Characterization of an electrorheological suspension of poly(vinyl alcohol) in corn oil

Suspensions of poly(vinyl alcohol) at 31% w/w in corn oil were studied. At 20 degrees C, yield stresses of 7, 39, 103 and 170 Pa, respectively at 0, 5 00, 1000 and 1500 Vdc/mm were obtained. At 25 degrees C and 500 Vrms/mm, me asurements in the range of 20 to 1000 Hz were made. Yield stresses were not obtained, but the electrorheological effect was less pronounced under an A C field than a DC field: at 20 Hz and steady shear rates of 10.8, 48.6 and 97.2 s(-1), the sheer stresses were 16, 30 and 50 Pa, respectively. Under 5 00 Vdc/mm, at the same shear rates, the shear stresses were 40, 65 and 90 P a. The shear stresses decrease exponentially as the frequency rises. The re producibility of this effect is good: the values stay between +/- 20% for t riplicate suspension samples.