Effect of amorphous/recycled polypropylene ratio on thermo-mechanical properties of blends for lubricant applications

This work focuses on the development of gel-like formulations for use as lubricating greases. These dispersions Were formulated using mineral oil and recycled/amorphous polypropylene blends. In particular, the influence of the polypropylene concentration ratio (Wi) on the rheology, thermal and some lubricant performance properties of polymer/oil blends were studied. The rheological responses of these systems were quite different, influenced mainly by the concentration of amorphous polypropylene. At intermediate temperatures (25 degrees C, 50 degrees C) and high recycled polypropylene concentrations (W-i > 0.5), the evolution of small-amplitude oscillatory shear (SAOS) functions was very similar to those found with other commercial lubricating greases. Samples with lower concentrations of amorphous polypropylene (12.5%) present maximum G(N)degrees values in the temperature range studied. An Arrhenius-type equation can be used to quantify the thermal dependence of the linear viscoelastic functions of these gel-like dispersions. In general, sample formulations studied exhibited values of the friction coefficient comparable to those found for traditional lithium lubricating greases. (C) 2013 Elsevier Ltd. All rights reserved.