In-situ polymerization modified calcium sulfate whiskers and their application in PP composites research

Calcium sulfate whiskers (CSW) exhibit significant surface polarity and high surface energy, leading to aggregation when directly incorporated into polymer matrices, significantly affecting the mechanical properties of the composites. Sodium oleate (SO) was used to modify CSW, introducing -C=C- active groups on the surface, followed by in-situ graft polymerization of sodium oleate-modified CSW (SO-CSW) with methyl methacrylate (MMA) to prepare CSW-g-PMMA composites. The modification mechanism of SO and PMMA on CSW, as well as the surface modification effects on CSW, were studied using DRIFT, XRD, XPS and TEM. The results show that oleic acid ions adsorb onto the surface of CSW in two forms. One is chemisorption, in which the oleic acid ions are adsorbed on the calcium ions site on the surface of CSW in a bridging way. The other is physical adsorption, oleic acid ions and dissolved calcium ions in the form of precipitation adsorbed on the outermost layer of CSW. After in-situ polymerization, PMMA was successfully grafted onto the surface of CSW, and the thickness of the surface PMMA coating layer was approximately 67 nm. CSW-g-PMMA was used as a filler in the melt blending with polypropylene (PP) to prepare PP composites. CSW-g-PMMA mainly toughens and enhances the mechanical properties of PP composites in the form of crack bridging, crack deflection and pull-out effect.