Magnetic polyurethane elastomers containing various plasticizers were synthesized, and the effect of plasticizers on the magnetoelastic behavior has been investigated. The storage modulus for magnetic elastomers at 0 mT decreased with plasticizer content, whereas the storage modulus at 500 mT dramatically increased. The increment in the storage modulus by magnetic fields increased with plasticizer content indicating a well-developed chain structure of magnetic particles. It was found that the on-field storage modulus can be scaled by the off-field modulus independently of the kind of plasticizers.

The elastic modulus for bimodal magnetic elastomers has been investigated by compression measurements under large deformation. The bimodal magnetic elastomers consist of carbonyl iron magnetic particles and zinc oxide nonmagnetic particles. The Young's modulus for monomodal magnetic elastomers was 8.94 × 104 Pa at 0 mT and 1.65 × 105 Pa at 320 mT, respectively. The relative change in the Young's modulus for monomodal magnetic elastomer was 1.8, and it was raised to 5.8 only by mixing with the nonmagnetic particles of 9.6 vol. %. It is considered that the modulus enhancement originates from the stress transfer by the additional chains of magnetic particles via nonmagnetic particles. The electric resistivity analysis revealed that 27% of magnetic particles in a strand of chains were replaced by nonmagnetic particles. It was shown in the present study that the bimodal magnetic elastomers endured against a compression load of 30 N.

We synthesized layered magnetic elastomers with polymer films and investigated the magnetoelastic behavior using dynamic viscoelastic measurements. The storage modulus at 0 mT was nearly independent of the sheets of films, while the storage modulus at 500 mT dramatically increased. The storage modulus at 500 mT for magnetic elastomers with 4 films was 2.1 MPa, which was 1.3 MPa higher than that of magnetic elastomers without layered structure. It can be considered that the stress transfer among imperfect short chains of magnetic particles is enhanced by inserting polymer films.