(188ao) Surface Coating of Iron Particles Using Fluorinated Acrylate Via Reversible Addition Fragmentation Chain Transfer (RAFT) Polymerization for Magnetorheological Elastomers (MREs)

Magnetorheological Elastomers (MREs) were synthesized from silicone RTV (room temperature vulcanizing) elastomer with magnetically soft iron particles. The feasibility of MREs for a novel, fail-safe, variable stiffness isolator (VSI) is investigated as a base isolation bearing system. The proposed VSI system consists of a traditional steel-rubber vibration absorber, as the passive element, and a magnetorhelogical elastomers (MREs), with a controllable (or variable) stiffness behavior, as the passive-active element. The proposed system is fail-safe, i.e., in the event of an electronic or control system failure the passive element of the device (steel-rubber, and the MRE at passive-off state) retains the minimum required properties (off-state shear modulus ± 1 MPa). The proposed MR elastomer bearing consists of two components, one is the conventional rubber and the other is the embedded MRE that has controllable (adjustable) shear modulus under an applied magnetic field. The shear modulus of the MRE at off-state (without activation) is expected to be around 1 MPa. However, non?plasticized silicone?RTV MRE with 70 wt.% iron particle was fabricated and resulted in higher off-state shear modulus than expected (Eo > 1 MPa). Thus, the silicone?RTV MRE had to be plasticized using polydimethyl siloxane. Also, the optimum iron particles concentration in MRE has been studied in order to achieve maximum MR effect. According to the reported literature, the largest modulus change at saturation was at 27 vol.% of iron particles (approx. 75 wt.%). In order to reduce the effect of oxidation on the MREs, the RAFT polymerization technique was used for surface polymerization of iron particles with fluorinated acrylate as a monomer.