Yuji Hirose

Electrorheology of Polymer Blends Suspended in Silicon Oil

We studied the electrorheology of amorphous poly(lactic acid) (PLA), poly(vinyl acetate) (PVAc) and poly(ethylene glycol) (PEG) suspensions. For PEG suspensions, the yield stress was observed and increased with the increase in electric field. On the other hand, the PLA and PVAc suspensions did not show ER effect because electrophoresis and discharge between plates occurred. We also studied the ER effect of PLA/PEG and PVAc/PEG blend suspensions. These suspensions snowed the higher yield stress than the neat PEG suspension. It is considered that when the electrophoresis occurs in the weak electric field, the particles migrate to electrode. In general, ER effect is shown in the high electric field. It is considered that high electric field is required to cut this electrophoretic effect for development of striking ER effect. For PLA and PVAc suspensions, it is considered that the electrophoretic effect is too strong and does not show the ER effect.

Electrorheology of Poly(Ethylene Glycol) Suspension

We studied particle weight fraction, temperature and molecular weight dependences of ER effect for poly(ethylene glycol) suspension. For weight fraction dependence, yield stress was nearly constant from 20 to 30 wt% suspension but became low at 10 and 15 wt%. Yield stress became higher as temperature increased and the temperature dependence was strong as particle composition increased. From the study of molecular weight dependence, we observed the weakening yield stress of high molecular weight PEG. We also measured ER of two molecular weight PEG blend suspension and observed similar yield stress to neat PEG which have similar number‐average molecular weight.

Motion Control of Disc Electrode by Electrorheological Fluids

The electrorheological(ER) suspensions are sandwiched between two flat disc electrodes with the radial line patterns. The pattern electrodes are fixed on the parallel plate geometry on a stress‐controlled rheometer which was modified for the ER experiments. The motion of disk electrodes analyzed as a function of electrification modes to obtain the basic data for ER actuators.