Effect Of Polydopamine Reduced Graphene Oxide On The Curing Kinetics And Mechanical Properties Of Epoxy Composites

Graphene is regarded as promising filler for high-performance composites because of its superior mechanical, electrical, and thermal properties. However, due to strong interaction between graphene layers, nano-scaled graphene sheets tend to aggregate or restack when they are loaded in polymer matrix, which greatly limits its mechanics performance. Taking advantage of self-polymerization and reduced feature of mussel-inspired dopamine, pDop-rGO was successfully prepared through one-step chemical reduction and modification of graphene oxide. The morphology and structure of prepared pDop-rGO was systematically characterized. On the basis, the effect of pDop-rGO on the curing kinetics of epoxy composites was systematically studied. The effect of dispersion and surface chemical activity of pDop-rGO on the mechanical properties of epoxy-based composites was deeply discussed. The enhancement mechanism of pDop-rGO on epoxy composite materials was established. The main work is as follows:The pDop-rGO was successfully prepared through one-step in situ chemical reduction. The changes of surface functional groups and element content of GO before and after modification were analysis by FT-IR and XPS. The thermal stability was studied by TGA. The microscopic morphologies of GO and pDop-rGO were observed by SEM, TEM and AFM. Results show that compared to the original GO, a new absorption peak appeared at 1515 cm-1 in the spectrum of pDop-rGO and an extra Nls signal at 399.8 eV appeared at the same time. The weight loss of pDop-rGO was reduced to 50.78wt.% in comparison with 57.40wt.% of GO. The microstructure of GO and pDop-rGO was similar to each other. The thickness of the GO monolayer was determined to be 0.69nm. After the reduction with dopamine, the thickness of pDop-rGO sheet increased to 0.98 nm.Based on the non-isothermal DSC test method, and the application of Friedman and Malek method at the same time, the effect of GO or pDop-rGO on activation energy and curing mechanism of the EP system was systematically studied. The results show that compared to EP or EP/GO system, the addition of pDop-rGO reduced the curing reaction activation energy and improved the curing reactivity of resin system as a result of activated amine groups on the surface of pDop-rGO.Based on mechanics test, DMTA and Raman characterization methods, the influence of dispersion and surface chemical activity of pDop-rGO on the mechanical properties of epoxy-based composites was systematically discussed. The enhancement mechanism of pDop-rGO on epoxy composite materials was established. The results show that due to the high chemical reactivity of pDop-rGO's surface, pDop-rGO has better dispersion and enhanced effect than GO. The addition of the pDop-rGO obviously improved the mechanical properties of the epoxy resin, and the best performance was achieved at the addition of 0.2 wt.%. In addition, Raman tests show that the external stress is passed onto pDop-rGO effectively by matrix. The effective modulus of pDop-rGO was achieved at 107 GPa, GO has better interface bonding with epoxy resin after modified by dopamine.