以乙基硅油、羰基铁粉、十二羟基硬脂酸和氢氧化锂为原料,采用原位皂化法制备锂基磁流变脂(MRG),并分别在60,120,180 ℃下进行热氧化,研究了热氧化对MRG质量、分子结构、静态屈服应力和磁流变性能的影响。结果表明:热氧化会使MRG的质量发生损失,乙基硅油分子中的-CH₃、-CH₂-和Si-C₂H₅基团含量减少,交联Si-O-Si含量增加;随着热氧化温度升高,MRG的剪切应力和静态屈服应力增大,储能模量在磁场下的可调节范围变小;在60 ℃热氧化15 d时,MRG的磁流变效应仍能保持未热氧化的84.6%,但温度达到180 ℃时,磁性颗粒受磁场激励时的定向排列受阻,导致磁流变效应急剧下降。

Lithium-based magnetorheological grease (MRG) was prepared by in-situ saponification method with ethyl silicone oil, carbonyl iron powder, dodecyl hydroxy stearic acid and lithium hydroxide as raw materials, and then was thermally oxidized at 60, 120, 180 ℃, respectively. The effect of thermal oxidation on the mass, molecular structure, static yield stress and magnetorheological performance of MRG was studied. The results show that thermal oxidation could cause the mass loss of MRG, reduce the content of -CH₃, -CH₂- and Si-C₂H₅ groups in ethyl silicone oil molecules, and increase the content of crosslinked Si-O-Si. With the increase of thermal oxidation temperature, the shear stress and static yield stress of MRG increased, and the adjustable range of storage modulus under magnetic field became smaller. After thermal oxidation at 60 ℃ for 15 d, the magnetorheological effect of MRG still maintained 84.6% of that without thermal oxidation. When the temperature reached 180 ℃, the directional arrangement of magnetic particles excited by magnetic field was blocked, leading to the sharp decrease of magnetorheological effect.