A NEW INSTRUMENT FOR MEASURING THE VISCOELASTIC PROPERTIES OF DILUTE POLYMER-SOLUTIONS

A new oscillating capillary viscometer has been developed and used for measuring viscoelastic flow properties of dilute polymer solutions. T hese flow properties are determined from measurements of the pressure to volume flow relationships for sinusoidal flow in cylindrical glass capillaries. The theory for this measurement procedure is based upon t he known theory for oscillatory flow of a viscoelastic fluid in circul ar tubes and which is presented with a few supplementations in this pa per. The oscillatory flow is generated by a piezoelectric driver which is dipped directly into the aqueous solution. The advantage of this d river is that the excitation voltage for the piston is a direct measur e of the motion of the piston. Changes in pressure are measured with a sensitive low-pressure quartz transducer. The viscometer was tested w ith aqueous glycerol solutions and a gelatin gel. The viscoelastic flo w properties of dilute polymer solutions (gelatin, gelatin/color-coupl er, polyacrylamide) were then investigated in the frequency range 5 Hz to 150 Hz at very small volume flow amplitudes. The results presented illustrate the suitability of the method. The results are also evalua ted with regard to the stabilizing action of slightly viscoelastic gel atinous coating liquids in the high-speed coating process in the manuf acture of photographic materials.