edge-functionalized graphene-like platelets as cocuring agents and nanoscale additives to epoxy resin
Author
Kim, Kyung-Su
Advisor
Baek, Jong-Beom
Keywords
epoxy composite; graphite; graphene; edge-functionalization
Issue Date
2011-02
Publisher
Graduate school of UNIST
Abstract
Epoxy or polyepoxide is a thermosetting polymer formed from reaction of an epoxide "resin" with polyamine "hardener". Epoxy has a wide range of applications, including fiber-reinforced plastic materials and general purpose adhesives. In general, epoxies are known for their excellent adhesion, chemical and heat resistance, good-to-excellent mechanical properties and very good electrical insulating properties. Exfoliation of graphite, including into individual layers (graphene), is of great interest due to the exceptional properties. Graphite can be exfoliated into graphene sheets by physical and chemical methods, and graphene can also be grown by chemical vapor deposition on metal substrates as well as from single crystal silicon carbide. In this work, the method for edge-functionalization of ‘pristine’ graphite through “direct” Friedel-Crafts acylation in polyphosphoric acid/phosphorous pentoxide medium has been developed. Reactive 4-aminobenzoyl-functionalized graphite (AB-graphite) could be produced from the reaction between 4-aminobenzoic acid and ‘pristine’ graphite. The AB moiety at the edges of graphite played a role as molecular wedge to exfoliate the AB-graphite into graphene-like platelets, which was used as co-curing agents as well as nanoscale additives to epoxy resin. The physical properties of resultant epoxy/AB-graphite composites were improved due to efficient load transfer from graphene-like platelets to epoxy matrix through covalent links between the additives and matrix resin. Finally, the tensile strengths at break for pure epoxy and epoxy/AB-graphite with 4 wt% load were 61 MPa and 79 MPa, respectively. The value was approximately 30 % improved. In the case of Young’s modulus, the composite with 4 wt% of AB-graphite load displayed maximum average modulus 983 MPa, whose value was more than 40 % improvement. The remarkable improvement of tensile strength and Young’s modulus should be attributable to the covalent links between AB-graphite and epoxy matrix.
Description
Interdisciplinary School of Green Energy
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