MEASUREMENT OF VISCOSITY OF MULTICOMPONEN T GLASSES IN THE WIDE-RANGEFOR FIBER DRAWING

The viscosity-temperature behavior in the wide range 10(-2)similar to 10(12) Pa.s were presented for various glass systems: oxide, fluoride, halide, and chalcogenide. There is no single technique that can be ut ilized to measure the viscosity of glass over the entire range, spanin g roughly 14 orders of magnitude. The viscosity was measured by a pene tration viscometry method at low-temperature viscosity region (10(7) s imilar to 10(12) Pa.s) and by a rotational viscometry method at high-t emperature viscosity region (10(-2)similar to 10(1) Pa.s). It was foun d the viscosity can be expressed by the Cohen-Grest equation over a wi de temperature. The working point, T-w(10(3) Pa.s), the softening poin t, T-s(10(6.65) Pa.s) and the working range-temperature interval betwe en the T-w and the T-s were determined using the measured viscosity da ta and the viscosity-temperature equation. We discussed the technical term of fiber drawing from the viewpoint of viscosity-temperature beha vior and thermal stability of glass crystalized as a function of heat treatment time, to at the drawing temperature. The results indicate th at silica and lead silicate glasses are prefered for fiber drawing.