Effect of the graphene sheets derived from multistep oxidized carbon nanotubes on the performance of graphene sheets/poly(methyl methacrylate) composites

•The lengthwise opened variation tendency of MWCNTs could be adjusted by oxidation methods.•The lengthwise opened variation tendency have a significantly effect on the structure of obtained polymer composites.•Optimizing graphene sheets structure to obtain polymer composites with high performance.

Graphene sheets are produced using multi-walled carbon nanotubes (MWCNTs) under different methods and with varying oxidant content, via oxidation and reduction process. Then the graphene sheets are further added into poly(methyl methacrylate) (PMMA) as nanofiller to produce composites. The physicochemical properties of MWCNTs, as well as the microstructure and physical properties of graphene sheets and composites were investigated by Raman spectrometer, thermograviment analyzer (TGA), transmission electron microscope (TEM), scanning electron microscope (SEM) and universal testing machine, respectively. The results show that the lengthwise opened degree of MWCNTs increase with the potassium permanganate content increasing, meanwhile, the process of multistep add (3:2:1) 600 wt.% potassium permanganate within 2 h is the appropriate procedure and content of oxidant. Moreover, the multistep added method contributes to oxidize equably and form completed graphene sheets as nanofiller. The structure, the thermal stability and mechanical properties of composites can be severely affected by the different type graphene sheets. Thus, it is critical to tailor modified the preparation method of graphene sheets for obtaining composites with high performance.