Kaneko Masahiro, Kawai Mika, Mitsumata Tetsu
Graduate School of Science and Technology, Niigata University, Niigata 950-2181, Japan.
Gels. 2022 Sep 14;8(9):584. doi: 10.3390/gels8090584.
The effect of carrageenan concentration on the magneto-rheological effect of magnetic gels with a magnetic particle concentration of 50 wt.% was investigated under a magnetic field of 50 mT by dynamic viscoelastic measurements. The change in the storage modulus for magnetic gels due to the magnetic field was 3.0 × 10 Pa at a carrageenan concentration of 1.0 wt.% and increased with the concentration. The modulus change showed a maximum of 2.3 × 10 Pa at ~2.0 wt.% and became lower at higher concentrations. This is an interesting phenomenon, which was first observed in this study. The critical strain, the strain where the storage modulus intersects the loss modulus in the strain dependence of the modulus, was much higher than that for carrageenan gels, indicating a strong interaction between the magnetic particles and carrageenan. At 0 mT, the critical strain for the magnetic gels increased remarkably with decreasing the concentration, indicating that magnetic gels have a structure that does not flow easily at concentrations below 1.75 wt.%. It is considered that the structure hardly flows, hindering the movement of particles. At high concentrations, the SEM photographs showed both a particle network of magnetic particles and a dense carrageenan network. It can be considered that the movement of magnetic particles was hindered due to these factors at high concentrations.
通过动态粘弹性测量，在50 mT的磁场下研究了角叉菜胶浓度对磁性颗粒浓度为50 wt.%的磁性凝胶磁流变效应的影响。在角叉菜胶浓度为1.0 wt.%时，磁场引起的磁性凝胶储能模量变化为3.0×10 Pa，并随浓度增加而增大。模量变化在~2.0 wt.%时达到最大值2.3×10 Pa，在更高浓度时降低。这是一个有趣的现象，首次在本研究中观察到。临界应变，即储能模量与损耗模量在模量应变依赖性中相交处的应变，远高于角叉菜胶凝胶的临界应变，表明磁性颗粒与角叉菜胶之间存在强相互作用。在0 mT时，磁性凝胶的临界应变随浓度降低而显著增加，表明磁性凝胶在浓度低于1.75 wt.%时具有不易流动的结构。据认为，这种结构难以流动，阻碍了颗粒的运动。在高浓度下，扫描电子显微镜照片显示既有磁性颗粒的颗粒网络，也有致密的角叉菜胶网络。可以认为，在高浓度下由于这些因素磁性颗粒的运动受到了阻碍。
