Synergistic surface modification of anhydrous calcium sulfate by polydopamine/oleylamine and its application in reinforced HDPE composites

Abstract In the study, polydopamine and oleylamine cooperated to modify the surface of anhydrous calcium sulfate prepared from phosphogypsum, and HDPE matrix composites with different filler content were prepared by filling HDPE before and after modification. The results show that when the filler content is 5 wt%, the elongation at break of mCSA/HDPE composite is 31.7% and 89% higher than that of HDPE and CSA/HDPE. Respectively, when the filler content is as high as 25 wt%, the flexural strength is still 16.8% higher than that of HDPE. After modification, the compatibility and dispersibility of anhydrous calcium sulfate in HDPE were improved, and the crystal structure of anhydrous calcium sulfate was not significantly changed, thus the mechanical properties and thermal stability of mCSA/HDPE composites were improved. Overall, after modification, not only the mechanical properties of the composites are improved, but also the content of inorganic powder as filler added to HDPE is increased, which can be regarded as a method for effective utilization of phosphogypsum. Highlights Calcium sulfate was modified by polydopamine and oleylamine The mechanical and thermal properties of the modified calcium sulfate/HDPE composites are good. The resource utilization of phosphogypsum was carried out