Study On Preparation And Properties Of Carbon Nanotube And Graphene Reinforced Epoxy Resin Composites

Carbon nanotubes(CNTs) possess large aspect ratio, extraordinary mechanical performance, excellent chemical and thermal stability, rendering them the most promising candidate as ideal reinforcement for composite materials. However, the reinforcement effect in polymer matrix might be limited, because they are prone to aggregate, and have a weak interaction with polymer matrix. In order to improve the dispersion and interfacial strength of CNTs in polymer matrix, the multi-walled carbon nanotubes (MWCNTs) were modified by covalent, noncovalent, and hybrid functionalizations, respectively. Using solution blending method, three types of functionalized MWCNTs were incorporated into the epoxy resin (EP) with various mass fractions, to prepare MWCNTs/EP composites. The effect of the content and functionalization method of MWCNTs on the mechanical and thermal properties of the composites was studied through tensile test and thermal gravimetric analysis. The fracture sections of the tensile specimen were examined by using SEM.Graphene is single-layer or several layers of graphite crystal. It has high specific area, extraordinary mechanical, electrical and thermal properties. Its tensile modulus and strength are comparable with those of CNTs. Because of its limited size, graphene nanocomposites reported in document at present are almost functional composite materials. With the emerging of new methods for the preparation of large area sheets of graphene, they will probably be applied in the field of structural engineering. This paper presents the preparation of large area sheets of graphene with natural flake graphite. Firstly, graphite oxide was prepared by oxidizing natural flake graphite; then the graphite oxide was exfoliated in distilled water by sonication to prepare graphene oxide; finally, the graphene oxide was added in hydrazine hydrate and stirred for one week to produce large area sheets of graphene. Using solution blending method, graphene and MWCNTs were incorporated into the epoxy resin (EP) with various mass fractions, to prepare Graphene/MWCNTs/EP composites. The effect of the loading and size of graphene on the mechanical properties of the composites was studied by means of tensile test and SEM analysis. Therefore the probability and preparation methods of graphene nanocomposites becoming the future high-performance structural materials were explored.The main results are: (1) The hybrid functionalized composite (MWCNTs-Epon828-PPA/EP) exhibits the best mechanical and thermal properties comparing with covalent and noncovalent functionalized composites (MWCNTs-Epon828/EP, MWCNTs-PPA/EP). At 0.3% mass fraction of MWCNTs, the tensile strength, elastic modulus, and the elongation at break are increased by 30%, 62%, and 26%, compared with the pure EP, respectively.(2) In general a grapheme sheet is constitutive of 3 to 5 layers according to SEM and TEM images, which has wrinkled surface texture. These graphene sheets have a size around 15μm×20μm and a feasible dispersion.(3) At 0.1% mass fraction of graphene and MWCNTs, the tensile strength, elastic modulus, and the elongation at break of Graphene/MWCNTs-Epon828/EP composite are increased by 35%, 65%, and 34%, respectively. It exhibits the best mechanical properties in all composite prepared in this work. The epoxy resin composites reinforced with lower content graphene and MWCNTs demonstrate a better mechanical performance comparing with the composites only reinforced with MWCNTs.