Which rheological parameters control the isochomal workability of glass melts from the Container glass industry?

Abstract

Two species of brown glass which were characterized by industrial workability and quality criteria as "good" and " bad ", respectively, were investigated by the cylinder compression method and by the Christiansen method. Significant differences between the two species were found by means of the two methods in such a manner that the "good" brown glass samples indicate a better homogeneity and the corresponding melts a larger critical deformation rate, hc and therefore, a better isochomal workability than the " bad " brown glasses and melts. Additionally, the former ones show a larger ratio Fe²⁺/F_total with the consequence that they have a lower Newtonian viscosity at the same temperature. In contrast to the brown glass melts no clear differences in the rheological properties and isochomal workability could be detected between white Container glass melts which have also been characterized as "good" or as "bad". The white Container glass melts are classified to be less workable at equal viscosities than the brown glass melts. The stress generation modulus, E_max, and the normalized non-Newtonian viscosity, η/η0T, are less sensitive properties with respect to the redox State of the melts and to the homogeneity than the hc values. With the results of this study the limits of the sensitivity of the various properties resulting from the cylinder compression method were reached.