Preparation And Properties Of Graphene/Epoxy Composite

Being one of the most widely used polymer materials,epoxy resin(EP)has many excellent physical,chemical and mechanical properties,such as good dimensional stability,high hardness,good insulation performance,strong bonding strength,good chemical inertness,acceptable heat resistance,etc.But the brittleness and poor impact resistance of epoxy resin limits the further application of such epoxy resin to some extent.Graphene in 2D nanostructure with large size and high structural integrity has superior strength and modulus,high electrical conductivity and thermal conductivity.Numerous studies have shown that graphene can effectively improve the strength and toughness of epoxy resin;however,due to the Van der Waals force,graphene is easy to aggregate together in the polymer matrix,limiting the improvement effect of the graphene on the mechanical properties of epoxy resin.In this study,multi-layer graphene(MLG)was selected as the reinforcing material to enhance the mechanical properties of EP matrix.By mking use of a method of bubbling dispersion,the dispersion of graphene in EP matrix can be improved to a great extent,With the generation and expansion of air bubbles in plastic matrix,the spreading of membrane wall would arouse an effect of separating and stretching among the graphene particles embedded in the EP matrix.The effect must be able to not only make the graphene particle separated,but also accelerate the stretching and spreading of graphene in the matrix.As a result,the graphene is expected to disperse evenly in EP resin,and generate a stongly-matched interface between the graphene and the EP matrix,and thus realize a remarkable improvement towards the toughness of such high-performance composite.In this paper,the influence of bubbling time and graphene content on the microstructural characteristics was investigated in details,as well as the measurements of corresponding mechanical properties including the strength,deformation,elastic modulus,and toughness under the condition of tensile,compressive or flexural force.Analysis of the failure section of graphene/epoxy composite was deterrminded under scanning electron microscope(SEM),in which the graphese was found to disperse evenly in the EP matrix,and to behave a well-done contact with epoxy resin,which in turn resulted in a much higher roughness at the fracture surface of MLG/EP composity.According to the measurements of mechanical performances,the bubbling method used in this work must make a great contribution to upgrade the serving properties of MLG/EP composite,and consequantly the mechanical strength and elastic modulus was found to increased apparently with the bubbling time.As a result,the specimen obtained with a bubbling time of 8h behave a tensile modulus 91.180%higher than that obtained with mechanical agitation,while the flexural modulus increased with a rate of 83.33%and the compressive modulus 16.76%at the same time.,The experiments also proved the relationship between the graphese content and the dispersion effect,since the mechanical properties of MLG/EP composite increased with the graphene content to a certain extent,but further increasing of the graphene content resulted in a lowered mechanical property.The maximum property of composite was obtained with the MLG content of 0.45 wt%,where the tensile modulus increased with a rate of 70.59%in comparison of that of pure epoxy resin,and the flexural modulus increased by 42.59%and the compressive modulus increased by 24.32%.However a downward trend of the mechanical properties also observed from the composite with the higher content of graphene.In comparison to the method using dispersion agents,the bubbling dispersion method not only reduces the preparation cost,but also eliminates the dispersant existence between the grapheme and EP,and thus can improve the mechanical properties of such composite to some extent.Being compared with the ultrasonic dispersion method,bubble dispersion method is simple in processing,low consumption of energy,low cost of production,free of any pollution,and widely feasible for industrialized production in large scale.