Yanceng Fan

A high-performance magnetorheological material: preparation, characterization and magnetic-mechanic coupling properties

A novel high-performance magnetorheological material, named as magnetorheological plastomer (MRP), was developed by dispersing iron particles into a plastic polyurethane (PU) matrix. The dynamic properties (including storage modulus and loss factor) of the MRP material were systematically tested and the influences of the iron particle content and magnetic field were analyzed. It is found that the anisotropic MRP product with 80% iron particle weight fraction (A-MRP-80), shows a high dynamic property: the maximum magneto-induced storage modulus is 6.54 MPa; the relative MR effect reaches as high as 532%; the loss factor can be reduced to 0.03 by adjusting magnetic field. This kind of MRP shows a much higher magnetorheological performance than the previously reported magnetorhelogical elastomer (MRE). The mechanism for its high MR performance was proposed and the influence of the iron particle distribution and temperature on the dynamic properties were discussed.

Physically crosslinked poly(vinyl alcohol) hydrogels with magnetic field controlled modulus

Physically cross-linked isotropic and anisotropic poly(vinyl alcohol) (PVA) hydrogels containing micron-sized carbonyl iron particles were prepared through a cyclic freezing–thawing process. The PVA hydrogel can respond to a magnetic field and shows a magnetorheological (MR) effect, i.e., the modulus of the PVA hydrogel can be adjusted under a magnetic field. The chain-like structures of carbonyl iron are formed in the PVA hydrogel after orientation under a magnetic field of 1.5 T. Also some magnetic field induced oriented pores with a tunable diameter are observed in the dried PVA gel. The MR effect can be adjusted by changing the carbonyl iron content, the initial concentration of PVA solution and test frequency. The formation of aligned chain-like structures of carbonyl iron in the anisotropic PVA MR hydrogel improves the compression properties and the MR effect. At a carbonyl iron content of 70 wt%, the maximum absolute and relative MR effect of anisotropic PVA MR hydrogels are ∼1.24 MPa and ∼230%, respectively. The PVA hydrogels with good MR effects and moderate mechanical strength have potential applications in artificial muscle, soft actuators and drug release.

Preparation and mechanical properties of the magnetorheological elastomer based on natural rubber/rosin glycerin hybrid matrix

To improve the mechanical properties of the natural rubber based magnetorheological elastomers (MREs), rosin glycerin ester was added into the carrier matrix to enhance wettability and dispersibility of CI particles. Dynamic performance, including shear modulus, loss factor and viscosity of non-vulcanized matrix was measured by rheometer. In comparison to the natural rubber based MREs, the MR effect of these hybrid matrix MREs were higher and they can reach to 112% when the mass fraction of CI particles is only 60%. The contact angle was tested by drop shape analysis system (DSA) and it was found that the compatibility between the iron particles and matrix was improved. In combination of the microstructure and mechanical property analysis, a possible mechanism was proposed. Finally, the loss factor and tensile strength were studied.

Effect of maleic anhydride on the damping property of magnetorheological elastomers

In this study, maleic anhydride (MA) was selected as the compatibilizer to modify the interfaces of magnetorheological elastomers (MREs) for improving the damping property. Several samples of MREs with different contents of MA were prepared. The content of bound-rubber was measured by the extraction method. The microstructures were observed by using an environmental scanning electron microscope (SEM). The dynamic performances of these samples, including shear storage modulus, loss factor and MR effect were measured with a modified dynamic mechanical analyzer (DMA). The tensile strength was tested by using an electronic tensile machine. The experimental results indicate that both the content of bound-rubber and the compatibility between the magnetic particles and rubber matrix were enhanced with the increase of MA. The enhancement of the bond between the two phases resulted in different mechanical properties: the increase of shear storage modulus; the reduction of the loss factor; the stability improvement of the loss factor; the enhancement of the tensile strength; and the reduction of the MR effect.

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 ∼1053.5 KPa for the sample with 80 wt% carbonyl iron content, which is ∼878 times that of the blank foam and ∼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 ∼1.07 MPa and ∼27.1%, respectively. Moreover, the introduction of carbonyl iron particles can notably improve the acoustic absorption properties in the low frequency region.

Effect of Cyclic Deformation on Magnetorheological Elastomers

Fatigue properties of magnetorheological elastomer (MRE) samples were investigated based on cis-polybutadiene rubber by using a fatigue test machine. Three MRE samples with iron particles mass fraction of 60%, 70%, and 80% were fabricated, and their properties dependence of three strain amplitudes (50%, 75%, and 100%) were measured. The absolute magnetorheological (MR) effect, storage modulus, and loss modulus of MRE samples after fatigue were evaluated by a modified dynamic mechanical analyzer. The results revealed that MR effect, storage modulus, and loss modulus of MREs containing 80% iron particles depended strongly on the strain amplitudes and the number of cycles, while storage modulus and loss modulus of MREs containing 70% iron particles also depended on the strain amplitudes and the number of cycles but not as strongly as sample which contains 80% iron particles, but the properties of MREs containing 60% iron particles after cyclic deformation were almost independent of the fatigued conditions. In order to investigate the fatigue mechanism of MREs, the sample was carried out with a quasi-static tensile testing and its surface morphology during testing was observed in situ by scanning electron microscopy.