HDPE composites strengthened-toughened synergistically by L-aspartic acid functionalized graphene/carbon nanotubes hybrid nanomaterials

Ethylenediamine (EDA) covalently functionalized graphene sheets (GS-EDA) and acidized carbon nanotubes (MWNTs-COOH) were first prepared, followed by synthesizing l-aspartic acid functionalized GS-EDA/MWNTs-COOH (LGC) hybrid nanomaterials by using l-aspartic acid as a bridging agent. Then nanocomposites of high density polyethylene-g-maleic anhydride (HDPE-g-MAH) synergistic strengthening-toughening using LGC hybrids were prepared via melt compounding method. The surface structure of filler was characterized by using infrared (FTIR) and Raman spectrum. The synergistic strengthening-toughening effects of LGC hybrids on the HDPE-g-MAH were investigated by scanning electron microscopy (SEM), dynamic mechanical analysis (DMA), thermal gravimetric analysis (TGA), tensile, and impact tests. FTIR showed that EDA has been grafted on the graphene sheets, and COOH group has been introduced into MWNTs. The l-aspartic acid connected GS-EDA and MWNTs-COOH through chemical bonds. SEM observations showed that LGC hybrids were homogeneously dispersed in HDPE-g-MAH nanocomposites. Tensile and impact tests indicated that the mechanical properties of nanocomposites were improved obviously when LGC hybrid nanomaterials were incorporated simultaneously. DMA analysis indicated that the storage modulus of composites was higher than that of pure HDPE-g-MAH matrix. TGA results revealed that the maximum decomposition temperature of HDPE-g-MAH composites containing 0.75 wt % of LGC showed 11.5 degrees C higher than that of HDPE-g-MAH matrix. (C) 2017 Wiley Periodicals, Inc.