The effect of the epoxidation level of epoxidized natural rubber (ENR) on the physicochemical characteristics of magnetorheological elastomer (MRE) made from it was studied. MRE samples were fabricated by mixing ENR with additives and carbonyl iron particles (CIP), followed by vulcanisation at 150 °C for 30 min. The factors that are manipulated for this study include the epoxidation level of ENR, through the use of ENR 25 and ENR 50 as the polymer matrix, and the proportion of the components of the composite, through varying the amount of CIP added in the mixing step. The analysis was performed by measuring the physicochemical characteristics of the MRE, which include curing time, magnetisation, functional group composition, thermal stability, and morphology. The cure time ( t ₉₀ ) of the MRE increased with increasing CIP content while the scorch time ( t s ₂ ) decreased. Electron microscopy showed that the CIP were randomly distributed throughout the MRE samples, indicating an isotropic MRE. The MRE fabricated with ENR 25 and 70 wt% CIP had a considerably higher value of saturation magnetisation at 42.54 emu g ⁻¹ , whereas the MRE fabricated with ENR 50 and 70 wt% CIP had a saturation magnetisation of 40.80 emu g ⁻¹ . Hydrogen bonds were created between the epoxy bonds in the epoxidized rubber and the hydroxyl groups from the CIP and other additives. Thermogravimetric analysis indicated an improvement in thermal stability, as the addition of CIP delayed the thermal degradation of the MRE. The results showed that the epoxidation level of the natural rubber has a significant effect on the physicochemical characteristics of the MRE fabricated from it. Overall outcomes showed that both ENR 25 and ENR 50 could be used as an alternative matrix material for fabricating an MRE, with the choice falling on the application specification.

This paper investigated the effects of petroleum-based oils (PBOs) as a dispersing aid on the physicochemical characteristics of natural rubber (NR)-based magnetorheological elastomers (MREs). The addition of PBOs was expected to overcome the low performance of magnetorheological (MR) elastomers due to their inhomogeneous dispersion and the mobility of magnetic particles within the elastomer matrix. The NR-based MREs were firstly fabricated by mixing the NR compounds homogeneously with different ratios of naphthenic oil (NO), light mineral oil (LMO), and paraffin oil (PO) to aromatic oil (AO), with weight percentage ratios of 100:0, 70:30, 50:50, and 30:70, respectively. From the obtained results, the ratios of NO mixed with low amounts of AO improved the material physicochemical characteristics, such as thermal properties. Meanwhile, LMO mixed the AO led to the best results for curing characteristics, microstructure observation, and magnetic properties of the MREs. We found that the LMO mixed with a high content of AO could provide good compatibility between the rubber molecular and magnetic particles due to similar chemical structures, which apparently enhance the physicochemical characteristics of MREs. In conclusion, the 30:70 ratio of LMO:AO is considered the preferable dispersing aid for MREs due to structural compounds present in the oil that enhance the physicochemical characteristics of the NR-based MREs.

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Magnetorheological elastomer (MRE) made from natural rubber (NR) is a type of polymer composite material that has magnetic particles embedded in a non-magnetic matrix. Applications such as vibration, automotive bushings, and medical devices have utilized NR as a matrix-based MRE. Nevertheless, little information is available on rheological characteristics due to inhomogeneous dispersion and mobility of magnetic particles inside the elastomer matrix. The study’s main purpose was to investigate the characterization and rheological properties of magnetorheological elastomers based on natural rubber featuring petroleum- based oil (PBO). The NR-based MRE were combined with varying proportions of naphthenic oil (NO), light mineral oil (LMO), and paraffin oil (PO) to aromatic oil (AO) in ratios of 100:0, 70:30, 50:50, and 30:70, accordingly. All samples were produced at 60 weight percent of Carbonyl Iron Particles (CIPs). The linear viscoelastic region of the NR-based MRE was determined at a strain amplitude of around 0.01% for the rheological parameters. The MR effect showed an improvement for LMO, and PO showed potential in improving the MR effect when mixed with the low amount of AO. Meanwhile, NO showed a high MR effect at 29% without being mixed with AO. When NR-based MRE was mixed with different ratios of PBO, the results were different. Therefore, this study offers valuable insights, particularly serving as a guideline for formulating MRE using PBOs, which can be applied in specific MRE applications.

Rubber composites are widely used in engineering sectors, including automotive and biomedical applications. Extended exposure to heat and sunlight speeds up the aging process, resulting in physical and chemical degradation. This study investigates the effect of thermal aging on the microstructure, magnetic properties, chemical bonding, and thermal stability of epoxidized natural rubber (ENR) 25-based magnetorheological elastomer (MRE). ENR 25- based MRE samples with four different weight percentages (wt%) of carbonyl iron particles (CIPs) were fabricated and subjected to thermal aging at 100 °C for 72 h. The findings indicated that thermal aging induces microstructural roughness and increases void formation in the MRE. Magnetic saturation declined by nearly 45% across all samples due to oxidation. The increasing of glass transition temperature indicates a transition shifted to the right and were determined through DSC analysis software Additionally, Fourier transform infrared analysis revealed a significant increase in transmission percentages, particularly in the 10 wt% sample, highlighting oxidation-induced chemical changes. These findings contribute to a deeper understanding of the thermo-physicochemical behavior of ENR 25-based MRE, which is essential for optimizing their long-term durability in applications that require high thermal stability, such as vibration-damping systems and adaptive structures.