1997 Volume 37 Issue 4 Pages 383-390
An ultrawide range viscometer which is based on a combination of the indentation, parallel plate and rotating plate methods has been developed. A cylindrical glass sample is placed between spiked and smooth discs and pressed by a suitable load and its deformation rate is measured under an ascending temperature process. At first, the spike penetrates into a glass and then the surface of spiked disc causes a bulky creep of the sample. On melting of the sample, the concentric rotation method is used in which a disc is rotated at adequate speed and the torque exerted on the disc is measured. Thus, a wide range viscosity, extending from 1012 to 101Pa·s, can be sequentially determined by the measurements of indentation rate, creep rate and rotational torque. Since the principles and a mechanism of this viscometer are rather simple, the absolute value of the sample viscosity can be determined, at least to the right order, without any calibration using standard reference materials.
The reproducibility of the results was demonstrated by the measurements, covering the glassy to molten states, of polymer glasses up to 500 K, and of boron oxide and pyrex glasses up to 1270 and 1470 K, respectively.
