Porous material performs good deformation compression and has been widely used in soft actuators and sensors. In this study, a new kind of magnetorheological (MR) sponge was prepared by combining carbonyl iron particles with polyurethane porous structure. The static compressive property of MR foam was studied using a commercial rheometer. The relationship between magnetic particle composition, magnetic field and rheological properties was summarized and analyzed. The research contributes to a deeper understanding of magnetorheological sponge materials, and provides inspiration and theoretical basis for the design of soft actuators ,which may provide inspiration for novel application field

Huang, J. F.

Meng, Y. F.

English

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46  METALURGIJA 63 (2024) 1, 46-48J.F. HUANG, Y.F. MENGPREPARATION AND PERFORMANCE STUDY  OF MAGNETORHEOLOGICAL (MR) FOAMReceived – Primljeno: 2023-04-12Accepted – Prihvaćeno: 2023-07-25Original Scientific Paper – Izvorni znanstveni radPorous material performs good deformation compression and has been widely used in soft actuators and sensors. In this study, a new kind of magnetorheological (MR) sponge was prepared by combining carbonyl iron particles with polyurethane porous structure. The static compressive property of MR foam was studied using a commercial rheometer. The relationship between magnetic particle composition, magnetic field and rheological properties was summarized and analyzed. The research contributes to a deeper understanding of magnetorheological sponge materials, and provides inspiration and theoretical basis for the design of soft actuators ,which may provide inspira-tion for novel application field.Keywords: polyurethane; magnetorheological foam; scanning electron microscopy; magnetic properties; mechani-cal propertiesISSN 0543-5846METABK 63(1) 46-48 (2024)UDC – UDK 546.72-678.744:661.185:539.26:621.317.4:620.17=111INTRODUCTIONSoft matter refers to all complex substances between solids and ideal fluids, generally composed of macro-molecules or groups (solid, liquid, gas), such as liquid crystals, polymers, films, foams, surfactants, colloids, particulate matter, biological macromolecules, biologi-cal tissues [1,2]. With the advanced research on soft matter, complex rheological behavior tends to play an increasing role in the solution to technical challenges in some frontier field, Such as the application of flexible electronic devices such as liquid crystals, biomedical research, 4 D printing and other aspects. Among the vis-coelastic soft materials, porous polymer materials are attracting increasing attention because of their light weight, excellent elastic properties, ability to absorb or accommodate other medium, and low preparation costs [3]. In particular, its high compression set capability meets the demand for high-performance soft actuators, which can be applied to a variety of complex situations with design innovations in software grippers, mobile platforms and other soft- ware structures.Magnetorheological elastomers can be dividedinto many kinds according to the different substrates and magnetic particles [4].Magnetorheo-logical elastomers were first prepared by RIgbi[5] and others by adding ferromagnetic particles to natural rubber. Bossis [6] added different content of ferromag-netic particles to the silicone rubber matrix and applied a pre-structured magnetic field to study the properties, and the results showed that the rheological effect in-J.F. Huang, Y.F. Meng (E-mail: 13777905089@163.com),College of Mechanical Engineering, North China University of Science and Tech-nology, Hebei, Tangshan, China.creased linearly with the increase of ferromagnetic par-ticle content. Chen [7] studied the internal particle mi-crostructure of MRE and measured the corresponding shear modulus and found that the magnetorheological elastomer has the largest magnetorheological effect and less deformation in the shear mode.Although the magnetic elastomer has excellent char-acteristics, there is always a problem of unstable mate-rial properties and difficulty in improving the magnetic properties and mechanical properties at the same time, which is caused by the poor dispersion of magnetic par-ticles in the elastomer and serious agglomeration. Start-ing from the preparation process of magnetorheological elastomer [8,9], this paper combines the microstructure observation of magnetoelastomer, mechanical proper-ties and magnetic properties to improve the dispersion of magnetic particles in the elastic matrix and further optimize the performance of magnetoelastomers.MATERIALS AND METHODMagnetorheological sponge is prepared by combin-ing carbonyl iron powder magnetic particles with a low-density (PU) sponge elastic matrix using a silane cou-pling agent. Principles of magnetorheo-logical sponge synthesis is shown in Figure 1.Figure 1 Principles of magnetorheological sponge synthesis47J.F. HUANG et al.: PREPARATION AND PERFORMANCE STUDY OF MAGNETORHEOLOGICAL (MR) FOAMMETALURGIJA 63 (2024) 1, 46-48The carbonyl iron particles (CIPs) adopted in this study were purchased from Jikang material Corpora-tion, Hangzhou, China, with an average diameter of 10 μm. The silane coupling agent (SCA) is of KH-570 type produced by Macklin Biochemical Technology Corpo-ration, Shanghai, China. The matrix of the foam was a commercial soft polyurethane (PU) foam supplied from Paojia, China.Firstly, a precursor suspension was prepared by mix-ing CIPs deionized water together according to specific volume fraction. The calculation of particle quantity was based on the density of its bulk state and its ex-pected volume fraction. The volume fraction of SCA was chosen as 1 % to make reliable connection between CIPs and PU foam. The precursor was stirred under a mechanical agitator at a speed of 500 rpm for 30 min.Secondly, the PU foam was soaked in the precursor and the mixture was treated by ultrasonic waves for 5 hours. With the help of ultrasonic vibration, the CIPs move into the micropores of the foam matrix and fur-ther connect to the PU framework with the aid of SCA.Finally, the CIPs coated PU foam was dried in the oven at 80 °C for 4 hours. During the process, the con-nection between CIPs and PU framework become firm-er. As shown in Table 1:to the presence of CIPs on its surface as well as inside its cores. From the magnetization curves, under 500 mT, the magnetization of sample 1 is 23,7 mT, which reaches 85,37 % of the saturation magnetization value, the magnetization of sample 2 is 40,1 mT, which reach-es 86,23 % of the saturation magnetization value. Both samples have good magnetization characteristics, and sample 2 has better magnetization characteristics.MECHANICAL PROPERTIES MEASUREMENTA commercial rheometer (Physica MCR 302, Anton Paar Co, Austria) was adoptesdd to exert precise com-pression on the MR foams and measure the normal force provides by its viscoelastic properties. A solenoid coil with 8 000 turns was set around the mea-suring area, dwhich can provide a magnetic field up to 0.3 T along the vertical direction. A schematic representation on the measurement is shown in Figure 4:Table 1 Magnetic liquid composition ratioSample serialnumberGIPs/vol %DeionizedWater /vol %OMBT/ vol %1 5 94 12 15 84 1Morphological observation of magnetorheo- logical elastomers was performed using electron microscopes, as shown in Figures 2 a and 2 b.Figure 2 Scanning Electron Microscope(a) –  Electronically scanned  structural drawing;(b) –  Optical microscope  scanning.Figure 3 Magnetization curveFigure 4 Schematic representation on the measurementThe carbonyl iron particles were uniformly distribut-ed in the pores of the sponge, and there was no obvious particle agglomeration, and the corresponding energy spectrum mapping diagram and data table further proved that the Fe element was evenly dispersed on the sponge, and the bonding effect with the sponge was good.The magnetization properties of the MR foam was measured under a BKT-4500 vibrating sample mag-netometer (VSM), as shown in Figures 3 a and b. As a whole, the MR foam shows a ferromagnetic nature due 48  METALURGIJA 63 (2024) 1, 46-48J.F. HUANG et al.: PREPARATION AND PERFORMANCE STUDY OF MAGNETORHEOLOGICAL (MR) FOAMMECHANICAL ANALYSIS OF SPONGESThe two kinds of MR sponges were subjected to static mechanical compression experiments at a strain rate of 0,001 s−1. MR sponge exhibits complex mechan-ical behavior under external magnetic field strength and load pressure, Stress-strain relationship of MR sponge under different magnetic fields shown in Figures 5 a and b.the third stage. The porous tissue compacts with each other within the MR sponge, leading to a significant in-crease in stress.At the same time, the strength of the magnetic field where the MR sponge is located increases, the stress of MR increases under the same strain and the rate of in-crease increases. This is related to the magnetization of ferromagnetic particles to produce various anisotropic structures. Comparing two types of samples, under the same conditions, MR sponge with a large proportion of internal carbonyl iron has a faster rate of stress increase and a higher Young’s modulus.CONCLUSIONIn this study, a novel magnetorheological (MR) foam was prepared. When MR foams are loaded under the action of magnetic field, there are three stages: elas-tic stage, instability stage and nonlinear densification. The applied magnetic field increase the elastic deforma-tion of MR foam, and the Young’s modulus also in-creases with the proportion of carbonyl iron particles in MR foam. The study contributes to a deeper under-standing of MR foam, which may provide inspiration for novel soft robotic forms.REFERENCES[1] Nagel S R. Experimental soft-matter science [J]. Reviews of modern physics 89 (2017) 2,025002.[2] De Gennes P G. Soft matter [J]. Science 1992,256 (5056),495-497.[3] M. E. Davis, “Ordered porous materials for emerging ap-plications,” Nature 417 (2002) ,813-821.[4] Kuznetsova I E, Kolesov V V, Zaitsev B D, et al. Electro-physical and acoustic properties of magnetic elastomers structured by an external magnetic field[J]. Bulletin of the Russian Academy of Sciences, Physics 81 (2013) 945-949.[5] Bastola A K, Hossain M. A review on magneto-mechanical characterizations of magnetorheological elastomers [J]. Composites Part B: Engineering 200 (2020), 108348.[6] Runov V V, Bugrov A N, Smyslov R Y, et al. Mesostructu-re of composite materials based on segmented poly (ure-thane imide) containing ferrite nanoparticles [J]. Russian Journal of Inorganic Chemistry 66 (2021), 225-236.[7] Yan X, Hu M, Liu J, et al. Compressible metalized soft magnetic sponges with tailorable electrical and magnetic properties [J]. ChemNanoMat 6 (2020) 2,316-325.[8] Maslowski M, Miedzianowska J, Strzelec K. Reinforced, extruded, isotropic magnetic elastomer composites: Fabri-cation and properties [J]. Advances in Polymer Techno-logy 2019 (2019).[9] Zhu D, Handschuh-Wang S, Zhou X. Recent progress in fabrication and application of polydimethylsiloxane spon-ges [J]. Journal of Materials Chemistry A 5 (2017) 32, 16467-16497.(a) – sample 1; (b) – sample 2.Figure 5  Stress-strain relationship of MR sponge under different magnetic fieldsThe variation trend of its stress-strain curve is basi-cally the same, and can generally be divided into three stages: linear elastic stage, instability stage and nonlin-ear densification.When the strain range of MR sponge is 0,1~0,15, it is in the linear elastic stage. Due to the compression and stretching of the porous structure inside the MR sponge, as well as the anisotropic flux compression combined with ferromagnetic particles, the stress gradually chang-es with increasing strain, which is roughly linear. When the strain range of MR sponge is 0,15~0,3, it is in the instability stage. Plastic defor-mation and buckling of the porous structure inside the MR sponge, this mani-fests as a small stress change that can result in signifi-cant strain, and the stress change is slow at this stage. When the strain range of MR sponge is 0,3~0,5, it is in Note:  The responsible translator for English language is J.L. Miao - North China University of Science and Technology, China

Preparation and performance study of magnetorheological (MR) foam

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