The relation of the viscosity of glasses to load, temperature and time in the range 103–1013 poises. Part I
JSGT 1957 V41 T137-T156
By a fibre elongation method the influences of load, temperature, and time on the rates of elongation of various glasses in the viscosity range of 108–1013 poises were studied. Within this range it was found that the time-dependent characteristic of the viscosity which gives lower values in the early period of the measurement was influenced by the load applied, and the effect appeared more and more pronounced as the load was decreased. Under a fixed load this behaviour became less and less marked at higher temperatures. In a borosilicate glass of the Nonex type, a visco-elastic behaviour with a very short relaxation time was observed in the viscosity range of 108–1011 poises. The relaxation time became shorter at the higher temperatures. From the rheological point of view the authors have pointed out that the relation between the reciprocal of viscosity coefficient and time corresponds to that between a distribution function and time, and have observed that the long relaxation time disappears at higher temperatures and the short relaxation time disappears when the glass is given a suitable heat pretreatment. Furthermore, from the fact that the distribution of relaxation time before stabilisation differs from that after stabilisation, viscosity change with time is attributable to change of the glass structure. From this consideration the authors have explained the ways in which load, temperature, and time are related to the viscosity, by using the theories put forward by Douglas & Tool.
M. Watanabe & R. Koyama
