Tunable alignment and properties of FeO/natural rubber nanocomposites

Although aligned magnetorheological elastomers (MREs) have been reported, there is still a major challenge to prepare aligned magnetorheological elastomers based on natural rubber (NR) or other synthetic rubbers. The result is attributed to the fact that magnetic particles are difficult to align in one direction, and the orientation in solid rubber due to its high hardness restricts the movement of magnetic particles. Here, a new thermal–mechanical–magnetic coupling molding equipment was developed to simultaneously provide heat and magnetic field. Therefore, the magnetic particles can be easily aligned in the ultra-soft rubber matrix to form aligned magneto-rheological elastomers. Furthermore, the mechanical, magnetic, thermal and swelling properties of aligned and random magneto-rheological elastomers were investigated and compared in detail. The aligned magneto-rheological elastomers showed a higher tensile strength (16.7 MPa), magneto-rheological effect (171.0%) and magnetic saturation intensity (31.3 emu/g) compared to random magneto-rheological elastomers (14.8 MPa, 168% and 26.2 emu/g), respectively. Furthermore, the solvation swelling degree (90%) of aligned magneto-rheological elastomers was also lower than that of random magneto-rheological elastomers (147%), indicating a good solvent resistance. These results were attributed to the tailoring alignment of FeO nanoparticles in the natural rubber matrix. The work provides a new method to tailoring distribution and properties of magneto-rheological elastomers based on rubbers with high hardness suitable for various applications. Graphical abstract: [Figure not available: see fulltext.].