Influence of the dispersing agents to obtain polymer–clay nanocomposites processed in two-steps using thermokinetic mixer

Polymer nanocomposite performance depends not only on the compatibility between nanoparticles and polymer matrix, but also the sequence in which the nanoparticle is incorporated into the polymer and the compounding device applied. In this study, we report the morphology, oxygen permeability, thermal and mechanical properties of the polypropylene nanocomposites change due to the use of a thermokinetic mixer when specific preparation steps are followed based on the dispersing agents used. Two organically modified clays and dispersing agents were applied: montmorillonite and hydrotalcite; hydrogenated hydrocarbon resin and poly (propylene-g-maleic anhydride) as compatibilizer with different maleic anhydride content. For the nanocomposites containing montmorillonite, poly (propylene-g-maleic anhydride), with low maleic anhydride content and the hydrocarbon resin prepared using the thermokinetic mixer, a more efficient clay dispersion was achieved. As a result, an increase in mechanical stiffness (57% in the Young modulus), higher thermal stability and a decrease in oxygen permeability (58%) were obtained. However, samples prepared with hydrotalcite achieved a better distribution and dispersion by preparing directly on a twin-screw extruder. Wherein, higher mechanical stiffness (36% in the Young modulus) with reduction in the oxygen permeability (52%) was reached when poly (propylene-g-maleic anhydride) with low maleic anhydride content and the hydrocarbon resin were present. These results point to that by using the dispersing agents in combined with a proper mixing system is possible to improve polyolefin nanocomposite properties, increasing the range of application in the packaging industry.