Abstract
In this paper, the preparation of graphene oxide was achieved by Hummers method and the surface modification was achieved by poly(hexaneditiol), which was a synthetic thermotropic liquid crystalline polymer. The c-PHDT/GO/PF composites were prepared by blending, rolling and compression molding techniques. Then, the as-prepared samples were characterized by FTIR, Raman, XRD, TGA and POM to obtain information on their structures and properties. After that, the effects of c-PHDT/GO content on the mechanical properties, friction performance and dynamic mechanical performance of c-PHDT/GO/PF composites were studied by Mechanical and Dynamic Mechanical Analysis (DMA) methods. Also, Scanning Electron Microscope (SEM) was used for the characterization of wear and fracture surface morphology. The results revealed that the reinforcing effect of c-PHDT/GO was significant as a considerable enhancement on the mechanical performance of c-PHDT/GO/PF composite as compared to pure phenol-formaldehyde composites was observed: the impact strength, bending modulus and bending strength increased from 1.63 kJ/m2, 8.61 GPa and 41.55 MPa to 2.31 kJ/m2, 10.16 GPa and 54.40 MPa respectively at the c-PHDT/GO content = 0.75%. Moreover, the initial storage modulus increased by 28.4%, while the wear mass loss decreased by 17.8%. More importantly, the reinforcement by c-PHDT/GO was further enhanced as compared to GO/PF and p-PHDT/GO/PF composites, the impact strength of c-PHDT/GO/PF composite increased by 27.6% and 11.1%, the bending strength increased by 11.8% and 7.6%, the initial storage modulus increased by 16.2% and 4.2% and the mass loss due to wear decreased by 12.7% and 8.8%, respectively. Based on these results, we can conclude that the surface modification of GO by poly(hexanedithiol), which includes synergistic effect by c-PHDT and GO, improves the interfacial adhesion between GO and the resin matrix, thus reinforcing the composites.
Highlights
Graphene is a carbon nanometer material comprising a single and tightly packed 2D layer of sp2-hybridized carbon atoms that are bonded together in a hexagonal honeycomb lattice [1]
Based on studies reported [22]-[25], we present the fabrication of graphene oxide by modified Hummers method, followed by surface modification by synthetic PHDT to obtain modified graphene oxide (c-PHDT/GO)
The impact strength of c-PHDT/GO/Phenol-formaldehyde resin (PF) composite increased by 27.6% and 11.1%, the bending strength increased by 11.8% and 7.6%, as compared to GO/PF and p-PHDT/GO/PF respectively
Summary
Graphene is a carbon nanometer material comprising a single and tightly packed 2D layer of sp2-hybridized carbon atoms that are bonded together in a hexagonal honeycomb lattice [1]. Phenol-formaldehyde resin (PF) is a thermoset resin that has been widely applied in virtue of their excellent properties such as high strength, excellent thermostability and electrical insulation, and good dimensional stability. This material presents intrinsic advantages of resins such as flame retardance, ablation resistance and low smoke yield ratio [14] [15]. The thermostability and oxidation resistance are relatively weak due to the presence of phenolic hydroxyl and methylene groups [16] [17] For this reason, the strengthening and toughening of PF is a hot topic in the field of composite materials. The phenol-formaldehyde resin, thionyl chloride (analytical grade), N, N-Dimethyl formamide (analytical grade) and pyridine (analytical grade) were purchased from Shengquan Chemical Corporation, Jinhuada Pte Ltd. and Xilong Chemical Corporation respectively
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