Electrical conductivity and rheological properties of magnetorheological plastomer using conductive matrix and graphite for sensor applications

Abstract

Researchers have attempted to identify the best approach to utilize the Magnetorheology (MR) material such as in resistivity sensing-based devices. Magnetorheological Elastomer (MRE) material has attracted researchers due to its broad applications that require high electrical conductivity. However, the properties of MRE in a solid-like form is too rigid to be molded into certain devices, making the particles inside the matrix structure to remain trapped, thus resulting in poor electrical conductivity. Therefore, Magnetorheological Plastomer (MRP) is introduced which offers a new sensing capability due to its flexibility, soft nature, responsiveness to external magnetic field and simultaneously, conducts electricity. In this study, the rheology and resistance properties of Graphite (Gr) based Magnetorheological Plastomer (MRP) have been studied to enhance the electrical conductivity while maintaining the rheological properties. Even though previous studies have proven the capability of Gr in MRP in electrical and rheological properties, the effects of Gr in MRP are still low due to the use of non-conductive material as a matrix. Therefore, Polyvinyl Alcohol (PVA) material was used as a conductive matrix together with MRP with various content of Gr, from 0 to 10 wt.%, and the magnetic field-dependent electrical property was tested. The morphological aspect of Gr-MRP was identified using environmental scanning electron microscopy (ESEM). Besides, the magnetic property of MRP and Gr-MRP was tested using a vibrating sample magnetometer (VSM). The resistance value of Gr-MRP was assessed using a test rig under various applied magnetic flux densities. The results showed that the resistance of Gr-MRP decreased with the increase of Gr content up to 10 wt.%. The resistivity value reached a plateau at 400mT, with a value of 1.35×104 kΩ.m, possibly caused by the movement of Gr and CIPs assisted by an external magnetic field. Hence, the possible particle movement mechanism related to Gr and CIPs was also discussed. Moreover, the samples' electrical conductivity showed a proportional response to the addition of Gr value. The electrical conductivity of 10 wt.% Gr–MRP material was found to be the highest, approximately 178.06% as compared to 6 wt.%. It was also observed that with the addition of Gr, the conductivity properties were improved with the increasing of magnetic flux densities, while maintaining the storage modulus verified by using rheometer. This could contribute to the practicality of this material as a sensing detection device.