Cristallinity Evaluation of Oriented Nanocomposites Based on Polypropylene and Silica by Time Domain NMR

Hybrid films made of isotactic polypropylene (PP) and silica (SiO 2 ) are produced in a single‐screw extruder, followed by uniaxial orientation induced by winding at different speeds. Aiming their application in packaging, the influence of uniaxial orientation on properties of films containing pure (A200) and modified (R972, modified with dimethylchlorosilane) silicas is studied. The microstructural changes of the PP are evaluated by x‐ray diffraction (XRD) and by differential scanning calorimetry (DSC) and these data are correlated to nuclear magnetic resonance in the time domain (NMR‐TD). The orientation given to the films is monitored by intensity alterations of the XRD peaks, which are influenced by the nanoparticle concentration and the affinity between PP/silica. Through the DSC analysis, the nucleating effect of silica A200 at a concentration of 1 wt% is evidenced. Finally, the NMR‐TD corroborated the previous results, showing an increase in the stiffness of the more oriented nanocomposites due to the alignment of polymer chains.