Use of Amphiphilic Composites based on Clay/Carbon Nanofibers as Fillers in UHMWPE
In this work, it is proposed a new strategy to improve the dispersion of inorganic fillers in polymeric matrices by producing surface carbon nanostructures. Clay/carbon nanofibers particles were prepared and used as fillers to improve the mechanical and thermal properties of ultra-high molecular weight polyethylene (UHMWPE). Thermogravimetry (TG), differential scanning calorimetry (DSC), elemental analyses, Raman, X-ray diffraction (XRD) and scanning electron microscopy (SEM) showed that chemical vapor deposition (CVD) with ethanol at different temperatures, i.e. 700, 800 and 900 °C with and without Fe catalyst, can be used to produce carbon (0.5-3.6 wt.%), mainly as nanofibers, on the clay surface. The use of these clay/carbon particles as fillers in UHMWPE at 1 and 3 wt.% produced an increase in the yield stress from 16 to ca. 20 MPa and Young modulus from 314 MPa for pure UHMWPE to values near 395-408 MPa. Moreover, the presence of the carbon/clay composites led to a strong improvement of the thermal properties of the UHMWPE increasing the decomposition Tonset (degradation start temperature) from 445 up to 472 °C. It was also observed by the crystallization enthalpies that the UHMWPE increased the crystallinity from 55 to 80-85% in the presence of the carbon composites. These results are discussed in terms of the strong interactions of the hydrophobic carbon nanostructures on the clay surface with the polymer hydrophobic chains.