Nanostructured and Surface Polymerized Iron Particles for Magnetorheological Fluids

Abstract

A novel magnetorheological fluid, in which the surface of iron particles is coated with poly (butyl acrylate) by surface initiated atom transfer radical polymerization (ATRP), is investigated. The polymer coating procedure includes two steps, which are immobilization of initiator: 2-4(chlorosulfonylphenyl)-ethytrichlorosilane (CTCS) on the iron particles surface and graft polymerization of butyl acrylate from the surface. The surface coating is characterized by FTIR and SEM. This magnetorheological fluid has controllable off-state viscosity and high shear yield stress. Coating polymer on the iron particles surface by ATRP can significantly reduce iron particles settling and improve stability of the MR fluid. Polymerization kinetics of bulk butyl acrylate are investigated using differential scanning calorimetry (DSC). Glass transition temperature is obtained using the step-scan DSC method. The molecular weight and conversion can be controlled by the molar ratio of monomer to initiator, reaction temperature and time. The reaction is first order determined by the plot of In (M/MQ) against polymerization time. The overall activation energy is found to be 126kJ/mol by Kissinger's Method.

Polymer Brushes via Surface-Initiated Controlled Radical Polymerization: Synthesis, Characterization, Properties, and Applications

“…227,363,364 Alternatively, trichlorosilane-functionalized ATRP initiators such as [( 11 Similar to alumina substrates, ATRP initiators functionalized with triethoxy-or trichlorosilane moieties have been used to modify the surface of Fe 3 O 4 nanoparticles. [369][370][371][372][373][374][375][376][377] In these cases, the polymer brushes are believed to be tethered through a Fe-OsSi bond. Alternatively, ligand-exchange reactions can be used to graft ATRP initiators onto surfactantcoated Fe 3 O 4 nanoparticles.…”

Magnetorheology of core–shell typed dual-coated carbonyl iron particle fabricated by a sol–gel and self-assembly process

“…They are also used as core particle candidates for modificated or coated magnetic particles used in MR fluids. A range of core-shell structured composite particles, such as polymer-coated CI particles with poly (methyl methacrylate) [18], poly(butyl acrylate) [19], and polyaniline (PANI) [20], inorganics-coated CI particles with phosphate [21], and zirconia [22], have been fabricated using CI particles as a core material. Recently, urchin-like core-shell ZnO/CI particles were also reported [23], showing not only improved sedimentation and thermo-oxidation stability but also higher shear stress under the same applied magnetic field strength.…”

Magnetorheology of a Carbonyliron Microsphere Suspension with a Halloysite Additive and Its Damping Force Characteristics

“…They have the unique ability to undergo a rapid and reversible change from a liquid-like to a solid-like state within milliseconds upon the application of an external magnetic field, showing dramatic and tunable transitions in rheological properties [7][8][9][10] . In the absence of an external magnetic field, the magnetizable particles are distributed randomly and behave in a similar manner to a Newtonian fluid.…”

“…Magnetorheological (MR) fluids generally consist of micron-sized magnetic particles dispersed in a nonmagnetic fluid, such as mineral oil or silicone oil. − They have the unique ability to undergo a rapid and reversible change from a liquidlike to a solidlike state within milliseconds upon application of an external magnetic field, showing dramatic and tunable transitions in rheological properties. − In the absence of an external magnetic field, the magnetizable particles are distributed randomly and behave in a manner similar to that of a Newtonian fluid. On the other hand, under an external magnetic field, the dispersed particles form chain structures aligned in the applied field direction because of the induced dipole–dipole interaction .…”