Surface Modification of Magnesium Oxysulfate Whisker Based on SiO₂@silane Coupling Agent and SiO₂@polydopamine...

In this study, we fabricated high-performance polyethylene composites by constructing SiO₂@silane coupling agent (γ-methylacryloxypropyl trimethoxysilane) and SiO₂@polydopamine (PDA) double-layer structures on a magnesium oxysulfate whisker surface. In addition to realizing strong mechanical properties, the flame-retardant properties of the composites were effectively improved. Further increase in the initial crystallization temperature of the modified composites indicated that the dispersion of whisker in the matrix was improved. The drag effect of the modified whisker on the HDPE molecular chain was characterized by dynamic mechanical thermal analysis (DMTA) and the morphology of the impact-fractured surface was characterized by scanning electron microscopy (SEM); both confirmed the improved compatibility between the whisker and the matrix. The tensile strength of HDPE/MOSw@SiO₂@KH570 and HDPE/MOSw@SiO₂@PDA composites were 22.6% and 41.5% higher than that of the HDPE/MOSw composites, respectively. The impact strengths of the HDPE/MOSw@SiO₂@KH570 and HDPE/MOSw@SiO₂@PDA composites were 129% and 102% higher than that of the HDPE/MOSw composites, respectively. A stable carbon-silicate layer constructed by a SiO₂@KH570 and SiO₂@PDA double-layer structure delayed the combustion process. As a result, the limiting oxygen index (LOI) of HDPE/MOSw@SiO₂@KH570 and HDPE/MOSw@SiO₂@PDA composites increased from 22.5 to 22.9 and 23.5, respectively.