Modified phosphogypsum used as reinforcing material in composites

High-density polyethylene (HDPE)/phosphogypsum (PG) or polypropylene (PP)/PG composites were produced using mass-produced PG powders and a twin screw extruder. The modification effect of calcium stearate was studied by oil absorption value, contact angle, and FTIR. XRD analysis indicated that the PG phase was affected by different calcination temperatures. The mechanical properties of the composite materials were evaluated by tensile and impact tests. The dispersion of PG in the matrix was showed by scanning electron microscope (SEM). Within the weight fraction range studied (5, 10, 15, 20, 25, and 30 wt%), the Young’s modulus and tensile strength of the PG/HDPE composites increased significantly, but the impact strength and elongation at break decreased remarkably. Young’s modulus and impact strength of PG/PP composites increase prominently, but tensile strength and elongation at break are significantly reduced. Thermodynamic analysis showed that PG can improve the thermal stability of composite materials. The apparent density indicated that the composite material filled with PG has the property of being lighter in weight. In these experiments, the mechanical properties of compounding PG powder with HDPE or PP were significantly improved, but the toughness of composites decreased.