The inhibiting effect of basalt powder on crystallization behavior and the structure-property relationship of α-nucleated polypropylene composites

Basalt powder (BP) is a promising eco-friendly filler for polymeric composites. Due to its chemical composition, it can alter the effectiveness of various modifying agents used in the polymer industry. In this study, the influence of simultaneous addition of 5 wt% of basalt powder and 0.5 or 1 wt% of a sorbitol-based nucleating agent (NA) on the structure and properties of isotactic polypropylene (iPP) composites was analyzed. The potential chemical reactions of BP and NA were evaluated by Fourier transform infrared spectroscopy. The influence of the additives on the crystallization of the polymer was studied by differential scanning calorimetry, optical microscopy in polarized light, and rheological measurements. The kinetics of crystallization was analyzed using Mo and Friedman methods. The structure of the composites was observed by scanning electron microscopy. The mechanical properties were also evaluated. It was found that the BP reacts with the NA, which limits its ability to form the microfibrillated network in the melt. As a result, the crystallization behavior of the nucleated basalt-filled iPP is almost the same as in the case of the composite without the NA. However, the samples containing both NA and BP present good mechanical properties and adhesion between the polymer and the filler.