FREQUENCY-RESPONSE OF A SHEAR-STRESS TRANSDUCER INSTALLED IN A SLIDING PLATE RHEOMETER

A number of laboratories are currently using sliding plate rheometers equipped with shear stress transducers to study the nonlinear viscoela sticity and slip of molten polymers. In making such measurements, it i s sometimes essential to know to what degree the dynamic response of t he shear stress transducer itself is influencing the output signal. Ex periments should be designed to minimize this effect, but some attenua tion and phase shift is inevitable because of the presence of polymer inside the transducer. We have measured the dynamic response of a shea r stress transducer in situ in a sliding plate rheometer for two molte n polyethylenes. We have also developed a model for the transducer res ponse. In oscillatory shear experiments above a frequency of 1 Hz, the amplitude ratio and phase lead are significant for both materials stu died. (C) 1998 The Society of Rheology.