Load-dependent relaxation behaviour of various glass melts with different structural configurations

Abstract

Glass melts are usually treated in literature as thermorheologically simple fluids. The temperature-time equivalence of the relaxation behaviour is described by the WLF equation. This also for silicate melts well-known behaviour will be verified in the present paper with the help of the cylinder-compression method up to 240 Κ above Tg for very different melts. In addition it is shown that the relaxation behaviour is load-dependent above a certain load limit indicating a deviation from the conception of the thermorheological simplicity. The load-dependent relaxation behaviour is investigated for glass melts with very different network structures (chains, cross-linked chains and three-dimensionally connected structures). A clear correlation with structure is demonstrated in that way that the relaxation ability and its load dependence increase with decreasing degree of structural interconnection from a three-dimensionally to a one-dimensionally linked potential network structure.