Early-stage degradation of electrolytic iron particle-based magnetorheological elastomer under natural weathering conditions

Abstract

Magnetorheological elastomer (MRE) is a smart composite possessing properties that can be tuned by an external magnetic field, making them highly attractive for vibration isolation applications. Their reliable use in outdoor environments, however, requires a clear understanding of how natural weathering influences their performance and durability. While most previous research has addressed long-term or accelerated ageing conditions, the onset of environmental degradation of MRE remains insufficiently explored. Therefore, this study investigated the early-stage degradation of MRE, embedded with irregular electrolytic iron particles (MRE-EIP) over six weeks of natural weathering exposure. Weekly samples (W0-W6) were analysed using vibrating sample magnetometer (VSM), rheometer and low vacuum scanning electron microscope and the results were correlated with weathering data from the Malaysian Meteorological Department, Kuala Lumpur. The saturation magnetization, Ms finding shows minimal change from 111.63 Am2/kg in W0 to 113.79 Am2/kg in W6, likely attributed to the exposure of EIP following the removal of the aged localized surface over the six week exposure. Strain sweep results meanwhile, revealed the progressive stiffening, with the storage modulus (G′) increased from 0.22 MPa (W0) to 0.53 MPa (W6), accompanied by a narrowing linear viscoelastic (LVE) region, indicative of early embrittlement of the samples. Nevertheless, a temporary reduction in G′ for W3 suggested a moisture-induced plasticisation, from increased rainfalls that week. Besides, the absolute MR effect, ΔG′ increased from 0.23 MPa (W0) to 0.34 MPa (W6), indicating greater responsiveness of exposed EIP to the magnetic fields which enhanced the G′ accordingly. Morphological analysis confirmed the development of localized surface depressions suggests combine effects of UV-driven embrittlement and moisture plasticisation from rainfall, leading to localised EIP exposure, while the cross-sectional structure integrity remained intact. These findings provide the first detailed account of early-stage degradation in MRE-EIP under natural weathering, offering valuable insights into early failure mechanisms and guiding durability driven material design for outdoor smart material applications.