Poly(methyl methacrylate)‐coated carbonyl iron particles and their magnetorheological characteristics

Magnetorheological fluids (MRFs) are types of suspensions that contain magnetic particles and a carrier fluid, and are considered as semi‐active smart materials. By tuning the strength of an external magnetic field, like other traditional MRFs, a carbonyl iron (CI)–poly(methyl methacrylate) (PMMA) particle‐based MRF can change reversibly from a fluid‐like state to a solid‐like state within milliseconds. In the research reported, CI particles were encapsulated with PMMA via emulsion polymerization. After the polymerization, the fabricated CI–PMMA composite particles were dispersed in a suspension medium to prepare MRF. The synthesized CI–PMMA composite particle‐based MRF showed a shear stress of 60 kPa at the magnetic field strength of 0.6 T, and a greatly enhanced anti‐sedimentation stability.