Surface modification of calcium sulfate whisker using thiol-ene click reaction and its application in reinforced silicone rubber

The hemihydrate calcium sulfate whisker (HCSW) was modified by γ-(methacryloxy)propyl trimethoxy silane (KH570) and trimethylolpropane tris(3-mercaptopropionate) via wet modification and thiol-ene click reaction, and then the unmodified and modified HCSW were added into α, ω-dihydroxy polysiloxane (DPS) matrix to prepare silicon rubber composites. After the dual-surface modification, the surface of HCSW was transformed to hydrophobic, the hydration of whisker was obviously improved, and the whisker dispersed more evenly in the polymer. The mechanical properties, dynamic mechanical properties, and the medium resistance of the silicone rubber composite were compared. The tensile test shows that the silicone rubber shows better mechanical properties after adding the modified whiskers, among which HCSW-KH570-SH has the most significant reinforcement effect. Moreover, DPS/HCSW-KH570-SH shows the best medium resistance in toluene, gasoline, and water. The addition of modified whiskers can improve the storage modulus of silicone rubber significantly, while DMA and DSC show that the addition of modified whiskers can reduce the glass transition temperature of silicone rubber. The bound rubber indicates that the interface interaction between HCSW-KH570-SH and silicone rubber is the best.