Influence of Cobalt Fillers on Electromagnetic and Thermal Properties of Polyurethanes

Abstract

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.

Electromagnetic and Dynamic Mechanical Properties of Extruded Cobalt Ferrite-Polypropylene Composites

“…The significant reduction in the coercive field occurs only in the case of 45 wt% CoFe 2 O 4 proving that the interactions between magnetic clusters are not dominant except for the high loading near the percolation [19] . The independence of the coercive field on the magnetic loading in a certain regime is previously reported in magnetic polymer composites [5,18,20] . In our case, the substantial coercive field of CoFe 2 O 4 -PP composites should therefore be attributed to the stress induced during the extrusion process.…”

“…This equation may not hold for a higher magnetic loading and the saturation magnetization reported from other magnetic polymer composites is no longer proportional to the magnetic weight fraction beyond 55% [17,18] . From Figure 5, CoFe 2 O 4 -PP composites exhibit varying squareness from 0.35 to 0.39, which remains about the same as that of the CoFe 2 O 4 powder before the extrusion.…”

Dielectric and magnetic properties of polyvinylidene fluoride polymer composites highly loaded with nickel

“…It can be understood that the weight of particles keeps them in the middle of the substrate in the case of a low spinning speed resulting in non-uniform dispersion. Squareness, the ratio of remanence to saturation magnetization in Table 1, is comparable to that of other soft magnetic polymer composites, such as polyurethane/cobalt [14] and the maximum value of 0.14 in the case of 750 rpm is probably attributable to the largest Ni clusters observed in Figure 1A. Magnetizations of composites obtained from 3000 to 3750 rpm spinning are very weak.…”

Effect of Cobalt Fillers on Polyurethane Segmentations Investigated by Synchrotron Small Angle X-Ray Scattering

“…e characterizations of PU/Co composites by microscopy, DSC, vibrating sample magnetometry, complex permittivity, and permeability spectroscopy were presented elsewhere [2]. e SAXS experiment was carried out at BL 2.2, Siam Photon Laboratory, Synchrotron Light Research Institute, Nakhon Ratchasima, ailand [11].…”

“…It follows that Co is oen found in functional magnetic compounds and composites. In our previous work [2], the incorporation of 20%-60 wt.% Co powders in PU gave rise to magnetic permeability useful for magnetic devices and components. Moreover, the change in the dielectric properties of PU by the inclusion of Co can be utilized in antistatic propose.…”