Preparation Of Graphene/Epoxy Composites And Their Electrical,Thermal And Mechanical Properties

As a novel 2D carbon material, Graphene has been widely used to be combined with polymer to improve thermal conductivity, electrical conductivity and mechanical properties. In this paper, graphene oxide was used as precursor and assisted by other functional filler to make epoxy composites with improved mechanical properties, electrical conductivity and thermal conductivity. Firstly, the 3D graphene network aerogel strengthened with PPTA pulp fiber was prepared. Epoxy prepolymer was vacume infused into the micropores of fiber/graphene aerogel to get the high electrical conductivity and high compressive strength epoxy composite. Secondly,epoxy composites was filled with synergetic hybrid spherical alumina and GNP as thermal conductive filler, magnesium hydroxide as synergetic thermal conductive and flame retardant filler, to get epoxy composite with outstanding fire resistance and excellent thermal conductivity. At last, PPTA fiber was used to toughen epoxy. The graphene was loaded on the fiber to prepare epoxy composite with a great improvement in notch impact strength and electrical conductivity. The innovative results were listed as following:(1) graphene oxide was used as the raw material, aramid fiber (PPTA) as reinforcement elements to make fiber/Graphene three-dimensional aerogel(GOFAs). Furthermore, GOFA was annealed at 1300? to get the carbon fiber reinforced 3D Graphene aerogel. PPTA pulp fiber promote the formation of graphene aerogel. The compressive strength of GOFA was improved by 5 times than the pure 3D graphene. After the high temperature treatment, GCFA exhibit high electrical conductivities 103S·m-1 .Assembling the pulp fiber and graphene into the 3D aerogel structure resolve the dispersion of graphene and fiber in epoxy. So the fabricated Graphene aerogel endows epoxy with remarkable enhancements in both mechanical and electrical performances.Compared to those of neat epoxy, the compressive strength of the GOFA/epoxy composite are all significantly increased by 85%, while the GCFA/epoxy increased by 44.1% and its electrical conductivity is as high as 102 S· m-1, and moluls increased by 60%, respectively.(2) Spherical alumina (Al2O3) and GNP were used as hybrid filler to prepare Al2O3/GNP/epoxy with improved thermal conductivity. Epoxy prepolymer filled with spherical alumina exhibit a better processablity than that filled with non-spherical alumina. 2D Gnp filler was used as a synergetic filler with spherical alumina which promote the 3D thermal conductivity network formation in the composite. Under one total load, the thermal conductivity of composites was increased with the GNP content in the composite. Magnesium hydroxide (Mg(OH)2) was used as eco-flame retardant and thermal conductivity filler to endow the fire resistance of Al2O3/GNP/epoxy composite. Only 5 wt% Mg(OH)2 can make the GNP/Al2O3/Mg(OH)2/epoxy composite achieve V-0 grade.(3) PPTA fiber was selected to toughen epoxy. To enhance the other function of epoxy, graphene was loaded on the fiber with hydrothermal process. Epoxy was composited with PPTA fiber and graphene/PPTA fiber with a high load. How PPTA fiber and loaded graphene affect mechanical properties, electrical conductivity and glass transition temperature was investigated. The mechanism of tougnenning epoxy was deduced from the SEM pictures of impact frature. The results suggest that the notched impact strength of the composites increases as the increasing of PPTA fiber filler content. The notch impact strength was improved by 53% than the pure epoxy with 30% graphenen/PPTA filler load. Because the graphene was loaded on the fiber , a 3D conductivity network was formed in the composite. The electrical conductivity of graphene/PPTA/epoxy composite materials was increased significantly, the materials with a load of 3.28% graphene composites reached to 10-1 S·m-1. Toughening mechanism include microcrack formation, pull-out effect and fiber bridge to prevent the crack propagation,which toughened epoxy and endow epoxy electrical cconductivity.