Smart polyurethane foam with magnetic field controlled modulus and anisotropic compression property

A new kind of polyurethane (PU) magnetorheological (MR) foam was prepared via in situ polymerization and foaming for the first time. A chain-like structure of carbonyl iron particles in the liquid polyol is formed after orientation at a magnetic field and fixed in the PU foam after the in situ curing. The anisotropic PU MR foam possesses an anisotropic compression property. The compression strength along the magnetic chain direction reaches similar to 1053.5 KPa for the sample with 80 wt% carbonyl iron content, which is similar to 878 times that of the blank foam and similar to 57 times of that at the vertical direction of the same sample. The PU MR foam exhibits a magnetic field controlled shear modulus, i.e., MR effect, which can be adjusted by changing the orientation structure and content of the carbonyl iron, test frequency and magnetic field strength. The maximum absolute and relative MR effects for the anisotropic PU MR foam are similar to 1.07 MPa and similar to 27.1%, respectively. Moreover, the introduction of carbonyl iron particles can notably improve the acoustic absorption properties in the low frequency region.