SUMMARYBall milling technique was used for deposition of the polytetrafluoroethylene (PTFE) coating on the powder of TiFe intermetallic compound. Measurement of pressure-composition hydrogen absorption isotherms revealed that the polymer-coated TiFe intermetallic compound kept its hydrogen storage ability. The TiFe/PTFE material demonstrated resistance to surface poisoning even after a prolonged exposure to air and was not subjected to pulverization during multiple hydrogenation-dehydrogenation cycles.
The effect of the crystallization of polypropylene (PP) forming an immiscible polymer blend with polystyrene (PS) containing conductive multi-wall carbon nanotubes (MWCNTs) on its electrical conductivity and electrical percolation threshold (PT) was investigated in this work. PP/PS/MWCNTs composites with a co-continuous morphology and a concentration of MWCNTs ranging from 0 to 2 wt.% were obtained. The PT was greatly reduced by a two-step approach. First, a 50% reduction in the PT was achieved by using the effect of double percolation in the blend system compared to PP/MWCNTs. Second, with the additional thermal treatments, referred to as slow-cooling treatment (with the cooling rate 0.5 °C/min), and isothermal treatment (at 135 °C for 15 min), ultra-low PT values were achieved for the PP/PS/MWCNTs system. A 0.06 wt.% of MWCNTs was attained upon the use of the slow-cooling treatment and 0.08 wt.% of MWCNTs upon the isothermal treatment. This reduction is attributed to PP crystals’ volume exclusion, with no alteration in the blend morphology.
In this work, a study of the linear viscoelastic properties of co-continuous polypropylene/polystyrene blends filled with multiwall carbon nanotubes (MWCNTs) is presented. The YZZ rheological model [W. Yu et al., Polymer 51, 2091–2098 (2010)] is employed to correlate the rheological behavior of the blends with their microstructure and electrical properties. A test design involving a sequence of small amplitude oscillatory shear and a time sweep (simulating thermal annealing) is used to evaluate the morphology and evolution of electrical properties. It was shown that the YZZ rheological model could be successfully modified to be able to quantify a co-continuous morphology of filled composites. The calculated characteristic domain size was found to be in good agreement with the experimental data obtained via scanning electron microscopy. Furthermore, it is shown that the characteristic domain size slightly decreased after 30 min of thermal annealing. It was shown, as well, that thermal annealing promoted a reduction in the electrical percolation threshold (wt. % MWCNT) from 0.28 to 0.06.
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