Effect of Different Curing Conditions on the Morphological and Rheological Properties of Rigid Magnetorheological Foam

The study aims to investigate the effect of curing conditions on the magnetorheological (MR) foam that consists of carbonyl iron particles (CIPs) in the matrix of polyurethane (PU) foam. MR foams with 35 wt% of CIPs are fabricated via in situ method in two different curing conditions, particularly in the absence and presence of magnetic field known as isotropic and anisotropic conditions, respectively. The morphology between isotropic and anisotropic MR foams is compared, also with the virgin foam as control sample and correlation towards the changes of rheological properties are analyzed. The rheological properties of MR foams related to MR effect and storage modulus, under sweep frequencies at various magnetic fields, are further examined via rheometer. The results display an oriented structure of CIPs between the struts of MR foam after curing in anisotropic condition, whereas the random distribution of CIPs has been observed in the isotropic MR foam, and no CIPs identified in the struts of virgin foam. Meanwhile, in the rheological test, it is revealed that the anisotropic MR foam resulted in the highest MR effect, about 89% compared to the isotropic MR foam that possesses only 10%. The increment of storage modulus towards the on-state and off-state frequencies swept also slightly different for each curing conditions which revealed that the anisotropic MR foam obtained the highest value of storage modulus which is ~1.33 MPa compared to the isotropic MR foam and the virgin foam, that only presented at ~1.14 MPa and ~0.84 MPa, respectively. The results from this study are believed to contribute the body of knowledge in producing various dynamic performances of MR foams with controllable structures and properties, for different areas and applications.