Reprocessed Magnetorheological Elastomers with Reduced Carbon Footprint and their Piezoresistive Properties

Abstract Magnetorheological elastomers (MREs) are widely studied materials, however not many research papers have been initiated on their reprocessing. This paper presents a new type of recyclable MRE which is composed of thermoplastic polyurethane (TPU) and carbonyl iron particles (CI). The chosen TPU can be processed by injection moulding (IM) and allows several reprocessing cycles. Numerous types of injection moulded MREs, which have undergone several recycling cycles, have been prepared. The effect of thermo-mechanical degradation on the recycled MREs has been investigated. An apparent decrease in molecular weight of all examined matrices during reprocessing cycles was observed. These changes are attributed to the intermolecular bonding between the hydroxyl groups on the surface of the CI particles and the matrix. An evaluation of the mechanical properties of the matrices was conducted via tensile strength tests. Generally, MREs suffer from minor degradation due to reprocessing, yet the rheological and piezoresistivity properties are at an acceptable level despite using 100% of recyclates while in real applications only up to 30% of recycled material is used.