ISSN 0862-5468 (Print), ISSN 1804-5847 (online) 

Ceramics-Silikáty 32, (3) 209 - 226 (1988)


METODA PRO GRAFICKÉ ZPRACOVÁNÍ PRŮBĚHU TEPLOTNÍ ZÁVISLOSTI VISKOZITY SKLOVIN NA CHEMICKÉM SLOŽENÍ

GRAPHICAL PROCESSING OF THE TEMPERATURE DEPENDENCE OF VISCOSITY ON CHEMICAL COMPOSITION OF GLASS MELTS


 
Šašek Ladislav 1, Míka Martin 1, Rada Miroslav 1
 
1 Katedra technologie silikátů, Vysoká škola chemicko-technologická, Suchbátarova 5, 166 28 Praha 6
1 Department of Silicate Technology, Institute of Chemical Technology, 166 28 Prague 6

Pro popis teplotní závislosti viskozity sklovin v soustavě Na₂O-CaO-MgO-Al₂O₃-SiO₂ byl použit vztah log(log η) = A + B log T, ve kterém koeficienty A a B jsou závislé na chemickém složení skel. Tato závislost byla vyjádřena regresními polynomy třetího stupně, v nichž koeficienty byly určeny z experimentálních dat využitím metody plánovaných experimentů. Ve třísložkových diagramech CaO-MgO-Na₂O (obsah Al₂O₃ a SiO₂ byl konstantní) jsou zakresleny průběhy izoterm pro viskozity 10², 10³, 10⁴, 107.6, 10¹³, 1014.5 dPas. Grafické zpracování umožňuje rychlou orientaci ve vlivu chemického složení sklovin na průběh sledované závislosti.

The suggested method allows the temperature dependence of viscosity on chemical composition of container and flat glasses to be processed graphically while permitting the content of three components (Na₂O, CaO and MgO) to be varied and keeping a constant content of Al₂O₃ and SiO₂. The method makes use of a computer with plotter output. The mathematical model, expressed by third-degree polynomials, describes the temperature dependence of viscosity of the glasses with a maximum deviation of 11 °C from the values measured over the entire viscosity range studied (10²-1014,5 dPas) (Table VI). The individual isotherms are plotted in Figs. 7 through 12 with an accuracy of ± 0.05 °C. In these diagrams the experimental glasses are marked with rings. The course of the isotherms shows that at high temperatures at glass viscosity of about 10² dPas the effect of CaO-MgO substitutions is quite significant. A reduced content of Na₂, which brings about an increase in viscosity, can be completely compensated substituting by MgO with CaO. With decreasing temperature the effect of a change in the CaO/MgO ratio is becoming less marked, being already indistinct at viscosities higher than about 107.6 dPas. Graphic plotting of the effect of chemical composition on the temperature dependence of glass melt viscosity has the advantage of allowing the chemical composition of glass with a defined temperature dependence of viscosity to be determined very rapidly. Fig. 13 demonstrates the method for establishing the chemical composition of glasses with a desired slope of the temperature dependence of viscosity. The chemical composition of the glass is given by the intersection of the respective isotherms. The method can be used to advantage in glassmaking practice.


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