Design of a new streaming potential measurement flow cell for polymer films

We have designed a flat plate flow cell to measure the streaming potential of the obverse and reverse sides of polymer surfaces separately to obtain i nformation about the zeta -potential. Experiments involve an 0.3-mm flow pa ssage height, and the flow is verified to be laminar due to the Reynolds nu mber in the cell flow passage. At the maximum flow rate, Q(0) is 500 ml/min , and the inner diameter of the Teflon(R) inlet tube is chosen to be 10 mm to make the dynamic pressure in the inlet tube negligibly small compared to the total pressure loss. Because of this, a spanwise uniform flow can be a chieved downstream from the flow passage. The sample width is fixed at 20 m m and the pressure gradient measurement length is 250 mm, which is long eno ugh compared to the entrance length to obtain a fully developed flow. The z eta -potential values of nylon 66 film from this flow cell are reproducible and are comparable to values from an ordinary block cell used for various purposes obtained with the same film and nylon 66 fabric in the pH range 4- 8.