Interfacial adhesion between the iron fillers and the silicone matrix in magneto-rheological elastomers at high deformations

This work investigates the interfacial adhesion between the iron fillers and the silicone matrix in magneto-rheological elastomers at high deformations. Carbonyl iron powder, composed of mechanically soft spherical particles with a median size of 3.5 μm and a volume concentration of 3.5%, was mixed in a soft silicone matrix (Shore 00-20); the compound was then degassed and cured under temperature. The presence of a homogeneous magnetic field of 0.3 T during the curing process allowed the formation of particle chains. Tensile tests of these samples under scanning electron microscope showed interfacial slipping and debonding between the two phases. To improve interfacial adhesion, a silane primer was applied to the iron particles, following two different procedures, before the mixing and crosslinking process, thus giving two additional types of samples. In tensile testing lengthwise to the particle alignment, with engineering strains up to 150%, the structural responses of the different types of samples were compared. An enhanced adhesion of the iron fillers to the silicone matrix resulting in a reinforced matrix and increased tensile strength during the first loading path could be observed. Furthermore, scanning electron microscope images show that a more elaborated particle-matrix interface was obtained with the primer additive.