Microstructure-property relationships of urethane magnetorheological elastomers

摘要

Studies on the structure of urethane magnetorheological elastomers (MREs), with respect to their magnetic and mechanical properties, are reported. MREs were obtained from a mixture of polyurethane gel and carbonyl-iron particles cured in a magnetic field of 100 and 300 mT. Samples with different numbers of particles (1.5, 11.5 and 33 vol%) were produced. The microstructure and magnetic properties of the obtained MREs were studied. Also, the displacement of the samples in an external magnetic field was examined using a specially designed experimental set-up. The influences of the number of ferromagnetic particles and their arrangement in relation to the external magnetic field were investigated. It was found that the microstructure of the MREs depends on the number of ferrous particles and the fabrication conditions. The orientation of the iron particles into aligned chains is possible for a lower volume content of the ferromagnetic fillers. The high carbonyl-iron volume content in the matrix leads to the formation of more complex microstructures, similar to three-dimensional lattices. The magnetic measurements also confirmed the existence of the microstructure anisotropy for the MREs with 1.5 and 11.5 vol% of iron particles. The structural and magnetic anisotropy has not been found in the MREs with 33 vol% of Fe. To evaluate the effect of the external magnetic field on the magnetorheological properties, the displacement under magnetic field, the compressive strength, and the rheological properties were measured. The experiments showed that both the particle content and the field strength used during curing have a significant effect on the microstructure of the MREs and, in consequence, on their properties.