Response time and electrorheology of semidiluted gellan, xanthan and cellulose suspensions

Response times with electrical fields of gellan and xanthan dry powder suspensions of 25, 32 and 53 μm average diameter and concentrations of 1.0, 1.5 and 2.0% (w/w) dispersed in commercial corn oil were optically measured through a specifically designed set up. In all cases, the delay time was proportional to 1/Ea, where E is the applied field and a is an adjustable parameter. The values of parameter a were very different from the typical value of some known electrorheolgical fluids. Response time of gellan suspensions was shorter than the one obtained for xanthan and it is comparable to the time found by using silica particles in silicon oil. Response times for cellulose were very large and the fibrillation phenomenon was negligible for E<1.0 kv/mm. ity measurements of semidiluted xanthan, gellan and cellulose suspensions (1.0 and 1.5% w/w) under the influence of electrical fields, were performed in a parallel plates rheometer. Results in the range of stress <70 Pa showed that viscosity values of gellan suspensions were larger than those obtained with xanthan or cellulose under the same applied electric field at shear rates higher than 10 s−1. However, cellulose suspensions showed larger viscosity values compared with the ones measured with xanthan and gellan suspensions at very low shear rates. Dielectric measurements of cellulose, xanthan and gellan 1.5% w/w suspensions were performed in the range 100–8×104 Hz. Results agree with a Maxwell–Wagner type relaxation model.