Study on the mechanism of surface modification of magnesium oxysulfate whisker

Graphical abstract: - Highlights: • Physisorbed lauric acid was ruled out by FT-IR spectroscopy. • The inexistence of physisorbed magnesium laurate was proved by DSC analyses. • ¹³C NMR further verified the formation of COO–Mg< bonds on the surface of MOSw. • “Acid-base neutralization” was proved by the pH meter monitoring synchronously. • The type of surface modification of MOSw was proved to be chemical adsorption only. - Abstract: Hydrophobic-lipophilic magnesium oxysulfate whisker (MOSw) was prepared by surface modification with lauric acid and the surface morphology of MOSw was examined with field emission scanning electron microscope (FESEM). X-ray powder diffraction (XRD) was used to characterize the crystalline degree of MOSw and modified MOSw (MOSw-LA). Both FESEM and XRD suggested that modification occurred on the surface of MOSw exclusively. The inexistence of physisorbed lauric acid was proved by Fouier transform infrared (FT-IR) spectroscopy. Thermogravimetric analyses ruled out the possibility that magnesium laurate (LA-Mg) physisorbed on the surface of MOSw-LA. Solid state ¹³C nuclear magnetic resonance (¹³C NMR) further verified the formation of COO–Mg< bonds based on the significant changes of chemical shift and decrease in intensity. Hence, we confirmed that the type of surface modification of MOSw with lauric acid was chemical adsorption taken place between lauric acid and Mg<. In order to study the dynamic state approach of this reaction, a pH meter was employed to monitor the reaction process synchronously, and then we proposed a reaction mechanism which was similar to the “acid-base neutralization”. This research provides a detailed explanation for a kind of surface modification, which may be further used in the performance of whisker/polymer matrix composites