Synthesis of polypropylene composites with modified calcium sulfate whisker prepared from shale vanadium neutralization slag

In this study, the solid waste of shale vanadium neutralization slag (NS) was effectively utilized by preparing calcium sulfate whisker (CSW) filler and reinforcing polypropylene (PP) matrix. The stabilization and modification mechanism of stearic acid on CSW were analyzed. The results showed that stearic acid blocked the hydrophilic active sites of CSW by chemical links with the whisker surface to inhibit whisker hydration and organically modify the whisker with an active index of 0.72. NS/PP, modified NS(MNS)/PP and MCSW/PP composites were synthesized via melt extrusion and injection molding. The effects of whiskerizing and modification of NS on the mechanical properties and thermal properties of the composites were evaluated. The results showed that MCSW improved the thermal stability of PP with a 51 °C increase at 10 wt% filler content. PP matrix filled by MCSW has better elasticity and stickiness than MNS. Modified fillers have better dispersion and compatibility with PP matrix than unmodified NS particle. MCSW fractured or pulled out to uniformly transfer stress, indicating strong interfacial adhesion between CSW and matrix. MCSW has stronger heterogeneous nucleation than MNS to induce the transformation of α-crystalline form to β-crystalline form, which resulted in better performance in mechanical and thermal properties.