Magnetic polymer composites containing recycled neodymium-iron-boron (NdFeB) powder and natural rubber (NR) were prepared by the two-roll mill technique. Their mechanical and cure properties were studied as a function of NdFeB loading from 0-120 phr. With increasing magnetic loading, the cure time of the NdFeB-NR composites were exponentially decreased because of the reduction of the polymer chain crosslink. The tensile strength of the NR compound, related to the cure characteristics, was reduced by 40% by the addition of 10 phr NdFeB fillers because of the inhibition of the stress-induced crystallization. However, the variation in loading from 30-90 phr has modest effects on the tensile strength as well as elongation at break and the hardness. Furthermore, recycled NdFeB-NR composites had higher modulus and lower percentage of swelling in this magnetic loading regime. Simple tests confirmed the distribution of magnetic stray field around pieces of NdFeB-NR composites.

Physical properties of polyurethane (PU) can be modified for desired applications by adding appropriate fillers. In this work, cobalt (Co) powder of average diameter 2 μπι was filled in PU elastomers synthesized by a reaction between polyol and diisocyanate. Variation of Co loading (0, 20,40 and 60 wt.%) modified thermal properties of PU composites in terms of the shift in a melting temperature and the increase in heat absorption. From DC hysteresis loops, PU/Co composites exhibited ferromagnetic properties with improved magnetizations by the increase in Co loading. On the other hand, the coercive field was almost unvaried. For high frequency electromagnetic behaviors, the complex electrical permittivity (ε-je") and magnetic permeability (μ'-]μ") were sensitive to the frequency from 10 MHz up to 100 MHz and reached the modest values in the regime between 100 MHz and 1 GHz. At each frequency, the real part of permeability and permittivity of PU were raised by the inclusion of Co fillers. While the thermal behaviors were explained using the interaction between Co clusters and the PU matrix, the electromagnetic properties can be understood by taking into the account of interactions between Co clusters at high loading levels.